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How to Write a Research Paper Introduction (with Examples)

The research paper introduction section, along with the Title and Abstract, can be considered the face of any research paper. The following article is intended to guide you in organizing and writing the research paper introduction for a quality academic article or dissertation.

The research paper introduction aims to present the topic to the reader. A study will only be accepted for publishing if you can ascertain that the available literature cannot answer your research question. So it is important to ensure that you have read important studies on that particular topic, especially those within the last five to ten years, and that they are properly referenced in this section. 1 What should be included in the research paper introduction is decided by what you want to tell readers about the reason behind the research and how you plan to fill the knowledge gap. The best research paper introduction provides a systemic review of existing work and demonstrates additional work that needs to be done. It needs to be brief, captivating, and well-referenced; a well-drafted research paper introduction will help the researcher win half the battle.

The introduction for a research paper is where you set up your topic and approach for the reader. It has several key goals:

• Present your research topic
• Capture reader interest
• Summarize existing research
• Position your own approach
• Define your specific research problem and problem statement
• Highlight the novelty and contributions of the study
• Give an overview of the paper’s structure

The research paper introduction can vary in size and structure depending on whether your paper presents the results of original empirical research or is a review paper. Some research paper introduction examples are only half a page while others are a few pages long. In many cases, the introduction will be shorter than all of the other sections of your paper; its length depends on the size of your paper as a whole.

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Table of Contents

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The introduction in a research paper is placed at the beginning to guide the reader from a broad subject area to the specific topic that your research addresses. They present the following information to the reader

• Scope: The topic covered in the research paper
• Context: Background of your topic
• Importance: Why your research matters in that particular area of research and the industry problem that can be targeted

The research paper introduction conveys a lot of information and can be considered an essential roadmap for the rest of your paper. A good introduction for a research paper is important for the following reasons:

• It stimulates your reader’s interest: A good introduction section can make your readers want to read your paper by capturing their interest. It informs the reader what they are going to learn and helps determine if the topic is of interest to them.
• It helps the reader understand the research background: Without a clear introduction, your readers may feel confused and even struggle when reading your paper. A good research paper introduction will prepare them for the in-depth research to come. It provides you the opportunity to engage with the readers and demonstrate your knowledge and authority on the specific topic.
• It explains why your research paper is worth reading: Your introduction can convey a lot of information to your readers. It introduces the topic, why the topic is important, and how you plan to proceed with your research.
• It helps guide the reader through the rest of the paper: The research paper introduction gives the reader a sense of the nature of the information that will support your arguments and the general organization of the paragraphs that will follow. It offers an overview of what to expect when reading the main body of your paper.

What are the parts of introduction in the research?

A good research paper introduction section should comprise three main elements: 2

• What is known: This sets the stage for your research. It informs the readers of what is known on the subject.
• What is lacking: This is aimed at justifying the reason for carrying out your research. This could involve investigating a new concept or method or building upon previous research.
• What you aim to do: This part briefly states the objectives of your research and its major contributions. Your detailed hypothesis will also form a part of this section.

How to write a research paper introduction?

The first step in writing the research paper introduction is to inform the reader what your topic is and why it’s interesting or important. This is generally accomplished with a strong opening statement. The second step involves establishing the kinds of research that have been done and ending with limitations or gaps in the research that you intend to address. Finally, the research paper introduction clarifies how your own research fits in and what problem it addresses. If your research involved testing hypotheses, these should be stated along with your research question. The hypothesis should be presented in the past tense since it will have been tested by the time you are writing the research paper introduction.

The following key points, with examples, can guide you when writing the research paper introduction section:

• Highlight the importance of the research field or topic
• Describe the background of the topic
• Present an overview of current research on the topic

Example: The inclusion of experiential and competency-based learning has benefitted electronics engineering education. Industry partnerships provide an excellent alternative for students wanting to engage in solving real-world challenges. Industry-academia participation has grown in recent years due to the need for skilled engineers with practical training and specialized expertise. However, from the educational perspective, many activities are needed to incorporate sustainable development goals into the university curricula and consolidate learning innovation in universities.

• Reveal a gap in existing research or oppose an existing assumption
• Formulate the research question

Example: There have been plausible efforts to integrate educational activities in higher education electronics engineering programs. However, very few studies have considered using educational research methods for performance evaluation of competency-based higher engineering education, with a focus on technical and or transversal skills. To remedy the current need for evaluating competencies in STEM fields and providing sustainable development goals in engineering education, in this study, a comparison was drawn between study groups without and with industry partners.

• State the purpose of your study
• Highlight the key characteristics of your study
• Describe important results
• Highlight the novelty of the study.
• Offer a brief overview of the structure of the paper.

Example: The study evaluates the main competency needed in the applied electronics course, which is a fundamental core subject for many electronics engineering undergraduate programs. We compared two groups, without and with an industrial partner, that offered real-world projects to solve during the semester. This comparison can help determine significant differences in both groups in terms of developing subject competency and achieving sustainable development goals.

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The purpose of the research paper introduction is to introduce the reader to the problem definition, justify the need for the study, and describe the main theme of the study. The aim is to gain the reader’s attention by providing them with necessary background information and establishing the main purpose and direction of the research.

The length of the research paper introduction can vary across journals and disciplines. While there are no strict word limits for writing the research paper introduction, an ideal length would be one page, with a maximum of 400 words over 1-4 paragraphs. Generally, it is one of the shorter sections of the paper as the reader is assumed to have at least a reasonable knowledge about the topic. 2 For example, for a study evaluating the role of building design in ensuring fire safety, there is no need to discuss definitions and nature of fire in the introduction; you could start by commenting upon the existing practices for fire safety and how your study will add to the existing knowledge and practice.

When deciding what to include in the research paper introduction, the rest of the paper should also be considered. The aim is to introduce the reader smoothly to the topic and facilitate an easy read without much dependency on external sources. 3 Below is a list of elements you can include to prepare a research paper introduction outline and follow it when you are writing the research paper introduction. Topic introduction: This can include key definitions and a brief history of the topic. Research context and background: Offer the readers some general information and then narrow it down to specific aspects. Details of the research you conducted: A brief literature review can be included to support your arguments or line of thought. Rationale for the study: This establishes the relevance of your study and establishes its importance. Importance of your research: The main contributions are highlighted to help establish the novelty of your study Research hypothesis: Introduce your research question and propose an expected outcome. Organization of the paper: Include a short paragraph of 3-4 sentences that highlights your plan for the entire paper

Cite only works that are most relevant to your topic; as a general rule, you can include one to three. Note that readers want to see evidence of original thinking. So it is better to avoid using too many references as it does not leave much room for your personal standpoint to shine through. Citations in your research paper introduction support the key points, and the number of citations depend on the subject matter and the point discussed. If the research paper introduction is too long or overflowing with citations, it is better to cite a few review articles rather than the individual articles summarized in the review. A good point to remember when citing research papers in the introduction section is to include at least one-third of the references in the introduction.

The literature review plays a significant role in the research paper introduction section. A good literature review accomplishes the following: Introduces the topic – Establishes the study’s significance – Provides an overview of the relevant literature – Provides context for the study using literature – Identifies knowledge gaps However, remember to avoid making the following mistakes when writing a research paper introduction: Do not use studies from the literature review to aggressively support your research Avoid direct quoting Do not allow literature review to be the focus of this section. Instead, the literature review should only aid in setting a foundation for the manuscript.

Remember the following key points for writing a good research paper introduction: 4

• Avoid stuffing too much general information: Avoid including what an average reader would know and include only that information related to the problem being addressed in the research paper introduction. For example, when describing a comparative study of non-traditional methods for mechanical design optimization, information related to the traditional methods and differences between traditional and non-traditional methods would not be relevant. In this case, the introduction for the research paper should begin with the state-of-the-art non-traditional methods and methods to evaluate the efficiency of newly developed algorithms.
• Avoid packing too many references: Cite only the required works in your research paper introduction. The other works can be included in the discussion section to strengthen your findings.
• Avoid extensive criticism of previous studies: Avoid being overly critical of earlier studies while setting the rationale for your study. A better place for this would be the Discussion section, where you can highlight the advantages of your method.
• Avoid describing conclusions of the study: When writing a research paper introduction remember not to include the findings of your study. The aim is to let the readers know what question is being answered. The actual answer should only be given in the Results and Discussion section.

To summarize, the research paper introduction section should be brief yet informative. It should convince the reader the need to conduct the study and motivate him to read further. If you’re feeling stuck or unsure, choose trusted AI academic writing assistants like Paperpal to effortlessly craft your research paper introduction and other sections of your research article.

1. Jawaid, S. A., & Jawaid, M. (2019). How to write introduction and discussion. Saudi Journal of Anaesthesia, 13(Suppl 1), S18.

2. Dewan, P., & Gupta, P. (2016). Writing the title, abstract and introduction: Looks matter!. Indian pediatrics, 53, 235-241.

3. Cetin, S., & Hackam, D. J. (2005). An approach to the writing of a scientific Manuscript1. Journal of Surgical Research, 128(2), 165-167.

4. Bavdekar, S. B. (2015). Writing introduction: Laying the foundations of a research paper. Journal of the Association of Physicians of India, 63(7), 44-6.

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Home » Research Paper Introduction – Writing Guide and Examples

Research Paper Introduction – Writing Guide and Examples

Table of Contents

Research Paper Introduction

Research paper introduction is the first section of a research paper that provides an overview of the study, its purpose, and the research question (s) or hypothesis (es) being investigated. It typically includes background information about the topic, a review of previous research in the field, and a statement of the research objectives. The introduction is intended to provide the reader with a clear understanding of the research problem, why it is important, and how the study will contribute to existing knowledge in the field. It also sets the tone for the rest of the paper and helps to establish the author’s credibility and expertise on the subject.

How to Write Research Paper Introduction

Writing an introduction for a research paper can be challenging because it sets the tone for the entire paper. Here are some steps to follow to help you write an effective research paper introduction:

• Start with a hook : Begin your introduction with an attention-grabbing statement, a question, or a surprising fact that will make the reader interested in reading further.
• Provide background information: After the hook, provide background information on the topic. This information should give the reader a general idea of what the topic is about and why it is important.
• State the research problem: Clearly state the research problem or question that the paper addresses. This should be done in a concise and straightforward manner.
• State the research objectives: After stating the research problem, clearly state the research objectives. This will give the reader an idea of what the paper aims to achieve.
• Provide a brief overview of the paper: At the end of the introduction, provide a brief overview of the paper. This should include a summary of the main points that will be discussed in the paper.
• Revise and refine: Finally, revise and refine your introduction to ensure that it is clear, concise, and engaging.

Structure of Research Paper Introduction

The following is a typical structure for a research paper introduction:

• Background Information: This section provides an overview of the topic of the research paper, including relevant background information and any previous research that has been done on the topic. It helps to give the reader a sense of the context for the study.
• Problem Statement: This section identifies the specific problem or issue that the research paper is addressing. It should be clear and concise, and it should articulate the gap in knowledge that the study aims to fill.
• Research Question/Hypothesis : This section states the research question or hypothesis that the study aims to answer. It should be specific and focused, and it should clearly connect to the problem statement.
• Significance of the Study: This section explains why the research is important and what the potential implications of the study are. It should highlight the contribution that the research makes to the field.
• Methodology: This section describes the research methods that were used to conduct the study. It should be detailed enough to allow the reader to understand how the study was conducted and to evaluate the validity of the results.
• Organization of the Paper : This section provides a brief overview of the structure of the research paper. It should give the reader a sense of what to expect in each section of the paper.

Research Paper Introduction Examples

Research Paper Introduction Examples could be:

Example 1: In recent years, the use of artificial intelligence (AI) has become increasingly prevalent in various industries, including healthcare. AI algorithms are being developed to assist with medical diagnoses, treatment recommendations, and patient monitoring. However, as the use of AI in healthcare grows, ethical concerns regarding privacy, bias, and accountability have emerged. This paper aims to explore the ethical implications of AI in healthcare and propose recommendations for addressing these concerns.

Example 2: Climate change is one of the most pressing issues facing our planet today. The increasing concentration of greenhouse gases in the atmosphere has resulted in rising temperatures, changing weather patterns, and other environmental impacts. In this paper, we will review the scientific evidence on climate change, discuss the potential consequences of inaction, and propose solutions for mitigating its effects.

Example 3: The rise of social media has transformed the way we communicate and interact with each other. While social media platforms offer many benefits, including increased connectivity and access to information, they also present numerous challenges. In this paper, we will examine the impact of social media on mental health, privacy, and democracy, and propose solutions for addressing these issues.

Example 4: The use of renewable energy sources has become increasingly important in the face of climate change and environmental degradation. While renewable energy technologies offer many benefits, including reduced greenhouse gas emissions and energy independence, they also present numerous challenges. In this paper, we will assess the current state of renewable energy technology, discuss the economic and political barriers to its adoption, and propose solutions for promoting the widespread use of renewable energy.

Purpose of Research Paper Introduction

The introduction section of a research paper serves several important purposes, including:

• Providing context: The introduction should give readers a general understanding of the topic, including its background, significance, and relevance to the field.
• Presenting the research question or problem: The introduction should clearly state the research question or problem that the paper aims to address. This helps readers understand the purpose of the study and what the author hopes to accomplish.
• Reviewing the literature: The introduction should summarize the current state of knowledge on the topic, highlighting the gaps and limitations in existing research. This shows readers why the study is important and necessary.
• Outlining the scope and objectives of the study: The introduction should describe the scope and objectives of the study, including what aspects of the topic will be covered, what data will be collected, and what methods will be used.
• Previewing the main findings and conclusions : The introduction should provide a brief overview of the main findings and conclusions that the study will present. This helps readers anticipate what they can expect to learn from the paper.

When to Write Research Paper Introduction

The introduction of a research paper is typically written after the research has been conducted and the data has been analyzed. This is because the introduction should provide an overview of the research problem, the purpose of the study, and the research questions or hypotheses that will be investigated.

Once you have a clear understanding of the research problem and the questions that you want to explore, you can begin to write the introduction. It’s important to keep in mind that the introduction should be written in a way that engages the reader and provides a clear rationale for the study. It should also provide context for the research by reviewing relevant literature and explaining how the study fits into the larger field of research.

Advantages of Research Paper Introduction

The introduction of a research paper has several advantages, including:

• Establishing the purpose of the research: The introduction provides an overview of the research problem, question, or hypothesis, and the objectives of the study. This helps to clarify the purpose of the research and provide a roadmap for the reader to follow.
• Providing background information: The introduction also provides background information on the topic, including a review of relevant literature and research. This helps the reader understand the context of the study and how it fits into the broader field of research.
• Demonstrating the significance of the research: The introduction also explains why the research is important and relevant. This helps the reader understand the value of the study and why it is worth reading.
• Setting expectations: The introduction sets the tone for the rest of the paper and prepares the reader for what is to come. This helps the reader understand what to expect and how to approach the paper.
• Grabbing the reader’s attention: A well-written introduction can grab the reader’s attention and make them interested in reading further. This is important because it can help to keep the reader engaged and motivated to read the rest of the paper.
• Creating a strong first impression: The introduction is the first part of the research paper that the reader will see, and it can create a strong first impression. A well-written introduction can make the reader more likely to take the research seriously and view it as credible.
• Establishing the author’s credibility: The introduction can also establish the author’s credibility as a researcher. By providing a clear and thorough overview of the research problem and relevant literature, the author can demonstrate their expertise and knowledge in the field.
• Providing a structure for the paper: The introduction can also provide a structure for the rest of the paper. By outlining the main sections and sub-sections of the paper, the introduction can help the reader navigate the paper and find the information they are looking for.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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Organizing Your Social Sciences Research Paper

• 4. The Introduction
• Purpose of Guide
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The introduction leads the reader from a general subject area to a particular topic of inquiry. It establishes the scope, context, and significance of the research being conducted by summarizing current understanding and background information about the topic, stating the purpose of the work in the form of the research problem supported by a hypothesis or a set of questions, explaining briefly the methodological approach used to examine the research problem, highlighting the potential outcomes your study can reveal, and outlining the remaining structure and organization of the paper.

Key Elements of the Research Proposal. Prepared under the direction of the Superintendent and by the 2010 Curriculum Design and Writing Team. Baltimore County Public Schools.

Importance of a Good Introduction

Think of the introduction as a mental road map that must answer for the reader these four questions:

• What was I studying?
• Why was this topic important to investigate?
• What did we know about this topic before I did this study?
• How will this study advance new knowledge or new ways of understanding?

According to Reyes, there are three overarching goals of a good introduction: 1) ensure that you summarize prior studies about the topic in a manner that lays a foundation for understanding the research problem; 2) explain how your study specifically addresses gaps in the literature, insufficient consideration of the topic, or other deficiency in the literature; and, 3) note the broader theoretical, empirical, and/or policy contributions and implications of your research.

A well-written introduction is important because, quite simply, you never get a second chance to make a good first impression. The opening paragraphs of your paper will provide your readers with their initial impressions about the logic of your argument, your writing style, the overall quality of your research, and, ultimately, the validity of your findings and conclusions. A vague, disorganized, or error-filled introduction will create a negative impression, whereas, a concise, engaging, and well-written introduction will lead your readers to think highly of your analytical skills, your writing style, and your research approach. All introductions should conclude with a brief paragraph that describes the organization of the rest of the paper.

Hirano, Eliana. “Research Article Introductions in English for Specific Purposes: A Comparison between Brazilian, Portuguese, and English.” English for Specific Purposes 28 (October 2009): 240-250; Samraj, B. “Introductions in Research Articles: Variations Across Disciplines.” English for Specific Purposes 21 (2002): 1–17; Introductions. The Writing Center. University of North Carolina; “Writing Introductions.” In Good Essay Writing: A Social Sciences Guide. Peter Redman. 4th edition. (London: Sage, 2011), pp. 63-70; Reyes, Victoria. Demystifying the Journal Article. Inside Higher Education.

Structure and Writing Style

I.  Structure and Approach

The introduction is the broad beginning of the paper that answers three important questions for the reader:

• What is this?
• Why should I read it?
• What do you want me to think about / consider doing / react to?

Think of the structure of the introduction as an inverted triangle of information that lays a foundation for understanding the research problem. Organize the information so as to present the more general aspects of the topic early in the introduction, then narrow your analysis to more specific topical information that provides context, finally arriving at your research problem and the rationale for studying it [often written as a series of key questions to be addressed or framed as a hypothesis or set of assumptions to be tested] and, whenever possible, a description of the potential outcomes your study can reveal.

These are general phases associated with writing an introduction: 1.  Establish an area to research by:

• Highlighting the importance of the topic, and/or
• Making general statements about the topic, and/or
• Presenting an overview on current research on the subject.

2.  Identify a research niche by:

• Opposing an existing assumption, and/or
• Revealing a gap in existing research, and/or
• Formulating a research question or problem, and/or
• Continuing a disciplinary tradition.

3.  Place your research within the research niche by:

• Stating the intent of your study,
• Outlining the key characteristics of your study,
• Describing important results, and
• Giving a brief overview of the structure of the paper.

NOTE:   It is often useful to review the introduction late in the writing process. This is appropriate because outcomes are unknown until you've completed the study. After you complete writing the body of the paper, go back and review introductory descriptions of the structure of the paper, the method of data gathering, the reporting and analysis of results, and the conclusion. Reviewing and, if necessary, rewriting the introduction ensures that it correctly matches the overall structure of your final paper.

II.  Delimitations of the Study

Delimitations refer to those characteristics that limit the scope and define the conceptual boundaries of your research . This is determined by the conscious exclusionary and inclusionary decisions you make about how to investigate the research problem. In other words, not only should you tell the reader what it is you are studying and why, but you must also acknowledge why you rejected alternative approaches that could have been used to examine the topic.

Obviously, the first limiting step was the choice of research problem itself. However, implicit are other, related problems that could have been chosen but were rejected. These should be noted in the conclusion of your introduction. For example, a delimitating statement could read, "Although many factors can be understood to impact the likelihood young people will vote, this study will focus on socioeconomic factors related to the need to work full-time while in school." The point is not to document every possible delimiting factor, but to highlight why previously researched issues related to the topic were not addressed.

Examples of delimitating choices would be:

• The key aims and objectives of your study,
• The research questions that you address,
• The variables of interest [i.e., the various factors and features of the phenomenon being studied],
• The method(s) of investigation,
• The time period your study covers, and
• Any relevant alternative theoretical frameworks that could have been adopted.

Review each of these decisions. Not only do you clearly establish what you intend to accomplish in your research, but you should also include a declaration of what the study does not intend to cover. In the latter case, your exclusionary decisions should be based upon criteria understood as, "not interesting"; "not directly relevant"; “too problematic because..."; "not feasible," and the like. Make this reasoning explicit!

NOTE:   Delimitations refer to the initial choices made about the broader, overall design of your study and should not be confused with documenting the limitations of your study discovered after the research has been completed.

ANOTHER NOTE : Do not view delimitating statements as admitting to an inherent failing or shortcoming in your research. They are an accepted element of academic writing intended to keep the reader focused on the research problem by explicitly defining the conceptual boundaries and scope of your study. It addresses any critical questions in the reader's mind of, "Why the hell didn't the author examine this?"

III.  The Narrative Flow

Issues to keep in mind that will help the narrative flow in your introduction :

• Your introduction should clearly identify the subject area of interest . A simple strategy to follow is to use key words from your title in the first few sentences of the introduction. This will help focus the introduction on the topic at the appropriate level and ensures that you get to the subject matter quickly without losing focus, or discussing information that is too general.
• Establish context by providing a brief and balanced review of the pertinent published literature that is available on the subject. The key is to summarize for the reader what is known about the specific research problem before you did your analysis. This part of your introduction should not represent a comprehensive literature review--that comes next. It consists of a general review of the important, foundational research literature [with citations] that establishes a foundation for understanding key elements of the research problem. See the drop-down menu under this tab for " Background Information " regarding types of contexts.
• Clearly state the hypothesis that you investigated . When you are first learning to write in this format it is okay, and actually preferable, to use a past statement like, "The purpose of this study was to...." or "We investigated three possible mechanisms to explain the...."
• Why did you choose this kind of research study or design? Provide a clear statement of the rationale for your approach to the problem studied. This will usually follow your statement of purpose in the last paragraph of the introduction.

IV.  Engaging the Reader

A research problem in the social sciences can come across as dry and uninteresting to anyone unfamiliar with the topic . Therefore, one of the goals of your introduction is to make readers want to read your paper. Here are several strategies you can use to grab the reader's attention:

• Open with a compelling story . Almost all research problems in the social sciences, no matter how obscure or esoteric , are really about the lives of people. Telling a story that humanizes an issue can help illuminate the significance of the problem and help the reader empathize with those affected by the condition being studied.
• Include a strong quotation or a vivid, perhaps unexpected, anecdote . During your review of the literature, make note of any quotes or anecdotes that grab your attention because they can used in your introduction to highlight the research problem in a captivating way.
• Pose a provocative or thought-provoking question . Your research problem should be framed by a set of questions to be addressed or hypotheses to be tested. However, a provocative question can be presented in the beginning of your introduction that challenges an existing assumption or compels the reader to consider an alternative viewpoint that helps establish the significance of your study. 
• Describe a puzzling scenario or incongruity . This involves highlighting an interesting quandary concerning the research problem or describing contradictory findings from prior studies about a topic. Posing what is essentially an unresolved intellectual riddle about the problem can engage the reader's interest in the study.
• Cite a stirring example or case study that illustrates why the research problem is important . Draw upon the findings of others to demonstrate the significance of the problem and to describe how your study builds upon or offers alternatives ways of investigating this prior research.

NOTE:   It is important that you choose only one of the suggested strategies for engaging your readers. This avoids giving an impression that your paper is more flash than substance and does not distract from the substance of your study.

Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions. University College Writing Centre. University of Toronto; Introduction. The Structure, Format, Content, and Style of a Journal-Style Scientific Paper. Department of Biology. Bates College; Introductions. The Writing Center. University of North Carolina; Introductions. The Writer’s Handbook. Writing Center. University of Wisconsin, Madison; Introductions, Body Paragraphs, and Conclusions for an Argument Paper. The Writing Lab and The OWL. Purdue University; “Writing Introductions.” In Good Essay Writing: A Social Sciences Guide . Peter Redman. 4th edition. (London: Sage, 2011), pp. 63-70; Resources for Writers: Introduction Strategies. Program in Writing and Humanistic Studies. Massachusetts Institute of Technology; Sharpling, Gerald. Writing an Introduction. Centre for Applied Linguistics, University of Warwick; Samraj, B. “Introductions in Research Articles: Variations Across Disciplines.” English for Specific Purposes 21 (2002): 1–17; Swales, John and Christine B. Feak. Academic Writing for Graduate Students: Essential Skills and Tasks . 2nd edition. Ann Arbor, MI: University of Michigan Press, 2004 ; Writing Your Introduction. Department of English Writing Guide. George Mason University.

Writing Tip

Avoid the "Dictionary" Introduction

Giving the dictionary definition of words related to the research problem may appear appropriate because it is important to define specific terminology that readers may be unfamiliar with. However, anyone can look a word up in the dictionary and a general dictionary is not a particularly authoritative source because it doesn't take into account the context of your topic and doesn't offer particularly detailed information. Also, placed in the context of a particular discipline, a term or concept may have a different meaning than what is found in a general dictionary. If you feel that you must seek out an authoritative definition, use a subject specific dictionary or encyclopedia [e.g., if you are a sociology student, search for dictionaries of sociology]. A good database for obtaining definitive definitions of concepts or terms is Credo Reference .

Saba, Robert. The College Research Paper. Florida International University; Introductions. The Writing Center. University of North Carolina.

Another Writing Tip

When Do I Begin?

A common question asked at the start of any paper is, "Where should I begin?" An equally important question to ask yourself is, "When do I begin?" Research problems in the social sciences rarely rest in isolation from history. Therefore, it is important to lay a foundation for understanding the historical context underpinning the research problem. However, this information should be brief and succinct and begin at a point in time that illustrates the study's overall importance. For example, a study that investigates coffee cultivation and export in West Africa as a key stimulus for local economic growth needs to describe the beginning of exporting coffee in the region and establishing why economic growth is important. You do not need to give a long historical explanation about coffee exports in Africa. If a research problem requires a substantial exploration of the historical context, do this in the literature review section. In your introduction, make note of this as part of the "roadmap" [see below] that you use to describe the organization of your paper.

Introductions. The Writing Center. University of North Carolina; “Writing Introductions.” In Good Essay Writing: A Social Sciences Guide . Peter Redman. 4th edition. (London: Sage, 2011), pp. 63-70.

Yet Another Writing Tip

Always End with a Roadmap

The final paragraph or sentences of your introduction should forecast your main arguments and conclusions and provide a brief description of the rest of the paper [the "roadmap"] that let's the reader know where you are going and what to expect. A roadmap is important because it helps the reader place the research problem within the context of their own perspectives about the topic. In addition, concluding your introduction with an explicit roadmap tells the reader that you have a clear understanding of the structural purpose of your paper. In this way, the roadmap acts as a type of promise to yourself and to your readers that you will follow a consistent and coherent approach to addressing the topic of inquiry. Refer to it often to help keep your writing focused and organized.

Cassuto, Leonard. “On the Dissertation: How to Write the Introduction.” The Chronicle of Higher Education , May 28, 2018; Radich, Michael. A Student's Guide to Writing in East Asian Studies . (Cambridge, MA: Harvard University Writing n. d.), pp. 35-37.

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How to Write a Research Introduction

Last Updated: December 6, 2023 Fact Checked

This article was co-authored by Megan Morgan, PhD . Megan Morgan is a Graduate Program Academic Advisor in the School of Public & International Affairs at the University of Georgia. She earned her PhD in English from the University of Georgia in 2015. There are 7 references cited in this article, which can be found at the bottom of the page. This article has been fact-checked, ensuring the accuracy of any cited facts and confirming the authority of its sources. This article has been viewed 2,653,113 times.

The introduction to a research paper can be the most challenging part of the paper to write. The length of the introduction will vary depending on the type of research paper you are writing. An introduction should announce your topic, provide context and a rationale for your work, before stating your research questions and hypothesis. Well-written introductions set the tone for the paper, catch the reader's interest, and communicate the hypothesis or thesis statement.

Introducing the Topic of the Paper

• In scientific papers this is sometimes known as an "inverted triangle", where you start with the broadest material at the start, before zooming in on the specifics. [2] X Research source
• The sentence "Throughout the 20th century, our views of life on other planets have drastically changed" introduces a topic, but does so in broad terms.
• It provides the reader with an indication of the content of the essay and encourages them to read on.

• For example, if you were writing a paper about the behaviour of mice when exposed to a particular substance, you would include the word "mice", and the scientific name of the relevant compound in the first sentences.
• If you were writing a history paper about the impact of the First World War on gender relations in Britain, you should mention those key words in your first few lines.

• This is especially important if you are attempting to develop a new conceptualization that uses language and terminology your readers may be unfamiliar with.

• If you use an anecdote ensure that is short and highly relevant for your research. It has to function in the same way as an alternative opening, namely to announce the topic of your research paper to your reader.
• For example, if you were writing a sociology paper about re-offending rates among young offenders, you could include a brief story of one person whose story reflects and introduces your topic.
• This kind of approach is generally not appropriate for the introduction to a natural or physical sciences research paper where the writing conventions are different.

Establishing the Context for Your Paper

• It is important to be concise in the introduction, so provide an overview on recent developments in the primary research rather than a lengthy discussion.
• You can follow the "inverted triangle" principle to focus in from the broader themes to those to which you are making a direct contribution with your paper.
• A strong literature review presents important background information to your own research and indicates the importance of the field.

• By making clear reference to existing work you can demonstrate explicitly the specific contribution you are making to move the field forward.
• You can identify a gap in the existing scholarship and explain how you are addressing it and moving understanding forward.

• For example, if you are writing a scientific paper you could stress the merits of the experimental approach or models you have used.
• Stress what is novel in your research and the significance of your new approach, but don't give too much detail in the introduction.
• A stated rationale could be something like: "the study evaluates the previously unknown anti-inflammatory effects of a topical compound in order to evaluate its potential clinical uses".

Specifying Your Research Questions and Hypothesis

• The research question or questions generally come towards the end of the introduction, and should be concise and closely focused.
• The research question might recall some of the key words established in the first few sentences and the title of your paper.
• An example of a research question could be "what were the consequences of the North American Free Trade Agreement on the Mexican export economy?"
• This could be honed further to be specific by referring to a particular element of the Free Trade Agreement and the impact on a particular industry in Mexico, such as clothing manufacture.
• A good research question should shape a problem into a testable hypothesis.

• If possible try to avoid using the word "hypothesis" and rather make this implicit in your writing. This can make your writing appear less formulaic.
• In a scientific paper, giving a clear one-sentence overview of your results and their relation to your hypothesis makes the information clear and accessible. [10] X Trustworthy Source PubMed Central Journal archive from the U.S. National Institutes of Health Go to source
• An example of a hypothesis could be "mice deprived of food for the duration of the study were expected to become more lethargic than those fed normally".

• This is not always necessary and you should pay attention to the writing conventions in your discipline.
• In a natural sciences paper, for example, there is a fairly rigid structure which you will be following.
• A humanities or social science paper will most likely present more opportunities to deviate in how you structure your paper.

Research Introduction Help

Community Q&A

• Use your research papers' outline to help you decide what information to include when writing an introduction. Thanks Helpful 0 Not Helpful 1
• Consider drafting your introduction after you have already completed the rest of your research paper. Writing introductions last can help ensure that you don't leave out any major points. Thanks Helpful 0 Not Helpful 0

• Avoid emotional or sensational introductions; these can create distrust in the reader. Thanks Helpful 50 Not Helpful 12
• Generally avoid using personal pronouns in your introduction, such as "I," "me," "we," "us," "my," "mine," or "our." Thanks Helpful 31 Not Helpful 7
• Don't overwhelm the reader with an over-abundance of information. Keep the introduction as concise as possible by saving specific details for the body of your paper. Thanks Helpful 24 Not Helpful 14

You Might Also Like

• ↑ https://library.sacredheart.edu/c.php?g=29803&p=185916
• ↑ https://www.aresearchguide.com/inverted-pyramid-structure-in-writing.html
• ↑ https://libguides.usc.edu/writingguide/introduction
• ↑ https://writing.wisc.edu/Handbook/PlanResearchPaper.html
• ↑ https://dept.writing.wisc.edu/wac/writing-an-introduction-for-a-scientific-paper/
• ↑ https://writing.wisc.edu/handbook/assignments/planresearchpaper/
• ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3178846/

About This Article

To introduce your research paper, use the first 1-2 sentences to describe your general topic, such as “women in World War I.” Include and define keywords, such as “gender relations,” to show your reader where you’re going. Mention previous research into the topic with a phrase like, “Others have studied…”, then transition into what your contribution will be and why it’s necessary. Finally, state the questions that your paper will address and propose your “answer” to them as your thesis statement. For more information from our English Ph.D. co-author about how to craft a strong hypothesis and thesis, keep reading! Did this summary help you? Yes No

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How to write an effective introduction for your research paper

Last updated

20 January 2024

Reviewed by

However, the introduction is a vital element of your research paper . It helps the reader decide whether your paper is worth their time. As such, it's worth taking your time to get it right.

In this article, we'll tell you everything you need to know about writing an effective introduction for your research paper.

• The importance of an introduction in research papers

The primary purpose of an introduction is to provide an overview of your paper. This lets readers gauge whether they want to continue reading or not. The introduction should provide a meaningful roadmap of your research to help them make this decision. It should let readers know whether the information they're interested in is likely to be found in the pages that follow.

Aside from providing readers with information about the content of your paper, the introduction also sets the tone. It shows readers the style of language they can expect, which can further help them to decide how far to read.

When you take into account both of these roles that an introduction plays, it becomes clear that crafting an engaging introduction is the best way to get your paper read more widely. First impressions count, and the introduction provides that impression to readers.

• The optimum length for a research paper introduction

While there's no magic formula to determine exactly how long a research paper introduction should be, there are a few guidelines. Some variables that impact the ideal introduction length include:

Field of study

Complexity of the topic

Specific requirements of the course or publication

A commonly recommended length of a research paper introduction is around 10% of the total paper’s length. So, a ten-page paper has a one-page introduction. If the topic is complex, it may require more background to craft a compelling intro. Humanities papers tend to have longer introductions than those of the hard sciences.

The best way to craft an introduction of the right length is to focus on clarity and conciseness. Tell the reader only what is necessary to set up your research. An introduction edited down with this goal in mind should end up at an acceptable length.

• Evaluating successful research paper introductions

A good way to gauge how to create a great introduction is by looking at examples from across your field. The most influential and well-regarded papers should provide some insights into what makes a good introduction.

Dissecting examples: what works and why

We can make some general assumptions by looking at common elements of a good introduction, regardless of the field of research.

A common structure is to start with a broad context, and then narrow that down to specific research questions or hypotheses. This creates a funnel that establishes the scope and relevance.

The most effective introductions are careful about the assumptions they make regarding reader knowledge. By clearly defining key terms and concepts instead of assuming the reader is familiar with them, these introductions set a more solid foundation for understanding.

To pull in the reader and make that all-important good first impression, excellent research paper introductions will often incorporate a compelling narrative or some striking fact that grabs the reader's attention.

Finally, good introductions provide clear citations from past research to back up the claims they're making. In the case of argumentative papers or essays (those that take a stance on a topic or issue), a strong thesis statement compels the reader to continue reading.

Common pitfalls to avoid in research paper introductions

You can also learn what not to do by looking at other research papers. Many authors have made mistakes you can learn from.

We've talked about the need to be clear and concise. Many introductions fail at this; they're verbose, vague, or otherwise fail to convey the research problem or hypothesis efficiently. This often comes in the form of an overemphasis on background information, which obscures the main research focus.

Ensure your introduction provides the proper emphasis and excitement around your research and its significance. Otherwise, fewer people will want to read more about it.

• Crafting a compelling introduction for a research paper

Let’s take a look at the steps required to craft an introduction that pulls readers in and compels them to learn more about your research.

Step 1: Capturing interest and setting the scene

To capture the reader's interest immediately, begin your introduction with a compelling question, a surprising fact, a provocative quote, or some other mechanism that will hook readers and pull them further into the paper.

As they continue reading, the introduction should contextualize your research within the current field, showing readers its relevance and importance. Clarify any essential terms that will help them better understand what you're saying. This keeps the fundamentals of your research accessible to all readers from all backgrounds.

Step 2: Building a solid foundation with background information

Including background information in your introduction serves two major purposes:

It helps to clarify the topic for the reader

It establishes the depth of your research

The approach you take when conveying this information depends on the type of paper.

For argumentative papers, you'll want to develop engaging background narratives. These should provide context for the argument you'll be presenting.

For empirical papers, highlighting past research is the key. Often, there will be some questions that weren't answered in those past papers. If your paper is focused on those areas, those papers make ideal candidates for you to discuss and critique in your introduction.

Step 3: Pinpointing the research challenge

To capture the attention of the reader, you need to explain what research challenges you'll be discussing.

For argumentative papers, this involves articulating why the argument you'll be making is important. What is its relevance to current discussions or problems? What is the potential impact of people accepting or rejecting your argument?

For empirical papers, explain how your research is addressing a gap in existing knowledge. What new insights or contributions will your research bring to your field?

Step 4: Clarifying your research aims and objectives

We mentioned earlier that the introduction to a research paper can serve as a roadmap for what's within. We've also frequently discussed the need for clarity. This step addresses both of these.

When writing an argumentative paper, craft a thesis statement with impact. Clearly articulate what your position is and the main points you intend to present. This will map out for the reader exactly what they'll get from reading the rest.

For empirical papers, focus on formulating precise research questions and hypotheses. Directly link them to the gaps or issues you've identified in existing research to show the reader the precise direction your research paper will take.

Step 5: Sketching the blueprint of your study

Continue building a roadmap for your readers by designing a structured outline for the paper. Guide the reader through your research journey, explaining what the different sections will contain and their relationship to one another.

This outline should flow seamlessly as you move from section to section. Creating this outline early can also help guide the creation of the paper itself, resulting in a final product that's better organized. In doing so, you'll craft a paper where each section flows intuitively from the next.

Step 6: Integrating your research question

To avoid letting your research question get lost in background information or clarifications, craft your introduction in such a way that the research question resonates throughout. The research question should clearly address a gap in existing knowledge or offer a new perspective on an existing problem.

Tell users your research question explicitly but also remember to frequently come back to it. When providing context or clarification, point out how it relates to the research question. This keeps your focus where it needs to be and prevents the topic of the paper from becoming under-emphasized.

Step 7: Establishing the scope and limitations

So far, we've talked mostly about what's in the paper and how to convey that information to readers. The opposite is also important. Information that's outside the scope of your paper should be made clear to the reader in the introduction so their expectations for what is to follow are set appropriately.

Similarly, be honest and upfront about the limitations of the study. Any constraints in methodology, data, or how far your findings can be generalized should be fully communicated in the introduction.

Step 8: Concluding the introduction with a promise

The final few lines of the introduction are your last chance to convince people to continue reading the rest of the paper. Here is where you should make it very clear what benefit they'll get from doing so. What topics will be covered? What questions will be answered? Make it clear what they will get for continuing.

By providing a quick recap of the key points contained in the introduction in its final lines and properly setting the stage for what follows in the rest of the paper, you refocus the reader's attention on the topic of your research and guide them to read more.

• Research paper introduction best practices

Following the steps above will give you a compelling introduction that hits on all the key points an introduction should have. Some more tips and tricks can make an introduction even more polished.

As you follow the steps above, keep the following tips in mind.

Set the right tone and style

Like every piece of writing, a research paper should be written for the audience. That is to say, it should match the tone and style that your academic discipline and target audience expect. This is typically a formal and academic tone, though the degree of formality varies by field.

Kno w the audience

The perfect introduction balances clarity with conciseness. The amount of clarification required for a given topic depends greatly on the target audience. Knowing who will be reading your paper will guide you in determining how much background information is required.

Adopt the CARS (create a research space) model

The CARS model is a helpful tool for structuring introductions. This structure has three parts. The beginning of the introduction establishes the general research area. Next, relevant literature is reviewed and critiqued. The final section outlines the purpose of your study as it relates to the previous parts.

Master the art of funneling

The CARS method is one example of a well-funneled introduction. These start broadly and then slowly narrow down to your specific research problem. It provides a nice narrative flow that provides the right information at the right time. If you stray from the CARS model, try to retain this same type of funneling.

Incorporate narrative element

People read research papers largely to be informed. But to inform the reader, you have to hold their attention. A narrative style, particularly in the introduction, is a great way to do that. This can be a compelling story, an intriguing question, or a description of a real-world problem.

Write the introduction last

By writing the introduction after the rest of the paper, you'll have a better idea of what your research entails and how the paper is structured. This prevents the common problem of writing something in the introduction and then forgetting to include it in the paper. It also means anything particularly exciting in the paper isn’t neglected in the intro.

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• If you are writing in a new discipline, you should always make sure to ask about conventions and expectations for introductions, just as you would for any other aspect of the essay. For example, while it may be acceptable to write a two-paragraph (or longer) introduction for your papers in some courses, instructors in other disciplines, such as those in some Government courses, may expect a shorter introduction that includes a preview of the argument that will follow.  
• In some disciplines (Government, Economics, and others), it’s common to offer an overview in the introduction of what points you will make in your essay. In other disciplines, you will not be expected to provide this overview in your introduction.  
• Avoid writing a very general opening sentence. While it may be true that “Since the dawn of time, people have been telling love stories,” it won’t help you explain what’s interesting about your topic.  
• Avoid writing a “funnel” introduction in which you begin with a very broad statement about a topic and move to a narrow statement about that topic. Broad generalizations about a topic will not add to your readers’ understanding of your specific essay topic.  
• Avoid beginning with a dictionary definition of a term or concept you will be writing about. If the concept is complicated or unfamiliar to your readers, you will need to define it in detail later in your essay. If it’s not complicated, you can assume your readers already know the definition.  
• Avoid offering too much detail in your introduction that a reader could better understand later in the paper.
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Writing a scientific paper.

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What is a "good" introduction?

Citing sources in the introduction, "introduction checklist" from: how to write a good scientific paper. chris a. mack. spie. 2018..

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This is where you describe briefly and clearly why you are writing the paper. The introduction supplies sufficient background information for the reader to understand and evaluate the experiment you did. It also supplies a rationale for the study.

• Present the problem and the proposed solution
• Presents nature and scope of the problem investigated
• Reviews the pertinent literature to orient the reader
• States the method of the experiment
• State the principle results of the experiment

It is important to cite sources in the introduction section of your paper as evidence of the claims you are making. There are ways of citing sources in the text so that the reader can find the full reference in the literature cited section at the end of the paper, yet the flow of the reading is not badly interrupted. Below are some example of how this can be done:     "Smith (1983) found that N-fixing plants could be infected by several different species of Rhizobium."     "Walnut trees are known to be allelopathic (Smith 1949,  Bond et al. 1955, Jones and Green 1963)."     "Although the presence of Rhizobium normally increases the growth of legumes (Nguyen 1987), the opposite effect has been observed (Washington 1999)." Note that articles by one or two authors are always cited in the text using their last names. However, if there are more than two authors, the last name of the 1st author is given followed by the abbreviation et al. which is Latin for "and others". 

From:  https://writingcenter.gmu.edu/guides/imrad-reports-introductions

• Indicate the field of the work, why this field is important, and what has already been done (with proper citations).
• Indicate a gap, raise a research question, or challenge prior work in this territory.
• Outline the purpose and announce the present research, clearly indicating what is novel and why it is significant.
• Avoid: repeating the abstract; providing unnecessary background information; exaggerating the importance of the work; claiming novelty without a proper literature search. 
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Introductions

What this handout is about.

This handout will explain the functions of introductions, offer strategies for creating effective introductions, and provide some examples of less effective introductions to avoid.

The role of introductions

Introductions and conclusions can be the most difficult parts of papers to write. Usually when you sit down to respond to an assignment, you have at least some sense of what you want to say in the body of your paper. You might have chosen a few examples you want to use or have an idea that will help you answer the main question of your assignment; these sections, therefore, may not be as hard to write. And it’s fine to write them first! But in your final draft, these middle parts of the paper can’t just come out of thin air; they need to be introduced and concluded in a way that makes sense to your reader.

Your introduction and conclusion act as bridges that transport your readers from their own lives into the “place” of your analysis. If your readers pick up your paper about education in the autobiography of Frederick Douglass, for example, they need a transition to help them leave behind the world of Chapel Hill, television, e-mail, and The Daily Tar Heel and to help them temporarily enter the world of nineteenth-century American slavery. By providing an introduction that helps your readers make a transition between their own world and the issues you will be writing about, you give your readers the tools they need to get into your topic and care about what you are saying. Similarly, once you’ve hooked your readers with the introduction and offered evidence to prove your thesis, your conclusion can provide a bridge to help your readers make the transition back to their daily lives. (See our handout on conclusions .)

Note that what constitutes a good introduction may vary widely based on the kind of paper you are writing and the academic discipline in which you are writing it. If you are uncertain what kind of introduction is expected, ask your instructor.

Why bother writing a good introduction?

You never get a second chance to make a first impression. The opening paragraph of your paper will provide your readers with their initial impressions of your argument, your writing style, and the overall quality of your work. A vague, disorganized, error-filled, off-the-wall, or boring introduction will probably create a negative impression. On the other hand, a concise, engaging, and well-written introduction will start your readers off thinking highly of you, your analytical skills, your writing, and your paper.

Your introduction is an important road map for the rest of your paper. Your introduction conveys a lot of information to your readers. You can let them know what your topic is, why it is important, and how you plan to proceed with your discussion. In many academic disciplines, your introduction should contain a thesis that will assert your main argument. Your introduction should also give the reader a sense of the kinds of information you will use to make that argument and the general organization of the paragraphs and pages that will follow. After reading your introduction, your readers should not have any major surprises in store when they read the main body of your paper.

Ideally, your introduction will make your readers want to read your paper. The introduction should capture your readers’ interest, making them want to read the rest of your paper. Opening with a compelling story, an interesting question, or a vivid example can get your readers to see why your topic matters and serve as an invitation for them to join you for an engaging intellectual conversation (remember, though, that these strategies may not be suitable for all papers and disciplines).

Strategies for writing an effective introduction

Start by thinking about the question (or questions) you are trying to answer. Your entire essay will be a response to this question, and your introduction is the first step toward that end. Your direct answer to the assigned question will be your thesis, and your thesis will likely be included in your introduction, so it is a good idea to use the question as a jumping off point. Imagine that you are assigned the following question:

Drawing on the Narrative of the Life of Frederick Douglass , discuss the relationship between education and slavery in 19th-century America. Consider the following: How did white control of education reinforce slavery? How did Douglass and other enslaved African Americans view education while they endured slavery? And what role did education play in the acquisition of freedom? Most importantly, consider the degree to which education was or was not a major force for social change with regard to slavery.

You will probably refer back to your assignment extensively as you prepare your complete essay, and the prompt itself can also give you some clues about how to approach the introduction. Notice that it starts with a broad statement and then narrows to focus on specific questions from the book. One strategy might be to use a similar model in your own introduction—start off with a big picture sentence or two and then focus in on the details of your argument about Douglass. Of course, a different approach could also be very successful, but looking at the way the professor set up the question can sometimes give you some ideas for how you might answer it. (See our handout on understanding assignments for additional information on the hidden clues in assignments.)

Decide how general or broad your opening should be. Keep in mind that even a “big picture” opening needs to be clearly related to your topic; an opening sentence that said “Human beings, more than any other creatures on earth, are capable of learning” would be too broad for our sample assignment about slavery and education. If you have ever used Google Maps or similar programs, that experience can provide a helpful way of thinking about how broad your opening should be. Imagine that you’re researching Chapel Hill. If what you want to find out is whether Chapel Hill is at roughly the same latitude as Rome, it might make sense to hit that little “minus” sign on the online map until it has zoomed all the way out and you can see the whole globe. If you’re trying to figure out how to get from Chapel Hill to Wrightsville Beach, it might make more sense to zoom in to the level where you can see most of North Carolina (but not the rest of the world, or even the rest of the United States). And if you are looking for the intersection of Ridge Road and Manning Drive so that you can find the Writing Center’s main office, you may need to zoom all the way in. The question you are asking determines how “broad” your view should be. In the sample assignment above, the questions are probably at the “state” or “city” level of generality. When writing, you need to place your ideas in context—but that context doesn’t generally have to be as big as the whole galaxy!

Try writing your introduction last. You may think that you have to write your introduction first, but that isn’t necessarily true, and it isn’t always the most effective way to craft a good introduction. You may find that you don’t know precisely what you are going to argue at the beginning of the writing process. It is perfectly fine to start out thinking that you want to argue a particular point but wind up arguing something slightly or even dramatically different by the time you’ve written most of the paper. The writing process can be an important way to organize your ideas, think through complicated issues, refine your thoughts, and develop a sophisticated argument. However, an introduction written at the beginning of that discovery process will not necessarily reflect what you wind up with at the end. You will need to revise your paper to make sure that the introduction, all of the evidence, and the conclusion reflect the argument you intend. Sometimes it’s easiest to just write up all of your evidence first and then write the introduction last—that way you can be sure that the introduction will match the body of the paper.

Don’t be afraid to write a tentative introduction first and then change it later. Some people find that they need to write some kind of introduction in order to get the writing process started. That’s fine, but if you are one of those people, be sure to return to your initial introduction later and rewrite if necessary.

Open with something that will draw readers in. Consider these options (remembering that they may not be suitable for all kinds of papers):

• an intriguing example —for example, Douglass writes about a mistress who initially teaches him but then ceases her instruction as she learns more about slavery.
• a provocative quotation that is closely related to your argument —for example, Douglass writes that “education and slavery were incompatible with each other.” (Quotes from famous people, inspirational quotes, etc. may not work well for an academic paper; in this example, the quote is from the author himself.)
• a puzzling scenario —for example, Frederick Douglass says of slaves that “[N]othing has been left undone to cripple their intellects, darken their minds, debase their moral nature, obliterate all traces of their relationship to mankind; and yet how wonderfully they have sustained the mighty load of a most frightful bondage, under which they have been groaning for centuries!” Douglass clearly asserts that slave owners went to great lengths to destroy the mental capacities of slaves, yet his own life story proves that these efforts could be unsuccessful.
• a vivid and perhaps unexpected anecdote —for example, “Learning about slavery in the American history course at Frederick Douglass High School, students studied the work slaves did, the impact of slavery on their families, and the rules that governed their lives. We didn’t discuss education, however, until one student, Mary, raised her hand and asked, ‘But when did they go to school?’ That modern high school students could not conceive of an American childhood devoid of formal education speaks volumes about the centrality of education to American youth today and also suggests the significance of the deprivation of education in past generations.”
• a thought-provoking question —for example, given all of the freedoms that were denied enslaved individuals in the American South, why does Frederick Douglass focus his attentions so squarely on education and literacy?

Pay special attention to your first sentence. Start off on the right foot with your readers by making sure that the first sentence actually says something useful and that it does so in an interesting and polished way.

How to evaluate your introduction draft

Ask a friend to read your introduction and then tell you what they expect the paper will discuss, what kinds of evidence the paper will use, and what the tone of the paper will be. If your friend is able to predict the rest of your paper accurately, you probably have a good introduction.

Five kinds of less effective introductions

1. The placeholder introduction. When you don’t have much to say on a given topic, it is easy to create this kind of introduction. Essentially, this kind of weaker introduction contains several sentences that are vague and don’t really say much. They exist just to take up the “introduction space” in your paper. If you had something more effective to say, you would probably say it, but in the meantime this paragraph is just a place holder.

Example: Slavery was one of the greatest tragedies in American history. There were many different aspects of slavery. Each created different kinds of problems for enslaved people.

2. The restated question introduction. Restating the question can sometimes be an effective strategy, but it can be easy to stop at JUST restating the question instead of offering a more specific, interesting introduction to your paper. The professor or teaching assistant wrote your question and will be reading many essays in response to it—they do not need to read a whole paragraph that simply restates the question.

Example: The Narrative of the Life of Frederick Douglass discusses the relationship between education and slavery in 19th century America, showing how white control of education reinforced slavery and how Douglass and other enslaved African Americans viewed education while they endured. Moreover, the book discusses the role that education played in the acquisition of freedom. Education was a major force for social change with regard to slavery.

3. The Webster’s Dictionary introduction. This introduction begins by giving the dictionary definition of one or more of the words in the assigned question. Anyone can look a word up in the dictionary and copy down what Webster says. If you want to open with a discussion of an important term, it may be far more interesting for you (and your reader) if you develop your own definition of the term in the specific context of your class and assignment. You may also be able to use a definition from one of the sources you’ve been reading for class. Also recognize that the dictionary is also not a particularly authoritative work—it doesn’t take into account the context of your course and doesn’t offer particularly detailed information. If you feel that you must seek out an authority, try to find one that is very relevant and specific. Perhaps a quotation from a source reading might prove better? Dictionary introductions are also ineffective simply because they are so overused. Instructors may see a great many papers that begin in this way, greatly decreasing the dramatic impact that any one of those papers will have.

Example: Webster’s dictionary defines slavery as “the state of being a slave,” as “the practice of owning slaves,” and as “a condition of hard work and subjection.”

4. The “dawn of man” introduction. This kind of introduction generally makes broad, sweeping statements about the relevance of this topic since the beginning of time, throughout the world, etc. It is usually very general (similar to the placeholder introduction) and fails to connect to the thesis. It may employ cliches—the phrases “the dawn of man” and “throughout human history” are examples, and it’s hard to imagine a time when starting with one of these would work. Instructors often find them extremely annoying.

Example: Since the dawn of man, slavery has been a problem in human history.

5. The book report introduction. This introduction is what you had to do for your elementary school book reports. It gives the name and author of the book you are writing about, tells what the book is about, and offers other basic facts about the book. You might resort to this sort of introduction when you are trying to fill space because it’s a familiar, comfortable format. It is ineffective because it offers details that your reader probably already knows and that are irrelevant to the thesis.

Example: Frederick Douglass wrote his autobiography, Narrative of the Life of Frederick Douglass, An American Slave , in the 1840s. It was published in 1986 by Penguin Books. In it, he tells the story of his life.

And now for the conclusion…

Writing an effective introduction can be tough. Try playing around with several different options and choose the one that ends up sounding best to you!

Just as your introduction helps readers make the transition to your topic, your conclusion needs to help them return to their daily lives–but with a lasting sense of how what they have just read is useful or meaningful. Check out our handout on  conclusions for tips on ending your paper as effectively as you began it!

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Douglass, Frederick. 1995. Narrative of the Life of Frederick Douglass, an American Slave, Written by Himself . New York: Dover.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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How to write an introduction for a research paper

Learn how to write a strong and efficient research paper introduction by following the suitable structure and avoiding typical errors.

An introduction to any type of paper is sometimes misunderstood as the beginning; yet, an introduction is actually intended to present your chosen subject to the audience in a way that makes it more appealing and leaves your readers thirsty for more information. After the title and abstract, your audience will read the introduction, thus it’s critical to get off to a solid start.  

This article includes instructions on how to write an introduction for a research paper that engages the reader in your research. You can produce a strong opening for your research paper if you stick to the format and a few basic principles.

What is an introduction to a research paper?

An introduction is the opening section of a research paper and the section that a reader is likely to read first, in which the objective and goals of the subsequent writing are stated. 

The introduction serves numerous purposes. It provides context for your research, explains your topic and objectives, and provides an outline of the work. A solid introduction will establish the tone for the remainder of your paper, enticing readers to continue reading through the methodology, findings, and discussion. 

Even though introductions are generally presented at the beginning of a document, we must distinguish an introduction from the beginning of your research. An introduction, as the name implies, is supposed to introduce your subject without extending it. All relevant information and facts should be placed in the body and conclusion, not the introduction.

Structure of an introduction

Before explaining how to write an introduction for a research paper , it’s necessary to comprehend a structure that will make your introduction stronger and more straightforward.

A good hook

A hook is one of the most effective research introduction openers. A hook’s objective is to stimulate the reader’s interest to read the research paper.  There are various approaches you may take to generate a strong hook:  startling facts, a question, a brief overview, or even a quotation. 

Broad overview

Following an excellent hook, you should present a wide overview of your major issue and some background information on your research. If you’re unsure about how to begin an essay introduction, the best approach is to offer a basic explanation of your topic before delving into specific issues. Simply said, you should begin with general information and then narrow it down to your relevant topics.

After offering some background information regarding your research’s main topic, go on to give readers a better understanding of what you’ll be covering throughout your research. In this section of your introduction, you should swiftly clarify your important topics in the sequence in which they will be addressed later, gradually introducing your thesis statement. You can use some  The following are some critical questions to address in this section of your introduction: Who? What? Where? When? How? And why is that?

Thesis statement

The thesis statement, which must be stated in the beginning clause of your research since your entire research revolves around it, is the most important component of your research.

A thesis statement presents your audience with a quick overview of the research’s main assertion. In the body section of your work, your key argument is what you will expose or debate about it. An excellent thesis statement is usually very succinct, accurate, explicit, clear, and focused. Typically, your thesis should be at the conclusion of your introductory paragraph/section.

Tips for writing a strong introduction

Aside from the good structure, here are a few tips to make your introduction strong and accurate:

• Keep in mind the aim of your research and make sure your introduction supports it.
• Use an appealing and relevant hook that catches the reader’s attention right away.
• Make it obvious to your readers what your stance is.
• Demonstrate your knowledge of your subject.
• Provide your reader with a road map to help them understand what you will address throughout the research.
• Be succinct – it is advised that your opening introduction consists of around 8-9 percent of the overall amount of words in your article (for example, 160 words for a 2000 words essay). 
• Make a strong and unambiguous thesis statement.
• Explain why the article is significant in 1-2 sentences.
• Remember to keep it interesting.

Mistakes to avoid in your introduction

Check out what not to do and what to avoid now that you know the structure and how to write an introduction for a research paper .

• Lacking a feeling of direction or purpose.
• Giving out too much.
• Creating lengthy paragraphs.
• Excessive or insufficient background, literature, and theory.
• Including material that should be placed in the body and conclusion.
• Not writing enough or writing excessively.
• Using too many quotes.

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Organizing Academic Research Papers: 4. The Introduction

• Purpose of Guide
• Design Flaws to Avoid
• Glossary of Research Terms
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Choosing a Title
• Making an Outline
• Paragraph Development
• Executive Summary
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
• Content Alert Services
• Evaluating Sources
• Primary Sources
• Secondary Sources
• Tertiary Sources
• What Is Scholarly vs. Popular?
• Qualitative Methods
• Quantitative Methods
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
• Avoiding Plagiarism
• Footnotes or Endnotes?
• Further Readings
• Annotated Bibliography
• Dealing with Nervousness
• Using Visual Aids
• Grading Someone Else's Paper
• How to Manage Group Projects
• Multiple Book Review Essay
• Reviewing Collected Essays
• About Informed Consent
• Writing Field Notes
• Writing a Policy Memo
• Writing a Research Proposal
• Acknowledgements

The introduction serves the purpose of leading the reader from a general subject area to a particular field of research. It establishes the context of the research being conducted by summarizing current understanding and background information about the topic, stating the purpose of the work in the form of the hypothesis, question, or research problem, briefly explaining your rationale, methodological approach, highlighting the potential outcomes your study can reveal, and describing the remaining structure of the paper.

Key Elements of the Research Proposal. Prepared under the direction of the Superintendent and by the 2010 Curriculum Design and Writing Team. Baltimore County Public Schools.

Importance of a Good Introduction

Think of the introduction as a mental road map that must answer for the reader these four questions:

• What was I studying?
• Why was this topic important to investigate?
• What did we know about this topic before I did this study?
• How will this study advance our knowledge?

A well-written introduction is important because, quite simply, you never get a second chance to make a good first impression. The opening paragraph of your paper will provide your readers with their initial impressions about the logic of your argument, your writing style, the overall quality of your research, and, ultimately, the validity of your findings and conclusions. A vague, disorganized, or error-filled introduction will create a negative impression, whereas, a concise, engaging, and well-written introduction will start your readers off thinking highly of your analytical skills, your writing style, and your research approach.

Introductions . The Writing Center. University of North Carolina.

Structure and Writing Style

I. Structure and Approach

The introduction is the broad beginning of the paper that answers three important questions for the reader:

• What is this?
• Why am I reading it?
• What do you want me to think about / consider doing / react to?

Think of the structure of the introduction as an inverted triangle of information. Organize the information so as to present the more general aspects of the topic early in the introduction, then narrow toward the more specific topical information that provides context, finally arriving at your statement of purpose and rationale and, whenever possible, the potential outcomes your study can reveal.

These are general phases associated with writing an introduction:

• Highlighting the importance of the topic, and/or
• Making general statements about the topic, and/or
• Presenting an overview on current research on the subject.
• Opposing an existing assumption, and/or
• Revealing a gap in existing research, and/or
• Formulating a research question or problem, and/or
• Continuing a disciplinary tradition.
• Stating the intent of your study,
• Outlining the key characteristics of your study,
• Describing important results, and
• Giving a brief overview of the structure of the paper.

NOTE: Even though the introduction is the first main section of a research paper, it is often useful to finish the introduction very late in the writing process because the structure of the paper, the reporting and analysis of results, and the conclusion will have been completed and it ensures that your introduction matches the overall structure of your paper.

II.  Delimitations of the Study

Delimitations refer to those characteristics that limit the scope and define the conceptual boundaries of your study . This is determined by the conscious exclusionary and inclusionary decisions you make about how to investigate the research problem. In other words, not only should you tell the reader what it is you are studying and why, but you must also acknowledge why you rejected alternative approaches that could have been used to examine the research problem.

Obviously, the first limiting step was the choice of research problem itself. However, implicit are other, related problems that could have been chosen but were rejected. These should be noted in the conclusion of your introduction.

Examples of delimitating choices would be:

• The key aims and objectives of your study,
• The research questions that you address,
• The variables of interest [i.e., the various factors and features of the phenomenon being studied],
• The method(s) of investigation, and
• Any relevant alternative theoretical frameworks that could have been adopted.

Review each of these decisions. You need to not only clearly establish what you intend to accomplish, but to also include a declaration of what the study does not intend to cover. In the latter case, your exclusionary decisions should be based upon criteria stated as, "not interesting"; "not directly relevant"; “too problematic because..."; "not feasible," and the like. Make this reasoning explicit!

NOTE: Delimitations refer to the initial choices made about the broader, overall design of your study and should not be confused with documenting the limitations of your study discovered after the research has been completed.

III. The Narrative Flow

Issues to keep in mind that will help the narrative flow in your introduction :

• Your introduction should clearly identify the subject area of interest . A simple strategy to follow is to use key words from your title in the first few sentences of the introduction. This will help focus the introduction on the topic at the appropriate level and ensures that you get to the primary subject matter quickly without losing focus, or discussing information that is too general.
• Establish context by providing a brief and balanced review of the pertinent published literature that is available on the subject. The key is to summarize for the reader what is known about the specific research problem before you did your analysis. This part of your introduction should not represent a comprehensive literature review but consists of a general review of the important, foundational research literature (with citations) that lays a foundation for understanding key elements of the research problem. See the drop-down tab for "Background Information" for types of contexts.
• Clearly state the hypothesis that you investigated . When you are first learning to write in this format it is okay, and actually preferable, to use a past statement like, "The purpose of this study was to...." or "We investigated three possible mechanisms to explain the...."
• Why did you choose this kind of research study or design? Provide a clear statement of the rationale for your approach to the problem studied. This will usually follow your statement of purpose in the last paragraph of the introduction.

IV. Engaging the Reader

The overarching goal of your introduction is to make your readers want to read your paper. The introduction should grab your reader's attention. Strategies for doing this can be to:

• Open with a compelling story,
• Include a strong quotation or a vivid, perhaps unexpected anecdote,
• Pose a provocative or thought-provoking question,
• Describe a puzzling scenario or incongruity, or
• Cite a stirring example or case study that illustrates why the research problem is important.

NOTE:   Only choose one strategy for engaging your readers; avoid giving an impression that your paper is more flash than substance.

Freedman, Leora  and Jerry Plotnick. Introductions and Conclusions . University College Writing Centre. University of Toronto; Introduction . The Structure, Format, Content, and Style of a Journal-Style Scientific Paper. Department of Biology. Bates College; Introductions . The Writing Center. University of North Carolina; Introductions . The Writer’s Handbook. Writing Center. University of Wisconsin, Madison; Introductions, Body Paragraphs, and Conclusions for an Argument Paper. The Writing Lab and The OWL. Purdue University; Resources for Writers: Introduction Strategies . Program in Writing and Humanistic Studies. Massachusetts Institute of Technology; Sharpling, Gerald. Writing an Introduction . Centre for Applied Linguistics, University of Warwick; Writing Your Introduction. Department of English Writing Guide. George Mason University.

Writing Tip

Avoid the "Dictionary" Introduction

Giving the dictionary definition of words related to the research problem may appear appropriate because it is important to define specific words or phrases with which readers may be unfamiliar. However, anyone can look a word up in the dictionary and a general dictionary is not a particularly authoritative source. It doesn't take into account the context of your topic and doesn't offer particularly detailed information. Also, placed in the context of a particular discipline, a term may have a different meaning than what is found in a general dictionary. If you feel that you must seek out an authoritative definition, try to find one that is from subject specific dictionaries or encyclopedias [e.g., if you are a sociology student, search for dictionaries of sociology].

Saba, Robert. The College Research Paper . Florida International University; Introductions . The Writing Center. University of North Carolina.

Another Writing Tip

When Do I Begin?

A common question asked at the start of any paper is, "where should I begin?" An equally important question to ask yourself is, "When do I begin?" Research problems in the social sciences rarely rest in isolation from the history of the issue being investigated. It is, therefore, important to lay a foundation for understanding the historical context underpinning the research problem. However, this information should be brief and succinct and begin at a point in time that best informs the reader of study's overall importance. For example, a study about coffee cultivation and export in West Africa as a key stimulus for local economic growth needs to describe the beginning of exporting coffee in the region and establishing why economic growth is important. You do not need to give a long historical explanation about coffee exportation in Africa. If a research problem demands a substantial exploration of historical context, do this in the literature review section; note in the introduction as part of your "roadmap" [see below] that you covering this in the literature review.

Yet Another Writing Tip

Always End with a Roadmap

The final paragraph or sentences of your introduction should forecast your main arguments and conclusions and provide a description of the rest of the paper [a "roadmap"] that let's the reader know where you are going and what to expect.

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How to write an introduction for a research paper

Writing an introduction for a research paper can be one of the hardest parts of the writing process. How do you get started? In this post, we discuss the components of an introduction and explore strategies for writing one successfully.

What is an introduction?

The introduction to a research paper provides background information or context on the topic. It also includes the thesis statement and signposts that let the reader know what you will cover in the rest of the paper.

Depending on the type of research paper that you’re writing, you may also include a brief state of the field in your introduction. You might also put that in a separate section, called a literature review. Before you tackle writing your introduction, be sure to consult the assignment guidelines for your paper.

How to write an introduction

An introduction provides an overview of your topic and any background information that your readers need to know in order to understand the context. It generally concludes with an explicit statement of your position on the topic, which is known as your thesis statement.

The opening section

Many papers begin with a hook: a short anecdote or scenario that draws the reader in and gives a hint of what the paper will cover. A hook allows you to capture your reader’s attention and provides an anchor for the context that you will provide in the bulk of the introduction.

Most of your introduction should be taken up with background information, but this doesn’t mean that you should fill your opening section with overly general statements. Instead, provide key pieces of information (like statistics) that a reader would need to know in order to understand your main argument.

The thesis statement

Towards the end of the introduction, you should state your thesis, preferably in the form of "I argue that..." or "This paper argues that..." or a similar phrase. Although it’s called a “thesis statement,” your thesis can be more than one sentence.

Finally, an introduction contains a brief outline or "signposts" of what the rest of the article will cover (also known as forecasting statements). You can use language like, “in what follows,” or “in the rest of the paper,” to signal that you are describing what you’ll do in the remainder of the paper.

Tips for writing an introduction

1. don’t rely on generalizations.

An introduction is not simply filler. It has a very specific function in a research paper: to provide context that leads up to a thesis statement.

You may be tempted to start your paper with generalizations like, “many people believe that...” or, “in our society...,” or a general dictionary definition, because you’re not sure what kind of context to provide. Instead, use specific facts like statistics or historical anecdotes to open your paper.

2. State your thesis directly

Once you’ve provided the appropriate, and specific, background information on your topic, you can move on to stating your thesis. As a rule of thumb, state your thesis as directly as possible. Use phrases like “I argue that..” to indicate that you are laying out your main argument.

3. Include signposts

A strong introduction includes clear signposts that outline what you will cover in the rest of the paper. You can signal this by using words like, “in what follows,” and by describing the steps that you will take to build your argument.

4. Situate your argument within the scholarly conversation

Some types of research papers require a separate literature review in which you explore what others have written about your topic.

Even if you’re not required to have a formal literature review, you should still include at least a paragraph in which you engage with the scholarly debate on your chosen subject. Be sure to include direct quotes from your sources . You can use BibGuru’s citation generator to create accurate in-text citations for your quotes.

This section can come directly before your thesis statement or directly after it. In the former case, your state of the field will function as additional context for your thesis.

Frequently Asked Questions about how to write an introduction for a research paper

A good introduction provides specific background information on your topic, sets up your thesis statement, and includes signposts for what you’ll cover in the rest of the paper.

An introduction should include context, a thesis statement, and signposts.

Do not include generalizations, apologies for not being an expert, or dictionary definitions in your introduction.

The length of your introduction depends on the overall length of your paper. For instance, an introduction for an 8-10 page paper will likely be anywhere from 1-3 pages.

You can choose to start an introduction with a hook, an important statistic, an historical anecdote, or another specific piece of background information.

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• Dissertation

How to Write a Thesis or Dissertation Introduction

Published on 9 September 2022 by Tegan George and Shona McCombes.

The introduction is the first section of your thesis or dissertation , appearing right after the table of contents . Your introduction draws your reader in, setting the stage for your research with a clear focus, purpose, and direction.

Your introduction should include:

• Your topic, in context: what does your reader need to know to understand your thesis dissertation?
• Your focus and scope: what specific aspect of the topic will you address?
• The relevance of your research: how does your work fit into existing studies on your topic?
• Your questions and objectives: what does your research aim to find out, and how?
• An overview of your structure: what does each section contribute to the overall aim?

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Table of contents

How to start your introduction, topic and context, focus and scope, relevance and importance, questions and objectives, overview of the structure, thesis introduction example, introduction checklist, frequently asked questions about introductions.

Although your introduction kicks off your dissertation, it doesn’t have to be the first thing you write – in fact, it’s often one of the very last parts to be completed (just before your abstract ).

It’s a good idea to write a rough draft of your introduction as you begin your research, to help guide you. If you wrote a research proposal , consider using this as a template, as it contains many of the same elements. However, be sure to revise your introduction throughout the writing process, making sure it matches the content of your ensuing sections.

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Begin by introducing your research topic and giving any necessary background information. It’s important to contextualise your research and generate interest. Aim to show why your topic is timely or important. You may want to mention a relevant news item, academic debate, or practical problem.

After a brief introduction to your general area of interest, narrow your focus and define the scope of your research.

You can narrow this down in many ways, such as by:

• Geographical area
• Time period
• Demographics or communities
• Themes or aspects of the topic

It’s essential to share your motivation for doing this research, as well as how it relates to existing work on your topic. Further, you should also mention what new insights you expect it will contribute.

Start by giving a brief overview of the current state of research. You should definitely cite the most relevant literature, but remember that you will conduct a more in-depth survey of relevant sources in the literature review section, so there’s no need to go too in-depth in the introduction.

Depending on your field, the importance of your research might focus on its practical application (e.g., in policy or management) or on advancing scholarly understanding of the topic (e.g., by developing theories or adding new empirical data). In many cases, it will do both.

Ultimately, your introduction should explain how your thesis or dissertation:

• Helps solve a practical or theoretical problem
• Addresses a gap in the literature
• Builds on existing research
• Proposes a new understanding of your topic

Prevent plagiarism, run a free check.

Perhaps the most important part of your introduction is your questions and objectives, as it sets up the expectations for the rest of your thesis or dissertation. How you formulate your research questions and research objectives will depend on your discipline, topic, and focus, but you should always clearly state the central aim of your research.

If your research aims to test hypotheses , you can formulate them here. Your introduction is also a good place for a conceptual framework that suggests relationships between variables .

• Conduct surveys to collect data on students’ levels of knowledge, understanding, and positive/negative perceptions of government policy.
• Determine whether attitudes to climate policy are associated with variables such as age, gender, region, and social class.
• Conduct interviews to gain qualitative insights into students’ perspectives and actions in relation to climate policy.

To help guide your reader, end your introduction with an outline  of the structure of the thesis or dissertation to follow. Share a brief summary of each chapter, clearly showing how each contributes to your central aims. However, be careful to keep this overview concise: 1-2 sentences should be enough.

I. Introduction

Human language consists of a set of vowels and consonants which are combined to form words. During the speech production process, thoughts are converted into spoken utterances to convey a message. The appropriate words and their meanings are selected in the mental lexicon (Dell & Burger, 1997). This pre-verbal message is then grammatically coded, during which a syntactic representation of the utterance is built.

Speech, language, and voice disorders affect the vocal cords, nerves, muscles, and brain structures, which result in a distorted language reception or speech production (Sataloff & Hawkshaw, 2014). The symptoms vary from adding superfluous words and taking pauses to hoarseness of the voice, depending on the type of disorder (Dodd, 2005). However, distortions of the speech may also occur as a result of a disease that seems unrelated to speech, such as multiple sclerosis or chronic obstructive pulmonary disease.

This study aims to determine which acoustic parameters are suitable for the automatic detection of exacerbations in patients suffering from chronic obstructive pulmonary disease (COPD) by investigating which aspects of speech differ between COPD patients and healthy speakers and which aspects differ between COPD patients in exacerbation and stable COPD patients.

Checklist: Introduction

I have introduced my research topic in an engaging way.

I have provided necessary context to help the reader understand my topic.

I have clearly specified the focus of my research.

I have shown the relevance and importance of the dissertation topic .

I have clearly stated the problem or question that my research addresses.

I have outlined the specific objectives of the research .

I have provided an overview of the dissertation’s structure .

You've written a strong introduction for your thesis or dissertation. Use the other checklists to continue improving your dissertation.

The introduction of a research paper includes several key elements:

• A hook to catch the reader’s interest
• Relevant background on the topic
• Details of your research problem
• A thesis statement or research question
• Sometimes an outline of the paper

Don’t feel that you have to write the introduction first. The introduction is often one of the last parts of the research paper you’ll write, along with the conclusion.

This is because it can be easier to introduce your paper once you’ve already written the body ; you may not have the clearest idea of your arguments until you’ve written them, and things can change during the writing process .

Research objectives describe what you intend your research project to accomplish.

They summarise the approach and purpose of the project and help to focus your research.

Your objectives should appear in the introduction of your research paper , at the end of your problem statement .

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the ‘Cite this Scribbr article’ button to automatically add the citation to our free Reference Generator.

George, T. & McCombes, S. (2022, September 09). How to Write a Thesis or Dissertation Introduction. Scribbr. Retrieved 14 May 2024, from https://www.scribbr.co.uk/thesis-dissertation/introduction/

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How to write an introduction section of a scientific article?

An article primarily includes the following sections: introduction, materials and methods, results, discussion, and conclusion. Before writing the introduction, the main steps, the heading and the familiarity level of the readers should be considered. Writing should begin when the experimental system and the equipment are available. The introduction section comprises the first portion of the manuscript, and it should be written using the simple present tense. Additionally, abbreviations and explanations are included in this section. The main goal of the introduction is to convey basic information to the readers without obligating them to investigate previous publications and to provide clues as to the results of the present study. To do this, the subject of the article should be thoroughly reviewed, and the aim of the study should be clearly stated immediately after discussing the basic references. In this review, we aim to convey the principles of writing the introduction section of a manuscript to residents and young investigators who have just begun to write a manuscript.

Introduction

When entering a gate of a magnificent city we can make a prediction about the splendor, pomposity, history, and civilization we will encounter in the city. Occasionally, gates do not give even a glimpse of the city, and it can mislead the visitors about inner sections of the city. Introduction sections of the articles are like gates of a city. It is a presentation aiming at introducing itself to the readers, and attracting their attention. Attractiveness, clarity, piquancy, and analytical capacity of the presentation will urge the reader to read the subsequent sections of the article. On the other hand as is understood from the motto of antique Greek poet Euripides “a bad beginning makes a bad ending”, ‘Introduction’ section of a scientific article is important in that it can reveal the conclusion of the article. [ 1 ]

It is useful to analyze the issues to be considered in the ‘Introduction’ section under 3 headings. Firstly, information should be provided about the general topic of the article in the light of the current literature which paves the way for the disclosure of the objective of the manuscript. Then the specific subject matter, and the issue to be focused on should be dealt with, the problem should be brought forth, and fundamental references related to the topic should be discussed. Finally, our recommendations for solution should be described, in other words our aim should be communicated. When these steps are followed in that order, the reader can track the problem, and its solution from his/her own perspective under the light of current literature. Otherwise, even a perfect study presented in a non-systematized, confused design will lose the chance of reading. Indeed inadequate information, inability to clarify the problem, and sometimes concealing the solution will keep the reader who has a desire to attain new information away from reading the manuscript. [ 1 – 3 ]

First of all, explanation of the topic in the light of the current literature should be made in clear, and precise terms as if the reader is completely ignorant of the subject. In this section, establishment of a warm rapport between the reader, and the manuscript is aimed. Since frantic plunging into the problem or the solution will push the reader into the dilemma of either screening the literature about the subject matter or refraining from reading the article. Updated, and robust information should be presented in the ‘Introduction’ section.

Then main topic of our manuscript, and the encountered problem should be analyzed in the light of the current literature following a short instance of brain exercise. At this point the problems should be reduced to one issue as far as possible. Of course, there might be more than one problem, however this new issue, and its solution should be the subject matter of another article. Problems should be expressed clearly. If targets are more numerous, and complex, solutions will be more than one, and confusing.

Finally, the last paragraphs of the ‘Introduction’ section should include the solution in which we will describe the information we generated, and related data. Our sentences which arouse curiosity in the readers should not be left unanswered. The reader who thinks to obtain the most effective information in no time while reading a scientific article should not be smothered with mysterious sentences, and word plays, and the readers should not be left alone to arrive at a conclusion by themselves. If we have contrary expectations, then we might write an article which won’t have any reader. A clearly expressed or recommended solutions to an explicitly revealed problem is also very important for the integrity of the ‘Introduction’ section. [ 1 – 5 ]

We can summarize our arguments with the following example ( Figure 1 ). The introduction section of the exemplary article is written in simple present tense which includes abbreviations, acronyms, and their explanations. Based on our statements above we can divide the introduction section into 3 parts. In the first paragraph, miniaturization, and evolvement of pediatric endourological instruments, and competitions among PNL, ESWL, and URS in the treatment of urinary system stone disease are described, in other words the background is prepared. In the second paragraph, a newly defined system which facilitates intrarenal access in PNL procedure has been described. Besides basic references related to the subject matter have been given, and their outcomes have been indicated. In other words, fundamental references concerning main subject have been discussed. In the last paragraph the aim of the researchers to investigate the outcomes, and safety of the application of this new method in the light of current information has been indicated.

An exemplary introduction section of an article

Apart from the abovementioned information about the introduction section of a scientific article we will summarize a few major issues in brief headings

Important points which one should take heed of:

• Abbreviations should be given following their explanations in the ‘Introduction’ section (their explanations in the summary does not count)
• Simple present tense should be used.
• References should be selected from updated publication with a higher impact factor, and prestigous source books.
• Avoid mysterious, and confounding expressions, construct clear sentences aiming at problematic issues, and their solutions.
• The sentences should be attractive, tempting, and comjprehensible.
• Firstly general, then subject-specific information should be given. Finally our aim should be clearly explained.

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• Research Guides

Empirical Research: Defining, Identifying, & Finding

Introduction.

• Defining Empirical Research

The Introduction Section

• Database Tools
• Search Terms
• Image Descriptions

The Introduction exists to explain the research project and to justify why this research has been done. The introduction will discuss: 

• The topic covered by the research,
• Previous research done on this topic,
• What is still unknown about the topic that this research will answer, and
• Why someone would want to know that answer.

What Criteria to Look For

The "Introduction" is where you are most likely to find the  research question . 

Finding the Criteria

The research question may not be clearly labeled in the Introduction. Often, the author(s) may rephrase their question as a research statement or a hypothesis . Some research may have more than one research question or a research question with multiple parts. 

Words That May Signify the Research Question

These are some common word choices authors make when they are describing their research question as a research statement or hypothesis. 

• Hypothesize, hypothesized, or hypothesis
• Investigation, investigate(s), or investigated
• Predict(s) or predicted
• Evaluate(s) or evaluated
• This research, this study, the current study, or this paper
• The aim of this study or this research

You might also look for common question words (who, what, when, where, why, how) in a statement to see if it might be a rephrased research question. 

What Headings to Look Under

• General heading for the section. 
• Since this is the first heading after the title and abstract, some authors leave it unlabeled. 
• Likely where the research question is located if there is not a separate heading for it. 
• Explicit discussion of what is being investigated in the research. 
• Should have some form of the research question.
• Often a separate heading where the authors discuss previous research done on the topic. 
• May be labeled by the topic being reviewed. 
• Less likely to find the research question clearly stated. The authors may be talking about their topic more broadly than their current research question. 
• Single "Introduction" heading. 
• Includes phrase "this paper."
• Includes question word "how." 
• You could turn the phrase "how people perceive inequality in outcomes and risk at the collective level" into the question "How do  people perceive inequality in outcomes and risk at the collective level?"
• Labeled "Introduction" heading along with headings for topics of literature review. 
• Includes phrase "this research investigates." 
• Includes question word "how."
• You could turn the phrase "how LGBTQ college students negotiate the hookup scene on college campuses" into the question "How do LGBTQ college students negotiate the hookup scene on college campuses?"  
• Beginning of Introduction section is unlabeled. It then includes headings for different parts of the literature review and ends with a heading called "The Current Study" on page 573 for discussing the research questions.  
• Includes the words and phrases "aim of this study," "hypothesized," and "predicted." 
• You could turn the phrase "examine the effects of racial discrimination on anxiety symptom distress" into the question "What are the effects of racial discrimination on anxiety symptom distress?"
• You could turn the phrase "explore the moderating role of internalized racism in the link between racial discrimination and changes in anxiety symptom distress" into the question "How doe internalized racism moderate the link ink between racial discrimination and changes in anxiety symptom distress?"
• << Previous: Identifying Empirical Research
• Next: Methods >>
• Last Updated: Apr 2, 2024 11:25 AM
• URL: https://libguides.memphis.edu/empirical-research

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• Published: 13 May 2024

First in vitro measurement of VHEE relative biological effectiveness (RBE) in lung and prostate cancer cells using the ARES linac at DESY

• Hannah C. Wanstall 1 , 2 , 3 ,
• Florian Burkart 4 ,
• Hannes Dinter 4 ,
• Max Kellermeier 4 ,
• Willi Kuropka 4 ,
• Frank Mayet 4 ,
• Thomas Vinatier 4 ,
• Elham Santina 5 ,
• Amy L. Chadwick 5 ,
• Michael J. Merchant 5 ,
• Nicholas T. Henthorn 5 ,
• Michael Köpke 4 ,
• Blae Stacey 4 ,
• Sonja Jaster-Merz 4 &
• Roger M. Jones 1 , 3  

Scientific Reports volume  14 , Article number:  10957 ( 2024 ) Cite this article

Metrics details

• Biological physics
• Cell biology
• Medical research

Very high energy electrons (VHEE) are a potential candidate for radiotherapy applications. This includes tumours in inhomogeneous regions such as lung and prostate cancers, due to the insensitivity of VHEE to inhomogeneities. This study explores how electrons in the VHEE range can be used to perform successful in vitro radiobiological studies. The ARES (accelerator research experiment at SINBAD) facility at DESY, Hamburg, Germany was used to deliver 154 MeV electrons to both prostate (PC3) and lung (A549) cancer cells in suspension. Dose was delivered to samples with repeatability and uniformity, quantified with Gafchromic film. Cell survival in response to VHEE was measured using the clonogenic assay to determine the biological effectiveness of VHEE in cancer cells for the first time using this method. Equivalent experiments were performed using 300 kVp X-rays, to enable VHEE irradiated cells to be compared with conventional photons. VHEE irradiated cancer cell survival was fitted to the linear quadratic (LQ) model (R 2  = 0.96–0.97). The damage from VHEE and X-ray irradiated cells at doses between 1.41 and 6.33 Gy are comparable, suggesting similar relative biological effectiveness (RBE) between the two modalities. This suggests VHEE is as damaging as photon radiotherapy and therefore could be used to successfully damage cancer cells during radiotherapy. The RBE of VHEE was quantified as the relative doses required for 50% (D 0.5 ) and 10% (D 0.1 ) cell survival. Using these values, VHEE RBE was measured as 0.93 (D 0.5 ) and 0.99 (D 0.1 ) for A549 and 0.74 (D 0.5 ) and 0.93 (D 0.1 ) for PC3 cell lines respectively. For the first time, this study has shown that 154 MeV electrons can be used to effectively kill lung and prostate cancer cells, suggesting that VHEE would be a viable radiotherapy modality. Several studies have shown that VHEE has characteristics that would offer significant improvements over conventional photon radiotherapy for example, electrons are relatively easy to steer and can be used to deliver dose rapidly and with high efficiency. Studies have shown improved dose distribution with VHEE in treatment plans, in comparison to VMAT, indicating that VHEE can offer improved and safer treatment plans with reduced side effects. The biological response of cancer cells to VHEE has not been sufficiently studied as of yet, however this initial study provides some initial insights into cell damage. VHEE offers significant benefits over photon radiotherapy and therefore more studies are required to fully understand the biological effectiveness of VHEE.

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Dosimetry and radioprotection evaluations of very high energy electron beams

Introduction.

Very high energy electron (VHEE) radiotherapy is typically described as electrons accelerated to energies in the 100–250 MeV range. The idea of using VHEE as a novel radiation to treat cancer was first developed by Desrosiers et al. 1 over 20 years ago. Since this initial investigation, interest in VHEE as a novel radiotherapy technique has expanded, with the development of the first VHEE radiotherapy device announced in 2022, as a collaboration between CERN, Centre Hospitalier Universitaire Vaudois (CHUV) and industry partner THERYQ. The radiotherapy device is expected to be operational by 2024, with first clinical trials planned for 2025 2 , 3 . The VHEE radiotherapy device under development will deliver VHEE at ultra-high dose rates (UHDR) with the aim to deliver FLASH radiotherapy, a novel treatment that uses UHDR to spare healthy tissue. A key driver for this collaboration is that VHEE is thought to be an ideal candidate for FLASH radiotherapy due to the fast and efficient dose delivery capabilities of electrons.

Another benefit of VHEE would be potential advantages during irradiation of cancers located in inhomogeneous regions, such as lung and prostate 4 , 5 . This is due to VHEE having relative insensitivity to regions of varying densities, such as air pockets, in comparison to the dose deposited as a result of irradiation with photons or protons. Increasing electron energy results in a reduced penumbra 1 , 4 and therefore reduced dose scatter through a patient, indicating higher beam energies could be ideal for radiotherapy. Comparisons between VMAT and VHEE treatment plans indicate that VHEE resulted in similar or superior dose distribution for cases that include lung and prostate cancers 6 .

Electron energy in the range of 100–250 MeV significantly increases penetration depth so that the treatment of deep seated tumours would be possible 4 . Electrons in the (6–20 MeV) energy range have a long history of being used in the clinic for various superficial radiotherapy treatments due to their lower energy and therefore there reduced penetration 7 , 8 .

Although significant progress has been made in the development of VHEE for radiotherapy treatment, one aspect with extremely limited data is radiobiology. To our knowledge, there is no published in vitro or in vivo data at the time of writing. First investigations into the biological effectiveness of VHEE have been completed using theoretical models and by measuring damage to plasmid DNA, as a simplistic biological model. These studies aim to quantify the relative biological effectiveness (RBE) of VHEE. RBE is defined as the ratio of two doses where the radiation of interest (VHEE) is compared to a reference modality 9 , typically 250 kVp X-rays. The first experimental investigation into VHEE measures single strand (SSB) and double strand (DSB) DNA breaks to pBR322 plasmid DNA in response to 100–200 MeV electron irradiation (in comparison to 60 Co X-rays) 10 . RBE of VHEE was measured to be ~ 1.1–1.2, where yield of DSBs was the biological measure. This result was validated in response to 35 MeV electrons in an identical plasmid model, with SSB yield as the biological endpoint 11 . Monte Carlo simulations of VHEE have predicted their RBE to be ~ 1.0, with no significant difference relative to photons 12 .

If VHEE radiotherapy is to be implemented clinically, characterisation of VHEE RBE is critical in both cancer and healthy tissue. As the field progresses, it is expected that RBE measurements will be completed across both in vitro and in vivo models, to fully understand the interaction of this novel radiotherapy modality with biological matter, ranging from DNA to tissues. An important step in this process is an RBE measurement of cells in vitro. This will provide initial measurements that can be used to direct in vivo studies, as well as patient research and treatment.

Currently, investigative studies into VHEE radiobiology are extremely limited. One of the most critical obstacles is the lack of biological facilities in close proximity to VHEE accelerators. The overlap of physics and biology research means that very few facilities have the required infrastructure for good aseptic technique to support repeatable radiobiology. The experiment was therefore chosen to be completed at ARES, DESY due to the availability of facilities in close proximity to the VHEE beamline.

To produce radiobiology results with statistical significance, a minimum of three repeats of any in vitro experiment is typically required, with all samples undergoing identical experimental conditions. The repetition of sample irradiation can require considerable durations of VHEE beam time, which is typically competitive and limited. The ability to replicate exact irradiation conditions can present a problem for VHEE accelerators. The machine needs to be highly stable between irradiations and ideally maintain consistent beam energy, shape and alignment throughout all experimental repeats. This can provide a problem in facilities with a rotation of users, as beam conditions will typically be altered frequently and replicating a very specific previous set of conditions can take significant additional time. This is a symptom of current VHEE research machines. Development into clinical use necessitates beam consistency, which will improve beam stability and functionality, improving the feasibility of radiobiology experiments.

Another hurdle with current VHEE accelerators in a research setting is achieving the required field size, which in most cases will be significantly larger than the electron beam. Electron beam size varies between accelerators. At DESY’s ARES facility we used a Gaussian beam with σ ≃ 1.3 mm. Current VHEE accelerators including the CERN linear accelerator for research (CLEAR), the sources for plasma accelerators and radiation compton with lasers and beams (SPARC) and the next linear collider test accelerator (NLCTA) have a Gaussian beam within a range of σ ≃ 1–5 mm 13 . This is considerably smaller than the irradiation area required for most typical in vitro experiments where irradiations are commonly performed in cell culture flasks with cells adherent to the flask surface (ranging between 25 and 225 cm 2 culture area) or well plates (typical area of ~ 13.0 × 8.5 cm). Approaches to increase beam size include using materials such as foils or water to scatter the beam, otherwise pencil beam scanning can provide an overlapping dose profile. Both methods increase irradiation time of the sample which can be problematic when short time points post-irradiation are being investigated. This is particularly an issue when trying to obtain ultra-high dose rates. One way to achieve these dose rates would be by using traditional scattering methods. If spot-scanning methods were to be used to achieve ultra-high dose rates, an extremely high scanning speed (estimated at ~ 5.1 m/s) would be required to create dose rates within the FLASH range 13 .

The consideration of all these features can make a successful radiobiology experiment with VHEE more difficult, expensive and lengthy than experiments with more established modalities such as photons or protons. Fortunately, the current interest into using VHEE for medical applications has yielded several VHEE accelerator development projects worldwide, giving an optimistic outlook on the suitability of VHEE accelerators for radiobiology research. To progress the translational pathway for VHEE, there is a scientific need for radiobiological studies, which will allow informed treatment planning evaluations, and provide evidence to underpin an ethical plan for in vivo experiments. Ideally, experiments would be guided by a base of radiobiological studies, of which there are a limited number, due to the limitations discussed.

A collaboration between the University of Manchester (UK), and DESY (Germany) was initiated to attempt the in vitro irradiation of cancer cells using scanning methods. A radiobiology experiment measuring cell survival was the aim of the experiment, in an attempt to develop a VHEE irradiation protocol for further radiobiology experiments at DESY, as well as measuring the biological response to VHEE for the first time in cancer cells. This initial investigation into cancer cell survival was completed at the ARES RF linear accelerator with target energies of 100–155 MeV electrons, which was achieved following its finalised construction in 2021 14 . ARES demonstrated low energy jitter with a momentum stability of 6E-5 over a 16 h interval at 155 MeV 14 . The location of dedicated BSL-2 biology laboratory located in the nearby PETRA III experimental hall, as well as a highly stable VHEE beam meant that a protocol for the irradiation of cancer cells in vitro could be successfully developed.

Dose uniformity

To obtain a uniform dose profile over the sample areas, various spot spacing’s (0.8–2.6 mm) were tested using a constant Gaussian beam with σ = 1.3 mm. It was decided that all samples should be irradiated in a ‘serpentine pattern’—an irradiation spot pattern that is represented in Fig.  1 .

Example of the stage movement to irradiate using the ‘serpentine’ scanning pattern. The scanning pattern was used to create rectangular uniform dose fields over the sample area. Blue dots represent the irradiation spots and the black arrows represent direction of stage movement.

1.8 mm spot spacing was quantified as having the highest dose uniformity based on X and Y dose profiles and standard deviation across all pixel values, based on EBT3 film data. This spot spacing was therefore used for irradiation of all samples. An example of this irradiation area using EBT3 Gafchromic film is indicated in Fig.  2 .

( a ) Figure represents an example of the irradiated film pattern shown initially in the accelerator hall with irradiated samples. ( b ) Example of scanned film 24 h post irradiation. The scanned film is representative of the 7 × 12 irradiation pattern with 1.8 mm spot spacing that was used to irradiate all cell samples. The uniformity is indicated by the consistent darkening of the film within the rectangular area which is quantified further for all irradiated samples in Table 1 . EBT3 Gafchromic film scanned using the Epson perfection V850 pro scanner. ( c ) A plot representing the percentage dose to sample. Average dose uniformity of the irradiated area is 4.54% (σ). A 3D representation of the scanned film image indicated. The pixel values from the scanned data have been converted to dose (%). X and Y axis indicates the size of the irradiated area.

Figure  2 provides a visual example of the uniformity, which has been quantified below in Table 1 . The average dose for each irradiated sample area has been supplied for each individual sample. Average dose was measured as well as the standard deviation of pixels across the irradiated area of interest for each sample. Uniformity has been presented as the standard deviation from the mean (σ) across all pixels on the film for each sample irradiation (within the sample area of interest). These measurements show that the mean standard deviation across all samples is 4.54%, with a maximum deviation of 4.93 ± 1.25% for the lowest dose and a minimum of just 3.99 ± 0.60% for the 4.0 Gy dose point. It should also be noted that the dose uniformity of the EBT3 film itself is quoted between 2–3%, based on the manufacturers’ measurements 13 . Mean dose uniformity is also presented in respect to each dose where no trends are observed in correlation with increasing or decreasing average dose. Uniformity is therefore observed to be consistent between individual irradiations at each dose point to within 1.30% error. The homogeneity Index (defined by Eq. ( 1 )) across samples ranged from 0.19 ± 0.02 (4.0 Gy) to 0.30 ± 0.08 (1.5 Gy). These results are consistent with the uniformity measurements, suggesting that the lowest dose is the least uniform, whereas the intermediate dose 4.0 Gy is the most.

Dose repeatability

Another critical factor was the ability to repeat specific doses to obtain experimental repeats that can be compared. This was tested by analysing mean dose to each individual sample for each dose and experimental repeat. Comparisons have also been made between two experimental runs several months apart (January and May 2023) where different beam charges were used. The dose repeatability was measured as mean dose ± standard deviation (σ) across six irradiated samples, for each supplied charge. The film measured doses were 1.5 ± 0.1, 2.5 ± 0.2, 3.2 ± 0.3, 4.0 ± 0.1, 6.0 ± 0.3 and 6.7 ± 0.4 Gy as shown in Fig.  3 .

( a ) All points represent measured dose from EBT3 Gafchromic film, within the irradiated sample area. Dose to sample was altered by the number of 18.3 pC electron pulses at each spot within the rectangular irradiation pattern. The number of pulses that corresponds to each dose is indicated on the x axis. Six repeats of each dose point was completed, represented by six separate points for each number of pulses. Error bars are indicative of the standard deviation across pixels in the measured area, specified in Table 1 . The mean across six samples for each number of pulses is indicated by the dotted black line and corresponding black number. Points represent those that were measured in the May 2023 experimental run only. ( b ) Graph represents the dose measured from EBT3 Gafchromic film in response to increasing charge during experimental runs at ARES in both January and May 2023. Individual points represent mean values across six repeats and error bars are indicative of standard deviation measured across six irradiation repeats. During the January and May 2023 experimental runs, pulses with charges of 22.5 and 18.3 pC respectively were used, which is the factor responsible for the differing total charges between the two data sets.

The correlation between charge and dose has been plotted with linear fits. Information regarding the fits is specified in Table 2 below.

Cell survival of A549 and PC3 cells in response to VHEE and X-ray irradiation

A549 and PC3 cells were irradiated with doses of 154 MeV electrons, and 300 kVp X-rays, in matched experimental conditions. It was observed at higher doses that PC3 cells had low colony formation, so the cell survival in response to the two higher doses have not been indicated for this study. Results are presented below in Table 3 and Fig.  4 .

Curves indicate the proportion of cell survival ( S ) of A549 ( a ) and PC3 ( b ) cells in vitro in response to dose ( D ) of 154 MeV electrons and 300 kVp X-rays. Error bars are standard deviation where n = 3 for cell survival error and n = 6 for electron dose error. Fitted lines are the linear quadratic (LQ) model, with fitting parameters and goodness of fit indicated in Table 4 .

Differences in cell survival were not found to be significant when using a two-way ANOVA test to compare between modalities at each specific dose for either cell line. The data is shown in Fig.  4 , fitted to the linear quadratic (LQ) model.

Measuring the relative biological effectiveness of VHEE

The RBE of VHEE was determined using values taken from the LQ fits to VHEE and X-ray cell survival data. Fitting parameters to the LQ models to each data set are detailed below in Table 4 . Goodness of fit to the LQ model is also presented as well as D 0.5 and D 0.1 , which represent the dose required to obtain 50% and 10% cell survival respectively. Values for VHEE RBE have been calculated from the D 0.5 and D 0.1 values to provide a quantification of the biological effectiveness of 154 MeV electrons in comparison to photons.

As indicated in Table 4 , the RBE of VHEE can be observed to be 0.99 (D 0.5 ) and 0.93 (D 0.1 ) for A549 lung cancer cells, and 0.74 (D 0.5 ) and 0.93 (D 0.1 ) for PC3 prostate cancer cells. All sets of data were indicated to fit the LQ model with an R 2 value > 0.95. α and β values varied significantly. A549 α values were 0.06 and 0.10 for X-rays and VHEE respectively. The respective X-ray and VHEE β values were 0.07 and 0.05, resulting in α/β ratios of 0.84 and 2.13. A major difference was in the α value for the PC3 cell line, with 0.30 (X-ray) and 0.01 (VHEE) calculated as the best fitting parameters available. Combined with β values of 0.11 and 0.16 for X-ray and VHEE respectively, this resulted in highly different α/β ratios of 2.83 and 0.06.

This study shows for the first time that cell cultures can be successfully irradiated with VHEE using a spot scanning method, to complete cell survival experiments. Dose uniformity across the irradiated sample area was measured to be 4.54% when using EBT3 Gafchromic films. This was considered to be a small error when also considering that the inherent uniformity error of the Gafchromic film is quoted to be 2–3%, in optimal conditions 15 . Gafchromic films have previously been studied to be a reliable dosimetry method for VHEE within their intended dose range 16 , 17 and has been used for several experimental studies using VHEE thus far 5 , 10 . However, the film error is a limitation across all measurements in this study. Eventually, higher accuracy dosimetry could be achieved using ionisation chambers. Although not an issue for the dose rates used in this study, ultra-high dose rates do currently present a problem for standard chambers due to inefficient charge detection 18 . Developments such as the novel flashDiamond detector 19 provide options to advance the precision and accuracy of dose to samples in an optimised experimental set up.

Separate from measuring accurate and precise dose to samples, repeatability of dose is one of the most important aspects of radiobiology. Dose to samples can vary significantly even with consistent beam parameters and conditions. Even small amounts of position jitter in the beam can change the obtained dose by a significant amount, especially when irradiating within a small area. Changes in amount and shape of dark current spots also needs to be considered and measured in experimental VHEE linac. High beam stability is required to obtain repeatable results and this was provided by the ARES linear accelerator, as well as low dark current throughout the experimental runs. To quantify repeatability, average dose to each sample was measured across six irradiated samples as well as the standard deviation from the mean (σ) of all pixel values in the irradiated area of interest as a measure of uniformity. Overall, the average standard deviation from the mean (σ) when combining all irradiation repeats at each dose is 4.54% This varies slightly between doses, with the 1.5 Gy having the largest standard deviation over six irradiated samples (4.93%) and the lowest standard deviation occurring at doses of 4.0 Gy (3.99%). Again, these values must be considered alongside the 2–3% dose error of the film.

This was determined as a successful response, however the dose error does limit the ability of radiobiologists to explore more nuanced responses to VHEE. For example, if we aim to explore and quantify differences in RBE that are most likely within a 0–10% difference of our reference modality, then a large number of studies will have to be performed to demonstrate statistical significance given typical dose uncertainty. The development of VHEE machines with highly stable beams for medical applications is an absolute requirement of clinical applications. Higher accuracy dosimetry for VHEE machines would be also be beneficial to improve on current radiobiological studies and drive clinical translation.

Another limitation of this study is fact that experiments across modalities were completed at different laboratories and times. RBE studies with VHEE would be more scientifically rigorous if there was availability to a photon reference modality in the same location. An ideal facility would allow scientists to perform comparable sets of experiments with X-rays alongside these with VHEE to have matched controls, timings, protocol and reduce inter-lab variation.

The spot scanning method was used to complete the irradiations, with the cells in suspension within 0.5 ml Eppendorf tubes. This method was chosen to maintain a small irradiation area (the serpentine pattern covered a ~ 10 × 20 mm area) and keep the irradiation time for each sample to under 5 min. This method could be utilised to cover larger areas such as flasks and well plates, however the considerably longer irradiation times would have to be taken into account, and the effect of this on the cells measured.

During the VHEE irradiation, cells remained in the accelerator hall for ~ 1 h. It must be considered that the Eppendorf tube environment is sealed and at room temperature, as well as the cells being in suspension. For these reasons, the same protocol was recreated for X-ray irradiated samples, with cells maintained in identical Eppendorf tubes for the same length of time. The effect of these environmental conditions were tested in unirradiated samples. Any effects on cell survival was measured using the plating efficiency for these unirradiated cells. There were no statistical differences between those cells plated immediately after counting, and those stored in suspension within the Eppendorf tubes. Plating efficiency had a larger variance in A549 cells than with PC3 cells, but no differences can be recognised between the two conditions. This test was critical for ensuring that using this alternate methodology was not introducing unpredicted levels of stress to the cells manifesting as the loss of proliferative capability, with could impact the overall result. The lack of difference between conditions was reassuring and the implication was that we could irradiate in the comparably small area of the 0.5 ml Eppendorf tube rather than a flask or well plate.

The cell survival was then measured in response to several doses and the LQ model was fitted to this data, as represented in Fig.  4 . A high quality of fit to the LQ model indicated that both cell lines responded to both VHEE and X-ray irradiation as per the commonly described radiobiological model. The α/β values varied considerably between modalities, even in the case of A549 cells where the data points for VHEE and X-ray were noticeably similar. Due to the high goodness of fit of the LQ model to both cell lines and modalities, the fits were used to determine values for D 0.5 and D 0.1 .

The quantification of VHEE RBE was completed by calculating D 0.5 and D 0.1 , the dose required to kill 50% and 90% of cells respectively. The ratio of these doses was taken to calculate VHEE RBE values of 0.99 and 0.93 for A549 and 0.74 and 0.93 for PC3 cells. Average values for A549 and PC3 cells between the two conditions are 0.96 and 0.84 respectively, suggesting that the efficiency of VHEE cell killing is higher for lung cancer than prostate cancer in this case. Overall, the results indicate that VHEE have an RBE that is slightly less than, but close to 1.0. More investigations must be completed to add to the landscape of VHEE RBE.

Experimental investigations of VHEE RBE with plasmid DNA suggest an RBE of 1.1–1.2 (10). It is possible that the RBE > 1 for plasmids does not translate into a cancer cell model, and that the RBE for cell killing is closer to 0.9–1.0 based on the LQ fits. On the other hand, when measuring cell death at each dose point, there was no significant difference between VHEE and X-ray irradiated suggesting that RBE of VHEE is the same as that of photons. Our result is similar to another study investigating electron RBE using cell survival as the biological endpoint. Herskind et al. 20 measured the RBE of 10 MeV electrons to be 0.98 and 0.91 for MCF7 (breast cancer) and HUVEC (endothelium) cells respectively, suggesting that electrons across a range of energies have an RBE of > 1 when measuring cell survival. An RBE value of 0.84 for cell survival has also predicted for electron energies in the 6–18 MeV range using Monte Carlo modelling 21 . It should be noted that clinically, an RBE of 1 is used for electrons and has been for several decades.

Micronuclei are markers of DNA damage and are commonly used to measure RBE. Micronuclei frequency has been used as a biological endpoint to predict electron RBE as 1.1–1.3 across three studies 22 , 23 , 24 for electrons in the 1.5–8 MeV. Cell types measured were human lymphocytes and an ovarian cancer cell line. A recent systematic review of the literature did however highlight micronuclei frequency as an unreliable assay for quantifying biological effect between radiation modalities 25 . Naturally, more data is required as this is the first published response of cancer cells to VHEE and an overall picture of electron RBE is needed to predict biological effects accurately. Similar experiments with other cell types, including healthy cells, and eventually in vivo models is certainly required to fully understand the biological effect of VHEE.

Cell culture

A549 (human lung adenocarcinoma) and PC3 (human prostate adenocarcinoma) were cultured under sterile conditions in Roswell Park Memorial Institute (RPMI) 1640 medium (Gibco, 11875093) supplemented with l -Glutamine and 10% fetal bovine serum (FBS) (Gibco, 10270-106). Cells were cultured at 37 °C, 5% CO 2 .

Cell samples irradiated with 154 MeV electrons were cultured and prepared in the Biology Laboratory located in the PETRA III experimental hall, Deutsches Elektronen–Synchrotron (DESY) facility in Hamburg, Germany. In the case of cell samples irradiated with 300 kVp, cell culture and sample preparation took place in the Oglesby Cancer Research Centre (OCRB).

Cells were authenticated and routinely tested for mycoplasma contamination.

Irradiation of A549 and PC3 cells in vitro

A549 and PC3 cells were irradiated with a range of doses across two research centres. Irradiations with 154 MeV electrons were completed at ARES and irradiations with 300 kVp X-rays were completed at the Oglesby Cancer Research Centre (OCRB), using an Xstrahl CIX3 cell irradiator.

Cells were prepared in suspension to a concentration of 5 × 10 5 cells/ml in a 200 μl volume of cells. Cells were irradiated in 0.5 ml Eppendorf tubes (Eppendorf, 0030121023) at doses of 1.4, 2.3, 3.0, 3.7, 5.7 and 6.3 Gy for both 154 MeV electrons and 300 kVp X-rays. Three statistical repeats were completed for each dose and cell line. Physical beam parameters for the VHEE and X-ray irradiations are specified in Table 5 below.

Once samples were prepared, cells remained in suspension at room temperature for approximately 2 h including transport time to and from irradiation source, irradiation and seeding time. Figures referring to plating efficiency using this protocol, as well as images of colony formation are available in the Supplementary section of this manuscript.

X-ray experimental setup on Xstrahl CIX3 cell irradiator at OCRB

0.5 ml Eppendorf tubes containing A549 or PC3 cells in suspension were irradiated with 300 kVp X-rays by lying tubes flat on the internal turntable within the Xstrahl CIX3 cell irradiator. The turntable ensured uniform irradiation over the samples from the vertical X-ray source. Dose to samples was measured based on the X-ray exposure time, with a dose rate of 2.13 Gy/min ± 0.8% used. A 0.7 mm copper filter was used.

Electron experimental set up at ARES

Cells were prepared and irradiated in 0.5 ml Eppendorf tubes and transported from the Biology Laboratory to the ARES accelerator hall in a polystyrene box. Samples were loaded in the custom made C250 aluminium sample holder as indicated in Fig.  5 . Rectangles of EBT3 Gafchromic film were secured in front and behind the samples in the irradiated area to measure dose for each irradiation. The sample holder was attached to a Thorlabs translation stage (Thorlabs, LTS300/M) to ensure precise movements of the samples, therefore creating a uniform scanned dose over the Eppendorf tube volume. Figure  6 shows the schematic of the beamline as well as the samples in the experimental area.

A labelled photograph of the experimental area during the May 2023 run after irradiating cancer cells. Significant components of the experimental area are indicated including the sample location, the aluminium sample holder and EBT3 Gafchromic film for measurement of dose to samples. Note that during the irradiation, an identical rectangular section of EBT3 Gafchromic film was placed behind the sample, but has been removed here for visibility of the Eppendorf tubes and sample holder.

A schematic representation of the ARES beamline is indicated. Electrons are generated by a normal conducting RF photoinjector, and are then accelerated using an S-band system. Focussing and steering of the beam are provided by several quadrupole magnets, as well as a dipole and corrector magnets. Current measurements are provided by the turbo integration current transformer (ICT). A 50 μm thick Titanium foil separates the accelerator vacuum from air. The electrons then terminate in the experimental area at an energy of approximately 154 MeV.

Samples were irradiated in a pre-optimised scanning pattern that consisted of overlapping Gaussian beam spots, achieved by the movement of the stage in a ‘serpentine’ pattern. Beam size was maintained at 1.3 mm σ for all experiments and the scanning pattern consisted of a 7 × 12 spot pattern using 1.8 mm spot spacing. Beam charge was maintained at 18.3 pC per pulse. Dose to samples was altered by varying the number of pulses administered at each spot in the 7 × 12 pattern. 1, 2, 3, 4, 6, and 7 pulses per spot corresponded to doses of 1.4, 2.3, 3.0, 3.7, 5.7 and 6.3 Gy respectively. Post-irradiation, the accelerator hall was accessed immediately, cells were removed and transported to the biology laboratory for processing.

Measuring cell survival using clonogenic method

Cell survival was measured in both cell lines using a clonogenic assay. Cells were seeded into six well plates within 1 h post-irradiation. Three seeding densities were used per dose, with each seeding density prepared in duplicate, using pre-optimised seeding densities. Cells were then incubated for 8 (A549) or 11 (PC3) days at 37 °C, 5% CO 2 . After the incubation time, cells were washed with PBS and colonies were fixed and stained with 0.7% crystal violet solution (Sigma–Aldrich, V5265) prepared in 30% methanol (Fisher Scientific, M/4000/21). Colonies were counted, with a colony defined a cluster of > 50 cells.

The Xstrahl machine for irradiations with 300 kVp X-rays was calibrated twice per annum to current national standards by the Christie Medical Physics team using an ionisation chamber. Ionisation chamber and probes are calibrated by Christie Medical Physics team annually. At the time of writing, the most recent dosimetry checks measured the X-ray dose rate at 2.13 Gy/min, with a percentage error of 0.8%. Collating dosimetry data from the previous 2 years shows that the maximum percentage error on the dose is 1.3% which has therefore been used to plot the X-ray error bars in Fig.  4 . Dose measurements were also completed using EBT3 Gafchromic film to validate average dose and uniformity of the irradiation field.

Dosimetry of VHEE at ARES was completed by simulating the dose delivered for a given charge using TOPAS Monte Carlo simulation (version 3.7.0) 29 , 30 , with validation using EBT3 Gafchromic film. EBT3 film was calibrated using a medical 15 MeV electron linac at the Christie Hospital, Manchester, UK. All calibration and reference films were scanned on an Epson perfection V850 pro scanner (Epson, B11B224401) at 300 dpi. Measured dose refers to the average of red and green colour channels in every instance.

Film was placed directly in front of and behind samples to measure dose received in the irradiated region directly behind the Eppendorf tube. The difference between the measured dose behind and in front of the tube was calculated to be 6.3%, which was applied uniformly to the dose measured behind the sample to calculate values for the dose received by the sample volume.

Dose uniformity in the irradiated area was measured as the standard deviation across all pixels on the EBT3 film within the irradiated area, as measured using Image J software.

The homogeneity index was calculated using the equation:

where HI is the homogeneity index, P max and P min are the maximum and minimum pixel dose on the Gafchromic film in the sample area.

Dose repeatability was calculated by measuring the standard deviation (σ) of the average doses of six individually irradiated samples, with access to the accelerator hall in between each irradiation.

Fitting of radiobiological model to cell survival data

The linear quadratic (LQ) model was fitted to cell survival data in response to radiation dose. The equation,

where S is the proportion of surviving cells, D represents Dose (Gy) and α (Gy −1 ) and β (Gy −2 ) are both fitting parameters that are described further for each data set in Table 4 . All fits were completed using GraphPad Prism (version 8) software.

Statistical analysis

A Student’s paired t test was used to compare between the unirradiated plating efficiencies for two plating methods.

A two way analysis of variance (ANOVA) was applied to the irradiated cell survival for A549 and PC3 datasets separately to determine differences between radiation modalities at each dose. This was followed up by a Sidak’s multiple comparisons test to identify statistical differences between VHEE and X-ray cell survival. p -values < 0.05 were considered to be statistically significant.

The statistical analysis for both tests was completed using GraphPad Prism (version 8). The threshold for statistical significance used throughout was p  < 0.05.

Data availability

The data underlying this article is available in the article, presented in table format throughout. Any other data or specific information underlying this article will be shared on reasonable request to the corresponding author.

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Acknowledgements

This work was supported by the UK Research and Innovation (UKRI), Engineering and Physical Sciences Research Council (EPSRC) [EP/T517823/1] and the UK Research and Innovation (UKRI), Science and Technology Facilities Council (STFC), Cockcroft Institute [ST/V001612/1]. The authors also acknowledge support from DESY (Hamburg, Germany), a member of the Helmholtz Association HGF. We are pleased to acknowledge support from several groups including Rob Bristow’s group at the Oglesby Cancer Research Centre (OCRB), UK and the Centre for Structural Systems Biology (CSSB), Germany for the kind donation of A549 and PC3 cells. Thank you to all technical groups at DESY for their work and support in the ARES implementation, maintenance and operation.

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Contributions

Biological experiments, analysis, dosimetry work and preparation of the main manuscript was completed by H.C.W. At ARES, H.D., F.M., W.K., M.Ke., T.V., B.S. and S. J-M., operated the beam for the duration of all cell irradiations and testing. F.B. provided supervision and advice throughout the experiment at ARES. M.Ko. supervised biology work at DESY and maintained the laboratory facilities located in the PETRA III experimental hall. R.M.J., M.J.M., E.S., N.T.H. and A.L.C. provided supervision throughout the project and contributed to the ideas and development of the overall work. Reviews of the manuscript were made by all authors.

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Wanstall, H.C., Burkart, F., Dinter, H. et al. First in vitro measurement of VHEE relative biological effectiveness (RBE) in lung and prostate cancer cells using the ARES linac at DESY. Sci Rep 14 , 10957 (2024). https://doi.org/10.1038/s41598-024-60585-7

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• Published: 10 May 2024

Total knee arthroplasty: does ultra-early physical therapy improve functional outcomes and reduce length of stay? A retrospective cohort study

• Lynn Thwin 1 ,
• Brian Rui Kye Chee 1 ,
• Yan Mei Yap 2 &
• Kelvin Guoping Tan 1  

Journal of Orthopaedic Surgery and Research volume  19 , Article number:  288 ( 2024 ) Cite this article

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The Enhanced Recovery After Surgery (ERAS) Society recommends that after total knee arthroplasty (TKA), patients should be mobilized early. However, there is no consensus on how early physical therapy should be commenced. We aim to investigate whether ultra-early physical therapy (< 12 h postoperatively) leads to better outcomes.

This is a retrospective cohort study of 569 patients who underwent primary TKA from August 2017 to December 2019 at our institution. We compared patients who had undergone physical therapy either within 24 h or 24–48 h after TKA. Further subgroup analysis was performed on the < 24 h group, comparing those who had undergone PT within 12 h and within 12–24 h. The outcomes analyzed include the Oxford Knee Scoring System score, Knee Society Scores, range of motion (ROM), length of stay (LOS) and ambulatory distance on discharge. A student’s t test, chi-squared test or Fisher’s exact test was used where appropriate, to determine statistical significance of our findings.

LOS in the < 24 h group was shorter compared to the 24–48 h group (4.87 vs. 5.34 days, p  = 0.002). Subgroup analysis showed that LOS was shorter in the ultra-early PT (< 12 h) group compared to the early PT (12–24 h) group (4.75 vs. 4.96 days, p  = 0.009). At 3 months postoperatively, there was no significant difference in ROM, ambulatory distance or functional scores between the < 24 h group and 24–48 h group, or on subgroup analysis of the < 24 h group.

Patients who underwent physical therapy within 24 h had a shorter length of stay compared to the 24–48 h group. On subgroup analysis, ultra-early (< 12 h) physical therapy correlated with a shorter length of stay compared to the 12–24 h group (4.75 vs. 4.96 days, p  = 0.009) - however, the difference is small and unlikely to be clinically significant. Ultra-early (< 12 h) physical therapy does not confer additional benefit in terms of functional scores, ROM or ambulatory distance. These findings reinforce the importance of early physical therapy after TKA in facilitating earlier patient discharge.

Introduction

Total knee arthroplasty (TKA) is the mainstay of treatment for late stage osteoarthritis, and is being performed with increasing frequency each year.

Multiple preventive strategies have been documented in the literature - surgical and nonsurgical - in an attempt to slow the progression of knee osteoarthritis [ 1 , 2 , 3 ]. However, with many countries facing an aging and more active population, the incidence of severe knee osteoarthritis requiring joint replacement continues to increase. [ 4 , 5 ]

The Enhanced Recovery After Surgery (ERAS) Society recommends that TKA patients should be mobilized as early as possible after surgery to aid quicker recovery [ 6 ]. Studies have suggested that early physical therapy helps to improve functional outcomes, range of motion (ROM) as well as in-hospital length of stay (LOS) [ 7 , 8 , 9 , 10 , 11 , 12 ]. In addition to improving functional outcomes, safely reducing the hospital LOS also helps with reducing healthcare costs as one of the main cost contributors in a TKA is the length of inpatient stay [ 13 , 14 ].

Early initiation of physical therapy (PT) post-op has been proposed as one of the ways to reduce LOS [ 7 , 15 ]. It has been shown that PT can be safely initiated as early as post operative day zero (POD 0) [ 15 ]. Some studies showed that early initiation of PT may allow a more efficient and productive PT session on subsequent days resulting in better ROM and functional outcomes [ 9 , 11 ]. Early initiation of PT can also reduce the development of complications such as deep vein thrombosis, pulmonary emboli, chest infections and urinary retention [ 16 ]. However, the definition of early PT varies from study to study. Some studies use the number of post-operative days in their definition, while others use the number of hours from the time of surgery.

In addition, while many of the studies have concentrated on the LOS as well as safety aspects of early rehabilitation, only one study has looked at the functional outcomes associated with early PT [ 11 ]. The benefit for patients in terms of functional outcomes has not been adequately studied in the existing literature.

This study aims to investigate how the timing of physical therapy affects the functional outcomes as well as LOS of patients undergoing TKA.

This is a retrospective cohort study of 569 patients who underwent primary TKA between August 2017 and December 2019 at our institution. Institutional review board approval was obtained before performing this study (NHG DSRB 2020/00095). The data was prospectively collected from our institution’s existing knee registry.

The inclusion criteria comprises:

Patients who underwent unilateral TKA.

Patients who were discharged home.

Patients who commenced physical therapy within 48 h of their surgeries.

Patients who underwent unicompartmental knee arthroplasty, revision knee arthroplasty (for any cause), or bilateral total knee arthroplasty were excluded. Patients discharged to community rehabilitation centers were also excluded.

Patient demographics and surgical data were collected for all patients, including age, gender, body mass index (BMI), side (left or right), comorbidities and duration of operation.

All the patients were admitted to the hospital on the day of surgery. The length of stay was calculated from their date of admission to the date of discharge in terms of days. The timing of each case was determined by the availability of operative resources and the primary surgeon’s preference.

The TKAs were performed using medial parapatellar approaches. All the patients received either a peripheral nerve block or periarticular injection intra-operatively. The type of anesthesia was also recorded as spinal anesthesia or general anesthesia. After the surgery, all patients were first transferred to the post-anaesthesia care unit (PACU) and thereafter to the general wards for inpatient care.

Patients were selected for physical therapy based on availability of the physiotherapists and timing of the surgery. Patients who arrived in the ward from PACU after office hours commenced their physical therapy on the following day after their surgery. All patients received physical therapy within 48 h from the time of their respective surgeries.

The aims of physical therapy were the same regardless of whether it was commenced on the day of surgery or the subsequent days. The physical therapists determined the length and frequency of therapy sessions according to the needs of individual patients.

The patients were started on continuous passive motion (CPM) on the day of their surgery. The physical therapists would assist the patients to sit over the edge of bed, and also initiate active and active assisted knee range of motion (ROM) exercises. As the patients progressed, they would be taught transfers, started on gait training, stair climbing and activities of daily living exercises.

The patients were deemed safe for discharge after they were able to ambulate with a walking aid, clear ground level obstacles safely, have adequate pain control and a clean and dry surgical site.

The amount of distance covered on the day of discharge as well as their knee ROM were recorded.

Functional outcomes were measured using the Oxford Knee Score (OKS) and Knee Society Score (KSS) and KSS (function), and were collected until three months after the operation.

The time taken from the end of surgery to the start of physical therapy was recorded. During the analysis, the patients were grouped into those that commenced physical therapy within 24 h and 24–48 h after operation. The < 24 h group was also further subdivided to < 12 h and 12–24 h. We defined patients who received PT within 24 h as early PT and those who received within 12 h as ultra-early PT. Differences in outcomes were compared between < 24 h and 24–48 h groups, and a subgroup analysis of the < 24 h group was also performed to determine whether ultra-early physical therapy has an effect on the outcomes measured.

Statistical methods

Descriptive statistics of the demographic data and outcome variables were calculated. Numerical variables were presented as mean ± standard deviation or median (IQR) and Student’s t-test was used when appropriate. Categorical variables were presented as numbers and percentage and Chi-square test or Fisher Exact test was used when appropriate. A two tailed significance level of 0.05 was used for all the tests. All statistical analyses were conducted using IBM SPSS Statistics 19.

A total of 1312 patients underwent TKA during the specified period. Of these, 569 patients had unilateral surgery and were discharged home, and were hence included in the study. 478 patients underwent PT within 24 h and 91 patients within 48 h. There were no significant differences in age, gender, BMI and preoperative hemoglobin levels, pre op range of motion as well as functional scores between the two groups (Table  1 ).

There was no statistical significance between the groups with regards to co-morbidities (Table  2 ).

There was significant reduction in LOS in the < 24 h group compared to 24–48 h group (4.87 vs. 5.34 days, p  = 0.002). There were no significant differences in other functional outcome measures between the 2 groups. (Tables  3 and 4 ). There was no increase in the complication rates between the two groups of patients.

A subgroup analysis was performed for the < 24 h group to determine whether patients who received ultra-early physical therapy (< 12 h) have shorter LOS as well as other functional outcomes compared to those who underwent early physical therapy (12–24 h). The ultra-early physical therapy group showed a shorter length of stay (4.75 vs. 4.96 days, p  = 0.009). There was no significant difference in PROM, ambulatory distance at discharge and functional outcome between the ultra-early PT and early PT group (Table  5 ).

Early mobilization is an integral part of enhanced recovery after surgery (ERAS) [ 17 ]. The ERAS society recommends that patients should be mobilized as soon as possible after surgery - this helps to reduce the length of stay and counteract the adverse physiological effect of prolonged bed rest [ 6 ]. In current literature, studies have shown that early mobilization or rehabilitation after total knee arthroplasty improves functional outcomes as well as reduces the length of hospital stay [ 7 , 11 , 12 , 18 , 19 ].

Our study’s findings correlate with that of previous studies which have found that early mobilization on POD 0 following TKA leads to shorter LOS [ 13 , 15 , 20 ]. Chen et al. found in their prospective cohort study that patients who ambulated with PT on POD 0 had a shorter LOS than those patients who did not [ 15 ]. Similarly, Den Hertog et al’s randomized controlled trial showed that patients who were in a POD 0 fast-track rehabilitation program had a shorter LOS compared to standard rehabilitation programs in their randomized control trial [ 7 ]. In our study, all patients received PT within POD1. Patients in the ultra-early group received PT on POD0 while patients in the early (12–24 h) group and > 24 h group had PT on POD 1. Although both ultra-early and early physical therapy showed benefits in terms of LOS, our results show that there is diminishing benefits to ultra-early physical therapy (LOS: 4.75 vs. 4.96 days comparing < 12 h and 12–24 h) compared to that of early physical therapy (LOS: 4.87 vs. 5.34 days comparing < 24 h and 24–48 h). Although the ultra-early physical therapy (< 12 h) group showed a lower LOS compared to the 12–24 h group, the small difference (4.75 vs. 4.96 days) is unlikely to be clinically significant. In the healthcare setting where resources and manpower are finite and limited, it would be necessary to weigh the benefits of a slightly reduced LOS from ultra-early physical therapy against manpower and resource limitations.

In addition, the recorded mean LOS in our study is longer than what has been reported in previous literature (Bohl et al.: median of 32 h for POD0 PT and 31 h for POD1 PT; Chen et al.: mean of 2.8 days for POD0 PT and 3.7 days for POD1 PT). There are 2 main factors that could have contributed to our longer LOS, which are: the higher average age of our patients, and the difference in criteria for safe discharge by our physical therapists. The average age of our patients’ population (67.7 years) was several years older than patients in other studies (Bohl et al. 63.7 years, Chen et al. 62.3 years) [ 8 , 15 ]. This could contribute to slower recovery from the initial surgery as well as a slower rehabilitation process. Secondly, there is a strict criteria for safe discharge from the physical therapists at our institution. These include the ability to ambulate with a walking aid, clear ground level obstacles safely, achieve adequate pain control and a clean and dry surgical site. In the study by Bohl et al. 2019, there was no explicit criteria that was mentioned for safe discharge. An arbitrary term of being “cleared” by the physical therapist was used to denote when a patient was safe to be discharged from the acute hospital ward [ 8 ]. Chen et al’s study defined their discharge criteria, which included being able to ambulate 100ft and being able to climb up and down stairs. However, the amount of assistance required and the type of mobility aid required to achieve these discharge criteria were not mentioned. In addition, patients who were discharged to skilled nursing facilities and rehabilitation facilities were also included in their study. We have observed that in our local population, a significant percentage of patients have the expectation of only being discharged when they are close to independent ambulation. This would have a great impact on the LOS as a larger number of PT sessions would be needed to get these patients back to or close to their premorbid function.

Our data finds that at 3 months follow-up, there was no significant difference in change in OKS and KSS functional scores - differing from results from other studies in the current literature. Larsen et al. conducted a randomized controlled trial to investigate the effects of accelerated rehabilitation and physical therapy after arthroplasty. Their study involved a heterogenous group of 87 patients who had undergone either total hip arthroplasty (THA), total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA). They found that at 3 months follow-up, there was a significant gain in quality of life (QOL) using the EQ−5D score compared to baseline [ 11 ]. However, a subgroup analysis of TKA patients did not reveal any significant difference in the functional outcomes - it appears that their findings were skewed by significantly better results experienced by the THA patients who had undergone early physical therapy. Furthermore, the intervention group not only received earlier physical therapy, but they were also provided with pre-operative education and longer physical therapy sessions. Patients in the intervention group were also cohorted in the same ward. Thus, while Larsen et al’s study shows better functional outcomes after earlier intervention, it is difficult to isolate these effects to merely early initiation of physical therapy.

While other studies have found an increase in ROM with early initiation of physical therapy, our study did not find similar results [ 9 , 10 ]. Labraca et al’s randomized controlled trial had patients placed into two groups - those receiving physical therapy either before 24 h or after 24 h postoperatively. Patients who received physical therapy within 24 h showed significantly better LOS, ROM and gait scores. While our study found a similar correlation between earlier physical therapy and a shorter LOS, it did not find that earlier physical therapy led to increased ROM at discharge.

There are several strengths to our study. Firstly, the data was collected prospectively, which reduces the risk of recall bias. Secondly, other studies investigating the early initiation (POD 0 vs. POD 1) of PT mainly use LOS as an outcome factor. The present study not only uses LOS, but also compares the ROM, ambulation distance as well as early functional outcome score (3 months) to determine the difference in outcomes when PT is initiated ultra-early, early or after 24 h from surgery. Thirdly, our sample size ( n  = 569, ultra-early PT n  = 216, early PT n  = 262, > 24 h n  = 91) is relatively large when compared to other recent studies. Finally, our study isolates time to PT as the independent variable between treatment groups - other than this, there were no differences in intervention across treatment groups.

We recognise several limitations to our study. Firstly, the patients were not randomized and patients who were not well medically, not motivated to undergo PT or underwent surgeries later in the day were self-selected to be in the 12–24 h group or 24–48 h group. This might result in selection bias in the study. Secondly, our study focuses on patients who were discharged home. Over half of our TKA patients are discharged to subacute facilities for further rehabilitation prior to being discharged home - our study does not address the effects of earlier physical therapy on this significant patient population. Thirdly, LOS was defined as the time between admission and discharge at our institution. Besides the effects of earlier physical therapy, other non-related issues such as medical complications, patient preference and administrative discharge paperwork may also influence a patient’s length of stay and obscure the differences due to earlier physical therapy.

Our study shows that early commencement of physical therapy within 24 h is important in reducing the LOS (4.87 vs. 5.34 days comparing < 24 h and 24–48 h).

Ultra-early physical therapy (< 12 h) confers additional benefit in terms of length of stay (4.75 vs. 4.96 days, p  = 0.009) compared to the 12–24 h group - however, the difference is small and unlikely to be clinically significant. Ultra-early (< 12 h) physical therapy does not confer additional benefit in terms of functional scores, ROM or ambulatory distance.

These findings reinforce the importance of early physical therapy after TKA in facilitating earlier patient discharge.

Where resources permit, physical therapy should be initiated on the day of operation, and ideally as soon as the patient returns to the ward.

Data availability

Data is provided within the manuscript or supplementary information files.

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L.T., B.C. and Y.Y. contributed to the main manuscript text.L.T. and Y.Y. prepared the figures.K.T. oversaw the research idea and contributed to revisions.All authors reviewed the manuscript.

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Thwin, L., Chee, B.R.K., Yap, Y.M. et al. Total knee arthroplasty: does ultra-early physical therapy improve functional outcomes and reduce length of stay? A retrospective cohort study. J Orthop Surg Res 19 , 288 (2024). https://doi.org/10.1186/s13018-024-04776-y

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DOI : https://doi.org/10.1186/s13018-024-04776-y

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