Kinds of Sources

When searching for specific biomechanical knowledge it is important to keep in mind the kind of source you are reading. There is a definite hierarchy of the scholarly or academic rigor of published research and writing. Figure 1.9 illustrates typical examples of this hierarchy. Although there are exceptions to most rules, it is generally true that the higher up a source on the hierarchy the better the chance that the information presented is closer to the current state of knowledge and the truth. For this reason professionals and scholars focus their attention on peer-reviewed journals to maintain a knowledge base for practice. Some publishers are now "publishing" electronic versions of their journals on the world wide web (WWW) for subscribers or make papers available for free after a certain waiting period.

Most scholarly journals publish original research that extends the body of

Figure 1.9. The many kinds of biomechanics sources of information and the hierarchy of their academic rigor.

knowledge, or review papers that attempt to summarize a body of knowledge. Many journals also publish supplements that contain abstracts (short summaries of a research study) of papers that have been accepted for presentation at a scholarly meeting or were published in another journal. While the review of these abstracts is not as rigorous as a full journal article, abstracts do provide students with clues about what the most recent research is fo cusing on. Reading biomechanics research will be challenging for most undergraduates. Appendix A provides a comprehensive glossary of biomechanics terms that will help you when reading the biomechan-ics literature related to your professional interests.

In the middle of academic rigor are edited proceedings, edited books, and professional journals. These publications have varying degrees of peer review before pub lication, as well as varying rules on what constitutes acceptable evidence. At the bottom of the credibility chain are popular press publications (magazines/newspapers) and hypertext on the worldwide web. While these sources are appropriate for more subjective observations of laypersons, there are serious threats to the validity of the observations from these sources. The major problems with webpages are their impermanence (unlike archival research literature) and the lack of review (anyone can post a webpage). Another good example is the teaching and coaching tips published by the Physical Education Digest ( Most of tips and cues are opinions of coaches and teachers in popular press magazines that have not been tested by scientific research. It is possible that some of these opinions are correct and useful, but there is little evidence used to verify the advice, so kinesiol-ogy professionals should verify with other primary sources before using the advice. The next section will summarize a quick method for checking the credibility of various sources for biomechanical knowledge.

Evaluating Sources

The previous section clearly suggests that certain sources and kinds of evidence are more likely to be accurate. When evaluating the credibility of sources that fall at similar levels of rigor, the "me" test can be easily applied to judge the chance of the advice being a good and balanced representation of reality. The "m" stands for motivation. What is the motivation for the person or source providing the information? Sources with little financial interest in to making the observations/claims and who are dedicated to advancing a body of knowledge or human potential (scholarly journals) are much more likely to provide accurate information. The motivation of the popular press (TV, newspapers, magazines) and the internet (WWW) involves profit and self-promotion based on numbers of viewers and, therefore, is more prone to sensationalize and to not weigh all the evidence.

The "e" in the acronym stands for the key element of all science: evidence. Science is based on logical analysis and the balance of many controlled studies. This weighing of all the evidence stands in stark contrast to the more emotional claims of the popular press. The more emotional and sensational the language, even if it talks about "the latest study," the more likely you are reading only part of the whole picture. Remember that the structure of knowledge is a complicated structure built over time using many small pieces. The "latest" piece of the knowledge puzzle may be in error (see the next section) or will be rejected by most scholars as having flaws that make it less valuable as other research.

This simple "me" strategy is just the first step in learning more professional strategies for weighing evidence. In medicine and allied health there are formal methods for classifying the strength of scientific evidence called "evidence-based practice" to assist in diagnosis and treatment (Hadorn et al., 1996; Sackett et al., 1996). Authors have called the sports medicine and kinesiology professions to more consistently focus on using critical review of evidence to support practice (Faulkner et al., 2006; Knudson, 2005; Shrier, 2006).

One formidable barrier to a kinesiology professional's ability to weigh biomechani-cal evidence is the technical and specialized terminology employed in most studies. Throughout this text many of these measurement systems and mechanical terms are covered. Appendix A provides an extensive glossary of biomechanical terms and quantitative measurement systems. Two papers that provide good summaries of biome-chanical and exercise science terms are available (Knuttgen & Kraemer, 1987; Rogers & Cavanagh, 1984). Students re


On your next trip to a physician or other medical professional's waiting room, evaluate the nature of the articles and advertisements in the magazines and displays you encounter. Do advertisements related to claims in the articles appear near the article? Do the articles talk about several studies, their relative merits, as well as the percentage of subjects with various responses? Does the professional you are visiting sell supplements or products to patients? If so, what does this tell you about motivation and potential conflicts of interest between practice and profits? The biomechanics of most health and human performance problems in human movement are classic examples of complicated problems, with many interrelated factors and variability in the response of individuals to treatment.

viewing biomechanical studies should ask their instructor for assistance when the text or these sources do not clear up their understanding.

A Word About Right and Wrong Answers

The increasing amount and complexity of research and technology tends to give many people a false sense of the correctness of numbers. Few people will question a measurement if some machine output numbers on a printout, unless they are very familiar with the measurement. Like our knowledge-versus-information discussion, it is very important for kinesiology professionals to understand that the process of reviewing and weighing the evidence is often more important than finding the perfect or "right" answer. Such absolutes in a complicated world are quite rare, usually only occurring when a technique change would run against a law of physics or one of our principles of biomechanics. These principles (and laws) of mechanics are the application tools developed throughout this book.

So the good news is that biomechanics helps kinesiology professionals solve problems, while the bad news is that most of these everyday questions/problems do not have easy, dichotomous (right/wrong) answers. There are many factors that affect most phenomena and there is variation in nearly all phenomena. In fact, all true science is written using statistics to account for this variation. Statistics use estimates of data variation to attach a probability to any yes/no decision about the data. If you read a study that says an observation was significant at the 0.05 level, this only means that the result is not likely a fluke or observation due to chance variation alone. It is possible that chance alone created this "difference," and p < 0.05 means that in the long run there is about a 1-in-20 chance that the observation or decision about the data is wrong. Since most studies use this error standard (p < 0.05), this means that, out of twenty studies on a particular topic, one likely reports an incorrect observation from chance variation alone. A common misconception among laypersons is that statistics in a scientific study "proves" things. Statistics only provide tools that allow scientists to place probability values about yes/no decisions on the numbers observed in their research. Proof is a long-term process requiring critical review of the whole body of research on the issue. Remember this when television news broadcasts sensationalize the results of the "latest" study on some health issue or you are tempted to believe

Interdisciplinary Issue: Too Much Performance?

Recent controversies about sport performance enhancement through steroids and genetics parallel the issues related to biomechanics and improvements in equipment. Engineers and biomechanists have used advances in technology to improve the materials and design of sports equipment, although the use of tools in sport has a long history (Minetti, 2004). Jenkins (2004) presents a nice review of how improvements in equipment materials has dramatically affected performance in several sports. These are truly interdisciplinary controversies because there are ethical, safety, athlete, coaching, and sport/historical perspectives on performance. One example of technology correcting too much performance is the new rules for the javelin in the mid-1980s.The center of gravity of the the javelin was moved forward to decrease throwing distances because many athletes were throwing the old javelin over 100 m.Advances in biomechanics and computer technologies have also been used to modify technique, training, and equipment for the olympics (Legwold, 1984; Sheppard, 2006).

that one biomechanical study settles a particular issue.

Biomechanical knowledge is constantly changing and usually cannot be easily classified into always right or wrong answers, so there are two important professional tools you must not forget to use. These tools will work quite well with the biomechanical tools (nine principles) developed in this text. These two tools are the Swiss Army Knives™ or Leathermen™ of your professional toolbox because of they are so flexible and important. One is your ability to access biomechanical knowledge, and the other is the critical thinking necessary to evaluate and integrate knowledge so it can be applied in solving human movement problems. You are not likely going to remember everything in this book (though you would be wise to), but you should have the knowledge to access, and critical thinking tools that allow you to find, evaluate, and apply biomechanics to human movement. The rest of this text will illustrate and explicate the nine principles of biomechanics, which are tools you would do well to never forget when helping people improve their movement.

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