The 100 Most Influential Studies in Sports Medicine

One measure of the impact of a scientific idea is how often it gets cited by other scientists. The top-cited paper of all time, according to a 2014 analysis by Nature, has now been cited by 344,007 other scientific articles since its publication in 1951. (The topic? You’d never guess, for reasons we’ll get into below.) Researchers’ job prospects are influenced by their h-index, a measure that rewards having a high number of heavily cited papers (and perhaps, though no one would actually admit it, by their Kardashian index, which compares their cumulative citations to the number of Twitter followers they have).

You can also use similar techniques to analyze entire fields, which is what a new study led by Omeet Khatra of the University of British Columbia attempts for sports and exercise medicine. In the Orthopaedic Journal of Sports Medicine, Khatra and his colleagues put together a list of the 100 articles with the most citations in the field, offering a snapshot of the influence of both individual papers and broader trends. There are a bunch of interesting findings, but perhaps the most telling is this: only one of the 100 papers is a randomized controlled trial, which is the gold-standard type of experimental evidence.

The Field

One key caveat for this analysis is that the boundaries of sports and exercise medicine are pretty hazy. Khatra’s definition includes managing sports injuries, enhancing athletic performance, and the use of exercise to improve health. That’s very broad, but the method used to identify top papers was a little more idiosyncratic. They started by identifying a list of 46 journals focused on sports and exercise medicine, and then identified the 100 most-cited articles from within those journals.

That means significant papers published in non-specialist journals don’t show up on the list. A.V. Hill’s original 1923 study on VO2 max was published in the Quarterly Journal of Medicine; Karlman Wasserman’s 1964 paper on the anaerobic threshold was published in the American Journal of Cardiology. In fact, you’d expect that the most ground-breaking findings are the most likely to make it into generalist journals like Nature and Science (where, for example, a classic 1937 paper on the aerobic power of world record-setting runners was published).

So it’s not a comprehensive list, but it still covers a large fraction of the field. It’s dominated by Medicine & Science in Sports & Exercise, the flagship journal of the American College of Sports Medicine, which contributes no less than 49 of the papers. Next on the list are the American Journal of Sports Medicine, with 18, and Sports Medicine, with 7. The oldest paper on the list is from 1973, reflecting the field’s relatively recent emergence as a distinct discipline: MSSE, for example, was only launched in 1969.

The Champion

Topping the list with 7,228 citations was Gunnar Borg’s 1982 paper, “Psychophysical bases of perceived exertion.” Borg is the guy who advanced the concept of a subjective scale of perceived effort, which originally ran from six to 20, although there’s a more logical modified version that runs from zero to ten. He started developing this idea in the 1960s, but the 1982 English-language paper is the one that gets cited whenever people talk about perceived effort. (Another one of Borg’s papers on the topic, from 1973, shows up at 48th on the list.)

You might not think that asking people to assign a number to how hard they’re working is a major scientific breakthrough. But Borg’s work has had a huge influence. He argued that his scale is “the single best indicator of the degree of physical strain,” integrating signals from the muscles, lungs, heart, and brain. In the last two decades, more and more researchers have taken that argument seriously as they’ve attempted to explain the brain’s role in determining our physical limits, and also as a practical tool for guiding training. Bottom line: I’d say Borg’s paper is a worthy champion.

The Themes

The largest group of papers on the list focus on methodological tools: how to run a VO2 max test, how to calculate body composition, how to calibrate your pedometers and accelerometers, what validated questionnaires to use to ask your subjects about their exercise habits, and so on. That’s also what’s observed in other fields: the all-time most cited paper that I mentioned at the top is a methods paper on “protein measurement with the folin phenol reagent.”

Methods papers may not sound all that exciting, but they can certainly be controversial. Several of the papers on the list focus on statistics, including the number nine paper, from 2008, by Will Hopkins and colleagues: “Progressive statistics for studies in sports medicine and exercise science.” That approach to statistics is designed to tease out subtle performance effects in studies with small sample sizes. But it has come under intense criticism, most notably following a 2018 article in FiveThirtyEight by Christie Aschwanden arguing that it is more likely to produce false-positive findings than traditional statistical methods.

Another big bucket is official guidelines, mostly the ones issued by the American College of Sports Medicine on topics including resistance training, exercising with cancer, hydration, weight loss, blood pressure, and workouts for older adults. These are useful overviews to cite in the introduction to an article when you want to back up general claims like “exercise is good for you” or whatever, but they’re not particularly ground-breaking.

After that, it’s more of a mixed bag. The most popular part of the anatomy is the knee, which is the focus of 15 papers, mostly relating to ACL injuries. Next is the brain, which features in three papers on concussion in sport. Two other themes that rack up multiple mentions: the enduring mystery of delayed-onset muscle soreness, and the emerging health scourge of too much sitting.

There are three papers on the physiology of soccer, one on the biomechanics of baseball pitching, and one on Hakan Alfredson’s famous heel-drop protocol for Achilles tendinosis, which squeaks in at 98th place. (Funny backstory: Alfredson is an orthopedic surgeon who had Achilles problems back in the 1990s. When his boss refused to give him time off for surgery because the condition wasn’t serious enough, he decided to aggravate his Achilles with painful heel drops—but accidentally healed himself.)

The Evidence

I mentioned at the top that only one of the studies on the list is a randomized controlled trial, meaning that subjects were randomly assigned to either receive either an intervention or a placebo. Instead, most of the experimental papers use lower levels of evidence such as cohort studies and case series, neither of which use randomization or control groups. The biggest single category, with 38 papers, is narrative reviews, which survey the results of multiple studies on a topic but don’t pool them into one big meta-analysis.

I think most sports scientists would agree that the field needs more randomized trials, along with other methodological improvements like bigger subject groups and more sophisticated statistical analyses. But the faults in the top-100 list probably aren’t specific to sports science. Watson and Crick’s discovery of the structure of DNA and Einstein’s theory of general relativity don’t make their respective lists either: the biggest breakthroughs become textbook material that doesn’t even require a citation. “If citations are what you want,” Yale University chemist Peter Moore told Nature, “devising a method that makes it possible for people to do the experiments they want at all, or more easily, will get you a lot further than, say, discovering the secret of the Universe.”


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Outside Magazine: Health

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