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Genetic testing can’t capture complexity of athletic performance

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Leveraging advances in genetic testing, scientists have spent years searching for the genes that contribute to athletic success. However, as more studies are published, they reveal it is unlikely that society’s current understanding of the subject will allow anyone to identify athletic potential based on genetics.

As athletes look to gain an edge, genetic testing has the potential to help identify athletic talent and explain where it comes from, but the science is not yet reliable enough to make accurate predictions.

Researchers from Stanford University’s department of medicine reached this conclusion in a study published in 2016. While the researchers admit scientists have known for 30 years that certain physiological traits important for sports performance have genetic components, it is too hard to identify all of them.

In the early days, there were great hopes to find THE sports gene,” wrote the study’s primary author, C. Mikael Mattsson. “However, due to the wide range of traits and factors contributing to athletic performance, such a quest is inevitably bound to fail.”

The study suggests the reason this pursuit is bound to fail is due to deficiencies in past research. To remedy this, the Stanford researchers point out those interested in sports genetics should learn from the past mistakes of human disease genetics. In their conclusion, the researchers highlight four ways to do this.

The first way is to look at a larger number of traits than past studies. Most current tests look at individual genes that contribute to endurance, power and recovery. However, since the attributes that contribute to sports performance and the underlying genes associated with them are so complex, basing analyses on such a narrow set of genes will not help move this field forward.

The second way, they suggest, is to use much larger sample sizes to better identify common traits. The researchers also claim that finding rare traits with greater impacts on performance require studies across ethnic groups and families.

The third way is scientists must demonstrate the results of past research can be replicated, avoiding generalizations about the impact certain genes have on a population. This will also require analyses on specific ethnic groups, as well as different sexes.

The final way is by collaboration and focusing on better study design to help overcome the overestimations and incomplete associations that make current sports genetic testing inaccurate.

Nature versus nurture

Others believe testing for sports genes isn’t sufficient by itself for different reasons. In David Epstein’s book “The Sports Gene,” he uses his experience as a college runner to highlight the importance of non-genetic factors of an athlete’s success.

The truth is, even at the most basic level, it’s always a hardware and software story,” Epstein wrote. “Sport skill acquisition does not happen without both specific genes and a specific environment, and often the genes and the environment must coincide at a specific time.”

A review of the book by The Washington Post explained Epstein’s findings that factors such as an athlete’s passion and determination are equally important qualities when compared to any genetic advantages.

At the same time, Epstein doesn’t deny the potential impact of genetics. Like the Stanford researchers, a review from The New York Times pointed out Epstein’s understanding of the situation’s complexity. As an example of how athletes can reach similar performance levels through different genetic pathways, Epstein compared himself to an old college teammate.

While Epstein said running came naturally to his teammate, he had to work many times harder to achieve the same level of performance. This led him to theorize that while he had a low baseline running ability but the potential for rapid growth, his teammate had a high baseline running ability with less room to improve.

This allowed both runners to reach similar levels of skill, but the New York Times review pointed out how the difference in their paths changed the way they were perceived.

It was David who got credit for guts and grit, while Scott was written off as a head case who was squandering his talent,” journalist Christie Aschwanden wrote. “Narratives matter, Mr. Epstein argues, and many of the ones we tell are flat wrong.”

While some genetic tests can claim to predict a person's athletic potential, some professional cyclists found their results didn't line up with their actual performance. (Photo courtesy JONATHAN NACKSTRAND/AFP/Getty Images)

A misleading market

The narratives that come out of genetic testing in sports can be as unexpected as they are wrong. In an article published on Bicycling.com, author Bill Gifford laid out his quest to crack the validity of sports gene testing after results claimed he had low aerobic potential.

While Gifford is the first to admit he is far from an elite cyclist, he said he expected at least an above average rating. Eventually this led him to wonder whether there was either a mistake with his test or if it provided incomplete information.

To find out, Gifford sent additional genetic tests to different companies and persuaded some professional cyclists to take part to see how their results compared. Retired cyclist Jens Voigt and Olympic cyclist Taylor Phinney both had high aerobic potential, but former professional Phil Gaimon received the same result as Gifford.

The difference between Gifford and Gaimon, though, is a long career on both domestic and international cycling teams. So, if Gaimon could succeed in an endurance sport such as cycling with low aerobic potential, what did that mean about the importance of genetic testing and sports?

Gifford’s journey took an even more confusing turn when the results from the three other genetic testing companies came in. One confirmed the results of his first test. Another labeled his potential as normal. One said he “was a genetically gifted endurance god.” This led Giffords to wonder whether each company used different methodologies, and if any of them could be trusted.

“They absolutely could be using different variants to test the same phenotype,” said Emily Spencer, the Associate Director of the Scripps Research Translational Institute in La Jolla, California, who spoke to Gifford for his article. “It doesn’t necessarily mean either is ‘wrong,’ just that neither is the complete story.”

Genetic testing potential low, for now

Together, these three looks at genetic testing in sports paint a similar picture: Science still can’t definitively point to a person’s athletic success using genetics. There simply hasn’t been enough research testing enough genes in enough people.

However, no one seems to rule out the possibility of accurate genetic testing in the future. Once scientists can fully understand the complexity of which genes give the greatest athletic benefits, tests might finally be a viable tool.

Jason Krell is a masters of sports journalism student at Arizona State University

Editor’s note: For the coming 2019-2020 academic year, the Global Sport Institute’s research theme will be “Sport and the body.” The Institute will conduct and fund research and host events that will explore a myriad of topics related to the body, including the use of genetic engineering in sport.

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