Emily Hu had always considered herself a mediocre athlete. Short legs made her a terrible runner, she says, and poor upper body strength made pull-ups an exercise in frustration. But the 33-year-old Californian stayed in shape through the years by practicing martial arts and hitting the gym regularly, never losing the desire to be “really strong.”
So no one was as shocked as Hu when she showed up at her first powerlifting competition three years ago, which she’d entered out of “pure curiosity,” and swept all three events — squat, bench press, and dead lift. It was a breakthrough moment, with Hu discovering previously untapped potential that transformed her self-perception.
“I thought, if monkeying around at the gym could get me these results, think what hiring a professional could do,” recalls the medical device researcher. Hiring a coach and training some 10 hours per week has since produced phenomenal results: Hu is now a champion powerlifter, ranking in the world’s top 10 overall and breaking two world records in the bench press.
Another shot of curiosity prompted Hu last year to undergo direct-to-consumer (DTC) genetic testing to reveal markers for athletic performance. But she was skeptical that such tests, which are said to spot athletic prowess or help tailor training to optimize performance, would yield any surprises.
This time, Hu was right: No revelations awaited. If anything, the results of the test, which analyzed 58 gene variants indicating performance type and genetic predisposition for injury, were underwhelming. They revealed she carries a variant in the ACE gene that’s associated with strength and power-oriented performance, meaning “my ability to build muscle mass is higher than the average person,” Hu says. “But there was nothing else that made me special as an athlete.”
“My guy friends were hoping I was a freak of nature, which explains why I can whip them in the gym,” she adds, “but I’m pretty much just slightly stronger than the average girl.”
Bold Claims Met with Caution
Hu’s genetic testing seems to underscore the notion that her winning athlete status is due to far more than DNA destiny. But a growing market for DTC genetic tests for athletic performance has created a tug of war between some testing companies making bold claims — particularly to parents eager to groom their offspring as sports phenoms — and genetics experts cautioning that existing scientific evidence hasn’t yet caught up to the promises.
Concern is so strong that an international panel of experts issued a consensus statement in the British Journal of Sports Medicine in November 2015 declaring that no child should be subjected to genetic testing to determine sporting talent or boost performance. (See “Ethical and Legal Issues Surround Testing Kids for Sports Performance,” page 31.) With limited knowledge of the role of genes in sports performance, the group is concerned that DTC tests — typically costing hundreds of dollars or more — misrepresent the science behind the tests to fleece the public.
People are interested in finding out if their genetic profile means they should focus on strength or endurance. But from that to the idea that the tests being sold can actually predict anything about performance? At the moment, that’s a far leap.
“It’s not money well spent,” says panel member Claude Bouchard, the John W. Barton Sr. chair in genetics and nutrition at Pennington Biomedical Research Center in Baton Rouge, Louisiana. “Most companies will tell consumers these genetic variants have the potential to define your predisposition to become an athlete, that you have the genetic characteristics shared by world-caliber athletes. That’s their main pitch.
“Many of them also say knowing about your DNA profile could guide you in individualizing your training regimen in order to optimize performance, which is even more complicated,” Bouchard adds. “But none of their genomic markers have that potential — none.”
Perhaps predictably, not everyone in the field shares Bouchard’s hard-line stance. There is notably more debate over the value of genetic tests in shaping athletes’ training and injury prevention efforts. But there’s no question about the massive interest among coaches, parents, and even casual athletes as the tests became easier to find, Bouchard says, particularly over the last five years.
As of late last year, more than three dozen companies around the world were marketing genetic tests in relation to sport or exercise performance or injury, a number that has almost doubled since 2013. Since they’re sold directly to consumers, often by mail, people of any age can easily do the cheek swab that tests typically require; it’s unclear if all companies require buyers to prove they’re over 18.
Some DTC companies push the idea of gaining a competitive advantage by being tested. “The earlier the child starts, the easier it is to get a head start over other children,” one company asserts. Other claims are less sensational, exhorting consumers to “Take advantage of your inherent strengths and overcome your limitations” or “Discover how your genes contribute to your athletic traits.”
Most-Studied Variants Linked to Power, Endurance
Much of the newer research on how genes contribute to athletic performance stems from initial studies done more than 30 years ago on how genes involved in exercise response impacted risk for health problems such as cardiovascular disease and diabetes, Bouchard notes. But when the data also seemed relevant to sports, a new field was born that to date has led to more than 1,400 studies on genetics and athletic performance. Upwards of 200 genetic variants have since been linked to physical performance, with more than 20 variants associated with elite athlete status.
“However,” says Bouchard, “for each of these variants there are as many negative reports as there are positive studies. On balance, the evidence is extremely weak that some common genomic variants have a favorable or detrimental effect on physical performance.”
Of all mutations studied, two have received the most attention: the ACE and the ACTN3 genes. Two different variants of the ACE gene, which helps regulate blood pressure and cardiac and respiratory efficiency, spell very different scenarios. One indicates a predisposition for endurance events, notably triathlons; the other — affecting Hu — denotes enhanced performance in strength- and power-related tasks.
Meanwhile, the ACTN3 gene produces a protein regulating the function of so-called fast-twitch muscle fibers, which produce rapid, forceful muscle contractions needed for activities such as sprinting and weight lifting. Carrying the ACTN3 R577X variant has been associated with elite sprinters.
Beyond those two, research on mutations related to injury predisposition and nutrition — both of which can affect optimal sports performance — is becoming more widespread. A variant in the COL1A1 gene, for example, is associated with anterior cruciate ligament (ACL) ruptures, considered the most severe injury sustained in sports; a variant in the HFE gene leads to higher risk for hemochromatosis, an overload of iron that can result in overwhelming fatigue.
“A Far Leap” for Genetic Variants to Predict Performance
But how accurately can these variants actually predict how well someone will perform in sports?
“It’s not difficult to imagine that we know genes can influence your response to training — that’s absolutely clear,” says Mikael Mattsson, a visiting assistant professor of physiology at Stanford University in California and managing investigator of its ELITE study, which is analyzing the world’s best endurance athletes to determine if they share a specific genetic profile as well as inherited and environmental factors in performance.
“People are interested in finding out if their genetic profile means they should focus on strength or endurance,” Mattsson adds. “But from that to the idea that the tests being sold can actually predict anything about performance? At the moment, that’s a far leap.”
Mattsson’s view is backed by scientists’ assertions that only limited information can be gleaned from the weak, scattered efforts undertaken by many of the studies so far, most of which focus on single-marker genetic tests. Another drawback is that a large percentage of a population may carry a specific mutation without ever becoming especially competitive in sports. An estimated 20 million of the United Kingdom’s 65 million residents, for example, have the ACTN3 variant, but only a tiny fraction are elite athletes.
“These genomic tests have no scientifically established predictive value,” says Bouchard, noting that MoTrPAC, a major research initiative launched in 2015 by the National Institutes of Health, should generate useful data. “We’re seeding for the long term, but it takes a lot of resources, it’s expensive, and there’s no other way around it. Most studies so far are small and underpowered, and the literature is full of false positives.”
Not All DTC Testing Companies “Shady,” Officials Say
But leaders of some DTC companies contend that their tests’ value is not necessarily as cut and dried as scientists argue and that more nuanced purposes are just as valid.
“Someone may want to understand why is it that she works out like a maniac in the gym all the time but has no muscle definition,” notes Trisha Brown, a licensed certified genetic counselor and CEO of Kinetic Diagnostics in Berkeley, California. “She may have a variant showing her strength training response is decreased compared to others, and it’s meaningful to her that she doesn’t respond at a rate that some others might.”
Kinetic Diagnostics and the London-based DNAFit are two DTC companies that explain on their websites about the several dozen variants their tests analyze. But such transparency isn’t the norm. Only 18 of the 39 companies selling such tests clearly presented information on their websites about the genetic variants they evaluate.
“There are loads of companies and the quality of each is quite different,” says Craig Pickering, head of sports science for DNAFit and a former Olympic athlete for the U.K. in sprinting and bobsled. “It’s an unregulated industry, so we have to take the initiative here. We’re aware that from the outside looking in, it looks like the industry could be doing some shady stuff, so we’re really being proactive.”
Ultimately, Pickering, Brown, and academic experts all agree that athletic excellence isn’t achieved only through inborn talent, but through a complex set of factors including training, nutrition, injury prevention, and — not least of all — determination and grit.
“I don’t think any test out there can truly predict athletic ability, although I think it can be helpful in picking a sport or a position on the field,” Brown says. “But if you don’t have passion, you’re not going to become an elite athlete.”