Sports Genes

THE SPEED GENE

YANNIS PITSILADIS always keeps a few cotton swabs and Ziploc bags in his carry-on, just in case he runs into a world-record holder. In a decade of traveling to Ethiopia, Kenya and, more recently, Jamaica, Pitsiladis has learned that the concentration of elite track and field athletes in the three countries—sprinters in Jamaica and distance runners in Ethiopia and Kenya—is so high that he is liable to bump into one on a plane in Kingston or at a table in a coffee shop in Eldoret, Kenya.

Whenever he meets such athletes, Pitsiladis, a biologist at the University of Glasgow, entreats them to give him saliva or bits of the insides of their cheeks. Pitsiladis is collecting the DNA of champions to see what they are made of. In his lab he has stored the biological blueprints of nearly a thousand elite long-distance runners and sprinters, among them many African world champions and world-record setters, both living and dead. Pitsiladis has begun scanning these genomes for performance genes, so that humanity might know the slate upon which nurture can etch greatness.

Scientists have linked more than 200 genes—albeit tenuously in most cases—to physical performance. Take ACTN3, the so-called speed gene, one of the most thoroughly studied performance genes. In 2003 a seven-scientist team published a study in The American Journal of Human Genetics in which 429 elite Australian athletes were tested for the ACTN3 gene. All people have two copies of that gene, each of which comes in one of two variants, R or X. The R variant instructs the body to produce alpha-actinin-3, a protein found only in fast-twitch muscle fibers, the kind that contract rapidly and violently to facilitate explosive movement, while the X variant prevents the protein from being created.

Eighteen percent of the "normal" people used as a control group had two X copies, and thus none of the power protein in their muscles. But not a single one of the 32 Olympic sprinters in the study had two X variants. Similarly, of the sprinters whom Pitsiladis has analyzed so far, not one current or former world-record holder has two X variants.

Such findings quickly transcended mere chatter at an academics' cocktail party: In the wake of the '03 study, the Manly Warringah Sea Eagles of Australia's National Rugby League began testing players so that workouts could be tailored for those apparently more disposed to explosive powerlifting and sprinting; and for $169 Atlas Sports Genetics in Boulder, Colo., will test your child for ACTN3 so that you can decide early on whether to steer the tot toward sprints or endurance sports. And it goes beyond ACTN3: The Duke football team, for instance, sought institutional permission to submit players' DNA to a university researcher who will look for genes that predispose players to particular injuries.

Studies that assess genes with an eye toward differentiating Joe Frazier from Joe Montana and Joe Mauer from Joe Sixpack now come out regularly, identifying stretches of DNA that appear to influence the power of someone's grip, for example, or the strength of his ACL. Genes have been implicated not only in how much better an individual's aerobic capacity will get with regular bicycle training—the answer for some people, surprisingly, is "not at all"—but also in how likely he is to get off the couch in the first place.

Still, as more and more genes with subtle effects on athleticism have been identified, the predictive value of any single-gene test for talent, such as the ACTN3 tests offered commercially, has fallen essentially to nil. In 2008 Pitsiladis tested Colin Jackson, a British former world-record holder in the 110-meter hurdles, for ACTN3. "He had the right version," Pitsiladis says, "but so do I." And so do billions of people worldwide, but that doesn't make them world-class sprinters. In fact, it seems that all an ACTN3 test can do consistently is tell someone he isn't going to make the Olympic 4 × 100 relay team. But even that sweeping conclusion leaves room for exceptions, such as the Jamaican sprinter who was recently found to have the "wrong" copies of the explosiveness gene, or the Spanish long jumper who also has them yet sailed more than 27 feet and twice made the Olympics.

"He obviously still found a way to be pretty springy," says Carl Foster, director of the Human Performance Laboratory at Wisconsin--La Crosse and co-author of several ACTN3 studies. "If you want to know if your kid is going to be fast," Foster adds, "the best genetic test right now is a stopwatch. Take him to the playground and have him race the other kids."

The case of the curiously alpha-actinin-3-deficient long jumper means that running and jumping are influenced by a tangled skein of genes, not to mention training. So far, around two dozen genes have made strong scientific cases for inclusion in the equation of explosiveness, as have about two dozen for endurance.