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Gene Influences Speed in Elite Athletes
By Nancy Touchette

Most track coaches sense that some runners are born sprinters and others are destined to go the distance. Despite identical training regimens, some athletes are built for speed and others for endurance. Now a new study suggests that a person’s genes may affect athletic ability.

Sprinter Jearl Miles-Clark, Olympic gold medal winner and currently ranked #1 U.S. female in the 400-meter dash.

Researchers in Australia find that a common variation of a muscle gene can influence whether a person is better at sprinting or endurance events.

“The genetic makeup of a marathon runner is different from a 100-meter sprinter,” says Kathryn North of the University of Sydney in Australia, who led the research. “Our genes have evolved to suit our environment. If you are out hunting lions, there is an advantage to being very fast, but if you are out walking around gathering berries all day, you are going to need endurance.”

The gene, called alpha-actinin-3 (ACTN3), codes for a protein that is only produced in fast-twitch muscle fibers. Fast fibers are powered by glucose and are responsible for generating power and speed. Slow-twitch muscle fibers are fueled by oxygen and are efficient for slower, sustained activity.

About 20 percent of the general population harbors a variation in ACTN3 that stops the protein from being made. The researchers looked for variations in the gene among a population of elite athletes at the Australian Institute of Sport in Canberra, a national center dedicated to identifying and training Olympic-caliber athletes.

They found that a higher percentage of sprinters tended to harbor two copies of the normal form of ACTN3, and a higher percentage of endurance athletes had two copies of the variant form of the gene.

Muscle cells appear to compensate for the lack of ACTN3 by producing a similar protein, called alpha-actinin-2, which is normally produced in slow-twitch muscle fibers. People who only produce alpha-actinin-2 have muscles that may be more suited to endurance activities.

Lance Armstrong, five-time winner of the Tour de France, a test of endurance.

Many other genes and environmental factors are likely to affect athletic ability. North estimates that 10 to 30 genes may be involved. For example, in a study of Russian athletes, a gene called ACE was shown to influence whether a person is better at sprinting or endurance.

Once all the genes that influence athletic performance are identified, North predicts, coaches and personal trainers could assess a person’s genes and decide what kind of training program might work best. And the military could test new recruits to see what types of activity might be a good match for their genes.

“Actinin is not the whole story,” she says. “But one might envision that in the future, a panel of genes could be used to predict whether an individual is better suited to sprint or endurance training.”

North and her colleagues are also examining the role of ACTN3 in disease. The researchers discovered the mutation while studying patients with muscular dystrophy, because fast-twitch fibers are more severely affected by the disease than are slow-twitch ones. They are now trying to determine whether ACTN3 variants might increase the risk of developing muscular dystrophy and other muscle-wasting diseases.

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Yang, N., et al. ACTN3 genotype is associated with human elite athletic performance. Published online in American Journal of Human Genetics, July 23, 2003.

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