Genetics and Athletics: Is It in You?

BY Mike Melia  May 12, 2010 at 11:15 AM EST

Great athletes are often referred to as “naturals” in their respective sports, but how much of their talent can be traced back to DNA is still uncertain to scientists. Are there genes that make some of us fantastic sprinters? Was Michael Jordan just born with the right mitochondrial makeup to be a basketball star?

Since the release of the full human genome in 2003, researchers have been trying to pinpoint the specific genes and genetic mechanisms for everything from diseases to intelligence. Athletics is no exception. In this week’s Sports Illustrated, which hits newsstands Wednesday, David Epstein writes about the latest research to examine how much of athletic performance is genetic.

“Essentially everybody falls in the muddled middle, differing by only a handful of genes,” Epstein writes. “It’s as if we’ve all played genetic roulette over and over, moving our chips around, winning sometimes and losing sometimes and gravitating toward mediocrity.”

There are some genetic markers that have been identified to contribute to athletic ability. The ACTN3 gene, for example, has been linked with speed. We all have two copies of ACTN3, which controls the production of a protein found in muscle fibers responsible for explosive or quick movement. Although we all have two copies of the gene, it comes in two variants, an R and X. The X variant prevents the protein for being created, so having two X variants of ACTN3 blocks the muscles from getting this quick movement protein. Researchers who have been examining the DNA of current and former world-record-holding runners are yet to find even one of them with two Xs, while eighteen percent of the control group of “normal” people did.

“Another 2006 study, of more than 37,000 pairs of adult fraternal and identical twins from six European countries and Australia, concluded that about half to three quarters of the variation in the amount of exercise people engaged in could be accounted for by their genetic makeup, while environmental factors, such as access to a gym, often had less influence,” writes Epstein.

However, other studies have highlighted the impact of environmental factors on athletic performance. Ethiopians and Kenyans hold claim to the 18 fastest marathon times in history, and the top 10 100-meter sprinters are all of African descent. Genetically however, Ethiopians and Kenyans vary widely, more so than general populations outside of Africa. Yannis Pistaladis of the University of Glasgow has been studying the East African runners and found that 81 percent of elite Ethiopian runners relied on running to get to and from school as children.

We spoke with David Epstein about these findings and how they may affect the future of competitive sports.