Do you have the exercise gene?

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Last fall, there was a flurry of excitement about the tests being offered by Atlas Sports Genetics, which promised to determine whether you had a predisposition to strength or endurance sports depending on the presence of a variant in the ACTN3 gene. Overbearing parents of young toddlers rushed to sign up.

In a similar vein, it’s now well established that the desire to exercise — the seemingly personal choices we make about whether to spend our leisure hours playing violin or simulating stairclimbing on a machine at the gym — depends to a significant degree on genetic factors. In fact, a 2006 study of more than 85,000 adult twins from seven different countries found that between 48% and 71% of the variance in exercise behaviour is explained by genetic factors.

“So what’s the gene,” you ask, “and do I have it?”

Well, you’re in luck: a new study has been accepted for publication in a future issue of Medicine & Science in Sports & Exercise, titled “Genome-Wide Association Study of Exercise Behavior in Dutch and American Adults.” They did find genetic linkages, and here they are:

Thirty-seven novel SNPs in the PAPSS2 gene and in two intergenic regions on chromosomes 2q33.1 and 18p11.32 were associated with exercise participation (pooled P values <1.0 x 10-5). Previously reported associations (ACE, CASR, CYP19A1, DRD2, LEPR, and MC4R genes) or linkage findings (2p22.3, 4q28, 4q31.21 7p13, 9q31, 11p15, 13q22, 15q13, 18q12.2, 18q21.1, 19p13.3, and 20q12) were not replicated…

So what does that mean? They found tons of links between genes and exercise behaviour. But they didn’t find the same links that 10 past studies have found, and none of the links so far appears to have a strong effect. Instead, there appear to be a whole bunch of genetic factors that each contribute a little bit to your exercise behaviour. In identical twins, they’re all the same. But in the rest of us, there’s no single gene that divides couch potatoes from Ironmen.

Interestingly, this is similar to some of the criticism levelled at Atlas Sports Genetics:

“The idea that it will be one or two genes that are contributing to the Michael Phelpses or the Usain Bolts of the world I think is shortsighted because it’s much more complex than that,” [Dr. Stephen Roth of the University of Maryland] said, adding that athletic performance has been found to be affected by at least 200 genes.