The Genetics of Fitness
Why do some people respond to an aerobic workout routine by becoming incredibly fit, but others who exercise just as hard for months end up no fitter than when they began? According to the new study, which will soon be published in The Journal of Applied Physiology, part of the answer may depend on the state of specific genes. For the study, researchers from the Pennington Biomedical Research Center in Baton Rouge, La., and other institutions examined the genomes of 473 healthy white volunteers. In such studies, researchers examine virtually the entire genome of people with various traits, often diseases. The aim is to discern whether tiny segments of DNA called single-nucleotide polymorphisms, or SNPs (pronounced “snips”), recur frequently in those with the traits.
The presence of particular SNPs suggests that a particular snippet of the genome affects susceptibility to a disease or, in this case, exercise. Each of the volunteers had already completed a carefully supervised five-month exercise program, during which participants pedaled stationary bicycles three times a week, at controlled and identical intensities. Some wound up much fitter, as determined by the increase in the amount of oxygen their bodies consumed during intense exercise, a measure called maximal oxygen capacity, or VO2 max. In others, VO2 max had barely budged.
The researchers identified 21 specific SNPs, out of the more than 300,000 examined, that differed consistently between the two groups. One SNP in particular, located on a gene known as ACSL1, seemed especially potent, possibly accounting for as much as 6 percent of the difference in response among people. But, said Claude Bouchard, who holds the John W. Barton Sr. Endowed Chair in Genetics and Nutrition at Pennington and was lead author of the study, “far more research is needed before we can say” just how any particular gene influences the body’s response to aerobic exercise, let alone what additional genes might be involved in that response.