To Stay on or Leave the Couch?

The New York Times reports this week on a new genetic test that purports to indicate whether an individual is likely to benefit aerobically from exercise.

The test is based on the findings of a 2010 study published in the Journal of Applied Physiology that examined the genetics of why certain people respond well to endurance exercises while others do not. In that study, researchers from several European and US research institutions used RNA expression profiling to produce a 29-RNA molecular classifier that predicts low maximal oxygen consumption, or VO_2max — a measure of the body's "ability to consume and distribute oxygen to laboring muscles," the Times writes.

Low VO_2max is a strong risk factor for premature mortality, according to the study's authors, and the authors hypothesized that the classifier genes that they identified would harbor DNA variants that contribute to a heterogeneous VO_2max response.

The group genotyped muscle tissue from volunteers who had completed six to 20 weeks of endurance training, and found that variations in their molecular classifier did indeed have a significant correlation with how much the rigorous exercise affected their overall fitness.

The lead author of the study, James Timmons, a professor of systems biology at Loughborough University in the UK, went on to co-found a company called XRGenomics, which now sells a test based on the findings.

Users are sent a cheek swab and asked to return a small tissue sample to the company, which in a few weeks provides information regarding whether the individual is a "low" or "normal" responder to aerobic exercise. The test costs around $318 for a basic report and about $478 for a more detailed explanation of the findings along with customized exercise recommendations from the company.

The test, called XRpredict+, is not the first genetic test on the market to gauge potential athletic performance or response to certain exercises, but it may be the most reliable given that it is based on a peer-reviewed study.

Nevertheless, critics of the test note that it relies on VO_2max, which is only one measure of how someone responds to exercise, thus limiting the assay's effectiveness, the Times reports. In addition, critics worry that users may take negative results to signify that they are destined to not benefit from exercise, and thus make the unhealthy choice of not bothering to exercise at all.