Are You Genetically Programmed to Respond to Exercise?

While there is abundant evidence that exercise is of benefit to all of us, there is a growing body of evidence that some of us respond to it better than others. This was not exactly a surprise to me, because back in my teen years I decided to become a champion runner. I set upon a rigorous program of running every day, with the goal in mind of increasing both my speed and endurance, and thus finally qualifying for my school’s mixed-gender track team. Honestly, my goal was somewhat less than an altruistic desire to win medals for my school; I had a crush on a member of the track team and hoped that if I made the team I’d have a better shot at a romance.

Alas, neither was to be. My endurance did increase, but my running speed never really did. I got healthier and more fit, but never fit enough to win races. I always felt that this was some kind of failing on my part, and that if I’d just worked out harder, I might have made the fitness grade. But research performed in Finland and published in Medicine and Science in Sports and Exercise makes me feel a little better. The fault may have been in my genes, not in my determination.

Everyone benefits from exercise, but some more than others

In the Finnish study, 175 adults with a basically sedentary lifestyle completed a 21-week exercise program. A third of the subjects walked or jogged, another third lifted weights several times a week, and the final third did both, while their fitness levels and muscular strength were carefully monitored. The initial objective of the study was to determine which of these three exercise regimens produced the highest levels of fitness.

The results were on one level disappointing, in that none of the three forms of exercise proved superior. But they revealed another, more interesting phenomenon – many of the subjects improved their fitness levels and strength tremendously, others saw only minor levels of improvement, and a few (8 percent) actually became less fit. Some became more aerobically fit but not stronger, some vice-versa, and a few showed no improvements in either area. As the researchers wrote with more than a hint of understatement, there were “large individual differences in the responses to both endurance and strength training.”

Several theories were proposed for why this was true. The first, naturally, was genetics. Biology professor James Timmons instituted a follow-up study and found that his researchers could make fairly accurate predictions of who would respond most successfully to endurance exercise training based on how 29 genes were expressed in their muscle structure. Interestingly, the 29 genes don’t necessarily have a direct relationship to exercise; rather, they control the ability to develop new blood vessels in muscles.

The result? New tests to tell whether you have “good exercise genes” or not

Following up on Timmons’ work, a company called XRGenomics has developed a series of tests that can be used (even at home) to determine whether you are a “low” responder to endurance training or a “high” responder. You simply take a swab sample from the inside of your mouth, send it to the company, and they’ll send you back a report on your gene fitness quotient. This test and report doesn’t come cheap, however; the basic test kit plus a detailed report that provides customized exercise recommendations from the company’s scientific advisory board costs $480.

While the results of these DNA tests may be of interest to those with deep pockets, and of use to those who hope to become competitive athletes, one co-author of Timmons’ original study cautions that you shouldn’t read too much into them, and that their predictive value is negligible. The tests can indicate a general responsiveness to endurance training or a lack thereof, but are based on only one measurement – VO12 max, the ability of your body to process oxygen and distribute it to your muscles. The tests will not tell you whether or not an endurance training exercise program will help you to lose weight, or lower your blood pressure; those things are controlled by a different set of genes.

Still, the results of these tests might be seen as positive by people who have undertaken aggressive exercise programs and are wondering why they don’t seem to have benefitted from them as much as their neighbors have. But even if your genes don’t make the grade, that doesn’t mean you won’t benefit from exercise. The genes being tested for account for only 23% of your body’s response to and ability to benefit from exercise, after all; the other 77% is still up to you. If you don’t wind up having “good exercise genes” you may never become a champion athlete, but you’ll be slightly healthier after each workout anyway, and that’s nothing to sneeze at.

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Juliette Siegfried, MPH

Juliette Siegfried, MPH, has been involved in health communications since 1991. Shortly after obtaining her Master of Public Health degree, she began her career at the National Institutes of Health in Bethesda, Maryland. Juliette now lives in Europe, where she launched ServingMed(.)com, a small medical writing and editing business for health professionals all over the world.

Juliette's resume, facebook: juliette.siegfriedmph, linkedin: juliettes, (+31) 683 673 767

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