DNA’s Role in Aerobic Exercise Capacity

by Sarah Gold

As a student at the Friedman School, I’m surrounded by marathon runners, triathletes, fitness instructors, and other exercise fanatics. Of course, we are all concerned about health and fitness; we’re studying nutrition! But how is it that so many of us are such serious, often competitive, athletes? Sometimes it seems like it’s just in our blood. Or maybe it’s in our DNA?

A recent study, conducted as part of the HERITAGE Family cohort study, shows evidence that genetics may play a role in the ability to increase overall physical fitness level. The HERITAGE Family Study, founded in 1992, was developed to look at the role of DNA in cardiovascular and metabolic responses to aerobic training as well as the effects of regular exercise on risk factors for cardiovascular disease and diabetes. To date, over 120 articles have been published from this study. The latest paper discussed the relationship between specific genes and the ability to increase physical fitness level over a 5-month period, as measured by maximal oxygen capacity, or VO2 max.

473 individuals from 99 all-white families completed a 20-week cycling program; all were considered healthy, but sedentary prior to the study. The participants rode the bike 3 times per week for increasing time intervals, reaching specific heart-rate goals each ride. VO2 max measurements were taken at baseline and at the end of the 20-week program.

After the intervention, participants saw a wide range of aerobic fitness improvement, none of which correlated with age, sex, body mass index, or perceived commitment. The researchers did, however, find a relationship between the presence of specific single nucleotide polymorphisms, or SNPs (pronounced ‘snips’ in the molecular biology world), and physical fitness level. SNPs, which are tiny segments of DNA, can vary among individuals. This variation allows researchers to identify an interaction between certain SNPs and physical activity level. In fact, the researchers identified 21 SNPs that accounted for about 50% of the variance in training ability. SNPs have been tied to susceptibility to disease in previous research; however, this was the first study to test the relationship between them and exercise ability.

Study results showed that those possessing 19 of the 21 SNPs, or specific DNA variations, led to a 3-fold improvement of VO2 max when compared to those who carried 9 or fewer of the SNPs.  Interestingly, one of the SNPs, which was said to account for 6% of the variation alone, is located on a gene that has previously been tied to lipid metabolism. It is hypothesized that this association may be responsible for the difference in exercise ability. This study was replicated in 247 HERITAGE Family Blacks from 105 families and results, while positive, were not quite as strong and fewer of the SNPs appeared to be involved in the process.

Does this mean that if you find yourself struggling to increase your endurance level, you are lacking these specific SNPs? Not necessarily. These results are preliminary and further, larger studies are necessary to apply these findings to the general public. Additionally, as shown with the comparison of the Caucasian and Black participants, ethnicity likely plays a role in the process.

This is a big step in understanding the interplay between genetics and physical activity levels. However, it’s unclear what we can do with this information at the moment. I will say, though, this is certainly not an excuse for those who find exercise difficult to sit on the couch. Even if you’re not significantly increasing your aerobic capacity, exercise still provides several important health benefits.

Sarah Gold is a first year Nutrition Communication student and is also part of dual program with Simmons to pursue her Dietetic Internship. A born New Yorker, but Cali girl at heart, you can find Sarah on the ski slopes, on a bike, or in the kitchen testing out new recipes.

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