Why do some people get fitter than others?

Two women running outdoorThe response to exercise training is often described in general terms, with the assumption that the group average represents a typical response for most individuals. However, in reality, it is more common for individuals to show a wide range of responses to identical exercise programs. In 1999, a large study published by Claude Bouchard and colleagues, reported that 20 % of us show little or no gain in maximal oxygen consumption (VO2max) with exercise training. This is a concern, since a high VO2max is associated with decreased rates of cardiovascular morbidity and mortality. Exploring the phenomenon of high responders and low responders following the same exercise program may provide helpful insights into mechanisms of training adaptation and methods of training prescription.

By studying rats with inborn large differences in exercise response (High Responders and Low Responders), our research group has, together with long-term collaborators at the University of Michigan, explored the cardiac differences at genetic and cellular level. After 8 weeks of exercise training, the High Responders increased their VO2max with 40%, whereas the Low Responders showed no improvement.

Print screen from New York TimesYou can also read about this study in The New York Times, “Exploring Why Some People Get Fitter Than Others”.

We found that the High Responders hearts grew and resembled athlete’s heart and improved cardiomyocyte contractility after exercise training, whereas no improvements were found in the Low Responders, indicating that changes in cardiomyocyte contractility accompany changes in VO2max. When studying every single gene expressed in the heart, the gene with the largest difference between High Responders and Low Responders was osteoglycin, which previously has been linked to cardiac growth.

Read also: Tailor exercise for your DNA

This gene represents an interesting target to further study the mechanisms behind differences in responses to exercise training. After working on this study for about 10 years, it was finally published last week in the high-ranked Journal of the American College of Cardiology.

The potential lesson of the new study would seem to be that we should closely monitor our body’s response to exercise.

“If after months of training, someone is not able to run any farther than he or she could before, maybe it is time to change the intensity or frequency of the workouts or try something else, like weight training. The genes that control the body’s responses to that activity are likely to be very different than those involved in responses to aerobic exercise”, Leader of CERG, professor Ulrik Wisloff said to The New York Times.

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Ulrik Wisløff, Professor and leader of CERG, researcher Anja Bye and researcher Tomas Stølen

One thought on “Why do some people get fitter than others?

  1. Duh! We are all different? If we were machines, then that question would really mean something. #Thetrainer

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