People who are unfit – who have low maximal oxygen consumption or low aerobic capacity – are at an increased risk for early death. Unfortunately, exercise won’t fix this for everybody. Some people become much fitter after endurance training, but 20% of us don’t respond at all. And how fit you are before training doesn’t always correlate with how fit you will become after training. Someone who doesn’t exercise could have quite high aerobic capacity and someone who has trained for a long time might have quite low aerobic capacity.
So a group of scientists looked to see whether gene variations might explain the different responses to exercise. When this study was done, in 2010, it was still expensive and time consuming to sequence the whole genome. So they first looked for genes that were turned on or off (had higher or lower expression) in muscle after exercise, then sequenced these genes to look for variations. They then sorted out which variations occurred in people who became much fitter after 20 weeks of endurance training and which occurred in people who didn’t respond to exercise training.
In the first stage, 24 young healthy men trained three times a week for 20 weeks. Then gene expression levels were measured in a muscle biopsy from each man. Eight hundred genes were changed in muscle by exercise training. These genes were involved in energy production (oxidative phosphorylation) and muscle contraction and stiffness (calcium signalling and extracellular matrix). However, only 29 genes predicted whether someone responded to training or not. The scientists then double checked that these 29 genes were altered in a second group that trained for 10 weeks, and they were.
So the scientists went on to see whether they could find mutations or variations in these genes that predicted response to exercise training, and whether any variations were inherited. To do this, they enrolled 99 families in an endurance training program. The families trained three times a week for 20 weeks. Their maximum oxygen consumption was measured before and after training and the 29 exercise predictor genes were sequenced in each family member. It turned out that the increase in fitness in response to exercise is 47% heritable. So if you have a fit parent, that doesn’t mean that you will be fit, and vice versa. The increase in maximal oxygen consumption was 47% heritable. Variants in 11 genes accounted for 23% of the variability in response to exercise. The genes were: SVIL; SLC22A3; NRP2; TTN; H19; ID3; MIPEP; CPVL; DEPDC6; BTAF; DIS3L.
A bigger study with more participants might be able to uncover more variants or account for a higher percentage of the variability in exercise-induced aerobic fitness. Or these results may simply show that different people respond optimally to different exercise. So if you like yoga more than running, maybe your body responds better to yoga? Maybe one day we’ll have a genetic test that predicts the best type of exercise for each person. For now we don’t know enough to be sure about anything except that some exercise is better than doing nothing at all.
The Scientific Paper: