Plenary Session at ECSS Barcelona 2013, Does Pain Produce Gain?
Uncertainties Regarding Some of the Expected Benefits of Regular Exercise
Bouchard, C.
Pennington Biomedical Research Center
From a public health perspective, regular exercise is beneficial for everyone. This view is based on cross-sectional and longitudinal
epidemiological studies and on observed average responses in exercise intervention studies. However, this notion needs to be critically evaluated considering the body of data on human variation in response to regular exercise. The concept of individual differences in the response to exercise was first defined three decades ago in a series of experiments with monozygotic twins and nuclear families. A powerful way to investigate the biological basis of human variation in the response to regular exercise is to use transcriptomic and genomic technologies. Whole-genome transcriptomics from skeletal muscle samples yielded a panel of 29 transcripts whose abundance profile accounted for 58% of the variance in VO2max gains among 24 sedentary men trained for 6 weeks, and these findings were replicated in a second study. A genome-wide association study was undertaken in the HERITAGE Family Study based on 324,611 single nucleotide polymorphisms (SNPs). Multivariate regression analyses showed that the top 21 SNPs explained 49% of the variance in VO2max trainability. A predictor score was constructed based on allelic composition at these SNPs, with a theoretical range from 0 (no beneficial alleles) to 42 (two copies of the beneficial alleles at all 21 loci). The difference in VO2max trainability between those carrying 9 or less of these alleles and those carrying 19 or more was threefold. Similar observations have been made for the training-induced changes in exercise hemodynamic, insulin and glucose, and lipid and lipoprotein traits. These results suggest that it may eventually be possible to predict who will benefit the least or the most from regular exercise for common cardiometabolic risk factors or physical performance. An examination of the response distribution for risk factor traits to regular exercise in HERITAGE yielded suggestive evidence that there were adverse responders. Further exploration in five other exercise intervention cohorts revealed that the prevalence of adverse responders reaches about 10% for a given risk factor while about 7% among almost 1,700 adults experienced multiple adverse responses. It is critical to be able to identify molecular predictors of the ability to respond to regular exercise not only for our understanding of the underlying biology, but also to screen individuals at risk of developing potentially harmful response patterns and to define realistic expectations at the individual level. It is simply not true that adverse responders, nonresponders, and low responders have failed to exercise hard enough. It is time to move away from the “no pain, no gain” model and to embrace the personalized exercise medicine paradigm.
