James, you put your finger on a question that has been bugging me for some time. Is there an element of reverse causation? That is, might the drive to do exercise stem from a genetical background that also improves health expectancy? It's certainly not binary, one or the other, but until now I have found it very difficult to disentangle this issue. I have seen individual cases throughout my research work with study participants that support either assumption. There are those who at late middle-age and with some chroniic conditions because of sedentary lifestyles were able to turn around their health completely and sustained that turn around. These would support the prevalent causation theory. But I also encountered individuals who had obviously very favourable genomes, as evidenced in their high VO2max despite no history of training that would explain it They pursued other types of exercise and health routines).