It is straightforward enough to prove that exercise extends healthy (but not average or overall) life span in studies of mice. It is far less straightforward to demonstrate that same proof in human epidemiological data. We can’t put humans into carefully controlled groups stratified by life-long differences in exercise and follow them from birth to death, as is the case for mice. As a consequence, near all studies of physical activity and longevity produce only correlations, as there is no practical way to derive causation given the data to hand. It is felt that these correlations likely reflect causation because of the extensive animal studies and the essential similarities of biochemistry between the mammalian species involved, but that isn’t the same thing as a rigorous determination. The editorial here is a discussion of this point; the authors look at the limitations and challenges that face any attempt to generate better evidence in support of the generally accepted proposition that exercise causes extended healthy life span in humans.
While epidemiological findings show that increased physical activity (PA) lengthens the life span, it has been argued that intervention studies do not support PA causing
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