Physical exercise follows a J-shaped curve regarding mortality risk: a lack of activity is deleterious, but an excess of exercise can also become detrimental to health.

noli's read

The concept of a J-shaped curve is widely supported by observational research in epidemiology. The study cited by Siim Land (PMID: 26187713, an observational cohort study) confirms that moderate activity is associated with an optimal reduction in mortality, while extremely high activity levels (often observed in elite endurance athletes) may show an attenuation of these benefits, or even a slightly increased risk for the cardiovascular system. However, it is crucial to note that the term "too much" is extremely relative: for the vast majority of the population, reaching these levels of excessive exertion is very difficult. What is sometimes interpreted as a risk of "over-exercising" could also be linked to other uncontrolled confounding factors. In summary, science confirms that the benefit is not strictly linear, but the risk linked to overtraining is often overestimated compared to the risk linked to a sedentary lifestyle.

the sources

No named source held this one up — that absence is part of the verdict.