How often you move matters more than how hard. Pick something you would still do on a mediocre Tuesday.

What the research says

A review of physical activity and health that sets out the downsides as well as the gains names injury, disordered eating and burnout among the real risks of pushing hard. It is a narrative review rather than a pooled analysis, so treat it as a considered overview and not a measurement. The caution still stands: harm tends to show up at the heroic end, not at the steady end.

Strength of evidence: one line of research. A single study, or a theoretical account.