Grip strength is also an excellent marker of longevity/imminent death - but this is probably not a result of exercise, and certainly not grip-strength exercise.

Grip strength is also an excellent marker of longevity/imminent death - but this is probably not a result of exercise, and certainly not grip-strength exercise. Science is not assuming that what seems like a very reasonable guess is true, and questioning such assumptions must be "pedantic." Instead, we do the experiments and know one way or another. PS - one of the things that happens when most people exercise is more UV exposure as they walk, run or cycle: and previous studies have shown UV exposure to be more important for longevity than exercise per se.