[failwhaleshark]

This makes anecdotal, qualitative sense: low-/medium-intensity cardio for extended durations. The challenge is to do volume of such exercise with minimum body impact (not running, especially not barefoot running downhill). Swimming, elliptical, and possibly bicycling seem ideal for least risks of debilitating joint wear and arthritis in later life.

Furthermore, exercise involves inflammation and cellular damage. Does extreme exercise volume increase the risks of cancer, aging, and/or reduction in lifespan?