the rambam writes that keeping the body healthy is part of serving hashem, “for one cannot understand or have any knowledge of the Creator if he is ill” (hilchos deos 4:1). and he gives actual rules: exercise and exertion protect from sickness and build strength, while whoever is idle and does not exercise “will be full of pain all his days” and his strength will fade (deos 4:14 to 4:15). this is not health advice in a medical sefer. it sits in the laws of deos, the path of serving hashem.

1. is exercise a mitzvah or just good sense? does keeping the body strong carry the status of halacha, a duty, or a recommended practice?

2. why does the rambam put it in deos, among anger and humility, instead of somewhere about the body? what does that say about what the body is for?

3. given how blunt he is, why do so many observant people ignore it entirely? yeshiva life can mean zero exercise for years. is there any source that pushes the other way, or is the neglect just habit?

4. edge cases: does it count if the goal is looking good rather than health? a gym with mixed genders and loud music? where does taking care of the body end and vanity or bittul torah begin?

bottom line: what does halacha actually demand about exercise and a strong body, and why is it so ignored when the rambam was this direct?