Is it permissible for a husband to work as a bodybuilding trainer and write nutrition and protein programs, as well as prescribe injections for those over twenty years of age, knowing that he does not sell them and only charges a fee for organizing the program?

If it is medically proven that these injections are beneficial, do not contain intoxicants, and do not harm adults, then there is no impediment to prescribing them to trainees or selling them to them. There is also no objection to the fee the husband receives for guiding them to what will improve their bodies, as this is a legitimate activity.