Combat and contact sports are the exception to 'train through it'. Wrestling, BJJ, boxing, rugby, and team sports with mandatory jewelry-removal rules are genuinely incompatible with a healing piercing — a fresh piercing can't have jewelry removed for practice without risking closure, and it can't take impact either. The honest answer is to pierce at the start of your off-season and count forward: lobes need six to eight weeks, most cartilage six to nine months, before they'll tolerate removal-and-refit cycles or a stray elbow.
For healed piercings, retainers solve the rulebook problem. Glass or polymer retainers replace metal jewelry for practice and pass most referee checks; swap them in right before training and put your jewelry back after. Keep the swap brief and your hands clean — even healed channels tighten surprisingly fast when empty, some within hours.
For helmet sports with healed cartilage, low-profile flat-backs beat hoops permanently: nothing for the strap to catch, nothing to lever against the shell. This is one of those places where the everyday-jewelry rules and the athlete rules agree completely.