the short answer
A good personal trainer bio names who you help, states the outcome you deliver, adds one line of proof, and ends with a clear call to action. The best examples are specific and outcome-led, written to one ideal client rather than everyone - tightened to a few short lines for Instagram, or expanded into two or three sentences for a website.
Use the templates below as a starting point, then swap in your niche, your outcome, and your voice - a bio you copied word for word reads like everyone else's.