Quick answer
Place the main light to the side and slightly above, turn your body until shadows describe shape, then expose for highlights so bright skin and mirrors do not clip.
Find directional light
Overhead panels often flatten faces but can define the torso when you step just behind the brightest pool. Side light from a window or strip light creates clearer separation.
Control the background
Move away from clutter, bright signs and mirrors showing other people. A darker, simpler background gives the subject more visual weight.
Edit with restraint
Start with white balance and exposure, then add modest contrast and texture. Heavy clarity, crushed blacks and orange skin make an image look processed rather than strong.
Common questions
Is overhead gym lighting always bad?
No. Change your position and body angle so the shadows work for you.
Should I use flash?
Only where the gym permits it and other members are not disturbed.