Approachability outranks formality here

A trainer's portrait sells a service to a stranger, usually at thumbnail size on a phone, to someone deciding whether they want to spend an hour a week with this person.

What that changes about the brief

The reader is not assessing credentials. They are assessing whether the person seems approachable, and formality actively works against that.

This is the opposite of a legal portrait, where restraint is the signal — and the two side by side are a useful reminder that there is no single correct professional headshot.

The common error

A portrait so specific to a gym setting that it fails to read small. Equipment, dramatic lighting, a busy environment — all of it becomes texture competing with the face.

What survives

High contrast, a tight crop, frontal light. The same three as everywhere, and they matter more here because the image is almost never seen large.

The check

View it at thumbnail size on a phone. If the gym survives and the person does not, the setting won.