He is doing special exercises to strengthen his flexor hallucis brevis.

I started exercises to strengthen the abductor hallucis muscle.

He had difficulty walking due to an injury to his extensor hallucis brevis.

He started a special exercise to strengthen his flexor hallucis longus.

He was swimming freely as if he was a fish playing in the pot.

He is a person who follows his own path, and the phrase 'a big fish does not swim into a small stream' fits him perfectly.

He is doing special exercises to strengthen his abductor pollicis brevis.

He is doing special exercises to strengthen his abductor pollicis longus.