gym rat

Translations
человек, который постоянно занимается в спортзале
He is such a gym rat, he spends hours there every day.
Он такой человек, который постоянно занимается в спортзале, он проводит там часы каждый день.
Definitions
A 'gym rat' is a colloquial term used to describe a person who spends a significant amount of time at the gym, often engaging in weightlifting or fitness activities, and is highly dedicated to their physical fitness and bodybuilding goals.
Words
gym

noun
спортзал
rat

noun
крыса