physical culturist; athlete
Refers to a person devoted to physical culture or athletic training, often with a connotation of expertise or dedication. Slightly formal or old-fashioned; アスリート is more common for modern athletes.
He is known as a physical culturist and never misses his daily training.
That physical culturist also puts effort into coaching young athletes.
Compound of 体育 (physical education) and 家 (person, expert). The exact historical derivation is uncertain, but the term follows a common pattern for designating specialists.