健身 (jiànshēn) literally means 'to strengthen the body' — 健 (jiàn) means 'healthy, strong, robust', and 身 (shēn) means 'body'. As a compound verb, it refers to purposeful physical activity aimed at improving or maintaining physical fitness, such as weight training, cardio, yoga, or calisthenics. It emphasizes health-oriented exercise rather than competitive sport or casual movement.

The term is widely used in modern Chinese daily life — from gym memberships (健身房, jiànshēn fáng) to fitness apps and social media posts about workout routines. While it can be used as a noun (e.g., 我喜欢健身 — 'I like exercising'), its core function is verbal, often appearing after subject pronouns or time expressions (e.g., 每天健身, 'exercise every day'). It carries a positive, proactive connotation and reflects contemporary health consciousness in urban China.