Physical fitness is prospectively associated with Chinese language performance in primary school children over ten months

Physical fitness is linked to academic outcomes in children, but evidence comes mostly from Western alphabetic contexts; whether specific fitness dimensions relate to Chinese language performance remains unclear. We examined the bidirectional association between physical fitness and Chinese language performance and compared L-IFG activation during reading across composite health score levels. A 10-month design tracked 600 primary school students (grades 3–5). The composite health score was assessed with the National Student Physical Health Standard (body morphology, body function, physical fitness); Chinese language achievement came from provincial standardized examinations; cross-lagged panel models examined bidirectional predictions. An fNIRS subsample (excellent, n = 20; qualified, n = 18) completed homophone and synonym tasks. Only physical fitness showed significant bidirectional associations with language scores (fitness→scores: β = 0.067, p < 0.001; scores→fitness: β = 0.142, p = 0.001); body morphology and body function did not. In fNIRS tasks, the excellent group showed higher accuracy and shorter reaction times in the homophone task (q < 0.05) but no significant L-IFG differences. The composite health score is prospectively associated with Chinese language achievement, driven by physical fitness, consistent with the executive function theory. The fNIRS findings are exploratory and not mechanistic evidence; mechanisms were not tested, and larger samples are needed.