Associations of Physical Fitness and Postural Balance with Psychosocial Well-Being in Early Adolescents: A School-Based Cross-Sectional Study

Objective: This study aimed to examine the associations of morphological variables, maximal isometric handgrip strength (MIHS), and static postural balance with self-esteem, motivational climate, school climate, and health-related quality of life (HRQoL) in early adolescents. Methods: A cross-sectional study was conducted in 235 Chilean adolescents, in whom morphological variables, MIHS, and static postural balance were assessed using center-of-pressure (CoP) parameters under eyes-open (EO) and eyes-closed (EC) conditions. Psychosocial variables, including self-esteem, motivational climate, school climate, and HRQoL, were evaluated via validated questionnaires. Multiple linear regression analyses were performed to determine associations between physical and psychosocial variables. Results: Reduced CoP sway area and lower CoP velocity under eyes-closed conditions were significantly associated with higher self-esteem (R2 = 0.168; p < 0.001). Greater non-dominant MIHS and younger age were associated with more favorable perceptions of a task-involving motivational climate (R2 = 0.438; p < 0.001). Higher HRQoL scores were associated with male sex and better postural balance performance. Conclusions: Better static postural balance and greater muscle strength were associated with more favorable psychosocial outcomes, particularly self-esteem and HRQoL. However, these findings should be interpreted as associative rather than causal relationships due to the cross-sectional design.