Mutual associations between self-efficacy and physical fitness in Spanish adolescents: The EHDLA study

Importance: Physical fitness and self-efficacy are recognized as determinants of adolescent health. However, their potential bidirectional associations remain unclear. Understanding this relationship may support the development of integrated physical and psychological health interventions in adolescence. Objective: To examine the bidirectional association between physical fitness and self-efficacy in Spanish adolescents. Methods: This cross-sectional study used secondary data from the Eating Habits and Daily Living Activities (EHDLA) study, which included 618 adolescents (43.5% boys; aged 12–17 years) from the Region of Murcia, Spain. Physical fitness, including flexibility, speed-agility, cardiorespiratory fitness, and muscular fitness, was assessed using the Assessing Levels of Physical Activity and Fitness battery. Self-efficacy was measured using the Spanish version of the General Self-efficacy Scale. Associations were analyzed using Spearman's correlation coefficients and robust generalized linear models adjusted for relevant covariates. Results: Significant but weak bidirectional associations were observed between self-efficacy and several components of physical fitness, particularly cardiorespiratory fitness, lower-body muscular fitness, and speed-agility (all P < 0.001). Both higher physical fitness and greater self-efficacy independently predicted improved scores in other domains after adjusting for covariates. Interpretation: These findings suggest a bidirectional association between self-efficacy and physical fitness in adolescents, especially for cardiorespiratory fitness, lower-body muscular fitness, and speed-agility. Interventions targeting either physical or psychological factors may generate reciprocal benefits, highlighting the importance of integrated strategies for promoting adolescent health.