Abstract
Background: Understanding the relationship between physical fitness and body mass index (BMI) is critical for promoting adolescent health, particularly in Saudi Arabia, where cultural norms and rising obesity rates present unique challenges. This study aimed to investigate the impact of BMI, gender, and physical activity levels on lower limb strength and endurance, as measured by the Standing Long Jump (SLJ) and the 1 min Sit-to-Stand (STS) test, respectively. Methods: This cross-sectional study included 100 healthy Saudi adolescents (44 boys, 56 girls) aged 10-18 years. Lower limb strength and endurance were assessed using SLJ (cm) and STS (repetitions/min). Anthropometric measurements included BMI (kg/m(2)), weight (kg), and height (cm), while physical activity was assessed using the Physical Activity Questionnaire for Adolescents (PAQ-A). Mediation analysis was conducted to examine the potential indirect effects of BMI, PAQ-A score, and age on the relationship between SLJ and STS performance. Results: Boys significantly outperformed girls in both the STS (mean difference = 25.2 repetitions/min; p < 0.001) and SLJ (mean difference = 73.4 cm; p < 0.001). No significant gender differences were found in PAQ-A scores (p = 0.987). A strong positive correlation was observed between SLJ and STS performance (r = 0.768; p < 0.01). BMI was not significantly correlated with SLJ or STS performance. STS repetitions predicted superior SLJ performance both before (β = 0.55, p < 0.001) and after (β = 0.47, p = 0.004) adjustment for BMI, age, PAQ score, and gender. BMI transmitted only a small, non-significant share of this link (indirect β = 0.08, p = 0.122), indicating that the STS-SLJ association is largely direct (model R(2) for SLJ = 0.84). Conclusions: Explosive lower limb strength and gender were significant predictors of lower-body endurance, whereas BMI showed a limited association with performance. These findings underscore the importance of incorporating gender-specific strategies in adolescent fitness assessments and interventions, with a cautionary interpretation of BMI as a performance indicator.