Association Between Physical Activity, Body Mass Index, and Aerobic Capacity in Periurban Adolescents

Adolescence is a critical window for health behavior consolidation, yet the combined influence of physical activity level (PAL) and the body mass index (BMI) on aerobic capacity remains understudied, especially in transitioning periurban environments. This study examined the association between PAL, BMI, and aerobic capacity in adolescents from Montería, Colombia. A cross-sectional study was conducted among 112 adolescents (aged 12–17 years). Aerobic capacity was assessed using the 20 m shuttle run test (Course Navette), and PAL was measured via the validated Assessment of Physical Activity Levels Questionnaire (APALQ), following standard fitness assessment protocols. Multivariable linear regression models were utilized to estimate independent associations, adjusting for age and sex. The multivariable model was significant (F = 8.45; p < 0.001), explaining 21% of the variance in aerobic capacity (adjusted R2 = 0.21). PAL was positively and independently associated with aerobic capacity (B = 0.22; 95% CI: 0.05–0.38; p = 0.010), regardless of BMI. While age showed a positive association (B = 0.09; p = 0.032) and sex was inversely associated (B = −0.39; p < 0.001), BMI did not emerge as an independent predictor in the adjusted model (B = −0.04; p = 0.080). Aerobic capacity in adolescents is more consistently explained by behavioral factors (what they “do”) than by anthropometric status (what they “weigh”). These findings support a paradigm shift in pediatric public health, prioritizing high-intensity movement overweight control to improve cardiorespiratory fitness in transitioning urban territories.