Girls cite heavy backpacks as top barrier to walking or biking to school

To examine sex differences in perceived barriers to active commuting to school (ACS) among Spanish adolescents and analyzed the associations between these barriers and the mode of commuting, including potential sex-specific patterns. In this cross-sectional study, 707 adolescents (53.6% girls; mean age = 14.05 ± 1.18 years) self-reported their mode of commuting and perceived barriers to ACS. Sex differences in perceived barriers (continuous scores from 0 to 1) were examined using linear mixed-effects models. Associations between perceived barriers and mode of commuting (active vs. passive) were analyzed using mixed-effects logistic regression models, fitted with and without sex × barrier interaction terms. All models were adjusted for age and home–school distance, with school included as a random intercept. Overall, no significant associations were observed between sex and perceived barriers, except that girls reported carrying a heavy school backpack as a greater barrier than boys ( p = 0.006). In models without interaction terms, several perceived environmental, safety, and logistical barriers were associated with lower odds of ACS. Sex × barrier interaction analyses indicated modest sex-specific differences, with poor lighting, crime-related concerns, and hilly routes being more strongly associated with lower odds of ACS among girls. Perceived barriers to ACS were largely shared between boys and girls, underscoring the importance of addressing universal environmental and structural constraints related to distance, convenience, traffic, and weather. However, barriers linked to physical effort and safety appear to be particularly relevant for girls’ ACS. These findings suggest that while population-wide strategies are needed to reduce common barriers to ACS, targeted actions addressing physical effort and perceived safety may be especially important to promote ACS among girls. • Boys and girls showed similar overall patterns of perceived barriers. • However, girls perceived carrying a heavy school backpack as a greater barrier than boys. • Environmental and logistical barriers reduced the odds of ACS. • Only a few sex × barrier interactions emerged, mainly involving safety- and terrain-related barriers. • Interventions should focus on universal barriers while considering girls' safety context.