Effects of a school-based cycling intervention on commuting to school behavior and device-measured activity in Spanish adolescents: the PACO cluster-randomized controlled trial

Abstract Background Active commuting to/from school (ACS) is associated with multiple health and societal benefits, yet school-based interventions have shown limited success in changing adolescents’ commuting behavior, and their effects on psychosocial factors remain unclear. This study primarily examined the effects of a school-based cycling intervention on the usual mode and frequency of ACS, and ACS-related psychosocial outcomes in Spanish adolescents. Secondary outcomes included device-measured sedentary time and physical activity (PA). Methods A cluster-randomized controlled trial was conducted in eight Spanish secondary schools. A total of 256 adolescents (45.7% girls; mean age 14.4 years) were allocated to an intervention ( n = 127) or control group. The intervention consisted of four weekly sessions delivered during Physical Education classes over one month, combining cycling theory, skills training in closed circuits, and supervised on-road cycling in urban environments. Outcomes were assessed at baseline and post-intervention and included usual mode and weekly frequency of ACS, perceived barriers to ACS, basic psychological need satisfaction in ACS, motivation for ACS, and device-measured sedentary time and PA across daily segments. Results No significant between-group effects were observed for usual mode or frequency of ACS, nor for device-measured sedentary time or PA. Most psychosocial outcomes did not differ between groups. However, perceived environmental/safety barriers increased in the intervention group compared with controls (Δ = 0.22, p = 0.041). Moderation analyses showed that girls in the intervention group reported greater increases in amotivation for ACS than girls in the control group (Δ = 0.54, p = 0.018). Per-protocol analyses revealed higher external motivation (Δ = 0.40, p = 0.029) and amotivation (Δ = 0.38, p = 0.037) in the intervention group, with stronger effects among girls and adolescents from higher socioeconomic backgrounds. Conclusions The school-based cycling program did not change the commuting behavior or device-measured activity. Instead, participation was associated with increased awareness of environmental/safety barriers and higher amotivation, particularly among girls. Per-protocol analyses also revealed increases in external motivation and perceived barriers, particularly among girls and high-SES adolescents. These findings suggest that short-duration, skills-focused cycling interventions may heighten perceived constraints without being sufficient to support behavior change. Future programs may require longer duration, autonomy-supportive delivery, and complementary built environmental and family-level strategies to effectively promote ACS among adolescents. Trial registration ClinicalTrials.gov (Identifier: NCT03937336).