Résumé
Post-secondary students face elevated mental health risks, yet scalable, evidence-based prevention strategies remain limited. Physical activity (PA) is a promising intervention, yet implementation factors to support scalability are underexamined. Guided by the COM-B model, this three-arm parallel randomized controlled trial (hybrid effectiveness-implementation design), evaluated the effects of 6-week supervised one-on-one (1:1) and group PA, compared to a waitlist control, on mental health, social well-being, and PA behaviour. Outcomes were assessed at baseline (T1), 6-weeks (T2), and 1-month-follow-up (T3) using linear mixed-effects models. A mixed-methods process evaluation assessed implementation factors including acceptability (e.g., enjoyment), fidelity (e.g., COM-B processes), reach, and adherence. Quantitative outcomes were analyzed using descriptive statistics, t-tests, or chi-square tests, and qualitative data were analyzed thematically. Physically inactive students experiencing poor mental health were randomized (N = 115; M (SD)age = 25.42 (6.14); 76% women; 60% diagnosed mental illness) to 1:1 PA (n = 40), group PA (n = 41), or waitlist (n = 34). Relative to the waitlist, both PA formats reduced depression and psychological distress while improving well-being and social connectedness at post-intervention (T1–T2) and at follow-up (T1–T3). The 1:1 delivery reduced anxiety at both timepoints and improved social support at follow-up. Group delivery showed anxiety reductions at follow-up. All improvements were maintained (T2 to T3). 1:1 delivery showed higher adherence, acceptability, and greater fidelity to supporting students’ capability for physical activity. The findings highlight how delivery format, a key contextual factor in the PA–mental health relationship, influences both effectiveness and implementation.
