Introduction Most adolescents fail to achieve recommended levels of vigorous-intensity physical activity, despite the established benefits for cardiorespiratory fitness and vascular health. Supervised interventions can be effective, but are resource-intensive and lack scalability. Mobile health (mHealth) technologies may provide a cost-effective and accessible approach to support structured, individualised training for adolescents. The Motivating Adolescent Fitness (MOTAFIT) trial will assess the feasibility and acceptability of an mHealth-supported exercise intervention for adolescents to inform the design of a definitive randomised controlled trial (RCT). Methods and analysis MOTAFIT is a three-arm feasibility RCT targeting 120 adolescents aged 13–16 years from the Okanagan Valley, British Columbia. Participants will be randomised (1:1:1) to: (1) MOTAFIT, (2) active control or (3) control group. The 12-week intervention targets ≥40 min/week of vigorous-intensity exercise (≥80% HRmax), co-designed with an exercise specialist and supported by mHealth technology. Primary outcomes for feasibility, including recruitment, retention, adherence, fidelity and acceptability, will be assessed as part of a process evaluation. Secondary measures (cardiorespiratory fitness, vascular health and blood pressure) will provide preliminary estimates to guide future sample size calculations. Ethics and dissemination The study has received approval from the University of British Columbia Clinical Research Ethics Board (H22-03183) and the University of Victoria Human Research Ethics Board. Parental consent and adolescent assent will be obtained prior to participation. Findings will be disseminated via peer-reviewed publications, conferences and community engagement. Trial registration number NCT06409793 .
Koep et al. (Sun,) studied this question.