Feasibility of a school-based peer-led high-intensity interval training intervention: the Young Fitness Leaders project

While school-based high-intensity interval training (HIIT) has demonstrated efficacy for improving adolescents’ physical and mental health, interventions have largely been researcher-led, which limits scalability. This could be resolved via peer-led programmes, whereby older pupils (i.e., peer-leaders) deliver HIIT to younger pupils (i.e., peer-recipients). We aimed to explore the feasibility of a school-based peer-led HIIT intervention. Using a non-randomised controlled trial design, 44 Year 7 pupils (aged 12.1 ± 0.3 years [mean ± SD]) were recruited from one school in North East England, with 21 (8 girls) allocated as peer-recipients to an 8-week HIIT intervention, and 23 (17 girls) as controls. Five Year 12–13 pupils (aged 17.3 ± 0.4 years) were recruited as peer-leaders and received training on school-based HIIT based on boxing and whole-body exercises. Peer-leaders then delivered twice weekly HIIT sessions during morning tutor time. Primary outcomes were recruitment, retention, attendance and acceptability (explored in post-intervention focus groups with peer-recipients, peer-leaders and teachers). Secondary outcomes included intervention fidelity (via researcher field note observations and heart rate monitoring), and preliminary impact on physical fitness and psychological outcomes. Recruitment was 72% (21/29 eligible pupils), 74% (23/31) and 42% (5/12) for peer-recipients, controls and peer-leaders, respectively. All control participants completed the study; one peer-leader left the school, and two peer-recipients withdrew (94% overall retention). Intervention attendance (expressed as percentage of scheduled sessions) was 73 ± 31%. The intervention was generally well-received by peer-recipients, peer-leaders and teachers. The mean peak heart rate across all repetitions was 76% of age-predicted maximal, with a between- and within-participant variability of 6% points and 8% points, respectively. For the physical fitness and psychological outcomes, intervention effect directions were inconsistent and effect estimates imprecise. Peer-led HIIT may represent a scalable and feasible school-based physical activity model from a recruitment, retention, attendance and acceptability perspective. However, intervention heart rates and session observations suggest HIIT activities were not always delivered and performed as intended, which could limit intervention effectiveness in larger-scale trials. Future iterations of peer-led HIIT programmes should focus on refining intervention delivery by providing an enhanced training and support package for peer-leaders. The trial was registered on ISRCTN, the UK’s Clinical Study Registry on 6th March 2023 (https://www.isrctn.com/ISRCTN89390191). The trial registration number is ISRCTN89390191.