Purpose High-intensity interval training (HIIT) has emerged as a time-efficient strategy to improve children’s and adolescents’ health-related fitness in comparison to traditional training methods. However, little is known regarding the effects on cognitive function and mental health. Therefore, the aim of this systematic review was to evaluate the effect of HIIT on cognitive function (basic information processing, executive function) and mental health (well-being, ill-being) outcomes for children and adolescents. Methods A systematic search was conducted, and studies were eligible if they 1) included a HIIT protocol, 2) examined cognitive function or mental health outcomes, and 3) examined children or adolescents (5–18 yr). Separate meta-analyses were conducted for acute and chronic studies, with potential moderators (i.e., study duration, risk of bias, participant age, cognitive demand, and study population) also explored. Results A total of 22 studies were included in the review. In acute studies, small to moderate effects were found for executive function (standardized mean difference [SMD], 0.50, 95% confidence interval [CI], 0.03–0.98; P = 0.038) and affect (SMD, 0.33; 95% CI, 0.05–0.62; P = 0.020), respectively. For chronic studies, small significant effects were found for executive function (SMD, 0.31; 95% CI, 0.15–0.76, P < 0.001), well-being (SMD, 0.22; 95% CI, 0.02–0.41; P = 0.029), and ill-being (SMD, −0.35; 95% CI, −0.68 to −0.03; P = 0.035). Conclusions Our review provides preliminary review evidence suggesting that participation in HIIT can improve cognitive function and mental health in children and adolescents. Because of the small number of studies and large heterogeneity, more high-quality research is needed to confirm these findings.

BackgroundCardiorespiratory fitness (CRF) is an important marker of current and future health status. The primary aim of our study was to evaluate the impact of a time-efficient school-based intervention on older adolescents’ CRF.MethodsTwo-arm cluster randomised controlled trial conducted in two cohorts (February 2018 to February 2019 and February 2019 to February 2020) in New South Wales, Australia. Participants (N=670, 44.6% women, 16.0±0.43 years) from 20 secondary schools: 10 schools (337 participants) were randomised to the Burn 2 Learn (B2L) intervention and 10 schools (333 participants) to the control. Teachers in schools allocated to the B2L intervention were provided with training, resources, and support to facilitate the delivery of high-intensity interval training (HIIT) activity breaks during curriculum time. Teachers and students in the control group continued their usual practice. The primary outcome was CRF (20 m multi-stage fitness test). Secondary outcomes were muscular fitness, physical activity, hair cortisol concentrations, mental health and cognitive function. Outcomes were assessed at baseline, 6 months (primary end-point) and 12 months. Effects were estimated using mixed models accounting for clustering.ResultsWe observed a group-by-time effect for CRF (difference=4.1 laps, 95% CI 1.8 to 6.4) at the primary end-point (6 months), but not at 12 months. At 6 months, group-by-time effects were found for muscular fitness, steps during school hours and cortisol.ConclusionsImplementing HIIT during curricular time improved adolescents’ CRF and several secondary outcomes. Our findings suggest B2L is unlikely to be an effective approach unless teachers embed sessions within the school day.Trial registration numberAustralian New Zealand Clinical Trials Registry (ACTRN12618000293268).

This study provides evidence for the feasibility and preliminary efficacy of a teacher-facilitated high-intensity interval training intervention for older adolescents.

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Process evaluations can help to optimise the implementation of school-based physical activity interventions. The purpose of this paper is to describe the process evaluation of a school-based high-intensity interval training (HIIT) program for older adolescent students, known as Burn 2 Learn (B2L). B2L was evaluated via a cluster randomised controlled trial in 20 secondary schools (10 intervention, 10 control) in New South Wales, Australia. Teachers (n = 22 (55% female)) from the 10 intervention schools, delivered the program over three phases (Phases 1 and 2, 6 months; Phase 3, 6 months) to older adolescent students (n = 337 (50% female); mean ± standard deviation (SD) age = 16.0 ± 0.4 years). Process evaluation data were collected across the 12-month study period. Teachers delivered 2.0 ± 0.8 and 1.7 ± 0.6 sessions/week in Phases 1 and 2 respectively (mean total 25.9 ± 5.2), but only 0.6 ± 0.7 sessions/week in Phase 3. Observational data showed that session quality was high, however heart rate (HR) data indicated that only half of the students reached the prescribed threshold of ≥85% predicted HRmax during sessions. Over 80% of teachers reported they intended to deliver the B2L program to future student cohorts. Almost 70% of students indicated they intended to participate in HIIT in the future. Teachers considered the program to be adaptable, and both students and teachers were satisfied with the intervention. B2L was implemented with moderate-to-high fidelity in Phases 1 and 2, but low in Phase 3. Our findings add to the relatively scant process evaluation literature focused on the delivery of school-based physical activity programs.