School-based high-intensity interval training for children: a focused systematic review of implementation and...

Schools are an important setting for physical-activity promotion, but limited curriculum time can constrain the implementation of exercise programmes. High-intensity interval training (HIIT) may offer a brief format for increasing vigorous activity during physical education (PE), classroom activity breaks, or other school-day opportunities. This review examined school-based HIIT delivery models, physical and cardiovascular outcomes, cognition and other school-relevant outcomes, and implementation, feasibility, and safety reporting.

Five electronic databases were searched for English-language studies published from January 2010 to May 9, 2026. Two reviewers independently screened records, assessed full texts, extracted data, and appraised risk of bias, with disagreements resolved by consensus. Eligible controlled studies evaluated a clearly defined HIIT intervention delivered in a school setting to children aged approximately 5-12 years and reported at least one physical, cardiovascular, cognitive, school-relevant, or implementation outcome. Owing to substantial heterogeneity in interventions and outcomes, findings were synthesised narratively in accordance with the Synthesis Without Meta-analysis (SWiM) reporting guideline.

The searches identified 3,508 records; 1,370 duplicates were removed, 2,138 records were screened, 94 full-text reports were assessed, and six studies were included. Analysed sample sizes ranged from 18 to 67 participants. Interventions ranged from 6-minute classroom micro-sessions to 20-minute PE-based programmes delivered for 4-12 weeks. Some studies reported between-group or group-by-time findings favouring HIIT for selected functional-strength, aerobic-fitness, arterial-stiffness, and heart-rate-variability outcomes; other findings were limited to within-group change, and effects were not consistent across protocols. One study assessed inhibitory control and reported improvements after both HIIT and moderate-intensity continuous training, providing no evidence of a HIIT-specific cognitive advantage. No included study directly assessed mental health, academic attainment, attendance, or classroom engagement. Three studies were judged to have a high overall risk of bias and three raised some concerns.

School-based HIIT may be a brief adjunct to, rather than a replacement for, comprehensive PE. Preliminary findings suggest possible benefits for selected fitness and cardiovascular outcomes, while evidence for cognitive, mental-health, and academic benefits remains limited or absent. Given the small evidence base and risk-of-bias concerns, these findings should be interpreted cautiously. The current findings apply to the primary-school-aged samples represented and should not be extrapolated to adolescents. Larger, adequately powered school trials with stronger implementation and outcome reporting are required.