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The coronavirus disease 2019 (COVID-19) pandemic has exacerbated physical inactivity and emotional disorders among adolescents, creating an urgent public health need for effective and feasible school-based behavioural interventions. This study aimed to evaluate and compare the psychological and physical effects of two distinct exercise modalities—High-Intensity Functional Training (HIFT) and Moderate-Intensity Continuous Training (MICT)—implemented as 8-week school-based interventions for early adolescents. An 8-week cluster randomised controlled trial was conducted in a public middle school in China. Three intact classes of early adolescents were randomly allocated at the class level, using a random-number table, to HIFT (n = 39), MICT (n = 40), or a usual-curriculum control group (n = 36). Participants were boys and girls aged 11–12 years without known contraindications to exercise. Both intervention groups completed three supervised 40-minute sessions per week during physical education lessons. Primary outcome measures were body composition (body mass index and waist circumference), cardiorespiratory fitness assessed by maximal oxygen uptake (V̇O2max), muscular fitness (standing long jump, handgrip strength, and push-ups), and mood states assessed using the Profile of Mood States (POMS) questionnaire. Baseline demographic characteristics were compared using one-way analysis of variance (ANOVA) and chi-square tests. Intervention effects were analysed using three (group: HIFT, MICT, control) × two (time: pre-test, post-test) repeated-measures ANOVA with Bonferroni-adjusted post-hoc tests. Results are reported as mean changes with 95% confidence intervals (CI) and p values. A total of 115 students aged 11–12 years completed the trial, with no significant between-group differences in baseline demographic or fitness characteristics (all p > 0.05). Compared with MICT and control, the HIFT group showed greater improvements in cardiorespiratory fitness (V̇O2max Δ = +5.26 mL•kg⁻¹•min⁻¹, 95% CI 4.24–6.28, p < 0.001) and lower-body power, as well as a clinically meaningful reduction in waist circumference (Δ = −1.18 cm, 95% CI −1.83 to −0.53, p < 0.001). Regarding psychological outcomes, HIFT produced larger increases in positive mood indices such as vigor and self-esteem (both p < 0.01), whereas MICT led to greater reductions in negative mood states, including anger, depression, and fatigue (all p < 0.01). Both intervention groups showed significant decreases in total mood disturbance compared with the control group (p < 0.001). Our findings suggest that an 8-week school-based High-Intensity Functional Training programme is a feasible and effective alternative to Moderate-Intensity Continuous Training for early adolescents, producing larger gains in cardiorespiratory fitness, lower-body power and a small but clinically meaningful reduction in waist circumference. High-Intensity Functional Training was particularly effective in enhancing positive mood states such as vigour and self-esteem, whereas Moderate-Intensity Continuous Training produced greater reductions in anger, depression and fatigue, and still elicited measurable gains in aerobic fitness and muscular endurance. Both interventions reduced overall mood disturbance compared with usual physical education. Given the modest sample size and single-school setting, larger studies are needed to confirm these effects and refine exercise prescriptions for adolescent physical and emotional health. Chinese Clinical Trial Registry (ChiCTR2500110935 title “Research and Application of Key Technologies and Methods for Promoting the Physical Health of Middle School Students through Exercise” registered 22 October 2025 retrospectively registered, (http//www.chictr.org.cn).
Liu et al. (Fri,) studied this question.