School-based high-intensity interval training significantly improved cardiorespiratory fitness compared to no exercise control (SMD 0.33), though process evaluation reporting remains infrequent.
Meta-Analysis (n=25,104)
Does school-based high-intensity interval training (HIIT) improve cardiorespiratory fitness, body composition, muscular strength, and blood pressure in children and adolescents?
School-based HIIT interventions significantly improve cardiorespiratory fitness and body composition in children and adolescents, though process evaluation is frequently omitted in the literature.
Effect estimate: SMD 0.33 (95% CI 0.16 to 0.51)
BACKGROUND: Several systematic reviews have been published to investigate the effectiveness of high-intensity interval training (HIIT) in schools. However, there has been limited attention given to understanding the functioning of the intervention processes, which is of paramount importance for interpreting and translating the intervention effectiveness. The aim of this systematic review is to determine the extent to which process evaluation is measured in school-based HIIT interventions and to explore the effects of process evaluation and intervention characteristics on cardiorespiratory fitness (CRF), body composition, muscular strength, and blood pressure. METHODS: A comprehensive search was conducted in SPORT Discus (EBSCOhost), Web of Science, Scopus, Medline (Ovid) and Cochrane Central Register of Controlled Trials. The extent to which process evaluation is measured was narratively reported, alongside with the guidance of process evaluation of complex interventions by UK Medical Research Council. Meta-analyses and meta-regressions were conducted to determine the effects of process evaluation and intervention characteristics to the intervention outcomes. RESULTS: The literature search identified 77 studies reporting on 45 school-based HIIT interventions. In total, five interventions reported process evaluation in a section or in a separate study, and only one intervention adopted a process evaluation framework. On average, 6 out of 12 process evaluation measures were reported in all interventions. Subgroup analyses did not indicate any beneficial treatment effects for studies with process evaluation group, whereas all pooled data and studies without process evaluation group showed significant improvement for CRF and body composition. CONCLUSION: Process evaluation is frequently omitted in the literature of school-based HIIT in children and adolescents. Although reporting of process evaluation measures may not directly associate with better intervention outcomes, it allows accurate interpretation of intervention outcomes, thereby enhancing the generalisability and dissemination of the interventions.
Liu et al. (Fri,) conducted a meta-analysis in Healthy school-aged children and adolescents (n=25,104). School-based high-intensity interval training (HIIT) vs. Usual practice control group (e.g., regular physical education) was evaluated on Cardiorespiratory fitness (CRF) (SMD 0.33, 95% CI 0.16 to 0.51). School-based high-intensity interval training significantly improved cardiorespiratory fitness compared to no exercise control (SMD 0.33), though process evaluation reporting remains infrequent.