Key result
HIIT and SIT markedly improve cardiorespiratory fitness and reduce body fat mass versus control.
Why the study?
It remained unclear how baseline fitness levels influence the differential effects of high-intensity interval training and sprint interval training on cardiorespiratory fitness and body fat mass.
Does high-intensity interval training (HIIT) or sprint interval training (SIT) improve cardiorespiratory fitness and reduce body fat mass in healthy/trained versus overweight/obese individuals?
Meta-Analysis (n=666)
Does high-intensity interval training (HIIT) or sprint interval training (SIT) improve cardiorespiratory fitness and reduce body fat mass in healthy/trained versus overweight/obese individuals?
Effect estimate: SMD 1.54 (95% CI 0.89-2.18)
p-value: p=<0.00001
Both HIIT and SIT effectively improve cardiorespiratory fitness and reduce body fat, with HIIT being optimal for individuals with lower fitness levels and SIT preferable for time-efficient fat reduction in trained populations.
HIIT and SIT improve CRF and reduce fat mass; reinforces Level 1 evidence and extends modality-specific tailoring by fitness level.
Background: Interval training modalities, including high-intensity interval training (HIIT) and sprint interval training (SIT), are widely recognized for their efficiency and health benefits. However, it remains unclear how baseline fitness levels influence the differential effects of HIIT and SIT on key health-related outcomes. Objective: This meta-analysis aims to compare the effects of HIIT and SIT on cardiorespiratory fitness (CRF) and body fat mass, with subgroup analyses based on participants' health and training status. Methods: peak and body fat percentage. Data were synthesized using standard mean difference (SMD) or weighted mean difference (WMD), with subgroup analyses stratified by population type (healthy/trained vs. overweight/obese). This review was registered in PROSPERO (CRD420251016362; registered on 15 March 2025). Results: Both HIIT and SIT significantly improved CRF (SMD = 1.54; 95% CI: 0.89-2.18; p < 0.00001) and reduced body fat mass (WMD = -3.45%; 95% CI: -5.04 to -1.87; p < 0.0001) compared to control. Subgroup analyses revealed that HIIT was more effective in improving CRF in overweight/obese individuals (SMD = -0.97; p = 0.0004), while SIT was more effective in reducing fat mass among healthy or trained populations (WMD = 5.85; p < 0.00001). Conclusion: Both HIIT and SIT are effective interventions for enhancing CRF and reducing body fat, but their relative efficacy may depend on participants' baseline health status. HIIT appears optimal for individuals with lower fitness levels, while SIT may be preferable for time-efficient fat reduction in trained populations. Tailoring interval training prescriptions to individual characteristics is recommended. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251016362.
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Zhang et al. (2025) conducted a meta-analysis in Healthy, trained, overweight, or obese individuals (n=666). High-intensity interval training (HIIT) and sprint interval training (SIT) vs. Control (no exercise) was evaluated on Changes in VO2max/VO2peak (cardiorespiratory fitness) (SMD 1.54, 95% CI 0.89-2.18, p=<0.00001). Both high-intensity interval training and sprint interval training significantly improved cardiorespiratory fitness (SMD 1.54) and reduced body fat mass compared to control.
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