Key result
Real-world HIIT boosts VO2peak by ~7 mL/kg/min compared to passive controls.
Why the study?
HIIT improves cardiorespiratory fitness and cardiometabolic health in laboratory settings, but its effectiveness under real-world conditions remains less clear.
Does high-intensity interval training (HIIT) improve cardiorespiratory fitness and cardiometabolic health in adults in real-world settings?
Meta-Analysis (n=1,119)
Does high-intensity interval training (HIIT) improve cardiorespiratory fitness and cardiometabolic health in adults in real-world settings?
Real-world HIIT effectively improves cardiorespiratory fitness and selected cardiometabolic outcomes across diverse adult populations, with pronounced benefits in overweight, clinical, and previously untrained individuals.
Answers are grounded in this paper and cite their sources.
Supports real-world HIIT for fitness gains in practice; extends controlled-trial evidence to pragmatic adult populations.
High-intensity interval training (HIIT) is an effective exercise strategy for improving cardiorespiratory fitness (CRF) and cardiometabolic health in laboratory settings, yet its effectiveness in real-world conditions remains less clear. This systematic review and meta-analysis examined the effects of real-world HIIT on CRF and cardiometabolic outcomes in adults. We searched five major databases (inception to December 2025) for controlled and non-controlled reports of ≥1 cardiorespiratory or cardiometabolic outcome. Random-effects models were used to calculate weighted mean differences (WMD), with subgroup and meta-regression analyses to explore moderators. Thirty-one studies (n = 1119) were included. In the pooled pre–post analyses, HIIT was associated with significant within-group improvements in VO2max/peak (3.9 mL/kg/min), systolic (−4 mmHg) and diastolic blood pressure (−3 mmHg), triglycerides (−8 mg/dL), total cholesterol (−9 mg/dL), LDL (−10 mg/dL), and waist circumference (−1.7 cm) across interventions. In controlled comparisons, HIIT was superior to passive controls for VO2max/peak (6.9 mL/kg/min) and waist circumference (−2.9 cm), while superiority over active controls was limited to VO2max/peak (1.1 mL/kg/min). Moderator analyses revealed larger cardiometabolic benefits in overweight and clinical populations, and greater improvements in fasting glucose and blood pressure with higher exercise volume and longer intervention duration. In conclusion, real-world HIIT can effectively improve CRF and selected cardiometabolic outcomes across diverse adult populations. Specific cardiometabolic benefits appear to be pronounced in overweight, clinical, and previously untrained individuals. Notably, substantial heterogeneity and moderate methodological quality warrant cautious interpretation.
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Stefanovic et al. (2026) conducted a meta-analysis in Healthy and clinical/at-risk adults (n=1,119). High-intensity interval training (HIIT) vs. Passive controls, active controls, or pre-intervention baseline was evaluated on Change in VO2max/peak compared to passive controls (WMD 6.9 mL/kg/min, 95% CI 4.3 to 9.5, p=<0.001). Real-world high-intensity interval training significantly improved cardiorespiratory fitness, increasing VO2max/peak by 6.9 mL/kg/min compared to passive controls.
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