High intensity interval training and cardiometabolic health in the general population: A systematic review and meta-analysis of randomised controlled trials

Background: High intensity interval training (HIIT) remains a promising exercise mode in managing cardiometabolic health. Large-scale analyses are necessary to understand its magnitude of effect on important cardiometabolic risk factors and inform guideline recommendations. <br /><br />Objective: We aimed to perform a novel large-scale meta-analysis on the effects of HIIT on cardiometabolic health in the general population.<br /><br />Methods: PubMed (MEDLINE), the Cochrane library and Web of Science were systematically searched. Randomised controlled trials (RCT’s) published between 1990 and March 2023 were eligible. Research trials reporting the effects of a HIIT intervention on at least 1 cardiometabolic health parameter with a non-intervention control group were considered.<br /><br />Results: This meta-analysis included 97 RCT’s with a pooled sample size of 3399 participants. HIIT produced significant improvements in 14 clinically relevant cardiometabolic health parameters, including peak aerobic capacity (VO2) (Weighted mean difference [WMD]: 3.895 ml·min-1·kg-1, P<0.001), left ventricular ejection fraction (WMD: 3.505%, P<0.001), systolic (WMD: -3.203 mmHg, P<0.001) and diastolic (WMD: -2.409 mmHg, P<0.001) blood pressure, resting heart rate (WMD: -3.902bpm, P<0.001) and stroke volume (WMD: 9.516 mL, P<0.001). Body composition also significantly improved through reductions in body mass index (WMD: -0.565 kg·m2, P<0.001), waist circumference (WMD: -2.843cm, P<0.001) and percentage body fat (WMD: -0.972%, P<0.001). Furthermore, there were significant reductions in fasting insulin (WMD: -13.684 pmol·L-1, P=0.004), high sensitivity C-reactive protein (WMD: -0.445 mg·dL-1, P=0.043), triglycerides (WMD: -0.090 mmol·L-1, P=0.011) and low-density lipoprotein (WMD: -0.063 mmol·L-1, P=0.050), concurrent to a significant increase in high-density lipoprotein (WMD: 0.036 mmol·L-1, P=0.046).<br /><br />Conclusion: These results provide further support for HIIT in the clinical management of important cardiometabolic health risk factors, which may have implications regarding physical activity guideline recommendations.<br />