Abstract

Background: High-intensity interval training (HIIT) is an efficient time-based exercise type with an overwhelming and positive outcome on cardiovascular health, ahead of moderate-intensity continuous training (MICT). This exciting twist on high-intensity interval training (HIIT) has, to date, shifted researchers’ focus to non-exercise controls and MICT cardiovascular elements such as VO₂ max, blood pressure, vascular function, lipid profiles, and Resting Heart Rate (RHR). Methods: This interval training meta-analysis includes only HIIT studies with at least 80% of ages 20–40 at max heart rate from 4 weeks (assuming 80% of MHR max). HIIT shows improvement on the compared metrics compared with the non-exercise control: VO₂ max (4.3 mL·kg⁻¹·min⁻¹), systolic (4 mm), and diastolic (3 mm). Findings: Improvements in endothelial function and arterial stiffness, with reduced pulse wave velocity, are noted. HIIT is superior to MICT, with gains in VO₂ max of 3–4 mL·kg⁻¹·min⁻¹ and central systolic blood pressure, indicating marginally better vascular function and arterial stiffness. HIIT with gains identified seeks work. 2 or more work interval durations, 3 to 5 session frequencies, at least 8 weeks of total progression times, and work: no work ratios of 1:1 give the best results. Conclusion: Compliance remains high in supervised intervals, with minimal safety events; yet long-term sustainability beyond 12 months is less well substantiated. Comprehensive HIIT training remains a safe intervention with many benefits, and it can be easily tailored to assist individuals at risk in improving their cardiovascular health.