How many studies support HIIT?

High-intensity interval training (HIIT) is supported by several meta-analyses and randomized controlled trials showing improvements in cardiorespiratory fitness and body composition, including in clinical populations such as people with rheumatoid arthritis, stroke survivors, and adolescents with obesity. That's backed by 6 published studies in Vitaebase's database, including 4 randomized controlled trials and 2 meta-analyses, the most recent from 2024 -- a modest but real research base.