High-intensity interval training and cardiorespiratory fitness in adults: An umbrella review of systematic reviews and meta-analyses.
Level 1 - systematic review of randomized trials
Umbrella review of systematic reviews and meta-analyses
PubMed 38760916 · doi:10.1111/sms.14652
What was done
An umbrella review searched seven databases (MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus, and Web of Science) through February 2024 following PRIOR guidelines. Two independent reviewers extracted data and assessed methodological quality with AMSTAR-2 from systematic reviews with meta-analyses evaluating high-intensity interval training (HIIT) or sprint interval training (SIT) versus non-exercise control or moderate-intensity continuous training (MICT) on cardiorespiratory fitness (CRF) in adults.
What was found
Twenty-four systematic reviews with meta-analyses were included, representing 429 primary studies and 12,967 unique participants. Most systematic reviews received moderate-to-critically low AMSTAR-2 scores. HIIT (including SIT) significantly increased CRF compared to non-exercise controls (standardized mean difference [SMD]: 0.28 to 4.31; weighted mean difference [WMD]: 3.25 to 5.5 mL/kg/min) and MICT (SMD: 0.18 to 0.99; WMD: 0.52 to 3.76 mL/kg/min). Effects were reported across diverse populations (healthy adults, overweight/obesity, older adults, athletes) and modalities (low-volume, whole-body, home-based, aquatic, short SIT).
Why it matters
This synthesis confirms that HIIT effectively improves cardiorespiratory fitness across varied adult populations and provides modest incremental benefit over traditional continuous moderate exercise.
Limits
Most included systematic reviews exhibited moderate-to-critically low methodological quality on the AMSTAR-2 tool. The wide ranges in reported effect sizes indicate substantial heterogeneity in training protocols, durations, and baseline participant characteristics, and potential primary study overlap between included meta-analyses was not detailed in the abstract.