Slow and Steady, or Hard and Fast? A Systematic Review and Meta-Analysis of Studies Comparing Body Composition Changes between Interval Training and Moderate Intensity Continuous Training.
Level 1 - systematic review of randomized trials
Systematic review and multilevel meta-analysis of randomized controlled trials
PubMed 34822354 · doi:10.3390/sports9110155
What was done
Authors conducted a systematic review and multilevel meta-analysis searching PubMed/MEDLINE, Scopus, CINAHL, and sportrxiv. They included randomized controlled trials directly comparing interval training (IT) versus moderate intensity continuous training (MICT) on whole-body and regional body composition using validated measures in healthy children and adults, with training lasting at least four weeks at a minimum frequency of once per week.
What was found
The main model for fat mass changes showed a standardized effect of -0.016 (95% CI -0.07 to 0.04; I 2 = 36%). The main model for fat-free mass (FFM) changes showed a standardized effect of -0.0004 (95% CI -0.05 to 0.05; I 2 = 16%). GRADE assessment indicated high certainty for both main model outcomes, indicating minimal influence of training pattern on body composition.
Why it matters
This indicates that endurance training intensity patterns (intervals vs steady-state) do not meaningfully alter body composition outcomes differently. Individuals and clinicians can choose either modality based on adherence, time constraints, or preference.
Limits
The abstract does not state the total number of included studies or participants. The review was restricted to healthy populations and English-language publications or preprints, and regional body composition results and dietary control details were not reported in the abstract.
Cited by
- supports Six- and twelve-week high-intensity interval training studies show measurable but subtle body composition changes, specifically slight reductions in fat mass or percentage and slight increases in lean mass.