Does moderate intensity continuous training promote muscle hypertrophy? A systematic review and meta-analysis of randomized controlled trials.

Abstract

The effects of moderate-intensity continuous training (MICT) on muscle hypertrophy remain controversial, largely due to the absence of non-exercise control groups in several trials and considerable heterogeneity in training protocols, assessment methods, and participant characteristics. This systematic review and meta-analysis aimed to examine the effects of MICT on skeletal muscle hypertrophy. Following PRISMA guidelines, searches were conducted in MEDLINE, Embase, Web of Science, Scopus, and the Cochrane Library for chronic human interventions comparing MICT to non-exercise controls, reporting both whole-body and localized muscle mass outcomes (lower limb lean mass, muscle cross-sectional area, fiber cross-sectional area, and muscle thickness) in healthy adults without chronic diseases or musculoskeletal injuries. A random-effects model compared MICT vs. control for total and regional muscle mass outcomes combined and separately. Thirteen studies met the inclusion criteria. The standardized mean difference was 0.050 (95% CI: -0.147 to 0.248) for total and regional outcomes combined, and 0.080 (95% CI: -0.277 to 0.437) for regional outcomes alone. In conclusion, the current evidence does not consistently support a hypertrophic effect of MICT. However, this conclusion should be interpreted with caution due to variability in study design, populations, and measurement sensitivity.