Resistance training, skeletal muscle hypertrophy, and glucose homeostasis: how related are they? A Systematic review and Meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of intervention studies
PubMed 39484808 · doi:10.1139/apnm-2024-0128
What was done
Authors conducted a systematic review and random-effects meta-analysis of 33 intervention studies to examine whether resistance training-induced skeletal muscle hypertrophy (using fat-free mass as a surrogate marker) drives improvements in glucose metabolism. Random-effects meta-analyses and meta-regressions were conducted to assess confounding by biological sex and training parameters.
What was found
Resistance training showed significant within-study increases in fat-free mass (effect size [ES] = 0.24, 95% CI [0.10, 0.39], p = 0.002, I2 = 56%), but only a non-significant trend compared to control groups (ES = 0.42, 95% CI [-0.04, 0.88], p = 0.07). Within-study improvements occurred for 2 h glucose (ES = -0.30, 95% CI [-0.50, -0.11], p < 0.01, I2 = 43%), glucose area under the curve (ES = -0.40, 95% CI [-0.66, -0.13], p < 0.01, I2 = 76.1%), and insulin sensitivity (ES = 0.38, 95% CI [0.13, 0.62], p < 0.01, I2 = 53.0%). When compared with control groups, differences in 2 h glucose and glucose area under the curve were not statistically significant. Meta-regressions did not consistently find fat-free mass increases, biological sex, or training parameters to be moderators of glucose homeostasis changes.
Why it matters
While resistance training concurrently improves lean mass and glycemic control, hypertrophy does not appear to be the primary driver of glycemic improvements. Metabolic benefits likely stem from qualitative neuromuscular or metabolic adaptations rather than muscle mass accumulation alone.
Limits
The review relied on fat-free mass as an indirect surrogate for skeletal muscle hypertrophy. There was high heterogeneity across studies (I2 up to 76.1%), and between-group comparisons against controls failed to demonstrate statistically significant glycemic benefits. Detailed training parameters were inconsistently reported across the included trials.
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