Resistance Training Load Effects on Muscle Hypertrophy and Strength Gain: Systematic Review and Network Meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and network meta-analysis of 28 studies
PubMed 33433148 · doi:10.1249/MSS.0000000000002585
What was done
Authors conducted a systematic review and network meta-analysis searching MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science following PRISMA guidelines. The review included studies examining healthy adults performing resistance training to volitional failure with low (>15 RM), moderate (9-15 RM), or high (<=8 RM) loads. Standardized mean differences (SMD) were calculated for muscle hypertrophy and strength gains in overall and high-quality subgroups, with network meta-regressions evaluating participant-, design-, and training-related covariates.
What was found
Twenty-eight studies involving 747 healthy adults were included. For muscle hypertrophy, no differences were found between RT loads in overall (P = 0.113-0.469) or subgroup analyses (P = 0.871-0.995), though larger effects occurred in untrained individuals (P = 0.033) and trained participants performing more sessions (P = 0.031-0.045). For muscle strength, high-load and moderate-load training were both superior to low-load training in overall and subgroup analyses (SMD 0.60-0.63 and 0.34-0.35, respectively; P < 0.001-0.003). High load showed a non-significant advantage over moderate load (SMD 0.26-0.28, P = 0.068).
Why it matters
This review shows that muscle hypertrophy can be stimulated similarly across a broad spectrum of loads provided sets reach failure, whereas maximal strength development favors heavier loads.
Limits
Findings only apply to sets taken to volitional failure and cannot be extrapolated to non-failure training. Point estimates and confidence intervals for hypertrophy outcomes were not detailed in the abstract, and the total participant count across 28 studies is relatively modest (747 participants).