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BACKGROUND AND OBJECTIVE: This systematic review with meta-analysis investigated the influence of resistance training proximity-to-failure on muscle hypertrophy. METHODS: Literature searches in the PubMed, SCOPUS and SPORTDiscus databases identified a total of 15 studies that measured muscle hypertrophy (in healthy adults of any age and resistance training experience) and compared resistance training performed to: (A) momentary muscular failure versus non-failure; (B) set failure (defined as anything other than momentary muscular failure) versus non-failure; or (C) different velocity loss thresholds. RESULTS: There was a trivial advantage for resistance training performed to set failure versus non-failure for muscle hypertrophy in studies applying any definition of set failure effect size=0.19 (95% confidence interval 0.00, 0.37), p=0.045, with no moderating effect of volume load (p=0.884) or relative load (p=0.525). Given the variability in set failure definitions applied across studies, sub-group analyses were conducted and found no advantage for either resistance training performed to momentary muscular failure versus non-failure for muscle hypertrophy effect size=0.12 (95% confidence interval -0.13, 0.37), p=0.343, or for resistance training performed to high (>25%) versus moderate (20-25%) velocity loss thresholds effect size=0.08 (95% confidence interval -0.16, 0.32), p=0.529. CONCLUSION: Overall, our main findings suggest that (i) there is no evidence to support that resistance training performed to momentary muscular failure is superior to non-failure resistance training for muscle hypertrophy and (ii) higher velocity loss thresholds, and theoretically closer proximities-to-failure do not always elicit greater muscle hypertrophy. As such, these results provide evidence for a potential non-linear relationship between proximity-to-failure and muscle hypertrophy.
Refalo et al. (2022) studied this question.