Influence of Resistance Training Proximity-to-Failure on Skeletal Muscle Hypertrophy: A Systematic Review with Meta-analysis

Abstract

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.

Fig. 1

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow chart. Summary of the systematic literature search and study selection process

Fig. 2

Influence of resistance training (RT) performed to set failure versus non-failure on muscle hypertrophy with subgroup analyses based on study ‘theme’ (A or B). Studies presented were grouped into broad themes that involved RT performed to either momentary muscular failure versus non-failure (Theme A), or set failure (defined as anything other than momentary muscular failure) versus non-failure (Theme B). Point estimates and error bars signify the standardised mean difference between set failure and non-failure conditions and 95% confidence interval (CI) values, respectively. AD anterior deltoid, EF elbow flexors, PM pectoralis major, Quads quadriceps, RF rectus femoris, SD standard deviation, SMD standardized mean difference, TB triceps brachii, VL vastus lateralis, VM vastus medialis

Fig. 3

Influence of resistance training performed to high (> 25%) and moderate (20–25%) velocity loss on muscle hypertrophy based on studies in Theme C. Studies presented were grouped into Theme C that involved resistance training performed to different velocity loss thresholds. Point estimates and error bars signify the standardised mean difference (SMD) between high and moderate velocity loss conditions and 95% confidence interval (CI) values, respectively. PM pectoralis major, QF quadriceps femoris, RF rectus femoris, SD standard deviation, VeL velocity loss, VI vastus intermedius, VL vastus lateralis, VM vastus medialis

Fig. 4

Individual standardised effect sizes (pre-intervention to post-intervention changes in muscle size) for all velocity loss conditions [low (< 20%), moderate (20–25%), high (> 25%)] in each study from Theme C. Data presented were extracted from studies grouped into Theme C that involved resistance training performed to different velocity loss thresholds. The size of the dot point is based on a standardised effect size and a horizontal ‘jitter’ was applied to limit the overlap of dot points (as such, the dot point position on the x-axis is not a true representation of the velocity loss achieved and is rather limited to 0, 10, 15, 20, 25, 40 and 50% velocity losses). Positive effect size values indicate increases in muscle size from pre-intervention to post-intervention for each velocity loss condition

Fig. 5

Conceptual non-linear relationship between proximity-to-failure and muscle hypertrophy. Our results suggest that closer proximities-to-failure are associated with muscle hypertrophy in a non-linear manner. Although the order of resistance training conditions displayed allows for visual inspection of a potential non-linear relationship between proximity-to-failure and muscle hypertrophy, the true proximities-to-failure achieved in each of these resistance training conditions are unclear and likely vary. The far-right dot point represents the ‘momentary muscular failure’ condition. It is also likely that participants in the ‘set failure’ and ‘high velocity loss’ conditions reached momentary muscular failure at times. Data shown are effect size estimates for pre-intervention to post-intervention increases in muscle size for each resistance training condition