Table 1.
Summary of meta-analyses that investigated the effects of modify resistance training variables on hypertrophy.
| References | Variable | Aim | Studies (participants) | Interventions' duration | Heterogeneity (I2) | Findings/conclusions |
|---|---|---|---|---|---|---|
| Krieger (2010) | Volume | To compare the effects of single and multiple sets per exercise on muscle hypertrophy. | 8 (322) | From 6 to 24 weeks | NR | Multiple sets (2–3 sets) are associated with 40% greater hypertrophy-related than 1 set, in both trained and untrained subjects. the trend was observed that 4–6 sets could give an even greater response, but the small number of included studies prevents from establishing any definitive conclusions. |
| Schoenfeld et al. (2017a) | Volume | To elucidate the effects of total weekly volume on changes in measures of muscle mass. | 15 (390) | From 6 weeks to 6 months | NR | Although low volumes ( ≤ 4 weekly sets/muscle group) are enough to get substantial gains in muscle hypertrophy, the findings indicate a graded dose-response relationship whereby increases in volume produce greater gains in muscle hypertrophy. |
| Schoenfeld et al. (2019a) | Frequency | To investigate the effects of weekly training frequency on hypertrophic adaptations. | 25 (836) | From 6 to 30 weeks | 0% | Resistance training frequency does not significantly or meaningfully impact muscle hypertrophy when volume is equated. Conversely, a significant effect favoring higher frequencies were observed when volume was not equated. |
| Schoenfeld et al. (2016a) | Intensity | To compare the effects of low- vs. high-load training in enhancing post-exercise muscular hypertrophy. | 8 (191) | From 6 to 13 weeks | NR | Training with loads ≤ 60% 1RM can promote substantial increases in muscle hypertrophy in untrained individuals, and although a strong trend was noted for superiority of heavy loading regarding to muscle hypertrophy, no significant differences were observed. |
| Schoenfeld et al. (2017b) | Intensity | To compare changes in strength and hypertrophy between low- vs. high-load resistance training protocols. | 10 (630) | From 6 weeks to 1 year | NR | The findings indicate that changes in measures of muscle hypertrophy were similar when trained with low-loads compared to high-loads. |
| Grgic (2020) | Intensity | to explore the effects of low-load vs. high-load resistance training on type I and type II muscle fiber hypertrophy. | 10 (120) | From 6 to 12 weeks | 0-18% | This meta-analysis did not provide significant differences in hypertrophy when compared the effects of low-loads vs. high-loads (performed to momentary muscular failure) in both type I and type II muscle fibers. |
| Roig et al. (2009) | Contraction type | To determine if eccentric exercise is superior to concentric exercise in stimulating gains in muscle mass. | 20 (678) | From 4 to 25 weeks | 65% | Eccentric training appears to be more effective at increasing muscle mass than concentric training, maybe due to the higher forces developed during this type of exercise. Additionally, adaptations after eccentric training are highly specific to the velocity. |
| Schoenfeld et al. (2017c) | Contraction type | To compare the hypertrophic effects of concentric vs. eccentric training in healthy adults following regimented resistance training. | 15 (356) | From 6 weeks to 5 months | NR | Although both concentric and eccentric modes promote significant muscular hypertrophy, a small advantage favoring eccentric training was observed for promoting a hypertrophic response. |
| Schoenfeld et al. (2015) | Repetition duration | To determine whether alterations in repetition duration can amplify the hypertrophic response to resistance training. | 8 (239) | From 6 to 14 weeks | NR | Similar gains in hypertrophy were observed when training with repetition durations ranging from 0.5 to 8 s to concentric muscular failure. In addition, training at volitionally very slow durations (10 s per repetition) is inferior from a hypertrophy standpoint. |
| Nunes et al. (2020) | Exercises order | To analyze the effects of exercise order on muscular hypertrophy. | 11 (268) | From 6 to 12 weeks | 0% | The findings obtained indicated that gains in muscle hypertrophy are not influenced by the exercise order (multi-single vs. single vs. multi) within resistance training programs. |
| Grgic et al. (2019) | Time of day | To elucidate the effects of morning vs. evening resistance training on muscle hypertrophy. | 6 (221) | From 6 to 24weeks | 0% | The findings showed that increases in muscle size are similar irrespective of the time of day at which the training is performed. |
| Grgic et al. (2017) | Periodization | To compare the effects of linear periodization and daily undulating periodization resistance training programs on muscle hypertrophy. | 13 (303) | From 6 to 26 weeks | NR | The findings obtained indicated that the effects of the two periodization models (lineal and undulating) on muscle hypertrophy are likely to be similar. |
| Slysz et al. (2016) | BFR | To assess the effectiveness of BFR exercise on muscle hypertrophy compared to traditional resistance training. | 19 (377) | NR | NR | The findings showed that suggests that the addition of BFR to dynamic exercise training is effective for augmenting changes in muscle size. |
| Lixandrão et al. (2018) | BFR | To compare the effects of high-load vs. low-load resistance training associated with BFR on muscle gains. | 10 (222) | From 4 to 12 weeks | NR | The results obtained demonstrate similar muscle gains for high-load as compared with low-load resistance training associated with BFR. |
NR, non-reported; 1RM, one repetition maximum; BFR, blow flood restriction.