Purpose: This study aimed to analyze the effect of resistance training (RT) performed until volitional failure with low, moderate, and high loads on muscle hypertrophy and muscle strength in healthy adults and to assess the possible participant-, design-, and training-related covariates that may affect the adaptations. Methods: Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, MEDLINE, CINAHL, EMBASE, SPORTDiscus, and Web of Science databases were searched. Including only studies that performed sets to volitional failure, the effects of low- (>15 repetitions maximum (RM)), moderate- (9–15 RM), and high-load (≤8 RM) RTs were examined in healthy adults. Network meta-analysis was undertaken to calculate the standardized mean difference (SMD) between RT loads in overall and subgroup analyses involving studies deemed of high quality. Associations between participant-, design-, and training-related covariates with SMD were assessed by univariate and multivariate network meta-regression analyses. Results: Twenty-eight studies involving 747 healthy adults were included. Although no differences in muscle hypertrophy between RT loads were found in overall (P = 0.113–0.469) or subgroup analysis (P = 0.871–0.995), greater effects were observed in untrained participants (P = 0.033) and participants with some training background who undertook more RT sessions (P = 0.031–0.045). Muscle strength improvement was superior for both high-load and moderate-load compared with low-load RT in overall and subgroup analysis (SMD, 0.60–0.63 and 0.34–0.35, respectively; P < 0.001–0.003), with a nonsignificant but superior effect for high compared with moderate load (SMD, 0.26–0.28, P = 0.068). Conclusions: Although muscle hypertrophy improvements seem to be load independent, increases in muscle strength are superior in high-load RT programs. Untrained participants exhibit greater muscle hypertrophy, whereas undertaking more RT sessions provides superior gains in those with previous training experience.

The hamstrings-to-quadriceps muscle strength ratio calculated by peak torque has been used as an important tool to detect muscle imbalance, monitor knee joint stability, describe muscle strength properties and functionality, and for lower extremity injury prevention and rehabilitation. However, this ratio does not consider other neuromuscular variables that can also influence the antagonist to agonist muscle relationship, such as torque produced at multiple angles of range of motion, explosive strength, muscle size, muscle fatigue, or muscle activation. The aim of this study was to comprehensively review alternative methods of determining the hamstrings-to-quadriceps ratio. These include ratios calculated by angle-specific torque, rate of torque development, muscle size, fatigue index, and muscle activation (measured by electromyography). Collectively, the literature demonstrates that utilizing alternative methods of determining the hamstrings-to-quadriceps ratio can be functionally relevant for a better understanding of the neuromuscular mechanisms underpinning the interaction of strength between hamstrings and quadriceps. However, there is insufficient evidence to recommend any of the alternative methods as sensitive clinical tools for predicting injury risk and monitoring knee joint integrity. Future longitudinal studies, along with injury incidence, are needed to further investigate all alternative methods of determining the hamstrings-to-quadriceps ratio. These have potential to offer insight into how athletes and the general population should be trained for performance enhancement and injury reduction, and may be used along with traditional methods for a thorough assessment of an individual’s H:Q muscle balance.

The purpose of this investigation was to compare partial range-of-motion vs. full range-of-motion upper-body resistance training on strength and muscle thickness (MT) in young men. Volunteers were randomly assigned to 3 groups: (a) full range of motion (FULL; n = 15), (b) partial range of motion (PART; n = 15), or (c) control (CON; n = 10). The subjects trained 2 d · wk(-1) for 10 weeks in a periodized program. Primary outcome measures included elbow flexion maximal strength measured by 1 repetition maximum (1RM) and elbow flexors MT measured by ultrasound. The results indicated that elbow flexion 1RM significantly increased (p < 0.05) for the FULL (25.7 ± 9.6%) and PART groups (16.0 ± 6.7%) but not for the CON group (1.7 ± 5.5%). Also, FULL 1RM strength was significantly greater than the PART 1RM after the training period. Average elbow flexor MT significantly increased for both training groups (9.65 ± 4.4% for FULL and 7.83 ± 4.9 for PART). These data suggest that muscle strength and MT can be improved with both FULL and PART resistance training, but FULL may lead to greater strength gains.