Effects of concurrent high-intensity interval training and strength training on muscle function and aerobic capacity.

The purpose of this systematic review and meta-analysis was to assess the effects of concurrent high-intensity interval training and strength training on muscular strength, power, and endurance performance. Randomized and nonrandomized studies comparing strength training with concurrent training were identified through PubMed, SPORTDiscus and Web of Science. Data were pooled using a random-effects meta-analysis of standardized mean differences, and the level of significance was set at p<0.05. A total of 8,634 studies were initially identified, and 21 studies (n=569) that met the inclusion criteria were ultimately included in the analysis. No significant differences were observed between the strength training and the concurrent training groups in one-repetition maximum in the squat (standardized mean difference=-0.06, p=0.63) or countermovement jump performance (standardized mean difference=-0.12, p=0.38). In the subgroup analysis, sprint interval training and repeated-sprint training showed no significant effects on countermovement jump performance (standardized mean difference=0.14, p=0.40), whereas short high-intensity interval training and long high-intensity interval training protocols were associated with a significant negative effect (standardized mean difference=-0.53, p=0.006). A formal test for subgroup differences indicated that the effect of concurrent training on countermovement jump performance differed significantly according to the high-intensity interval training type (Qbetween=5.82, df=1, p=0.016). Overall, no statistically significant differences were observed in maximal strength or power performance between concurrent training incorporating high-intensity interval training and strength training alone. The subgroup analyses suggested possible differences according to the high-intensity interval training type. However, these findings were based on a limited number of studies and should therefore be interpreted with caution.