Effects of 8 weeks of high-intensity interval training or resistance training on muscle strength, muscle power and cardiorespiratory responses in trained young men.

Purpose: The aim of this study was to compare the effects of 8 weeks of resistance training (RT) and high-intensity interval training (HIIT) on muscle strength, muscle power and cardiorespiratory responses in trained young men. Methods: Twenty-two men [RT (n = 11); HIIT (n = 11)] performed 8 weeks of training, with frequency of 2 times per week. RT group performed 10 sets × 10–12 RM of Leg-press exercise, while HIIT group performed 10 sets of running × 60 s at 85–95% of maximal heart rate. Both groups performed 60 s of passive rest between sets. Maximal strength (one-repetition maximum [1RM] of Leg Press and Knee Extension), jump height (single-leg countermovement jump) and cardiorespiratory responses during Conconi Test (predicted VO2peak and heart rate at maximal and at deflection point) were evaluated at baseline and after training program. Results: 1RM of Leg Press increased in both training groups (p < 0.001), with higher gains in the RT group (RT = 32.2%, HIIT = 9.5%; p = 0.036; d = 1.86), 1RM of Knee Extension did not improve for either group (p = 0.065). Only the HIIT group improved jump height (RT = − 1.5%, HIIT = 14.2%; p = 0.002; d = 1.52) and cardiorespiratory capacity (RT = − 1.1%, HIIT = 3.2%; p = 0.006; d = 1.27). Conclusion: Despite RT group promoting higher strength gains, HIIT is also effective for improving strength, jump height and cardiorespiratory capacity, and it presents as a possible alternative for people who seek improvements in health variables. Trial registration: This study was registered in Brazilian Clinical Trials Registry (registration number RBR-7n8y9ky) on Mar 09th 2021 (retrospectively registered). [ABSTRACT FROM AUTHOR]