Effect Of Resistance Training To Muscle Failure Versus Volitional Interruption At High- And Low-Intensities On Muscle Mass And Strength.Nóbrega, Sanmy R.; Ugrinowitsch, Carlos; Pintanel, Lucas; Barcelos, Cintia; Libardi, Cleiton A.Journal of Strength & Conditioning Research: Post Acceptance: January 24, 2017 doi: 10.1519/JSC.0000000000001787 Original Research: PDF Only Abstract The purpose of the present study was to investigate the effects of resistance training (RT) at high- and low-intensities performed to muscle failure or volitional interruption on muscle strength, cross-sectional area (CSA), pennation angle (PA) and muscle activation. Thirty-two untrained men participated in the study. Each leg was allocated in one of four unilateral RT protocols: RT to failure at high (HIRT-F) and low (LIRT-F) intensities, and RT to volitional interruption (repetitions performed to the point in which participants voluntarily interrupted the exercise) at high (HIRT-V) and low (LIRT-V) intensities. Muscle strength (1-RM), CSA, PA and muscle activation by amplitude of the electromyography (EMG) signal were assessed before (Pre), after 6 (6W) and 12 (12W) weeks. 1-RM increased similarly after 6W (range: 15.8 - 18.9%, ES: 0.41- 0.58) and 12W (range: 25.6 - 33.6%, ES: 0.64 - 0.98) for all protocols. All protocols were similarly effective in increasing CSA after 6W (range: 3.0 - 4.6%, ES: 0.10 - 0.24) and 12W (range: 6.1 - 7.5%, ES: 0.22 - 0.26). PA increased after 6W (~3.5) and 12W (~9%; main time effect, P < 0.0001), with no differences between protocols. EMG values were significantly higher for the high-intensity protocols at all times (main intensity effect, P < 0.0001). In conclusion, both high- and low-intensity RT performed to volitional interruption are equally effective in increasing muscle mass, strength and PA when compared to RT performed to muscle failure. Copyright (C) 2017 by the National Strength & Conditioning Association.