Effects of Muscle Contraction Speed on Number of Repetitions, Exercise Duration and Muscle Activation during Push-up Exercise in Men. KINESIOLOGY, 2016, 18(1): 11-18. [PURPOSE] The purpose of this study was to examine the effects of muscle contraction speed on number of repetitions, exercise duration and muscle activation during push-up exercise in men. [METHODS] The study employed a randomized, counter-balanced crossover design with two testing sessions that were 3 months apart. Twelve, healthy, male collegiate students were asked to perform two exercises separately, normal-speed push-up (ECC: 1-s, CON: 1-s) and speedy-push-up (maximum speed), until repetition failure of volitional contraction. Outcomes were number of repetitions, exercise duration and muscle activation of the pectoralis major measured through surface electromyography (sEMG) during push-up exercises. The sEMG data were normalized to maximal voluntary isometric contraction (MVIC) and expressed as a percentage (%MVIC) in both ECC phase and CON phase. [RESULTS] Number of repetitions (t=-5.352, p<.001), exercise duration (t=-5.837, p<.001) and muscle activity (t=-4.525, p=.023) were significantly different between two exercise conditions. [CONCLUSIONS] Normal-speed push-up exercise increased exercise duration and muscular activity while, and speedy push-up exercise increased number of repetitions. Further studies are warranted to elucidate associations between muscle adaptation stimulus and muscle contraction speed.