Push-up exercises are commonly performed to strengthen the upper extremity muscles. However, the relationship between the push-up speed and upper extremity fatigue is not well understood. Accordingly, the present study investigated the effect of the push-up speed on the maximum possible number of push-up repetitions until fatigue and the upper-extremity muscle activity, respectively, in order to identify suitable push-up strategies for upper-extremity muscular strengthening. Fifteen healthy males participated in the study. Each subject performed push-ups at three different speeds (i.e., fast: 7 push-ups/10 s; regular: 5 push-ups/10 s; and slow: 4 push-ups/10 s) until fatigued. The muscle activity signals were measured during the push-up tests via surface electromyography. The strengthening effect of the push-up exercises was evaluated by measuring the myodynamic decline rate at the shoulder, elbow and wrist joints using an isokinetic dynamometer. The results showed that the maximum possible number of push-up repetitions at the fast push-up speed was around 1.34 and 1.33 times higher than that at the regular push-up speed or slow push-up speed, respectively. However, the endurance time (i.e., the time to fatigue) at the slow push-up speed was around 1.20 and 1.24 times longer than that at the fast push-up speed or regular push-up speed, respectively. Finally, at the slow push-up speed, the total muscle activations in the triceps brachii, biceps brachii, anterior deltoid, pectoralis major, and posterior deltoid, respectively, were 1.47, 2.43, 1.42, 1.48, and 1.91 times higher than those at the fast push-up speed. Therefore, the experimental results suggest that push-ups should be performed at a faster speed when the aim is to achieve a certain number of repetitions, but should be performed at a slower speed when the aim is to strengthen the upper extremity muscles.