The research was focused to analyse the muscle activation using sEMG during repeated physical activity. The purpose of this study was to find out differences between a sportsman and an untrained man in the timing of muscle activation during increasing load. Two men took part in the research. The untrained man (MN) 20 years old, 180 cm, 74 kg, sportsman (MS) 22 years old, 177 cm, 87 kg. Participants performed repeated flexion and extension in the elbow joint. Muscle activation has been tested using sEMG on the selected muscles: biceps brachii (BB), brachioradialis (B), trapezius p. descendez (TD), deltoideus p. acromialis (DA). Both participants performed test for 5, 8 and 12 kg load. Number of repetition was 10. In flexion, the time of muscle activations were the same or very similar for BB for both participants and longer in MN for B and DA, for TD were longer in MS for all loads. Differences were caused firstly by a different finishing time. In extension DA and B in MN, partly also TD were activated for a longer time. The time for activation of BB was mostly the same. Differences were caused mainly by the later start of the activation in MS. Also tendencies in prolonging and shortening the time of activation in relation to increasing load in both participants demonstrated different characteristics. Significantly longer time of muscle activation of MN has been proved only for B and DA for both kinds of movements. Differences between participants in the total time of activation at absolutely same load were expected especially because of the better movement efficiency, adaptation to the power load and movement technique in MS.