Effects of a 12-week power training of upper limbs on neuromuscular performance and mechanical efficiency (ME) was studied in 7 women. Isometric maximum, pure concentric (Cone), pure eccentric (Ecc), and stretch-shortening cycle (SSC) exercises with maximal and submaximal efforts were undertaken. The results showed that improvement in maximal performance due to training was seen as increased maximal isometric force and its rate of development (p < 0.05), and as improvement in maximal Cone and SSC force productions. ME, measured during submaximal exercise, did not change during the follow-up period. The improvements observed in the maximal isometric condition could not be explained by the increase in agonist EMG-activity. In the dynamic movements, however, the improved force production could have resulted from the simple improvement of coordination between agonist and antagonist muscles. The fact that the greatest improvements took place at higher shortening velocities of the concentric action (lightest load) and at the respective velocities of the SSC exercise emphasizes the specificity aspect of power training.