The influence of competition on the efficiency of an isometric muscle contraction

36 male Ss from collegiate intramural athletic teams were asked to maintain 50% of their maximum voluntary contraction on an iso-metric handle as long as possible. Ss were divided into 2 groups. One group performed individually while the other group, in teams of 3 Ss each, competed for a team prize. During the session, the active muscle was continuously monitored by EMG. The introduction of the motivational factors of competition and team presence did not increase the mean endurance time, but muscle EMG activity was significantly increased when additional motivational factors were introduced. It was concluded that team presence and competition are better described as stress factors which reduce the efficiency of the muscles. The reduction of efficiency is explained both in terms of increased activity of the antagonistic muscles and an increase in S's general arousal level.