Increase in simple reaction time of knee extension induced by simultaneous bilateral performance

Simple reaction time to an auditory stimulus was measured for separate unilateral and simultaneous bilateral knee-extension tasks. The latencies of the electromyographic discharge (155.3 msec.) and knee-joint movement (231.0 msec.) were longer in the bilateral condition than in the unilateral condition (139.2 and 218.8 msec., respectively), while the time difference between EMG onset and knee-movement onset was the same for the unilateral (79.5 msec.) and bilateral (76.2 msec.) conditions. Interhemispheric inhibition was discussed as the mechanism for this unilateral-bilateral difference.