Reaction Time of Wrist Flexion during Passive Elbow Movements

The effect of passive elbow movements on EMG-reaction times (EMG-RTs) of the wrist flexors was investigated for 10 subjects. Each subject flexed his left wrist responding to a tone stimulus during passive elbow flexion or extension in the pronated or supinated forearm position. The variation of EMG-RTs could not be attributed to passive lengthening or shortening of the wrist flexors but to the combination of movement directions between the active wrist flexion and the passive elbow movements. EMG-RTs decreased when both the active and passive movements were in the same direction and increased when they were in the opposite directions.