In between-hand choice reaction time (RT) tasks, the activation of the cerebral motor structures involved in the required response is accompanied by an inhibition of the structures involved in the alternative response. The objectives were (1) to check whether the inhibition observed at the central level can be accompanied by signs of deactivation at the peripheral level during response execution and (2) to assess whether time preparation affects response execution. Surface electromyographic (EMG) activity of the first dorsal interosseus was recorded during the performance of a between-hand choice visual RT task in which the foreperiod duration was manipulated. The contraction of the muscle involved in the required response was accompanied by a reduction in the EMG activity of the muscle involved in the nonrequired response. The foreperiod duration influenced this EMG pattern. The findings reveal peripheral signs of a deactivation of the non-required response and suggest that time preparation influences the activity of the muscles involved in both the required and the nonrequired response. The present results are compatible with the view that, at least in between-hand choice RT tasks, the motor command specifies both the activation of the central structures involved in the required response and the inhibition of the central structures involved in the nonrequired response. They further indicate that time preparation affects the activity of the response agonists.