Response preparation and control of movement sequences.

Two experiments investigated the response complexity effect using elbow extension/flexion movements. In the first experiment, RT for an extension movement was significantly less than RT for an extension/flexion movement. However, this difference in RT was not evident when participants were asked to pause at the reversal of the extension/flexion for approximately 260 ms. The second experiment manipulated the duration of the pause between these movements and also measured the electromyographical (EMG) activity of the triceps and biceps muscles. When the pause was reduced to 75 ms participants were not able to program the flexion portion of the movement at the reversal, forcing them to preprogram this movement; hence, increasing their premotor reaction time.