Experimental Design and Procedure
hand movements, adduction, abduction
Participants were asked to sit comfortably in a chair in an upright position during the experiment. They were instructed to practice the two motor tasks several times before the experiments.The experiments were arranged in a block paradigm (Fig. The experiment consisted of two motor tasks:
Hand: alternating opening and closing movement of the right hand.Shoulder: alternating movement of abduction and adduction of the right shoulder with the elbow flexed. The movement began with the upper arm by the person’s side and ended before the trunk began to tilt (range around 70–80 degrees).All tasks were performed at a frequency of 0.5 Hz, ensured by metronome guidance at a frequency of 1 Hz, corresponding to half of a complete movement. The metronome was switched on during both the motor tasks and rest periods to control for the effects of the auditory stimulus.The verbal instructions to start the motor tasks were ‘‘Hand” or ‘‘Shoulder’’ for hand, and shoulder movement tasks respectively, and the instruction to stop the motor tasks was ‘‘Stop’’. Participants did not know which motor task was to be performed until the instruction to initiate the motor tasks was given.The order of experimental sessions was randomized, and the pre-task baseline was 2 min in duration.
Block design. The blue bars represent hand movements and the black bars represent shoulder movements