Effects on Anticipatory Postural Adjustments by Repetition of the Tiptoe Movement

Abstract

The purpose of this study was to investigate the influence of repetition on anticipatory postural adjustments between two tiptoe movement tasks. Ten healthy young male (22.5 ± 2.6 years old) participated in this study. They stood on tiptoe from standing position as quickly as possible after an auditory stimulus. Single and repetitive tasks as the tiptoe movement task were performed. Electromyogram during the tiptoe movement was measured in the gastrocnemius (Gas), tibialis anterior (TA), biceps femoris (BF), rectus femoris (RF), erector spinae (ES) and rectus abdominus (RA). The characteristics of the initial tiptoe movement during each task were established by analysis of kinematics data. Onsets of each muscle activity, integrated electromyography (EMG) and center of pressure (COP) displacement prior to the onset of Gas were compared between the single and repetitive tasks. The onset of TA and RF in the repetitive task was earlier than that of the single task, and integrated EMG per unit time and COP displacement also changed. These results suggest that the central nervous system may transmit different motor commands to postural muscles during single and repetitive tasks, and anticipatory postural adjustment might be modulated by the repetition of task.