LEG MUSCLE ACTIVATION PATTERNS DURING SIT-TO-STAND UNDER VARIABLE COMPLIANCE SURFACES

The purpose of this study was to look if there were any differences in lower limb muscle activation patterns on various compliance surfaces during a sit-to-stand (STS) task. Previous studies have compared muscle activation patterns on stable versus unstable supporting surfaces but on the current research the surface stability was modified through four eight-way adjustable-stiffness shock absorbers mounted between two force plates creating stiffness conditions ranging from soft to very hard. Seventeen participants that were recruited randomly by a pool of volunteers performed a self-paced STS under eight surface stiffness conditions in randomized order. The mean EMG values of ten muscles during STS on various compliance surfaces were analysed and compared according under distinct phases of force profile. There were no statistically significant differences found in mean EMG of the muscles examined under different supporting surface stiffness conditions. It was found that muscle activation patterns during STS do not significantly change with variations of the surface compliance, suggesting that a STS movement skill is preprogramed, when the STS conditions are not known