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

"Adaptation" to Displacement Prisms Is Sensorimotor Learning

Observers reaching to a target seen through wedge shaped displacement prisms initially reach in the direction of displacement, correcting their reaches over a series of about 12 trials. With subsequent removal of the prisms, observers initially reach to the opposite side of the target, correcting over about 6 trials. This phenomenon has been called "adaptation" because of its similarity to the adaptation of sensory thresholds to prevailing energy levels. W e show, however, that this perturbation to visually guided reaching only mimics sensory adaptation initially. Subsequent changes show that this is sensorimotor learning. Error in pointing to targets is the commonly used measure. W e measured times for rapid reaches to place a stylus in a target. Participants wearing a prism worked to achieve criterion times previously established with normal, unperturbed vision. Blocks of trials with and without a prism were alternated. Both the number of trials to criterion and the mean times per block of trials decreased over successive blocks in a session, as well as over successive days. By the third day, participants were able to respond rapidly to perturbations. This reflects the acquisition of a new skill that must be similar to that acquired by users of corrective lens

A KINEMATIC ANALYSIS OF THE BREASTROKE KICK

The study investigated the contribution of the ankle joint in the breaststroke kick using three dimensional kinematic analyses. Methodology included applying reference markers to the right leg using anatomical reference points and then videotaping twelve competitive swimmers performing the breaststroke. A Matlab script was used to calculate relative angles (between the foot and shank), angular and relative angular velocities, and linear velocities. The results of a linear regression at