EFFECT OF RESISTANCE TRAINING ON POSTURAL STABILITY AND A SIT-TO-STAND TASK642

Abstract

This study was performed to assess changes in postural stability and performance of a sit-to-stand task in elderly (68±5 yrs; mean±S.D.) men and women after 12 weeks of resistance training. Leg strength was assessed with a 1-RM using a Cybex II™ isokinetic dynamometer and a Keiser™ isotonic machine. Postural stability was assessed during quiet standing and one-legged standing on a force platform. Three trials of a sit-to-stand task from a 38 cm high bench were filmed from a sagittal view. Subjects were randomly divided into training (TR; n=10) or control (CON; n=9) groups. The CON group was asked not to change their lifestyle over the 12 weeks of the study. Training consisted of 10 exercises. designed to isolate the major muscle groups of upper and lower body. Subjects performed 3 sets of 8-12 repetitions at 80-85% of 1-RM, 3x/wk. The increase in isotonic leg strength during the 12 wks was greater (p<0.05) in TR(380±41 N vs. 534±55 N) than CON (443±47 N vs. 471±47 N). Both TR (81±9 vs. 105±11 Nm) and CON(86±8 vs. 102±9 NM) groups significantly (p<0.05) increased isokinetic leg strength at 180°/s. No significant differences were found in stability measures. Total migration of the center of pressure (CP) during quiet standing decreased for both TR (35±13 vs. 28±17 cm. effect size (ES)=0.4) and CON (44±25 vs. 34±16, ES=0.4) after training. Kinematic analysis of the sit-to-stand task for 6 subjects indicated that TR achieved a greater peak hip flexion angle after training (116±8 vs. 126±3°, ES=3.0) than CON (115±11 vs. 119±11°, ES= 0.7). This adjustment was accompanied by a greater increase in peak shoulder flexion angle for TR (25±19 vs. 41±31°, ES=1.3) than CON(29±23 vs. 39±28°, ES=0.8). It was concluded that this program of resistance training had a limited effect on improving postural stability. However, greater contributions from the upper body to the sit-to-stand task were observed after training.