Repeated sit-to-stand exercise enhances muscle strength and reduces lower body muscular demands in physically frail elders

Abstract

Purpose: To examine the effect of a conditioning program consisting of repeated sit-to-stand exercise on knee extensor strength and muscular activities during body mass-based squat movement in physically frail elders.

Methods: Fourteen men and women aged 75 to 88 years who used the long-term care insurance system participated in the 12-week training program (48 reps/session, 3 sessions/week). Isometric knee extension torque (KET) during a maximum voluntary contraction (MVC) and electromyogram (EMG) activities of the rectus femoris and vastus lateralis muscles during the MVC and a body mass-based squat task were determined at baseline, and following 4 and 12 weeks training. KET was expressed relative to body mass (KET/BM) and EMG activities during the squat task were normalized to that during a MVC and averaged (QF %EMGmax).

Results: KET/BM increased from 1.07 ± 0.28 Nm/kg at baseline to 1.26 ± 0.26 Nm/kg at week 4 and 1.31 ± 0.28 Nm/kg at week 12 (P < 0.001), and QF %EMGmax decreased from 67.2 ± 17.2% to 49.3% at week 4 (P < 0.001) and 43.5 ± 7.7% at week 12 (P = 0.016). At each of the three measurement time points KET/BM was inversely correlated with QF %EMGmax (r = -0.78 to -0.86, P ≤ 0.001).

Conclusion: For physically frail elders, a short-term conditioning program consisting of repeated sit-to-stand exercise is effective in increasing knee extensor strength and reducing the muscular effort required for lowering and raising the body.

Keywords: Electromyogram; Muscular effort; Quadriceps femoris muscle.