Effect of Cushion Height on Muscle Activation During Sit to Stand Motion in Healthy Elderly Subjects

Effect of Cushion Height on Muscle Activation During Sit to Stand Motion

Abstract

Background: During 2nd phase of sit to stand motion, complex co-contraction pattern of activity at knee joint is in contrast to the flexion only of phase 1 and extension only of phase 3. In this study amplitude of activation of knee joint muscle (vastus medialis and biceps femoris) is assessed. As cushion height is an important factor in sit to stand motion, 30mm cushion, 60mm cushion and 90mm cushion on ideal chair for assessing amplitude of muscle activation during sit to stand have been used. OBJECTIVES: To assess muscle activation while using 30mm, 60 mm and 90 mm thickness cushion during Sit to stand (STS) motion in healthy elderly subjects. To compare between this 3 thickness of cushion. To correlate balance (time up and go score) with amplitude of muscle contraction during STS motion using different heights of cushion. Methods: The study included 75 healthy elderly individuals who were able to do Sit to stand motion (STS) independently. Amplitude of muscle activation of vastus medialis and biceps femoris muscle were assessed using surface Electromyography. Three times subject was told to do sit to stand motion on 30 mm, 60 mm and 90 mm cushion thickness respectively, average value of amplitude of muscle activation on 30mm, 60mm and 90mm cushion thickness was considered. Balance was assessed using Timed up and go scale (TUG). Results: There was no significant difference in the EMG activity of vastus medialis at 30 mm, 60 mm, and 90 mm cushion thickness. (p=0.442), there was significant difference in the EMG activity of biceps femoris at 30 mm, 60 mm, and 90 mm cushion thickness. (p=0.000) Friedman Test was used. There was increased electromyographic activity of biceps femoris muscle on 30 mm cushion thickness followed by 90 mm cushion thickness and less electromyographic activity at 60 mm cushion thickness during sit to stand motion. Multiple Comparisons - Bonferroni Adjusted Wilcoxon signed rank tests was used. Conclusion: This study suggests, the electromyographic activity of biceps femoris muscle during sit to stand motion was more on 30 mm cushion thickness followed by 90 mm cushion thickness and 60 mm cushion thickness. [Salvi S Natl J Integr Res Med, 2019; 10(6):46-49]