Muscles activity of the Back and Hamstring during Trunk Flexion and Extension Task in Healthy and Low Back Pain Women

Abstract

This paper describes the investigation of Surface Electromyography (sEMG) signals of back muscles and hamstring muscles during forward flexion and extension in healthy and low back pain (LBP) women. There were two groups of Malaysian females aged between 20 to 55 years old voluntary participated in this study. Group 1 consisted of 10 healthy females while group 2 consisted of 6 females suffered with low back pain. Every subject was trained to perform two types of forward flexion; maximum forward flexion (bowing as far as they can) and 90° forward flexion with hands on the knees. The electromyogram (EMG) and the motion signals were recorded during forward flexion of the trunk at the back and hamstring muscles. The findings indicated that the flexion relaxation phenomenon (FRP) was found only at the back muscles in healthy subjects during full flexion of the trunk, however it was absent at the hamstring muscles. For low back pain patients, the FRP was absent in both muscles. Mann-Whitney test showed astatistically significant differences in flexion relaxation ratio (FRR) between two groups during maximum forward flexion (p<0.05) and 90° forward flexion (p<0.001).KeywordsFlexion relaxation phenomenonlow back painback muscleshamstring muscles