Analysis of activity of muscles acting on ankle joint in sitting and standing from chairs of different heights

Abstract

When a person sitting on a chair stands and sits from the standing position the weight transfers from spine to ankle and from ankle to spine. Most significant joint loads occur during stand to sit and sit to stand movement than any other activity. Slight changes in loads on the knee joint, ankle joint and the lumbar spine are linked with greater angular displacement at knee, spine and hip joints. The movement of body segments with respect to each other moves the body center mass which causes greater forces in the joints. Incorrect simple activities contribute to increased loads which lead to increase in strains and inflammation. Tibialis anterior - dorsi- flexor of the ankle and soleus - plantar-flexor of the ankle are the important muscles required for all leg activities. The activity of these two muscles were monitored in this study. The subjects were asked to sit and stand from a chair of height 17.5 cm and a podium of height 12.5 cm which can be considered as a chair shorter than an ideal chair. An accelerometer mounted on the cervical spine was used to determine the position of the subjects. The EMG data epochs were classified using the accelerometer signal. Our study result shows that there is a significant difference in muscle activity between chair and podium while performing sit to stand actions and stand to sit actions observed from EMG signal analysis.