Muscle Activation and Movement Coordination.

• Main Author: Ljung, Carl
• Format: Others
• Language: English
• Published: KTH, Mekanik 2014
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148773

The purpose of this project was to empirically develop a method of using electromyography to identify how humans coordinate their muscles during certain sequences of movement and the effect of an injured anterior cruciate ligament to muscle coordination. In this study, more simple movements of the lower extremities are examined and relatively accurate hypothesizes can be made solely based on anatomical theory. However, a general method for electromyographic studies would open up the possibility of exploring muscle coordination in more complex movements. This would facilitate further research in scientific fields such as biomechanics and neurophysiology. Surface electromyography was used to acquire data of muscle activation from the primary muscle groups of the lower extremities, while body movements were recorded using video cameras. The neural signals sampled were rectified for systematic interference by the removal of electrical background noise and by centering the signal baseline. To address the problem of the neural signal pattern being random, a smoothing algorithm called "RMS EMG" that reflects the mean power of the signal was applied. Additionally, a high-pass filter was applied to filter out filter out frequencies outside the range of neural signals in muscles. In order to correlate the body movement sequences with the electromyographic data, the video recordings were compared with activity-time plots of the electromyographic data. By localizing and interpreting local peaks and change of gradients, the motions where structured into distinct phases and the muscle coordination was evaluated. Through investigation of both bilateral and unilateral movements the effects on an injured anterior cruciate ligament were studied. Results showed predominant muscle activation in the knee extensors during squatting and similar motions. Even though the motions included significant hip extension, the hamstrings displayed a nearly constant level of muscle activation throughout the movement. Activation of the muscles occurred simultaneously, but the motion appeared to be primarily executed by the knee extensors. During gait, muscle activation in the gastrocnemius was observed to be significantly higher than in any other muscle prior to the hind foot leaving ground. Injury to the anterior cruciate ligament appeared to cause an increase of muscle activation in the lateral side of the knee extensors compared to the medial side.