ELECTROMYOGRAPHIC STUDIES ON THE POSTURAL MUSCLES OF THE LOWER EXTREMITY,ESPECIALLY THE GASTROCNEMIUS / 解剖学报

ABSTRACT

Multilead electromyographic studies were made on 15 healthy young adult males to investigate the action of the postural muscles of the lower extremity,especially the gastro- cnemius.The results were as follows 1.In standing position,either both legs or one leg supported the body weight,the gastrocnemius of the weight bearing leg or legs as well as hamstring muscles showed some potentials.When changing the body position from standing to squatting or the re- verse,the gastrocnemius showed similar activity.It indicates that the gastrocnemius acts together with the hamstring muscles to counteract the action of the quadriceps in main- taining the extended position of the knee joint. 2.When one leg stands on the ground and the other hangs freely,then flex and extend the free leg slowly,no activity was recorded in the gastrocnemius.Similarly no activity was recorded in the gastrocnemius when flexing the knee joint in sitting position. It is,therefore,assumed that the gastrocnemius is not necessarily a flexor of the knee joint as usually considered,but an important extensor under certain conditions. 3.When rotate the leg medially or laterally on siting position,the both heads of the gastrocnemius showed activities.The rotation of the leg towards either direction is not the action of a single head although the medial head is always more active than the lateral one. 4.The activities were also shown in the gastrocnemius when standing on the toes or stepping forward of the weight-bearing leg in walking.It confirms the common view that the gastrocnemius is a flexor of the ankle joint. The activities of the quadriceps,hamstring muscles and soleus were also recorded and discussed.