Electromyographic Studies of the Standing Posture of Man

Abstract

The activity of leg muscles in the standing posture of man was researched by the electromyographic method. The method employed was the same as the previous report (This Journal vol. 61, p. 19, 1951), that is, the action current was lead by the coaxial needle electrode inset into the muscle in question. The results obtained are as follows;(1) The standing postures are classified into two groups, symmetrical and asymmetrical, and the symmetrical group is further divided into three, that is, relaxed posture(Ruhe Haltung by R. FICK), normal posture (Bequeme Haltung) and strained posture (Militarische Haltung).(2) In normal standing posture, it may be said, the most natural postre, knee and foot joints are not antagonistically fixed by M. gastrocnemius, M.soleus, M. biceps femoris etc., while hip joint is fixed antagonistically by M. iliopsoas and glutaeal muscles.(3) It may be said that the fixation of hip joint is concerned with the fundi of cellebelum, while fixation of knee and foot joint is related to the function of spinal cord and labyrinth respectively.(4) The activity of neuromusclar unit (motor unit) in standing posture is different in nature from that of volantary contraction. The spike discharge intervals which show remarkably irregurlar fluctuation and slow unduration are about 0.08-0.10 sec., and each neuromuscular unit shows the rotational activity, which is never seen in weak volantary contraction. These phenomena originate from the unsettledness of standing posture.