The role of the antigravity musculature during quiet standing in man.

The view that postural regulation is achieved by controlling the destabilising effects of gravity through myotatic reflex activity was examined using surface electromyography. Forty seconds of recordings were made of myograms from eighteen muscles in each of a sample of nine young adults. It was observed that antigravity muscular activity in standing is generally low and often absent, and that the myograms from the muscles of the right and left sides of the body differed appreciably, the two sides rarely working together. Some sudden and united bursts of antigravity muscle activity could be observed. These might well have been stretch reflex induced, but they were transient and rare. It is concluded that the view that postural control in quiet standing is continuously mediated in a simple way by stretch reflex mechanisms is probably not valid, and that other mechanisms for controlling posture remain to be identified.