Single motor-unit control by normal and cerebral-palsied males.

Single motor-unit (SMU) control was compared for three ambulatory cerebral-palsied and three neurologically unimpaired subjects. Both groups were similar in their abilities to produce a discrete whole muscle contraction, to isolate and maintain firing of a single motor unit, and to turn a unit on at a visual signal. Unit inter-spike intervals were very similar for both groups. However, the cerebral-palsied subjects showed a consistent inability to inhibit single motor-unit (or whole muscle) activity if the isolated unit had been firing for some time; normal subjects did not show a similar inability.