Postural adjustments in the monkey: effects of velocity on EMG sequence.

Monkeys were trained to perform flexion or extension movements of the elbow in a strictly restrained position. Even in these conditions, postural adjustments were still recorded. They appeared to be organized in a consistent pattern. When trials were ranked with increasing velocity, two kinds of EMG changes could be described: (i) those in the upper part of the body which may be triggered by anticipatory postural motor programs; (ii) those in lower limbs recruited only with higher velocities and that may correspond to semi-automatic programs organized at a lower level of the central nervous system.