Functional organization of the motor process underlying the transition from movement to posture.

In these experiments we studied the organization of the neural pattern of activity underlying the achievement and maintenance of final limb position. The examination of the alpha motoneuronal inputs to flexors and extensors acting on the elbow and wrist joints revealed that a change from one posture to another required a modulation of both flexors and extensors. For a given position, the final EMG level of flexors and extensors is more variable than the ratio between the alpha neuronal activity of these two antagonistic muscles. Further, the ratio was not significantly affected by the direction, amplitude or velocity of the movement. These results indicate that the final position could be coded in the central nervous system (CNS) as the ratio of activity in antagonistic muscles acting on a joint.