Motor control mechanisms. An overview

Recent experiments suggest a simple relationship between posture and movement. Posture appears to result from the CNS setting the activity levels of agonist and antagonist muscles around the joint, resulting in an equilibrium force, the ratios of which are different for different positions. Control of movement is accomplished by changing the set of opposing length-tension curves. However, the experimental evidence also indicates that during movement there is active control of the trajectory in addition to control of final position. A simple strategy of choosing a new posture via the length-tension curves and letting a limb move until equilibrium is established is not the control algorithm used by the vertebrate motor system.