The importance of intrinsic and extrinsic variables in the control of movements

Abstract

In this study, it is analyzed in intrinsic or extrinsic variables the central nervous system controls during the performance of the voluntary movements of the superior extremity. In accordance with the “Dual Strategy Hypothesis”, this system modulates the patterns of muscular activity in conformity with the demand of the task in terms of distance and velocity of execution. Generally, the literature review demonstrated that during the performance of simple and complex movements of the superior extremity. These patterns are linearly coupled with the muscle torque impulses (a force generated in the joint). In view of discussing about the joint, it could be argued that the Central Nervous System has a preference for controlling intrinsic variables during the execution of movements. On the other hand, the invariances observed in the hand path and in the speed of index finger can reveal that the Central Nervous System plans movements using extrinsic variables. This hypothesis is supported by evidences from new studies that compare the motor performance (in terms of accuracy) during the execution of an “extrinsic” and “intrinsic” task.