Central Activation of the Upper Limb Muscles in Humans Related to Creation of an Isometric Effort: Dependence on the Position of the Point of Force Application within the Operational Space

摘要

We examined the peculiarities of central coordination of motor commands coming to the muscles of theshoulder belt and shoulder in the course of generation of targeted isometric efforts by the arm. The dependence of these commands on changes in the effort direction and position of the forearm within the working space were analyzed. The intensity of the central commands was estimated according to the amplitudes of rectified and averaged EMGs recorded from the corresponding muscles. Sector diagrams of EMG activity of the above muscles depending on the direction of the effort vector, EV, were plotted [1]. Preferential sectors of activity where the efforts were formed due to activation of definite functional muscle groups were identified. As was found, the direction of these sectors depends significantly on the EV orientation. Differences between the patterns of coactivation of the examined muscles were demonstrated. Organization of the motor commands under conditions of creation of extensor efforts is distinguished by a more complex pattern than that related to flexor efforts. In the former case, the activity of extensor muscles is accompanied by more significant activation of the flexors.