Coordination of the dynamic phases of EMG activity in human elbow flexors in the performance of targeted tracking movements

We examined the peculiarities of central coordination of motor commands coming to the muscles of the shoulder 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.

Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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

Vereschaka

Gorkovenko

2011

“…At the expense of specific distributions of contractions of synergistic and antagonistic muscles, the velocity of the movements and the force developed are regulated. Alteration of the pattern of interaction of some muscles and their groups is an important factor influencing realization of the movements performed by the upper limb and of force fixation of the latter, since the limb is a mechanical system with a number of degrees of freedom [26][27][28][29][30][31][32][33][34]. Joints with a single degree of freedom are controlled by antagonistic muscles.…”

Section: Activation Of the Shoulder Belt And Shoulder Muscles In Genementioning

confidence: 99%

Activation of the Shoulder Belt and Shoulder Muscles in Humans Providing Generation of “Two-Joint” Isometric Efforts

Верещака

2014

This review deals with the processes of coordination of central motor commands (CMCs) that arrive at human arm muscles in the course of realization of "two-joint" voluntary isometric efforts. The dependence of formation of such motor events on changes in the direction of the generated effort is described. Differences between patterns of co-activation of the studied arm muscles under conditions of isometric contractions are presented. Based on the obtained data, directions of the developed efforts are classified as coinciding and, correspondingly, easier for realization (flexion-flexion and extensionextension in both joints), and as discordant "inconvenient" (extension in the shoulder joint-flexion in the elbow joint and flexion in the shoulder joint-extension in the elbow joint). Programming of coactivation of flexors and extensors of the shoulder and elbow joints seems to be possible at the level of CMCs. Predominant sectors of the activity of separate functional muscle groups during realization of the studied efforts are estimated. We found that the orientation of such sectors depends, in most cases, on the orientation of the effort vector but not on the position of the limb within the horizontal plane.

Activation of the Shoulder Belt and Shoulder Muscles of Humans Related to Different Rates of Generation of Two-Joint Efforts by the Forearm

Верещака

2011

We studied coordination of central motor commands (CMCs) coming to the muscles that flex and extend the shoulder and elbow joints in the course of generation of voluntary isometric efforts of different directions by the forearm. Dependences of the characteristics of these commands on the direction of the effort and rate of its generation were analyzed. Amplitudes of rectified and averaged EMGs recorded from a number of shoulder belt and shoulder muscles were considered correlates of the CMC intensity. The development of the effort of a given direction and rate of rise was realized in the horizontal-plane operational space; the arm position corresponded to the 30 deg angle in the shoulder joint (external angle with respect to the frontal plane) and 90 deg angle in the elbow joint. We plotted sector diagrams of the relative changes in the level of dynamic and stationary phases of EMG activity of the studied muscles for the entire set of directions of the efforts generated with different rates of rise. In the course of formation of rapid two-joint isometric efforts, realization of nonsynergic motor tasks (extension of one joint and flexion of another one, and vice versa) required significant activation of muscles of different functional directions for both joints. Time organization of EMG activity of extensors and flexors of the shoulder and elbow joints related to the maximum and relatively rapid generation of the effort (rise time 0.12 to 0.13 and 0.25 sec, respectively) was rather complex and included dynamic and stationary phases. With these time parameters of generation of the efforts (both flexion and extension), the appearance at the stationary effort of 40 N was controlled based on coordinated interaction of dynamic phases of the activation of agonistic and antagonistic muscles. It is concluded that CMCs coming to extensors and flexors of both joints upon generation of rapid isometric efforts are rather similar in their parameters to those under conditions of realization of the forearm movements in the space in an isotonic mode.