Peculiarities of Activation of Human Muscles in Realization of Cyclic Bimanual Movements with Different Organization of the Cycles

According to the characteristics of EMGs subjected to full-wave rectification and low-pass filtering, we examined coordination of central motor commands coming to muscles of the shoulder belt and shoulders in the course of realization of cyclic bimanual movements within a horizontal plane (close to those in sculling). The performance of different motor tasks was tested: (i) movements at a comfortable stroke rate (CSR); (ii) movements at a maximum rate (MR), and (iii) movements with the feedback (FB) information, where the subject could trace the movement rate and angles of rotation of one lever of the experimental set. Two levels of external loading could be applied to the levers of the set ("oars") in the direction counteracting efforts developed by the subject within the pulling phase. It was found that, in realization of the CSR test, the movement rate was greater at a higher loading than that in the case of a smaller mechanical resistance. The mean level of EMGs of the examined muscles under conditions of a higher loading in realization of the CSR test was greater than that in the FB test. The level of activation of the muscles in the course of the MR test demonstrated no dependence of the level of external loading. The level of correlations between EMG activities of similar muscles of the left and right upper limbs demonstrated a trend toward lowering under conditions of the presence of visual FB. It is supposed that the cognitive influence upon realization of the motor tasks is intensified under the above conditions, and the type of the performed movements becomes closer to the discrete mode.

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