The effect of the support afferentation on the parameters of the electromyographic activity and muscle tone of postural muscles in support unloading conditions

摘要

Researches, performed in space flights, model land-based experiments and experiments on animals showed that decrease of gravity loading results in significant decrease of tone of antigrav-ity muscles. Analysis of these disturbances development mechanisms revealed an important role of supportlessness in their genesis. It was suggested and experimentally demonstrated that removal of support (in weightlessness or its la/id-based models), and respectively, decrease of support afferent stimulation, results in significant decrease of tone muscular activity, that may become the trigger of changes in functioning of tone muscular control systems Transfer stiffness of ankle-joint flexors and extensors were studied - m. tibialis anterior (TA) and m. soleus (S) under conditions of supportlessness, namely seven-day dry immersion (Dl) and their electromyographic activity (EMG) at rest, during stimulation of various supporting areas of feet and under conditions of The results of study show that transition to Dl was followed consistently by the significant decline of electromyographic activity level of extensors. It was accompanied by the increase of flexor muscles activity. Restoration of the activity was observed only in case of Dl interruption or when mechanical stimulation of soles support zones was applied. It is important to emphasize that the response to the mechanical stimulation of the support zones of the soles carried out all features of systemic reactions. Stimulations of the fore foot zones was followed by clear contractions of ankle extensors. Stimulation of the fore feet zones on the oppo-site was followed by flexors contraction. During the first 24 hrs of Dl the m. soleus stiffness dropped down sharply. The stiffness of m. tibialis anterior on the opposite showed a deep tendency for an increase during the first 24 hrs of immersion and later slowly decreased. Mechanic stimulation of the foot support zones deceler-ated and moderated these changes in both muscles.