[Flexible and rigid connections in the regulation of motor activity].

The present investigation deals with the problem of versatile and rigid connections (N.P. Bechtereva), their functions and interrelations during repeated stereotype movements. The necessity of the versatile connections in the course of motor activity is demonstrated. Versatility depends on permanent variations of the contractile capacity of muscles during physical work as a result of fluctuations of the internal environment (intramuscular temperature, oxygen saturation, metabolite concentration), of a different initial elongation of muscle fubers and a simultaneous contraction of muscles not directly related to the test muscle activity. It was shown that different loadings and different levels of training lead to a variability of the relationship between rigid and versatile connections.