[2 phase of the working hyperemia of skeletal muscle].

The dynamics of the working hyperemia of cat m. gastrocnemius was studied by means of an electromagnetic flowmeter. Two phases could be distinguished in the increase in the rate of circulation. There proved to be a rapid increase of the blood flow during the I phase, and an abrupt reduction of this process during the II phase. The duration of the I phase failed to depend on the frequency of stimulation and on the number of the contracting motor units. The II phase was absent when the number of the contracting motor units was few or the frequency of stimulation was low. It is suggested that the dilatation of the precapillary arterioles is responsible for the I phase of the working hyperemia and the II phase is connected with the dilatation of the larger arteries.