[Blood flow in skeletal muscle during and after contraction: intravital microscopies studies]

Using an intravital video microscopy system, the red cell velocities, and the diameters of the capillaries and terminal arterioles were measured in rabbit tenuissimus muscle during and after contraction. Muscle contractions were produced by direct electric stimulation using square waves at 9 V of 0.1 msec duration and 2-6 Hz frequency. The red cell velocity gradually increased after stimulation. It was maximal after contraction in the capillaries, and was maximal during contraction in the terminal arterioles. When the stimulus frequency was high, then the maximal red cell velocity increased and returned to the level at rest more slowly than with low frequency, in both the capillaries and terminal arterioles. The proportion of capillaries with zero or very low velocities was reduced during and after contraction. There were few detectable changes in any capillary diameter during or after contraction. However the terminal arteriole diameter reduced during contraction and was dilated after contraction. These results suggest that the terminal arteriole might play an important part in the skeletal muscle blood flow control during and after contraction.