MUSCLE BLOOD-FLOW PATTERNS DURING EXERCISE IN PARTIALLY CURARIZED RATS

The distribution of blood flow within and among muscles of partially curarized (40-100 .mu.g/kg body wt) rats was studied during preexercise and at 1 min of low-speed treadmill exercise (15 m/min). Glycogen loss in the deep red muscles and parts of muscles was significantly reduced in the curarized animals during exercise, indicating the fibers in these muscles were recruited to a lesser extent and/or had lower metabolisms than fibers in the same muscles of control rats. Elevations in blood flow in the red muscles of the curarized rats were as great or greater than those in the control rats. Thus, reduced recruitment and/or metabolism of the deep red muscle fibers of the curarized animals was not accompanied by reduced blood flow. Apparently, there is a dissociation between red fiber metabolism and blood flow in the curarized rats during the 1st min of slow treadmill exercise. Release of vasodilator substances or local physical factors associated with muscle fiber activity are not solely responsible for the initial hyperemia during exercise.