Blood flow and glycogen use in hypertrophied rat muscles during exercise

Previous findings suggest that skeletal muscle that has enlarged as a result of removal of synergistic muscles has a similar metabolic capacity and improved resistance to fatigue compared with normal muscle. The purpose of the present study was to follow blood flow and glycogen loss patterns in hypertrophied rat plantaris plantaris and soleus muscles during treadmill exercise to provide information on the adequacy of perfusion of the muscles during in vivo exercise. Thirty days following surgical removal of gastrocnemius muscle, blood flows (determined with radiolabeled microspheres) and glycogen concentrations were determined in all of the ankle extensor muscles of experimental and sham-operated control rats during preexercise and after 5-6 min of treadmill exercise at 15 m/min. There were no differences (P greater than 0.05) in blood flows per unit mass or glycogen concentrations between control and hypertrophied plantaris or soleus muscles at either time, although both muscles were larger (P less than 0.05) in the experimental group (plantaris: 95%; soleus: 40%). None of the other secondary ankle extensor muscles (tibialis posterior, flexor digitorum longus or flexor hallicus longus) hypertrophied in response to removal of gastrocnemius. These results provide indirect evidence that O2 delivery in the enlarged muscles is not compromised during low-intensity treadmill exercise due to limited perfusion.