Cerebral blood flow at rest is about 750 mL/min and remains unchanged during any grade of muscular exercise. During exercise, coronary blood flow is increased by four to five times with 100% O2 utilization. Renal blood flow is also decreased by 50-80% in severe exercise. During strenuous exercise muscle blood flow can increase up to 20 times, i.e. about 50-80 mL/ 100 g/min muscle tissue.