Page 10, O2 Uptake, Exercise & Cor. Circ., Dr. D. Penney

Exercise (continued..):

Redistribution of blood flow occurs during exercise (Figure 3.05). As stated earlier, skeletal muscle, the kidneys, and the abdominal viscera each receive about 25% of cardiac output. With exercise, blood flow to skeletal muscle increases both as a percent of cardiac output and absolutely, in ml/min. Flow to the kidneys and the abdominal viscera, in contrast, decrease sharply, absolutely and relatively. Those tissues, along with skeleton, bone marrow, fat, etc. are treated as expendable circulations during exercise. Flow to the brain remains constant in ml but decreases relative to total flow. Coronary flow however increases in proportion to total flow and thus is constant on a percentage basis. This observation is consistent with the fact that cardiac work increases directly with cardiac output and this requires increased coronary flow. Skin blood flow is variable during exercise, depending upon both the ambient thermal conditions and the exercise level.