Coronary blood flow and exercise training

Exercise training has been viewed as a physiologic method of improving cardiac function and coronary blood flow reserve capacity. Little evidence exists in either human subjects or experimental animals to substantiate that there is any change in coronary blood flow reserve with an exercise training regimen. Mongrel dogs have been studied in the untrained and trained conditions. Studies have also been conducted during the training program to delineate sequential changes in cardiac function and coronary blood flow reserve. Myocardial oxygen consumption, coronary blood flow, contractile function of the heart, coronary blood flow response to a 10-second occlusion of a coronary artery, coronary blood flow response to atrial pacing, and heart rate have been measured in chronically instrumented animals. All dogs were studied at rest and during submaximal exercise on a motor-driven treadmill. Training was accomplished by 8 to 10 weeks of daily exercise. Heart rate during submaximal exercise was reduced and cardiac contractile function was increased after training. Coronary blood flow response to submaximal exercisewas not altered, and myocardial oxygen consumption was the same after training. The coronary blood flow response to a 10-second occlusion was reduced with training. Evidence from other studies suggests that the neural control of coronary blood flow is altered. Thus, exercise training does not appear to alter the coronary blood flow reverse in the mongrel dog, but there may be both structural and neural control difference of coronary vessels in the trained dog heart. More importantly, evidence is presented to suggest that some amount of exercise not leading to training may increase coronary blood flow reserve.