In 45 approximately 1-year-old purebred German shepherd dogs, the left circumflex and the right coronary arteries were chronically occluded by implantation of slowly swelling ameroid constrictors. Before the operation, 27 dogs were trained on a treadmill until they could run 8 mph on a 22% incline for 1 hour, 5 days per week. Two weeks after the operation, exercise was gradually resumed and con...