Improved exercise ventilatory responses after training in coronary heart disease during long-term beta-adrenergic blockade.
Exercise ventilatory responses of 7 men with well-documented myocardial infarction receiving long-term beta-adrenergic blockade were studied before and after 4 months of endurance training. Observations were obtained during graded levels of upright treadmill exercise continued until 85% of the predetermined symptom-limited heart rate (working heart frequency limit). This submaximal testing procedure revealed a significant slowing of the heart rate (p less than 0.005) together with an increased oxygen pulse (p less than 0.05) after training, for what was previously a maximal work load for the working heart frequency limit. In addition, all patients achieved an increased exercise duration and work load, accompanied by significant increases in maximal oxygen uptake (p less than 0.01), oxygen pulse (p less than 0.025), and respiratory exchange ratio, for their working heart frequency limit after exercise conditioning. These results show that prolonged physical training results in physiologic adaptations to cardiac rehabilitation in the presence of long-term beta-adrenergic blockade.