We evaluated maximal performance during cycle ergometry and treadmill exercise in 14 hypertensive male joggers treated with prazosin or atenolol in an unblinded, placebo-controlled, crossover design. Maximal oxygen uptake was measured during both exercise modalities; cardiac output was measured only during cycle ergometry using the acetylene rebreathing technique. Both drugs reduced resting systolic and diastolic blood pressures. Prazosin reduced total peripheral resistance during submaximal exercise but had little effect on maximal cycle and treadmill performance. Atenolol, in contrast, reduced treadmill duration, maximal oxygen uptake, and heart rate compared with placebo. Atenolol also increased stroke volume and the arterial-venous oxygen difference and reduced cardiac output during cycle exercise. Both drugs produced similar reductions in exercise diastolic pressure, but exercise systolic pressure was lower only during atenolol treatment. Prazosin was better tolerated by the subjects and was preferred by 10 of the men. We conclude that both drugs effectively reduced resting blood pressure, but the atenolol decreased exercise cardiac output and may impede exercise performance in physically active hypertensive subjects.
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