GORDON, N. F., J. P. VAN RENSBURG, D. P. VAN DEN HEEVER, N. B. KALLIATAKIS, and D. P. MYBURGH. Effect of dual β-blockade and calcium antagonism on endurance performance.Med. Sci. Sports Exerc., Vol. 19, No. 1, pp. 1–6, 1987. The effect of oral clinically used doses of propranolol, atenolol, nifedipine, propranolol + nifedipine, and atenolol + nifedipine on endurance performance and ventilatory responses to graded treadmill testing was studied in 12 healthy physically active men. Maximal exercise duration was reduced by propranolol (8.5%,P< 0.001) and its combination with nifedipine (11.1%,P< 0.001), and to a lesser degree by atenolol (3.2%, 0.05 <P< 0.1), nifedipine (2.1%,P< 0.05), and atenolol + nifedipine (3.9%,P< 0.01). Exercise duration and heart rate (HR) and ventilatory responses to maximal exercise were equivalent with a β-blockade reduced the HR and oxygen uptake, nifedipine accentuated the HR but did not alter ventilation, and all drugs modified the relative oxygen uptake corresponding to 85% of the maximal HR. Physiologic responses to submaximal exercise during combination therapy were similar to those during β-blockade alone. This study concludes that, in physically active men, nifedipine induces a small impairment of maximal performance, but does not accentuate the reduction in effort tolerance resulting from β-blockade. Furthermore, HR and ventilatory responses to exercise during combined β-blockade and calcium antagonism can be predicted from those during β-blockade alone.