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SUMMARY The effect of the beta1 selective adrenoceptor blocker, atenolol, on the physiological response to exercise was studied in 12 healthy young men. Oral atenolol (100 mg) and placebo were administered in a randomised double blind crossover fashion an hour and a half before an intermittent multistage cycle ergometer exercise test. At maximal effort oxygen consumption, pulmonary ventilation, carbon dioxide output, and respiratory exchange ratio were not modified by atenolol. In contrast, maximal heart rate and performance time were significantly reduced after atenolol. Nevertheless, because the relation of percentage of maximal oxygen consumption to percentage of maximal heart rate was not changed by atenolol both the absolute and relative oxygen consumption corresponding to 70% and 85%h of the maximal heart rate remained unaltered.These data suggest that recommendations of exercise intensity may be determined on the basis of a calculated percentage of the predetermined maximal heart rate in persons without symptomatic coronary heart disease receiving beta1 selective adrenoceptor blockers.

The effect of clinically used doses of propranolol, atenolol, nifedipine, propranolol plus nifedipine, and atenolol plus nifedipine on thermoregulatory responses of 11 healthy men was studied during 2-h block-stepping in heat. Drug intervention did not alter ventilation during exercise. In contrast, propranolol and atenolol produced equivalent reductions in exercise tachycardia, implying a similar level of beta 1-adrenoceptor blockade. The heart rate response to exercise was unaffected by nifedipine and during dual beta-adrenoceptor blockade and calcium antagonism was equivalent to that with beta-adrenoceptor blockade alone. While rectal temperature rises were not modified by drug ingestion, propranolol and, to a lesser degree, atenolol and combination therapy, but not nifedipine alone, attenuated skin temperature rises. Moreover, although atenolol, nifedipine, and their combination did not alter sweating, propranolol and its combination with nifedipine enhanced sweating during the 1st and 2nd h of exercise. This study concludes that nifedipine does not modify thermoregulation during exercise and allows for greater confidence of its use during cardiac rehabilitation. Furthermore, the present data confirm that propranolol does enhance sweating during exercise and demonstrate that this effect is not mediated simply by an earlier onset of rapid sweating nor abolished by concomitant calcium antagonism.