Int J Sports Med 1987; 08(1): 1-5
DOI: 10.1055/s-2008-1025631
© Georg Thieme Verlag Stuttgart · New York

Effect of Beta-Adrenoceptor Blockade and Calcium Antagonism, Alone and in Combination, on Thermoregulation During Prolonged Exercise*

N. F. Gordon1 , 3 , J. P. van Rensburg2 , H. M. S. Russell1 , A. J. Kielblock2 , D. P. Myburgh1
  • 1Institute for Aviation Medicine, Pretoria
  • 2The Industrial Hygiene Branch, Chamber of Mines of South Africa, Johannesburg, South Africa
  • 3MRC-University Circulation Research Unit, Department of Physiology, University of the Witwatersrand, Johannesburg, South Africa
* This study was supported by grants from ICI Pharmaceuticals (England and South Africa) and Exefit Lifestyle Fitness Centres (Johannesburg).
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Publication History

Publication Date:
14 March 2008 (online)

Abstract

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 beta1-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.