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Plasma catecholamine and ventilatory responses to cycling after propranolol treatment.

Medicine & Science in Sports & Exercise: December 1995
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SCHNEIDER, D. A., G. H. KAMIMORI, S. Y. WU, M. T. MCENIERY, and C. SOLOMON. Plasma catecholamine and ventilatory responses to cycling after propranolol treatment. Med. Sci. Sports Exerc., Vol. 27, No. 12, pp. 1616-1620, 1995. The purpose of the present study was to examine the relationship between minute ventilation ([latin capital V with dot above]E) and plasma concentrations of epinephrine (EPI) and norepinephrine (NE) during incremental cycling (20 W[middle dot]2 min-1) performed under conditions of [beta]-adrenergic blockade (80 mg of propranolol) and placebo in six untrained male subjects. No significant differences existed between treatments in O2 uptake, CO2 output, blood lactate, pH, or [latin capital V with dot above]E during the submaximal work stages of incremental exercise common to both treatments (20-220 W). During exercise with [beta]-blockade, EPI, and NE concentrations were both significantly elevated compared with control levels at every submaximal work stage. Significant positive correlations between [latin capital V with dot above]E and plasma levels of EPI and NE were found during both [beta]-blockade (r = 0.98 and 1.00) and control conditions (r = 0.98 and 0.96). Although the high correlations were unchanged during exercise with [beta]-blockade, the slopes of the regression lines for the [latin capital V with dot above]E-EPI and the [latin capital V with dot above]E-NE relationships were both significantly reduced compared with control conditions, [beta]-blockade resulted in elevated plasma levels of both EPI and NE compared with control conditions without causing a change in exercise [latin capital V with dot above]E. These findings suggest that catecholamines may not be important substances in regulating breathing during exercise.

(C)1995The American College of Sports Medicine