Effect of beta-adrenergic blockade on respiratory and metabolic responses to exercise

Abstract

The responses to oral propranolol (80 mg) and placebo were compared in normal subjects during three studies on a cycle ergometer (progressive exercise and two 5-min constant work rate studies at 50 and 70% maximum). Heart rate (HR), ventilation (VE), CO2 output (VCO2) and O2 uptake (VO2) were measured in each study and metabolites in venous blood in the 70% study. Propranolol reduced HR in all studies and endurance time during progressive exercise. During constant-work-rate exercise the changes with propranolol depended on time and work rate. At 50% max, VO2, VCO2, and VE were reduced in early exercise but were similar by min 5. At 70% max, VO2 and VCO2 were again lower initially with propranolol but then rose more rapidly. By min 5 VE was greater with propranolol, coinciding with a rapidly rising venous lactate. We interpret the initial reduction in VO2 and VCO2 to reduced cardiac output and muscle perfusion with propranolol. The resulting increase in anaerobic metabolism during heavy exercise would explain the increased VE at min 5. The metabolic data are compatible with glycogen being the predominant muscle fuel.

Effects of beta‐adrenoceptor blockade on exercise performance and respiratory response in healthy, physically untrained humans.

“…The decrease of submaximal Vo, afteradrenoceptor blockade found in the present study is consistent with almost all the published data (Pearson et al, 1979;Twentyman et al, 1981;Tesch & Kaiser, 1983;Butland et al, 1983;Sue et al, 1983), while the concomitant changes we have found in Vco, and VE are in agreement with only some of them (Twentyman et al, 1981;Butland et al, 1983;Sue et al, 1983).…”

“…The lack of changes on maximum work rate and PER is a finding apparently conflicting with most previously published reports (Pearson et al, 1979;Anderson et al, 1979;Rusko et al, 1980;Twentyman et al, 1981;Tesch & Kaiser, 1983;Petersen et al, 1983). These studies were carried out on subjects with high exercise capacity as a result of the prevalence of males, often physically fit and exercise trained.…”

“…Another reason for Vo, to be decreased (Twentyman et al, 1981;Petersen et al, 1983;Sue et al, 1983) may be a reduction of cardiac output which, despite an increased arterial mixed venous 02 difference (Ekblom et al, 1972;Epstein et al, 1965;Astrom, 1968) (Turner, 1983) and, particularly, on the reduction of ventilatory response to CO2 (Patrick & Pearson, 1980). Recently, Butland et al (1983) found a clear reduction of hyperventilation in exercising patients with emphysema and a good therapeutic effect in hyperventilating children has also been described (Joorabchi, 1977), after P-adrenoceptor blockade.…”

“…In fact, similar studies did not always show consistent results. For instance, all studies performed on healthy subjects who were able to reach high work rates (usually more than 200 W) showed a reduction of oxygen uptake and maximum work capacity after 3-adrenoceptor blockade (Pearson et al, 1979;Anderson et al, 1979;Twentyman et al, 1981;Tesch & Kaiser, 1983;Petersen et al, 1983), whereas no changes were found in studies carried out in subjects unable to reach such work levels, either healthy (Leitch et al, 1980) or suffering from mild hypertension (Fagard et al, 1980).…”

Beta 1‐selective and non‐selective beta‐adrenoceptor blockade, anaerobic threshold and respiratory gas exchange during exercise.

“…In more recent investigations, inferences have been drawn regarding the metabolic effects of P-adrenoceptor blocking drugs from respiratory gas exchange data (Pearson et al, 1979;Twentyman et al, 1981). Most recently, Petersen and colleagues (1983) have claimed that alterations in respiratory gas exchange during exercise after P-adrenoceptor blockade were minimal (Petersen et al, 1983 (1982) (acebutolol, pindolol).…”