Limitation of Work Performance in Normal Adult Males in the Presence of Beta‐Adrenergic Blockade

Abstract

The effect on work performance of a single oral dose of the cardio-selective beta-adrenoreceptor blocking agent, metoprolol, was compared with an equipotent dose of the non-selective agent, propranolol, in the same subjects. A number of biochemical and physiological variables including heart rate, oxygen consumption, ventilation, lactate, free fatty acid and glucose levels were measured. Following exercise in the presence of both active drugs, subjects complained of excessive leg fatique. For the group there was a significant reduction in the total work performed and the maximum heart rate achieved on both drugs. There was a significant correlation between plasma levels of metoprolol, reduction in total work performed and reduction in maximum heart rate. By contrast, after propranolol, there was a wide variation in work performed at a time when the reduction in maximum heart rate was similar for all subjects. This suggests for propranolol that a reduction in heart rate alone is an inappropriate guide to the impairment of work performance. There was a fail in the circulating level of free fatty acids at the end of exercise in the presence of both drugs and it is possible that this biochemical variable contributed to the decrease in work performance.

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

“…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.…”

“…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).…”

The effect of a week's beta‐adrenoceptor antagonism on daytime heart‐ rates, subjective responses to exercise, and physical activity in normal subjects.

“…The effects of the P-adrenoceptor antagonists on the heart rate response to progressive ergometer exercise are entirely consistent with previous studies (Anderson et al, 1979;Pearson et al, 1979;Wilcox et al, 1984 Lxolol. rate during the day or over 24 h (Carrageta et al, 1982;Floras et al, 1982;Rowlands et al, 1982).…”

The effect of acute vs chronic treatment with P–adrenoceptor blockade on exercise performance, haemodynamic and metabolic parameters in healthy men and women

“…A linear relationship between the dose of propranolol and the reduction in exercise induced heart rate has been demonstrated in one study [ 191, but there are great interindividual differences, and variations with race and gender in plasma concentration of propranolol [20]. Other studies have not found a consistent correlation between plasma concentration of propranolol and exercise induced heart rate response [21]. In line with this is the demonstration of similar reduction in heart rate independent of gender in spite of greater plasma concentrations of propranolol i n women than in men [22].…”

“…Seven healthy men, with mean age 30 (range [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] years, height 182 (range 176-192)cm and weight 83 (range 69-101) kg, and eight women, with mean age 25 (range 21-39) years, height 170 (range 163-180) cm and weight 61 (range 57-71) kg participated in the study. They were all moderately trained and gave their consent after being fully informed.…”