Exercise capacity, energy metabolism, and beta-adrenoceptor blockade

Summary

The effects of beta₁ and beta_1/2 blockade on exercise capacity were studied in 9 healthy normotensive subjects. Progressive maximal bicycle ergometer tests, followed by an endurance test at 80% of maximal work load, were performed during randomized, double-blind 3 day treatment periods with placebo, atenolol (beta₁) and oxprenolol (beta_1/2). The reduction of maximal work capacity (ca. 10%) was similar with atenolol and oxprenolol, despite a more pronounced maximal heart rate reduction with atenolol (from 175±2 to 132±3 beats · min⁻¹) than with oxprenolol (to 138±2 beats · min⁻¹). Exercise time during the endurance test was reduced from 36±4 min with placebo to 27±3 min with atenolol (p<0.05) and 24±3 min with oxprenolol (p<0.01) (atenolol vs. oxprenolol: p<0.05). During the endurance test, plasma glycerol and non-esterified fatty acid concentrations were reduced with both atenolol and oxprenolol. The glycerol reduction was more pronounced with oxprenolol than with atenolol, plasma NEFA concentrations being similar. Plasma glucose and lactate concentrations were reduced by oxprenolol but not with atenolol. These data show that submaximal exercise capacity at work loads representing similar relative exercise intensities is reduced during non-selective and beta₁-selective beta blockade. This reduction may be related to the effects of beta₁ blockade on energy metabolism, with possibly an additional effect of beta₂ blockade.