Isometric muscle endurance during acute β‐adrenergic blockade

Publisher Website
Google Scholar
Abstract
Isometric muscle endurance was measured in fourteen physically active men without (placebo) and after acute oral administration of 160 mg propranolol (Inderal®). Quadriceps muscle contractions were sustained at 65% maximum voluntary contraction (MVC) to exhaustion. Muscle biopsies were obtained from m. vastus lateralis at rest for subsequent histochemical analysis for myofibrillar ATPase and amylase‐PAS in order to determine fiber type composition and capillary density. The time to exhaustion was shorter (p< 0.01) during β‐blockade (0.82 ± 0.22) min than placebo (0.90 ± 0.23) min. Changes in endurance time, induced by β‐blockade, were not correlated with any of the muscle morphological or histochemical variables examined. It is concluded that muscular performance is impaired as a result of β‐blockade on muscle tissue irrespective of any concomitant change in central circulation.