title: Isometric muscle endurance during acute beta-adrenergic blockade.
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 less than 0.01) during beta-blockade (0.82 +/- 0.22) min than placebo (0.90 +/- 0.23) min. Changes in endurance time, induced by beta-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 beta-blockade on muscle tissue irrespective of any concomitant change in central circulation.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D000681:Amylases / Q000378:metabolism; D006801:Humans; D007537:Isometric Contraction / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009132:Muscles / Q000201:enzymology; D009210:Myofibrils / Q000201:enzymology; D011433:Propranolol / Q000494:pharmacology
chemical_list: D000319:Adrenergic beta-Antagonists; D011433:Propranolol; D000681:Amylases; D000251:Adenosine Triphosphatases