title: Effects of beta-adrenergic blockade on endurance and short-time performance in respect to individual muscle fiber composition.
abstract: Nine physically active males were studied three times with four different exercise tests after administration of placebo, 0.1 g atenolol, or 0.08 g propranolol in random order. The test modals were: bicycle ergometer exercise at 50% of VO2max, peak torque during knee extension, the Wingate muscle power test, and 2000 m track running. Muscle fiber composition had previously been determined. In subjects with a high percentage of slow-twitch fibers the beta-blockers caused a more marked impairment in the exercising muscles. This effect was more pronounced with the unselective beta-blocker propranolol than with atenolol. One interpretation of our findings is that peripheral sympathetic beta 2-receptors in skeletal muscles may contribute to regulating muscle metabolism.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D001262:Atenolol / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004311:Double-Blind Method; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000033:anatomy & histology*; D010807:Physical Endurance / Q000187:drug effects*; D005082:Physical Exertion / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology
chemical_list: D000319:Adrenergic beta-Antagonists; D001262:Atenolol; D011433:Propranolol