title: Effects of acute beta-adrenergic blockade on blood and muscle lactate concentration during submaximal exercise.
abstract: Heart rate and blood and muscle lactate concentrations were studied in 15 physically active males during submaximal exercise before and after oral administration of 80 mg propranolol (Inderal). First, a cycle exercise protocol, with a stepwise increased exercise intensity (30 W every 4 min until voluntary exhaustion) was performed before and after beta-blockade. Blood samples for lactate determination were obtained before each exercise intensity increase. In a second set of experiments, the procedure was repeated before and after beta-blockade, but exercise was terminated at the exercise corresponding to a blood lactate concentration of 4 mmol X l-1 l-1, as determined beforehand without beta-blockade (i.e., the same absolute work load was compared with and without beta-blockade), and a muscle biopsy was taken from m. vastus lateralis for subsequent lactate analyses. Following beta-blockade at low and high work loads, the heart rate decreased similarly by 22%-26%. Blood lactate concentration was unchanged at exercise intensities up to 150 W. At higher exercise intensities (180-240 W), a significant increase (P less than 0.05 - P less than 0.01) in blood lactate concentration occurred after beta-blockade. Muscle lactate concentration was unaffected by beta-blockade at a work load (130-230 W) where blood lactate was higher with than without blockade. Assuming a reduced blood flow to the exercising muscle, there are reasons to speculate that lactate production was diminished following beta-blockade even though blood lactate increased probably as a result of reduced lactate uptake by other organs.
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000328:Adult; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000187:drug effects* / Q000378:metabolism; D005082:Physical Exertion
chemical_list: D000319:Adrenergic beta-Antagonists; D007773:Lactates