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Query: UMLS:C0392674 (exhaustion)
 13,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Controversy exists concerning the effects of acute beta-adrenergic blockade on ventilation during exercise. Hence, the purpose of this study was to determine the effects of acute beta blockade on ventilation and gas exchange during incremental exercise. Nine male subjects underwent incremental exercise on a cycle ergometer (30 W.min-1) to exhaustion, with one trial being performed 60 min after the subject ingested propranolol hydrochloride (Inderal 1 mg.kg-1 BW) while the second test served as control. The treatment order was counterbalanced to preclude any ordering effect on the results, and 1 week separated the tests. Ventilation and gas exchange were monitored by open circuit techniques. No difference (p greater than 0.05) existed in VE, % Hb sat, VCO2, ventilatory threshold, and VE/VCO2 between treatments at the same exercise stage. VO2max was lowered from 3.82 to 3.26 l.min-1 (p less than 0.05) and HRmax was reduced from 190 to 150 bpm (p less than 0.05) as a result of beta blockade. These data suggested that acute beta blockade had no effect on exercise ventilation, but decreased HRmax at comparable work rates. In addition, VO2max and exercise time to exhaustion were hindered, probably due to beta blockade limitation of HRmax, and, thus, oxygen transport.
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PMID:Effects of beta-adrenergic blockade on ventilation and gas exchange during incremental exercise. 317 19

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.
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PMID:Effects of acute beta-adrenergic blockade on blood and muscle lactate concentration during submaximal exercise. 614 Feb 29

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.
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PMID:Isometric muscle endurance during acute beta-adrenergic blockade. 620 98

The aim of this study was 1) to establish the relationship between testosterone (T) levels and the intensity and duration of exercise in conscious dogs, and 2) to investigate the involvement of the sympathetic system in the response of plasma T to acute exercise. The experiments were performed on 14 male mongrel dogs (20-25 kg) trained to run on a motor driven treadmill. Testosterone (T), cortisol, epinephrine, norepinephrine, lactate and haematocrit were measured in arterial blood samples. A brief intensive exercise (leading to exhaustion within 5 or 20 min) induced a marked increase in plasma T, while during more prolonged (60 min) exercise plasma T showed an initial increase followed by a secondary decrease. Blockade of the beta adrenergic receptors with propranolol (Inderal 0.5 mg/kg i.v.) did not modify the changes of plasma T during exercise, but blockade of alpha adrenergic receptors with phentolamine (Regitine 0.5 mg/kg) lowered the exercise induced rise in plasma T.
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PMID:Effect of adrenergic receptor blockade on plasma testosterone response to exercise in conscious dogs. 800 41