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Int J Sports Med 1985; 06(6): 347-352
DOI: 10.1055/s-2008-1025869
© Georg Thieme Verlag Stuttgart · New York

Effects of Acute and Chronic Metoprolol Administration During Submaximal and Maximal Exercise

M. A. van Baak, W. Jennen, A. Muijtjens, F. T. J. Verstappen
  • Depts. of Pharmacology, Medical informatics and Statistics, and Physiology, University of Limburg, Maastricht, The Netherlands
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Publication Date:
14 March 2008 (online)

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Abstract

The effects of different dosages of the β1-adrenoceptor blocker metoprolol and of acute and chronic administration of this β-blocker during physical exercise were compared in healthy normotensive subjects. Placebo, 0.15 mg/kg, and 0.30 mg/ kg metoprolol were administered intravenously 10 min before a progressive bicycle ergometer test up to exhaustion. Thereafter, subjects were treated for 4 weeks with placebo or slow-release metoprolol (1 × 200 mg/day). At the end of each 4th week of treatment, a maximal exercise test was performed. Heart rate, ventilation, oxygen consumption, and plasma concentrations of free fatty acids, glucose, and lactate were determined at rest and during exercise.

After the low (0.15 mg/kg) i.v. dose, the heart rate during maximal exercise was reduced from 189 ± 2 to 155 ± 2 bts/min (P < 0.001). This reduction was significantly smaller than that after the high (0.30 mg/kg) i.v. dose (177 ± 3 to 137 ± 4 bts/min, P< 0.001) and during chronic treatment (176 ±3 to 132 ± 2 bts/min, P < 0.001). The difference between the high i.v. dose and chronic treatment was not significant. After the low i.v. dose, the heart rate was the only variable affected. After the high i.v. dose, the heart rate, exercise time, maximal oxygen uptake, and plasma glucose and free fatty acid concentration during maximal exercise were reduced, and maximal lactate concentration tended to be lower.

During submaximal exercise, no significant differences between placebo or β-blocker administration were found, except for heart rate, which was reduced after β-blockade.

No significant difference between the effects of i.v. administration of 0.30 mg/kg and of a 4-week chronic oral treatment with metoprolol was found. This indicates that no adaptation of the measured variables occurs during this time period.

Key-words

β-adrenoceptor blockade - exercise - metabolism - gas exchange - intravenous administration - chronic treatment

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