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Isometric muscle endurance during acute beta-adrenergic blockade
Acta Physiologica Scandinavica
|January 1, 1984
Summary
Beta-blockade with propranolol impairs isometric muscle endurance in physically active men. This reduction in endurance time occurs regardless of muscle fiber type or capillary density, suggesting a direct effect on muscle tissue.
Area of Science:
- Exercise Physiology
- Pharmacology
Background:
- Beta-blockers like propranolol are used to manage cardiovascular conditions.
- Their effects on skeletal muscle endurance are not fully understood.
Purpose of the Study:
- To investigate the impact of acute propranolol administration on isometric muscle endurance.
- To explore the relationship between beta-blockade, muscle morphology, and endurance performance.
Main Methods:
- Isometric quadriceps muscle endurance was tested in 14 men at 65% maximum voluntary contraction (MVC).
- Participants were tested under placebo and after 160 mg propranolol.
- Muscle biopsies analyzed myofibrillar ATPase and amylase-PAS for fiber type and capillary density.
Main Results:
- Time to exhaustion was significantly shorter with propranolol (0.82 min) compared to placebo (0.90 min).
- No correlation was found between endurance changes and muscle morphological/histochemical variables.
Conclusions:
- Acute propranolol administration impairs muscular performance.
- This impairment is likely due to direct effects on muscle tissue, independent of central circulation changes or specific muscle fiber characteristics.