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Effect of beta-adrenoceptor blockade on thermoregulation during prolonged exercise
Journal of Applied Physiology (Bethesda, Md. : 1985)
|March 1, 1985
Summary
Beta-blockers like propranolol and atenolol increase perceived exertion during exercise in heat. Propranolol significantly increased sweat production, while both drugs altered potassium levels, impacting thermoregulation.
Area of Science:
- Exercise Physiology
- Environmental Medicine
- Pharmacology
Background:
- Beta-adrenoceptor blockers are widely prescribed for cardiovascular conditions.
- Their impact on thermoregulation during exercise in heat is not fully understood.
- Understanding these effects is crucial for athletes and individuals exercising in hot environments.
Purpose of the Study:
- To investigate the effects of nonselective (propranolol) and selective (atenolol) beta-blockers on thermoregulation during prolonged exercise in heat.
- To compare the physiological responses to equipotent doses of these beta-blockers.
Main Methods:
- 11 healthy males ingested propranolol (160 mg/day), atenolol (100 mg/day), or placebo for 6 days.
- Subjects performed 2 hours of block-stepping (54 W) in a hot environment (33.2°C dry bulb, 31.7°C wet bulb).
- Physiological parameters including temperature, sweat production, and serum electrolytes were measured.
Main Results:
- Both propranolol and atenolol significantly increased the subjective perception of effort.
- Propranolol caused a greater increase in serum potassium (K+) post-exercise compared to placebo.
- An increased total sweat production was observed with propranolol and, to a lesser extent, atenolol.
Conclusions:
- Beta-blocker use during exercise in heat may alter thermoregulatory responses, notably increasing sweat production.
- The observed increase in perceived exertion requires further investigation into its underlying mechanisms.
- Clinical implications regarding exercise in heat while on beta-blockers warrant further study.