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Effect of beta-adrenergic blockade on thermoregulation during exercise
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 1, 1987
Summary
Beta-blockade (BB) impairs thermoregulation during exercise by reducing heat dissipation, leading to higher core body temperatures. This study investigated how BB affects exercise responses and heat loss mechanisms.
Area of Science:
- Exercise Physiology
- Cardiovascular Regulation
- Thermoregulation
Background:
- Conflicting reports exist regarding beta-blockade's impact on thermoregulatory reflexes during exercise.
- Understanding these effects is crucial for athletes and individuals on beta-blocker medication.
Purpose of the Study:
- To clarify the effects of beta-blockade on thermoregulatory responses during exercise in varying ambient temperatures.
- To investigate the mechanisms underlying altered heat dissipation under beta-blockade.
Main Methods:
- Six healthy men performed cycle ergometer exercise at 60% max O2 consumption in 22°C and 32°C.
- Subjects received either propranolol (a beta-blocker) or a placebo in a single-blind manner.
- Measurements included heart rate, esophageal temperature, forearm blood flow, and blood pressure.
Main Results:
- Beta-blockade effectively reduced heart rate and systolic blood pressure during exercise.
- Esophageal temperature was significantly elevated with beta-blockade at both temperatures.
- Reduced core-to-skin heat flux, indicated by decreased forearm blood flow and maximal forearm blood flow, contributed to the elevated temperature.
Conclusions:
- Beta-blockade impairs the body's ability to dissipate heat during exercise, leading to increased core temperature.
- Reduced heat loss is attributed to diminished peripheral vasodilation and potentially altered baroreceptor function.
- These findings highlight the importance of considering beta-blockade's thermoregulatory effects in exercise settings.