Effect of beta-adrenergic blockade on supramaximal exercise capacity

Area of Science:

• Exercise Physiology
• Pharmacology

Background:

• Beta-blockers are used to manage cardiovascular conditions.
• Their impact on high-intensity exercise performance and associated metabolic responses requires further elucidation.

Purpose of the Study:

• To investigate the effects of nonselective (bupranolol) and selective (metoprolol) beta-blockade on exercise capacity and metabolic responses during exhaustive running.
• To determine if changes in blood lactate and glucose levels explain the performance impairment.

Main Methods:

• Fourteen male students underwent treadmill running to exhaustion at a fixed intensity (22 km/h, 7.5% slope).
• Participants received oral doses of bupranolol, metoprolol, or placebo before exercise.
• Blood samples were analyzed for lactate, glucose, adrenaline, and noradrenaline.

Main Results:

• Both bupranolol and metoprolol significantly reduced running time to exhaustion compared to placebo.
• Increases in blood lactate and glucose levels post-exercise were significantly blunted by both beta-blockers.
• Plasma adrenaline and noradrenaline levels post-exercise did not differ significantly across conditions.

Conclusions:

• Beta-blockade impairs supramaximal exercise capacity, but blood lactate and glucose changes do not fully account for this reduction.
• Mechanisms beyond glycogenolysis inhibition likely contribute to the performance decrement observed with beta-blockers.