Abstract
Fourteen male physical education students performed a single bout of running until
exhaustion on the treadmill at 22 km/h and 7.5% slope. They received single oral doses
of 100 mg bupranolol (nonselective β-blockade), 100 mg metoprolol (β-1-selective blockade),
and placebo 60-90 min before running. Arterialized capillary blood was sampled repeatedly
until 30 min after exercise for assessment of lactate and glucose. Adrenaline and
noradrenaline were determined in venous plasma before and immediately after exercise.
Running time until exhaustion was 49.3 ± 2.3 s in the control experiment, 44.5 ± 2.0
s with metoprolol, and 42.7 ± 2.0 s with bupranolol. The reductions under β-blockade
were statistically significant. With both (β-blockers the increases of the lactate
and glucose blood levels were significantly reduced, the levels being almost identical
with metoprolol and bupranolol. The post-exercise levels of adrenaline and noradrenaline
did not differ significantly between the control, metoprolol, and bupranolol experiments.
It is concluded that determination of the lactate and glucose levels in blood did
not allow assessment of the mechanism by which β-blockade impairs the capacity for
supramaximal exercise. Besides reduced anaerobic energy release due to inhibition
of glycogenolysis, other β-blocker effects are considered.
Key words
supramaximal exercise - lactate - glucose - catecholamines - β-adrenergic blockade
