[Effect of bunitrolol on heart rate, metabolic parameters during physical exercise, and performance]

Plasma catecholamines, glucose, lactate, free fatty acids, and glycerol in the blood, as well as heart rate, oxygen intake, and work capacity have been examined in 9 healthy subjects (28.5 +/- 2 years) at rest, during submaximum and maximum ergometric exercise, after oral administration of a placebo and of 10 mg O-[3-(tert.-butylamino)-2-hydroxypropoxy]-benzonitril (bunitrolol, Stresson), respectively. The results are as follows: 1. As caused by the intrinsic activity of bunitrolol, the heart rate does not show nearly any reduction at rest and during submaximum physical exercise. At maximum exercise level the heart rate is 37 beats/min lower with bunitrolol. The limitation of heart function leads to a work capacity reduction of approx. 14%. 2. After administration of bunitrolol, adrenaline level is significantly lower at rest and during submaximum exercise than with placebo. At a 200 W level, the concentration is higher with bunitrolol, but the maximum results are not attained with placebo. In relation to the percentile of the maximum work capacity, plasma catecholamine level shows no differences with placebo and with bunitrolol, respectively, except that it is lower during maximum exercise and the recovery phase. 3. Glucose, free fatty acids, and glycerol levels show no significant changes with bunitrolol. Lactate decreases significantly after bunitrolol at submaximal exercise levels and during the recovery stage, which can be looked upon as an indication of a glycolysis restriction.