Effect of oral propranolol on the anerobic threshold and maximum exercise performance in normal man.

The effect of propranolol on the anaerobic threshold was studied in six healthy male volunteers. The subjects exercised on a cycle ergometer in a progressive exercise test to exhaustion with propranolol or no drug. Power output was increased by 30 W ever 2 min. Propranolol caused a significant reduction of heart rate by 20-45 beats per minute at all power outputs. In light and moderate exercise, no differences in oxygen uptake, ventilation, or blood lactate were observed in the propranolol and no-drug tests. The anaerobic threshold was not different between the no-drug (2.32 +/- 0.19 L O2/min, mean +/J- SD) and the propranolol (2.83 +/- 0.27 L O2/min) test; however, the heart rate at the anaerobic threshold was significantly lower in the propranolol (143 +/- 13 beats per minute) than the no-drug (187 +/- 9 beats per minute) tests. Above the anaerobic threshold, oxygen uptake was similar at a given power output but it reached a lower peak value (p less than 0.02) in the propranolol (3.16 +/- 0.16 L O2/min) versus the no-drug (3.64 +/- 0.39 L O2/min) tests. It was concluded that propranolol caused no change in anaerobic threshold in this specific progressive exercise protocol. The results suggest that a training intensity for endurance exercise bases on the anaerobic threshold does not need to be modified for subjects on propranolol medication.