-- In young well trained adults, adrenergic beta receptors blockade by pindolol or propranolol causes a relative bradycardia during running on a threadmill during 10 to 20 min at 50% VO2 max. 2. -- Pindolol activity is maximum for 5-7.5 mg ingested one hour before starting. In two subjects, tachycardia reappears for 30 mg : this secondary increase may be explained by an intrinsic sympathetic activity of pindolol. 3. -- Propranolol is about 14 times less active than pindolol without any intrinsic sympathetic activity.
