Comparison of the effects of pindolol and propranolol on exercise performance in young men with systemic hypertension

To determine the effect of intrinsic sympathomimetic activity (ISA) on exercise performance during beta blockade, 12 hypertensive men were studied. The subjects underwent graded treadmill testing while taking pindolol (a beta blocker with ISA), propranolol (a beta blocker without ISA) and placebo, in a double-blind, crossover fashion. Blood pressure, heart rate, oxygen consumption (VO2), cardiac output and stroke volume were determined at 25, 45, 60 and 75% of each subject's VO2 max. Heart rate was significantly lower with pindolol compared with placebo at all stages of exercise, but significantly higher compared with propranolol at all stages of exercise except at 75% of VO2 max and at VO2 max (no significant differences between the 2 beta blockers were recorded at these stages). Mean arterial pressure was statistically equivalent with pindolol and propranolol at all stages of exercise and significantly lower while beta-blocked compared with placebo conditions at 45, 60 and 75% of VO2 max. Cardiac output and VO2 were statistically equivalent across all 3 treatments at all submaximal levels of exercise. It was concluded that, although heart rate was significantly higher with pindolol compared with propranolol at the 3 lower rates of work, cardiac output and VO2 were not different between the drugs, thus making little impact on exercise performance.