Effect of alpha 1-adrenoceptor blockade on maximal VO2 and endurance capacity in well-trained athletic hypertensive men.

The effect of alpha 1-adrenoceptor blockade (doxazosin, 4 mg daily) on maximal VO2 and physical endurance capacity in 16 mildly hypertensive, athletic men was investigated in a randomized, placebo-controlled, double-blind, two-period of 4 weeks, cross-over study. The maximal workload obtained during graded bicycle ergometer exercise and the corresponding maximal VO2 were reduced by 16 +/- 3 W (mean +/- SE), (P = .00003) and 3 +/- 1 mL/(kg.min) (P = .0004), respectively, on doxazosin compared with placebo. The running time on a 5000 m track increased by 43 +/- 12 sec on doxazosin (P = .04). Heart rate was unchanged during the running session. Systolic blood pressure was reduced by 9 +/- 4.1 mm Hg (P = .04) immediately after finishing 5000 m. Six subjects reported side effects from doxazosin (headache, fatigue, and leg pain). Thus, antihypertensive treatment with alpha 1-selective adrenoceptor blockade moderately, but significantly, reduces maximal O2 consumption and high intensity physical endurance capacity in mildly hypertensive athletic men. Significantly reduced systolic blood pressure and unchanged heart rate immediately after running, combined with unchanged heart rate during the race may, however, suggest a safer exercise performance.