Oxygen Uptake and Plasma Catecholamines During Submaximal and Maximal Exercise After Long-Term β-Receptor Blockade

Abstract

β-receptor antagonists lower exercise heart rate and cardiac output, and can thus be expected to interfere with oxygen transport, and hence physical performance, particularly at higher levels of activity. Therefore, the effects of a 4-week and 15-month treatment period with the β₁-selective receptor blocker acebutolol (500 mg daily) on oxygen uptake and plasma catecholamines during submaximal steady-state and maximal exercise and on maximal work load were studied in eight WHO stage 1 hypertensive men (mean age 36.4 years).

Oxygen uptake, ventilation, and plasma noradrenaline, adrenaline, and dopamine concentrations during steady-state exercise were not significantly different from control conditions either after 4 weeks or after 15 months of receptor blockade, although heart rates were significantly (27% and 25%, respectively; (P < 0.01) reduced.

After the 4-week treatment period, maximal oxygen uptake (3.9% reduction, NS) and maximal work load (2.4% reduction, NS) tended to be slightly lower after acebutolol compared with control values; maximal oxygen pulse was significantly (P < 0.05) increased. However, after long-term treatment of 15 months, maximal oxygen uptake was virtually indentical compared with pretreatment values, and maximal work load tended to be higher (5.2%, NS); plasma noradrenaline and adrenaline concentrations were significantly (P < 0.05) enhanced. Since β-selective receptor blockers do not affect maximal oxygen uptake and maximal work capacity after long-term treatment, they appear preferable for patients taking part in preventive and rehabilitative training programs.

Key words

maximal oxygen uptake - plasma catecholamines - chronic β-receptor blockade - hypertension - exercise