EFFECT OF LONG-TERM ADRENERGIC Β-Receptor BLOCKING TREATMENT ON METABOLIC RESPONSES TO PROLONGED EXERCISE IN MAN

Frisk-Hoimbérg, Marianne; Juhlin-Dannfeldt, Anders; Jorfelt, Lennart

doi:10.1016/b978-0-08-021308-8.50545-7

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“…This clearly indicates that the aerobic capacity during submaximal exercise is not reduced. There are obviously two mechanisms involved in the maintenance of unchanged oxygen uptake and transport: oxygen extraction in the working muscle is enhanced and the arterio-mixed-venous oxygen difference thus widened (1,5,6,20) compensating for the reduction in cardiac output; in most cases with normal left-ventricular function, moreover, stroke volume increases (1,15,21,22,23,25) tending to compensate for the decrease of heart rate and thus to counteract the reduction of cardiac output. Furthermore, the results obtained in the present study after a 15-month long-term treatment with acebutolol indicate that also maximal oxygen uptake and maximal physical work capacity remain unchanged under chronic j3 -adrenoceptor blockade.…”

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confidence: 99%

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

Franz¹,

Lohmann²,

Koch³

1985

Int J Sports Med

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Beta-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 beta 1-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 less than 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 less than 0.05) increased. However, after long-term treatment of 15 months, maximal oxygen uptake was virtually identical compared with pretreatment values, and maximal work load tended to be higher (5.2%, NS); plasma noradrenaline and adrenaline concentrations were significantly (P less than 0.05) enhanced. Since beta 1-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.

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