S. M. Jilka

Cardiorespiratory alterations consequent to endurance exercise training during chronic beta-adrenergic blockade with atenolol and propranolol

A study was undertaken to determine if normal healthy subjects can increase their endurance capacity consequent to endurance training during chronic beta-adrenergic blockade. Forty-seven subjects, 17 to 34 years of age, were randomly assigned to 1 of 3 treatments (placebo, propranolol, 160 mg/day, and atenolol, 100 mg/day) and then completed a 15-week aerobic exercise training program. All groups reduced their submaximal steady-state heart rates consequent to training; submaximal oxygen uptake was slightly reduced; submaximal stroke volume was increased only in the placebo and atenolol groups; submaximal cardiac output was generally lower; and arterial-mixed venous oxygen difference was increased after training in all 3 groups, suggesting decreased muscle blood flow and increased oxidative capacity. Maximal oxygen uptake and maximal treadmill time were increased in all 3 groups after training. However, while still on medication the atenolol group had significantly greater increases in maximal oxygen uptake and maximal treadmill time compared with the propranolol group. Because most patients will remain on medication, these results suggest a distinct advantage for cardioselective blocking agents. It is concluded that beta-adrenergic blockade does not reduce the ability of normal healthy subjects to gain the benefits associated with cardiorespiratory endurance training.

Maximal exercise responses to acute and chronic beta-adrenergic blockade in healthy male subjects

Conflicting data on the alterations in the maximal exercise response to beta blockade (BB) may be the result of differences in the length of time the subject has been on medication, i.e., hours vs days. The purpose of this study was to examine maximal exercise responses during acute and chronic administration of BB. Twenty-eight healthy males, 14 untrained (UT) and 14 involved in a personal training regimen (TR), performed maximal treadmill tests after 1 d and 9 d under three double-blind, randomized conditions: a placebo (PLAC), propranolol (PROP) 80 mg b.i.d., and atenolol (ATEN) 100 mg o.d. Maximal heart rate (HR), oxygen consumption (VO2), ventilation (VE), and treadmill time were significantly reduced by PROP and ATEN after an acute and chronic dose when compared to PLAC (P less than 0.05) in both groups of subjects. Maximal HR was decreased more after 1 d of BB than after 9 d of BB with both PROP and ATEN in the UT subjects and with PROP only in the TR group. VO2max, VEmax, and treadmill time were also less attenuated after 9 d of BB; however, this trend did not reach statistical significance. The nonselective beta blocker, PROP, caused greater reductions in VO2max compared to the selective beta blocker, ATEN, in both groups of subjects. These data indicate that, other than a small change in maximal HR, there is no difference in the exercise response to acute and chronic BB in normal and highly conditioned individuals.

Alterations in plasma lipids consequent to endurance training and beta-blockade

Alterations in plasma lipids consequent to endurance training and beta-blockade. Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 288-292, 1989. The chronic use of beta adrenergic blockers (BAB) has been associated with reductions in HDL-cholesterol (HDL-C) and increases in triglycerides (TG). This study evaluated the impact of concurrent endurance exercise training and chronic medication with BAB on plasma lipid and lipoprotein profiles in healthy young adult males. Changes in plasma lipids and lipoproteins were investigated while exercise training under the influence of one of two nonselective BAB [sotalol (320 mg.d-1) and propranolol (160 mg.d-1)], one beta 1 selective BAB [atenolol (100 mg.d-1)], or a placebo control. Total cholesterol (TC), HDL-C, LDL-cholesterol (LDL-C), TG, and the ratios of TC/HDL and LDL/HDL were determined before and after endurance training programs of either 14 (N = 27, sotalol) or 15 (N = 47, propranolol/atenolol) wk duration. The subjects exhibited increases in maximal oxygen uptake of 12-20%. Despite increased endurance capacity, the subjects in both BAB and placebo control groups failed to demonstrate the expected increase in HDL-C and decrease in TG. In fact, HDL-C was significantly decreased post-training in the propranolol group. The placebo groups did decrease TC, LDL-C and the TC/HDL and LDL/HDL ratios, improving their CHD risk profile. Similar changes were not observed in the groups on BAB. Thus, with respect to the present population, BAB does appear to interfere with the usual training-induced improvements in the lipid profile. Endurance training may, however, reduce the deterioration in the lipid profile known to occur with BAB.