Effect of β-adrenoceptor blockade on postexercise oxygen consumption and triglyceride fatty acid cycling

In the recovery period after strenuous exercise, there is increased O-2 uptake, termed the excess postexercise O-2 consumption (EPOC), One of the mechanisms suggested to explain EPOC is activation of the triglyceride/fatty acid (TG/FA) cycle by catecholamines. The purpose of this study was to determine the effect of selective beta 1- and nonselective beta-adrenoceptor blockade on EPOC and the TG/FA cycle. Seven healthy young men each participated in three control and three exercise experiments in a randomized and balanced sequence. In the exercise experiments, subjects exercised for 90 minutes at 58% +/- 2% (mean +/- SD) of maximal O-2 uptake on a cycle ergometer, followed by a 4.5-hour bedrest. The control experiments followed the same protocol, but without exercise. In one control and one exercise experiment, the selective beta(1)-adrenoceptor antagonist atenolol (0.062 mg.kg(-1) body weight) was administered intravenously immediately after the exercise (EXAT) and at the corresponding time in the rest-control experiment (REAT), In a second set of control and exercise experiments, the nonselective P-adrenoceptor antagonist propranolol (0.15 mg.kg(-1) body weight) was administered (REPRO and EXPRO). In a third set of rest and exercise experiments, an injection of saline was given instead of beta-antagonist (RE and EX). TG/FA cycling was calculated by combining results obtained with a two-stage glycerol infusion and indirect calorimetry. O-2 uptake was significantly increased above control levels throughout the recovery period after exercise with the nonselective beta-adrenoceptor antagonist, beta(1)-adrenoceptor antagonist, and saline. However, there was no difference between the time course or magnitude of EPOC in the three situations. After 4.5 hours of bedrest, the mean increase in O-2 uptake was 8% to 9% in all three conditions. TG/FA cycling was increased after exercise, but no effects of beta-antagonists were observed. We conclude that EPOC and the rate of TG/FA cycling are not attenuated by selective beta(1)- or nonselective beta-adrenoceptor blockade after an acute prolonged exercise protocol. Copyright (C) 1998 by W.B. Saunders Company.