EFFECT OF BETA-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 o f the mechanisms suggested to explain EPOC is activation of the trigly ceride/fatty acid (TG/FA) cycle by catecholamines. The purpose of this study was to determine the effect of selective beta 1- and nonselecti ve beta-adrenoceptor blockade on EPOC and the TG/FA cycle. Seven healt hy young men each participated in three control and three exercise exp eriments in a randomized and balanced sequence. In the exercise experi ments, subjects exercised for 90 minutes at 58% +/- 2% (mean +/- SD) o f maximal O-2 uptake on a cycle ergometer, followed by a 4.5-hour bedr est. The control experiments followed the same protocol, but without e xercise. In one control and one exercise experiment, the selective bet a(1)-adrenoceptor antagonist atenolol (0.062 mg.kg(-1) body weight) wa s 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-ad renoceptor antagonist propranolol (0.15 mg.kg(-1) body weight) was adm inistered (REPRO and EXPRO). In a third set of rest and exercise exper iments, an injection of saline was given instead of beta-antagonist (R E and EX). TG/FA cycling was calculated by combining results obtained with a two-stage glycerol infusion and indirect calorimetry. O-2 uptak e was significantly increased above control levels throughout the reco very period after exercise with the nonselective beta-adrenoceptor ant agonist, beta(1)-adrenoceptor antagonist, and saline. However, there w as no difference between the time course or magnitude of EPOC in the t hree 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 increas ed after exercise, but no effects of beta-antagonists were observed. W e 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. Saun ders Company.