Effect of beta2 -adrenergic agonist and resistance training on maximal oxygen uptake and muscle oxidative enzymes in men.

Abstract

While beta2 -adrenoceptor stimulation has been shown to increase lean mass and to alter metabolic properties of skeletal muscle, adaptations in muscle oxidative enzymes and maximal oxygen uptake ( O2max ) in response to beta2 -adrenergic agonist treatment are inadequately explored in humans, particularly in association with resistance training. Herein, we investigated beta2 -adrenergic-induced changes in O2max , leg and arm composition, and muscle content of oxidative enzymes in response to treatment with the selective beta2 -adrenergic agonist terbutaline with and without concurrent resistance training in young men. Forty-six subjects were randomized to 4weeks of lifestyle maintenance (n=23) or resistance training (n=23). Within the lifestyle maintenance and resistance training group, subjects received daily terbutaline (8×0.5mg) (n=13) or placebo (n=10) treatment. No apparent treatment by training interactions was observed during the study period. Terbutaline increased leg and arm lean mass with the intervention, whereas no treatment differences were observed in absolute O2max and incremental peak power output (iPPO). Treatment main effects were observed for O2 -reserve (P<.05), O2max relative to body mass (P<.05), O2max relative to leg lean mass (P<.01), and iPPO relative to leg lean mass, in which terbutaline had a negative effect compared with placebo. Furthermore, content of electron transport chain complex I-V decreased by 11% (P<.05) for terbutaline compared with placebo. Accordingly, chronic treatment with the selective beta2 -adrenergic agonist terbutaline may negatively affect O2max and iPPO in relative terms, but not in absolute.