While beta -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 (V̇O ) in response to beta -adrenergic agonist treatment are inadequately explored in humans, particularly in association with resistance training. Herein we investigated beta -adrenergic-induced changes in V̇O , leg and arm composition, and muscle content of oxidative enzymes in response to treatment with the selective beta -adrenergic agonist terbutaline with and without concurrent resistance training in young men. Forty-six subjects were randomized to four weeks of lifestyle maintenance (n=23) or resistance training (n=23). Within the lifestyle maintenance and resistance training group, subjects received daily terbutaline (8·0.5 mg)(n=13) or placebo (n=10) treatment. No apparent treatment by training interactions were observed during the study period. Terbutaline increased leg and arm lean mass with the intervention, whereas no treatment differences were observed in absolute V̇O and incremental peak power output (iPPO). Treatment main effects were observed for V̇O -reserve (P<0.05), V̇O relative to body mass (P<0.05), V̇O relative to leg lean mass (P<0.01), and iPPO relative to leg lean mass, in which terbutaline had a negative effect compared to placebo. Furthermore, content of electron transport chain complex I-V decreased by 11% (P<0.05) for terbutaline compared to placebo. Accordingly, chronic treatment with the selective beta -adrenergic agonist terbutaline may negatively affect V̇O and iPPO in relative terms, but not in absolute. This article is protected by copyright. All rights reserved.