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 (V̇O_2max) 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 V̇O_2max, 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 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_2max and incremental peak power output (iPPO). Treatment main effects were observed for V̇O₂-reserve (P < .05), V̇O_2max relative to body mass (P < .05), V̇O_2max relative to leg lean mass (P < .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 < .05) for terbutaline compared to placebo. Accordingly, chronic treatment with the selective beta₂-adrenergic agonist terbutaline may negatively affect V̇O_2max and iPPO in relative terms, but not in absolute.