Inhaled salbutamol induces leanness in well-trained healthy females but not males during a period of endurance training: a randomised controlled trial

Abstract

Introduction Many athletes use short-acting inhaled β2-agonists multiple times weekly during training sessions to prevent exercise-induced bronchoconstriction, but it is unclear if treatment impairs training outcomes. Herein, we investigated performance adaptations in well-trained females and males training with prior inhalation of salbutamol. Methods 19 females and 21 males with maximal oxygen uptake (V′O2max) of 50.5±3.3 and 57.9±4.9 mL·min−1·kg−1, respectively, participated in this double-blinded, placebo-controlled, parallel-group study. We randomised participants to placebo or salbutamol inhalation (800–1600 µg·training day−1) for 6 weeks of combined endurance (1× per week) and high-intensity interval training (2× per week). We assessed participants’ body composition, V′O2max and muscle contractile function, and collected vastus lateralis muscle biopsies. Results Salbutamol induced a sex-specific loss of whole-body fat mass (sex×treatment: p=0.048) where only salbutamol-treated females had a fat mass reduction compared to placebo (–0.8 kg at 6 weeks; 95% CI: −0.5 to −1.6; p=0.039). Furthermore, salbutamol-treated females exhibited a repartitioning effect, lowering fat mass while gaining lean mass (p=0.011), which was not apparent for males (p=0.303). Salbutamol negatively impacted V′O2max in both sexes (treatment main effect: p=0.014) due to a blunted increase in V′O2max during the initial 4 weeks of the intervention. Quadriceps contractile strength was impaired in salbutamol-treated females (−39 N·m; 95% CI: −61 to −17; p=0.002) compared to placebo at 6 weeks. Muscle electron transport chain complex I–V abundance increased with salbutamol (treatment main effect: p=0.035), while content of SERCAI, β2-adrenoceptor and desmin remained unchanged. Conclusion Inhaled salbutamol appears to be an effective repartitioning agent in females but may impair aerobic and strength-related training outcomes.