Beta-2 agonists and exercise performance in humans

Abstract

Summary Aims Due to fears of doping effects, the World Anti-Doping Agency has put certain restrictions on the use of the pharmacological class of beta-2 agonists. In 2010, all beta-agonists are prohibited except salbutamol and salmeterol by inhalation, which require a declaration of use in accordance with the international standard for therapeutic use exemptions. Topics We reviewed the current literature to determine whether inhaled or oral beta-2 agonists enhance human performance and, based on our findings, we present hypotheses on the mechanisms that might account for the documented performance gains. Most of the trials were conducted after acute therapeutic inhalation and generally failed to show improved performance after such local low-dose administration, probably because of a lack of sufficient systemic bioavailability. In contrast, almost all trials after acute or short-term oral administration at therapeutic dosage demonstrated significantly improved performance, whatever the exercise intensity. The mechanisms by which the systemic administration of beta-2 agonists produces ergogenic effects are unknown, but the popular theory that salbutamol has an ergogenic effect due to its anabolic properties can be ruled out. The theory that it enhances substrate oxidation is incomplete, and both central and peripheral effects have been suggested. Future prospects Further studies are needed with particular focus on: (1) the effects of systemic administration of terbutaline or bambuterol ; (2) the effects of short-term supratherapeutic inhalation, and (3) the determination of a urinary threshold for terbutaline, salmeterol and formoterol.