PURPOSE: Ventilatory stimulation and its chemical control are important when b2 adrenergic agonists are used in asthma treatment. In elite athletes and general population, asthma is a very common condition. Use of beta 2 adrenergic agonists by competitive athletes is strictly prohibited by WADA in sport disciplines due to their assumed ergogenic action, such as an increase of peripheral chemosensitivity and metabolism, in endurance performance and muscle strength. The purpose of the present study is to investigate the effect of salbutamol to chemoreflex and the metaboreflex, its ergogenic contribution in nonasthmatic man.
METHODS: Eleven healthy male subjects were measured after 10 μg/min during 30 minutes intravenously salbutamol versus placebo following a double-blind, placebo-controlled, randomized cross-over design. The effects of the beta2-adrenergic agonist, salbutamol, on MSNA, ventilatory responses to hyperoxic hypercapnia (7% CO2 in O2), DVE/DPetCO2, and isocapnic hypoxia (10 % O2 in N2), DVE/DSpO2, and to an isometric muscle contraction followed by a local circulatory arrest (metaboreflex) were determined at rest, followed by an incremental cardiopulmonary exercise test and maximal isokinetic muscle strength test (Cybex).
RESULTS: During baseline, HR, SBP, VE and MSNA burst incidence, while MSNA burst frequency, Pet CO2, SaO2 remained unchanged. During hypoxia, HR and VE remained increased, however, MSNA, BP, SaO2, was unchanged during salbutamol compared to placebo. There were no changes in HR, MSNA, VE, SpO2 or PetCO2 during hypercapnia or metaboreflex stimulation with salbutamol.
In incremental cardiopulmonary exercise test only Ve/VO2 slope at maximal exercise and O2 pulse at anaerobic threshold were significantly changed by salbutamol, while there were no effects on HR, VO2 max, or other ventilatory equivalents. Salbutamol had any effects on maximal isokinetic muscle strength test (Cybex).
CONCLUSIONS: Acute intravenous salbutamol increases Ve at rest stimulating peripheral chemoreceptors with out any changes on aerobic exercise capacity and muscle strength. It is likely that systemic or hemodynamic effects of b2 adrenergic agonist rather than the bronchial actions are involved in the ergogenic effects of salbutamol in healthy subjects.