Sarah Koch’s PhD Thesis Defence

Title: “Exercise-induced bronchoconstriction – the effects of inhaled ß2-agonists on athletic performance in humans”

Chair: Dr. Bryan Gick (Linguistics)
Supervisory Committee: Dr. Michael Koehle, Research Supervisor (Kinesiology), Dr. Jordan Guenette (Rehabilitation Sciences)
Dr. Christopher Carlsten (Experimental Medicine)
University Examiners: Dr. Kristin Campbell (Rehabilitation Sciences), Dr. Colin Brauner (Zoology)
External Examiner: Dr. Kai-Hakon Carlsen (Institute of Clinical Medicine, University of Oslo)

The purpose of this thesis was to investigate the ergogenic potential of inhaled ß2-agonists (IBAs) in athletes with and without exercise-induced bronchoconstriction (EIB) from multiple angles: by assessing the effect of 400 μg of salbutamol, a commonly used IBA, in female athletes; and by analyzing athletic performance after the inhalation of the maximal daily dose of salbutamol, i.e. 1600 μg, by taking dose per kg of body mass into consideration. Furthermore, four methods of calculating the fall index (FI) in the eucapnic voluntary hyperpnea (EVH) challenge were evaluated.
Female (Chapter 2) and male cyclists (Chapter 3) were screened for EIB using the EVH challenge. On two subsequent visits, athletes performed one 10-km time trial per visit. In a randomized order, athletes inhaled either salbutamol or placebo before completing the time trials. Athletic performance was assessed using mean power output. In Chapter 4, the FIs of the EVH challenges from Chapters 2 and 3 were calculated using four previously published methods and compared to the pulmonary response to the placebo time trial. Additionally, the intensity of the EVH target ventilation, calculated as 30 x forced expiratory volume in 1 second (FEV1), was evaluated by comparing it to the highest generated ventilations in a graded maximal exercise test (GXT).
Despite significant increases in FEV1 after IBA use, athletic performance was not improved in female or male athletes, regardless of EVH status. In women, power output was decreased, despite a significant increase in oxygen consumption, suggestive of an increased stimulation of women’s adrenergic β2-system. Similarly, in male athletes, significant increases in heart rate, ventilation, and perceived leg discomfort could indicate an upregulation of the adrenergic nervous system, independent of the relative IBA dose. Lastly, there were significant differences between the four FI calculation methods, influencing the EVH interpretations. Normalizing FIs by the ventilations achieved during voluntary hyperpnea was not supported in athletes with high percent predicted values for FEV1 due to an increased risk of false-positives. The intensity of the EVH target ventilation ranged between 67% – 135% when normalized to the GXT ventilations.