Title: Investigating the susceptibility of cardiorespiratory responses to ozone during cycling exercise
Thesis Supervisor: Dr. Michael Koehle
Committee members: Dr. Bill Sheel, Dr. Valérie Bougault
Defence Chair: Dr. Karim Khan
Abstract: Ground-level ozone (O3) is a common airborne pollutant well recognized to impair pulmonary function and cause negative respiratory symptoms when inhaled. Due to a wide range of inter-individual variability in responses, a lack of consensus as to whether O3 exposure limits exercise capability exists. Healthy, well-trained male (n=13) and female (n=7) endurance athletes were recruited to complete a double-blinded, randomized crossover study to address the research question. Participants were screened for inclusion based on a cycling VO2max test (Visit 1), before resting exposure to 750 parts per billion (ppb) O3 (Visit 2) to assess pulmonary function changes. During experimental trials (Visit 3 & 4), participants completed submaximal and maximal cycling exercise protocols exposed to both O3 (170ppb) and room air (RA, <10ppb O3). Results (n=20, VO2max = 64.1 ± 7.0 ml/kg/min) indicated that pulmonary function was significantly reduced and development of adverse respiratory symptoms was increased following both resting and exercise O3 exposure. No differences between conditions in ventilatory pattern or oxygen consumption (VO2) throughout submaximal exercise bouts. Paired t-tests analyzing the last minute of a time-to-exhaustion (TTE) test at 105% of peak power showed lower relative VO2 (p=0.003), tidal volume (p=0.007) and minute ventilation (p=0.047) in O3 compared to RA, with insignificant trends towards lower exercise time (p=0.092). As differences in relative VO2 (p<0.001) and tidal volume (p=0.001) also existed when comparing each participant’s last shared minute between conditions, a respiratory limitation of oxygen transport to the exercising muscle groups during maximal exercise seems likely. Understanding the mechanisms that may lead to negative impacts of O3 during exercise is critical to maximizing performance in athletic events exposed to high levels of pollution.