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Abstract

Background: While exposure to greater effective doses of ozone (O₃) (product of the concentration of O₃, ventilation, and duration of exposure) during exercise results in greater decrements in pulmonary function, the effect of matched effective doses of O₃ at different exercise intensities on pulmonary function has seldomly been explored. Aim: To investigate whether exercise performed in O₃ results in greater decrements in forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁) when performed at a higher-intensity for a shorter duration compared to a moderate-intensity exercise performed longer when the effective dose of O₃ is matched across intensities. Methods: Fourteen endurance-trained athletes (6 female, VO₂max=56.9±9.6 ml/kg/min) completed steady-state exercise bouts at a moderate-intensity (average duration =43:53) and heavy-intensity (average duration =66:07) with different air conditions (180 ppb O₃ and room air ≤10 ppb) in a randomised fashion. Cumulative ventilation was controlled across trials to control for effective dose. Spirometry and dyspnea were assessed before, during, and after each exercise bout, while breathing mechanics were only assessed during exercise. Results: Compared to baseline measures using mixed-effects modeling, O₃ exposure resulted in worsened measures of FEV₁ (-7.48%, p-value