The impact of breathing route on pulmonary and sensory responses to ozone exposure during exercise in adults.

Ozone (O3) is a photochemical air pollutant known to reduce lung function and induce respiratory symptoms. This study aimed to determine whether breathing route influences O3-induced lung function changes during exercise. Thirteen recreationally active participants (6 females, V̇O2peak = 45.8 ± 5.3 mL/kg/min), with no history of cardiovascular or pulmonary disease or exercise-induced bronchoconstriction, completed a double-blind crossover study with four experimental visits. Participants performed 30 min of low-intensity cycling (90% of power at the first ventilatory threshold) while breathing exclusively nasally or orally under room air or 0.40 ppm O3. Spirometry was assessed before and after each trial, and dyspnea (Multidimensional Dyspnea Profile) every 5 min during exercise. O3 exposure impaired pulmonary function, reducing FEV1, FVC, PEF, FEF25-75, and FEV1/FVC (all p < 0.05). Regardless of environmental condition, oral breathing produced modestly greater post-exercise reductions in FEV1, PEF, FEF25-75, and FEV1/FVC than nasal breathing, but no breathing route × environment interaction was observed. Nasal breathing was associated with greater breathing effort and air hunger (p < 0.05). Thus, O3 exposure impaired pulmonary function and increased dyspnea regardless of breathing route. Although nasal breathing slightly attenuated overall post-exercise lung function decline, it did not protect against O3-induced pulmonary impairment and increased breathing discomfort during exercise.