Swimming versus running: effects on exhaled breath condensate pro-oxidants and pH

Purpose: The respiratory redox-state of swimmers can be affected by chronic exposures to chlorinated pools, and the effects of different exercises on it are unknown. Our aim was to compare two exercises performed at high-intensity and under habitual environmental conditions (swimming indoor vs. running outdoor) on the production of pro-oxidants (hydrogen peroxide and nitrite) and pH in exhaled breath condensate (EBC) and spirometry parameters in competitive swimmers chronically exposed to chlorinated pools. Methods: Seventeen men and women (mean age ± SD = 21 ± 2 years) swam 3.5 km in an indoor pool treated with Cl_2, and after 2-weeks, they ran 10 km outdoors. The pH_EBC, [H₂O₂]_EBC, [NO₂ ⁻]_EBC, [NO₂ ⁻]_EBC/[NO₂ ⁻]_Plasma and spirometry parameters were analyzed pre-exercise and 20 min and 24 h after exercise ended. Results: Two mixed models were applied to compare EBC parameters between swimming and running. Lower levels of [H₂O₂]_EBC and [NO₂ ⁻]_EBC (p = 0.008 and p = 0.018, respectively) were found 24-h post-swimming, and the same trend was observed for [NO₂ ⁻]_EBC/[NO₂ ⁻]_Plasma (p = 0.062). Correlations were found in both exercises between pre-exercise levels of pH_EBC, [H₂O₂]_EBC, [NO₂ ⁻]_EBC, and [NO₂ ⁻]_EBC/[NO₂ ⁻]_Plasma and their changes (Δ) after 24-h as well as between [H₂O₂]_EBC and [NO₂ ⁻]_EBC for basal levels and for changes after 24 h. A relationship was also found for running exercise between pulmonary ventilation and changes after 24 h in [H₂O₂]_EBC. Spirometry data were unaffected in both types of exercise. Conclusion: In competitive swimmers, at 24-h acute post-exercise follow-up, swimming decreased and running increased pro-oxidant biomarkers of pulmonary origin, without changes in lung function.