Abstract

Purpose The aerobic exercise affects the respiratory redox-state. The influence of different relative humidity (RH) levels on the formation of respiratory reactive chemical species associated with redox-state altered by exercise has been poorly explored. Our aim was to evaluate the effect of two different RH conditions (40% vs. 90%) on the concentration of hydrogen peroxide and nitrite in exhaled breath condensate ([H2O2]EBC and [NO2−]EBC) and spirometry parameters in recreational cyclists. Methods Sixteen men and women (12/4) (mean age±SD: 23.5±2.2 years) completed 60-min of cycling at 166.3±26.9 watts (70% of maximum load of ̇VO2-max.test, 49.3±7.6 mL·min−1·kg−1) at random 40%-RH and 90%-RH conditions separated by 7 days. The two-way RM-ANOVA test was applied to compare [H2O2]EBC, [NO2−]EBC, [NO2−]EBC/[NO2−]Plasma at rest and 80-min post-exercise (80-post); and spirometry parameters at rest, 20-post and 80-post. Results The interaction of factors (humidity × time) was significant in [H2O2]EBC, [NO2−]EBC, [NO2−]EBC/[NO2−]Plasma (p=0.005, p=0.030, p=0.043, respectively). At 40%-RH conditions, the same parameters were higher in 80-post than at rest (p<0.001, p=0.001, p=0.014, respectively). At the same time, the [H2O2]EBC and [NO2−]EBC/[NO2−]Plasma were higher in 40%-RH than 90%-RH (p=0.010, p<0.001, respectively). The interaction was significant in FEV1 (p=0.013) and FEF25-75% (p=0.023), but not in FEV1/FVC (p=0.362). At 80-post, the changes are kept in 90%-RH (p<0.001), diminishing in 40%-RH being similar to rest. Conclusion In recreational cyclists, 90%-RH prevents the increase of hydrogen peroxide and nitrite in exhaled breath condensate samples observed at 40%-RH and prolonging the bronchodilation until 80-post cycling exercise.