Lung function decline after mountain ultra-marathon is accompanied by reduced inspiratory pressure but not by detectable changes in CC16

PURPOSE: Mountain ultra-marathons (MUM) impose multiple stressors on pulmonary function inducing risk of airway epithelial damage. This study aimed to assess the magnitude of pulmonary function changes and the associated risks of airway damage induced by such a race. METHODS: Thirteen volunteers completed the MUM (330 km, 24,000 m elevation gain). Pulmonary function was assessed using standardized procedures before (pre-) and within 1 h after (post-) the race. Assessments included forced inhalation and exhalation maneuvers, as well as maximal inspiratory pressure (MIP) measurements. Venous blood samples were collected for the analysis of plasma club cell secretory protein 16 (CC16). Blood volume was determined using the carbon monoxide rebreathing method. RESULTS: ) (-12.2%, p = 0.002) and peak expiratory flow (-10.4%, p = 0.016) were reduced. MIP decreased by 14.5% (104 ± 29 vs. 90 ± 26 cmH₂O, p = 0.005). CC16 levels remained unchanged, even after normalization for plasma volume changes (p = 0.929). Slope ratio and β-angle of the maximal expiratory flow-volume curve changes were not significant (p = 0.101 and p = 0.055, respectively). Significant relationships showed that greater decreases in FVC (r = - 0.60, p = 0.026) and FEV₁ (r = - 0.62, p = 0.018) were associated with faster MUM completion times. CONCLUSION: The acute negative impact of MUM on pulmonary function has been confirmed. The extent of this impairment appears to be proportional to race duration. Biomarker analysis suggests that airway epithelial integrity remains preserved. The reduced pulmonary function could be due to respiratory muscle fatigue.