Effect of a breathing mask on type 2 mediator responses to subzero exercise in individuals without asthma

Objective Current evidence suggests that heat and moisture-exchanging breathing masks (HME) protect against exercise-induced bronchoconstriction (EIB). We aimed to explore whether mast cell mediator release following exercise in subzero conditions is affected by the use of an HME. To this end, 23 healthy, recreational-competitive endurance athletes aged 18–53 years without asthma performed a 30-min warm-up followed by a 4-min maximal, self-paced running time trial, with and without HME, in -15 °C. Concentrations of leukotriene E 4 (LTE₄) and 11β-prostaglandin F2α (11β-PGF2α) were measured in urine pre- and 60 min post-exercise and data analysed using repeated-measures ANOVA. Results LTE₄ decreased after the 4-min maximal exercise test ( p < 0.001), with no significant interaction with HME use. There was no effect of exercise alone nor HME on 11β-PGF2α responses to exercise. Taken together, we observed limited evidence of type 2 inflammation in healthy participants after brief, high-intensity exercise in the cold, with and without use of an HME. As the biomarker outcomes reported here were secondary and not powered in advance, these exploratory findings in a healthy cohort warrant further investigation using more robust airway challenges to better understand early airway responses and the potential for preventative strategies in athletes. Trial registration ISRCTN, Registered 01 April 2019, https//doi.org/10.1186/ISRCTN10018222.