Sjöström, Kennedy et al. 2020, Exercise in sub-zero temperatures and airway health

Review of airway health in cold-air endurance exercise. Exercise-induced bronchoconstriction is far more common in winter-endurance athletes than in the general population, driven by drying and cooling of the airway surface during high ventilation of cold dry air, not by thermal injury. Inspired air is substantially warmed before reaching the lower airways (around 30°C at the bronchi even at minus 18°C), so the “frozen lungs” fear does not apply to healthy people; airway irritation and bronchoconstriction, not freezing, are the real issue. Strong (mechanism); the prevalence figures come via the review’s cited primary studies.