Background Heavy endurance training in sub-zero environments increases risk of exercise-induced asthma. Heat-and-moisture exchangers (HME) can prevent exercise-induced bronchoconstriction but it is not known whether they protect against inflammatory responses to exercise in healthy individuals.

Objective To investigate whether use of an HME during exercise in a sub-zero environment affects post-exercise inflammatory responses.

Design Investigator-blind randomised crossover trial.

Setting Environmental chamber at -15°C.

Participants 23 healthy, trained participants aged 18–53 (15 male, 8 female, VO_2peak 57±6 and 50±4 mL/kg/min; mean±SD).

Interventions Two experimental trials with and without HME, consisting of 30-min moderate-intensity running followed by a 4-min maximal running time-trial. Plasma samples were obtained pre- and 1h-post-exercise and analysed for a panel of 10 cytokines using a multiplex immunoassay.

Main Outcome Measurements Plasma cytokine concentrations (GM-CSF, IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, IL-13, IL-17E/25, TNF-α). Data were log-transformed then analysed using two-way repeated-measures ANOVA; one participant was an extreme outlier and excluded.

Results Five cytokines (GM-CSF, IL-1β, IL-4, IL-13, IL-17E/25) returned <20% concentrations within detection limits and were excluded from further analysis. The other cytokines returned >85% samples in range. IL-6, IL-8 and IL-10 increased after exercise (IL-6: F=36, p<0.0001; IL-8: F=39, p<0.0001; IL-10: F(1,21)=8.9, p=0.0072). There was a trend towards a greater post-exercise increase in IL-10 with HME (HME: median 0.062 (range -0.203–1.053) pg/mL; no-HME: 0.047 (-0.079–0.50) pg/mL; F=3.0, p=0.096). There were no significant interactions for other cytokines.

Conclusions Use of an HME during exercise in a sub-zero environment did not affect systemic pro- and anti-inflammatory cytokine responses to exercise. Local inflammatory markers in the lungs may be relevant to investigate in future studies.