Influence of exercise duration on respiratory function and systemic immunity among healthy, endurance-trained participants exercising in sub-zero conditions

Abstract

Background: Strenuous endurance exercise in sub-zero temperatures can cause airway damage that may lead to EIB. Prolonged exercise can also elicit greater immune perturbations than short-duration exercise. However, the influence of exercise duration on lung function and systemic immunity in sub-zero temperatures has not been established. Additionally, it is currently unknown whether atopic disposition, which is risk factor for EIB, influences respiratory responses in a sub-zero climate. The aim of this study was to compare respiratory and systemic immune responses to two cold air running trials of short and long duration, as well as to examine whether the responses differed between atopic and non-atopic subjects.

Methods: Eighteen healthy, endurance-trained subjects (males/females: 14/4; age: 29.4 ± 5.9 years old; BMI: 23.1 ± 1.7; atopic/non-atopic: 10/8) completed two moderate-intensity climate chamber running trials at - 15 °C, lasting 30 and 90 min, in a randomized, cross-over design. Lung function (spirometry and impulse oscillometry), serum CC16, respiratory symptoms, and blood leukocyte counts were examined before and after the trials.

Results: Lung function was not significantly affected by exercise or exercise duration. CC16 concentration increased after both trials (p = 0.027), but the response did not differ between trials. Respiratory symptom intensity was similar after each trial. There was a greater increase in neutrophils (p < 0.001), and a decrease in eosinophils (p < 0.001) after the 90-min bout. The 90-min protocol increased X5 compared to the 30-min protocol only in atopic subjects (p = 0.015) while atopy increased lower airway symptoms immediately after the 90-min session (p = 0.004).

Conclusions: Our results suggest that a 90-min bout of moderate-intensity exercise at - 15 °C does not cause substantial lung function decrements, airway epithelial damage or respiratory symptoms compared to 30 min running in the same environment, despite a heightened redistribution of white blood cells. However, exercise at - 15 °C may cause airway injury and evoke respiratory symptoms, even at moderate intensity. Atopic status may lead to greater peripheral bronchodilation and higher frequency of respiratory symptoms after long-duration exercise in cold.

Trial registration: 01/02/2022 ISRCTN13977758. This trial was retrospectively registered upon submission to satisfy journal guidelines. The authors had not initially registered the study, as the intervention was considered to be a controlled simulation of exercise in a naturally occurring environment (i.e. sub-zero air) for healthy volunteers.

Keywords: Airway epithelial damage; Airway injury; Atopy; Cold air exercise; Exercise-induced bronchoconstriction; Impulse oscillometry; Respiratory symptoms; Spirometry.

Fig. 1

Schematic representation of the experimental trials. Participants remained in the environmental chamber at 0–3 min post-exercise for the symptom reports

Fig. 2

Relative changes in lung function parameters in response to exercise. Data are expressed as % change from baseline values for each trial. Shown are means and 95% confidence intervals of the difference between the baseline and the two post-trial values; Grey: 30-min trial; Black: 90-min trial. For X5, negative change scores represent X5 becoming more negative

Fig. 3

X5 response to exercise in cold, between atopic and non-atopic participants. Open circles represent atopic individuals and closed circles non-atopic participants. Panel A: Change in X5 from baseline; data are mean and standard deviation. Grey points and lines represent the 30-min trial and black points the 90-min trial. Panel B: Mean difference in X5 between 30- and 90-min trials with 95% CI. *, significant difference between 30-and 90-min trials, p < 0.05

Fig. 4

Leukocyte counts before, 10 and 65 min after the 30- and 90-min trials. Grey points and lines indicate 30-min trial and black points and lines 90-min trial. The data were log-normally distributed and are presented using a log₂ scale on the y axis. Displayed are geometric mean and 95% confidence intervals. Significant main effect of time compared to baseline, *p < 0.05, **p < 0.01; ***p < 0.001; $, compared to + 10 min, p < 0.05; Significant difference within trial compared to baseline, ###, p < 0.001; Significant difference between trials, ††, p < 0.01

Fig. 5

Serum CC16 concentration before, 10 and 65 min after the 30- and 90-min trials. Data are mean and standard deviation. Significant difference from baseline, *p < 0.05; ***p < 0.001