Mid Sweden University

Purpose: To investigate whether use of an HME in sub-zero temperatures affects the physiological demands of fixed-intensity submaximal exercise, and whether the effect of the HME differed between sexes.

Methods: Twenty-three healthy, trained participants (15 male, 8 female, VO2peak 57 ± 6 and 50 ± 4 mL·kg-1·min-1; mean ± SD) gave written, informed consent to participate in the study. Participants completed two experimental trials, with and without HME. Each experimental trial consisted of 30-min submaximal treadmill running in -15°C. Muscle oxygenation (SmO2) and relative deoxyhaemoglobin concentration [HHb] were determined using wireless near-infrared spectroscopy sensors placed bilaterally on m. vastus lateralis. Nineteen complete datasets were obtained (12 men and 7 women) and analysed using linear mixed models.

Results: There were significant sex × trial interactions for SmO2 (p=0.007) and [HHb] (p=0.009); in the men only, SmO2 was lower (-3.8%, 95% CI: -1.9–-5.6%) and [HHb] was higher (0.42 AU, 95% CI: 0.2–0.65) from 5 min into the HME trial, whereas in the women there was no difference between trials.

Conclusion: The lower SmO2 and higher [HHb] in the men during fixed-intensity exercise with HME indicates greater O2 extraction at the tissues. Thus, an HME could be interpreted as increasing the physiological demands of exercise in men. We could speculate that airflow limitation from the HME could be exacerbated by higher absolute rates of ventilation resulting in reduced tissue oxygen delivery.

Practical Applications: Our observations could have implications for athletes when deciding whether to use an HME during training and competition.