A heat and moisture-exchanging mask impairs self-paced maximal running performance in a sub-zero environment.

Purpose: Heat-and-moisture-exchanging devices (HME) are commonly used by endurance athletes during training in sub-zero environments, but their effects on performance are unknown. We investigated the influence of HME usage on running performance at - 15 °C.

Methods: Twenty-three healthy adults (15 male, 8 female; age 18-53 years; [Formula: see text] men 56 ± 7, women 50 ± 4 mL·kg·min) performed two treadmill exercise tests with and without a mask-style HME in a randomised, crossover design. Participants performed a 30-min submaximal warm-up (SUB), followed by a 4-min maximal, self-paced running time-trial (TT). Heart rate (HR), respiratory frequency (f), and thoracic area skin temperature (T) were monitored using a chest-strap device; muscle oxygenation (SmO) and deoxyhaemoglobin concentration ([HHb]) were derived from near-infra-red-spectroscopy sensors on m. vastus lateralis; blood lactate was measured 2 min before and after the TT.

Results: HME usage reduced distance covered in the TT by 1.4%, despite similar perceived exertion, HR, f, and lactate accumulation. The magnitude of the negative effect of the HME on performance was positively associated with body mass (r = 0.22). SmO and [HHb] were 3.1% lower and 0.35 arb. unit higher, respectively, during the TT with HME, and T was 0.66 °C higher during the HME TT in men. HR (+ 2.7 beats·min) and T (+ 0.34 °C) were higher during SUB with HME. In the male participants, SmO was 3.8% lower and [HHb] 0.42 arb. unit higher during SUB with HME.

Conclusion: Our findings suggest that HME usage impairs maximal running performance and increases the physiological demands of submaximal exercise.