Effects of Wearing an N95 Respirator or Cloth Mask Among Adults at Peak Exercise

This randomized crossover trial examines the effects of wearing a cloth mask or N95 respirator vs no mask at peak exercise among healthy, active adults.


Introduction
For the majority of apparently healthy adults, mask wearing while at rest or during activities of daily living is recommended to be safe and effective for reducing the risk of person-to-person airborne transmission of SARS-Cov-2. 1,2 Original research has yet to find evidence showing an effect of mask wearing on clinical indicators of exercise safety. 3 In this study, we tested whether mask wearing during exercise stress testing (EST) to peak exhaustion provokes clinically indicated safety concerns.

Methods
In this randomized crossover trial (ClinicalTrials.gov Identifier: NCT04415879), 20 never-smoker, apparently healthy, recreationally active men and women participated in treadmill EST under each of the experimental conditions: no mask, N95 (3M 8200 N95 respirator), and cloth mask (Boco Gear PM2.5 activated carbon filter). A random number generator determined the order whereby experimental conditions would be performed. Participants provided voluntary verbal and written informed consent during study enrollment and prior to EST.
The Cleveland Clinic institutional review board reviewed and approved this study in accordance with the Declaration of Helsinki. The trial protocol is available in Supplement 1. The design and execution of this study also followed the Consolidated Standards of Reporting Trials (CONSORT) reporting guideline for crossover trials. A full description of the study methods, including the CONSORT flow diagram, can be viewed in the eAppendix of Supplement 2.

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Individualized EST had participants self-select a constant treadmill belt speed that would be used across experimental conditions. Treadmill grade always increased from 0.0% to 2.0% at minute 2; and thereafter by 1.0% each minute until achieving peak exhaustion. Heart rate, rating of perceived exertion, and oxyhemoglobin saturation measurements were acquired throughout EST. Reported peak V O 2 for mask conditions reflect rest-topeak exercise changes in oxygen saturation that occurred as compared with the no mask condition.    The independent experimental condition effect on continuous variables was tested using mixed-effects analysis of variance modeling. The randomized EST order was set as a random effect in models. Two-tailed significance was determined using an alpha level set at .05. Statistical analysis was performed using SAS statistical software version 9.4 (SAS Institute) from October to December 2020.

Results
Of 20 participants, there were 9 women (45%); the mean (SD) age and mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) for women in the sample were 35 (11) years and 25.1 (4.2), respectively, which did not differ significantly from the men in the sample Adjusting comparisons of peak V O 2 for perceived breathing resistance resulted in no significant experimental condition main effect (Figure).

Discussion
This crossover trial found that perceived breathing resistance at peak exercise is uniquely and significantly elevated when EST is performed while wearing a mask. Performing EST with a mask yielded lower peak V O 2 and heart rates as compared with no mask. However, each experimental condition resulted in peak exercise values that generally remained within normal limits, and no EST required termination due to clinically indicated safety concerns. Thus, although it is possible that wearing a mask exerted a physical limitation on exercise capacity, the clinical relevance of such a possibility is not supported by these data.
A limitation of this study was the lack of exercise ventilation and gas exchange data collected during EST. This limited our ability to potentially identify where a major physiological limitation to exercise occurred during masked trials. However, having access to these data would likely not have changed the conclusion that performing EST with a mask is generally clinically safe but likely to provoke exaggerated symptoms. The subjective experience of high breathing resistance should not be overlooked as being potentially impactful to reducing how well individuals are able to perceptually tolerate vigorous-to-peak intensity exercise.