Abstract: Protective masks may impose variable breathing resistances on the wearer depending on the types of masks (e.g. surgical masks, N95 vs P100), filter properties (e.g. fiber diameter, packing layers), and fit characteristics (e.g. loose vs. tight fitting) which may adversely affect breathing comfort and cardiopulmonary function during physical activity. Previous studies investigating the impact of added breathing resistance due to mask-wearing on physiological responses and exercise performance provides inconsistent results, especially when tested under variable metabolic demands. Therefore, the present study was undertaken to determine whether added breathing resistance during graded exercise impairs aerobic exercise performance. Sixteen young men (age: 22.3 ± 3.1 years, height: 176.4 ± 4.8 cm, weight: 75.3 ± 8.3 kg) were recruited to participate in the present study. The participants performed a maximal exercise test using a cycle ergometer under the four conditions of breathing resistance in a counterbalanced order. The breathing resistance was implemented using a customized breathing resistor using actual filtering facepiece samples and set at no breathing resistance (CON), 18.9 Pa (BR1), 22.2 Pa (BR2), and 29.9 Pa (BR3). Measurements included maximal power output, endurance time, respiratory gas variables, oxygen saturation, heart rate, respiratory rate, changes in respiratory pressure, and subjective perception. Two-way repeated-measures ANOVA was carried out to compare physiologic and subjective variables between conditions over time and the statistical significance level (α) was set at .05. There was a significant reduction in exercise performance based on decreased maximal power output and endurance time together with detrimental effects on both physiological (e.g. decreased maximal oxygen consumption, minute ventilation, respiratory rate, oxygen saturation) and perceptual (e.g. increased ratings of exertion and breathing comfort) outcomes. Further, changes in respiratory pressure: positive and negative pressure during exhalation and inhalation, respectively, become significantly greater with a higher breathing resistance as exercise intensity increases, implicating elevated respiratory muscle load and thereby increased metabolic cost of breathing. In conclusion, breathing resistance that is commonly experienced when wearing tight-fitting facemasks/respirators impairs ventilatory response to graded exercise and consequently, causes mild to moderate exercise-induced hypoxemia leading to a decrement in aerobic performance.
