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Perceived respiratory effort at the heart rate of 130 and 150 beats per minute using different face masks. Grey shaded boxplots represent respiratory effort at PWC150. Asterisks indicate statistically significant differences (Bonferroni corrected p < 0.003). 0 = no respiratory effort, 10 = maximum respiratory effort. PWC, physical working capacity; MedMask, medical face mask; FFP2exhal, filtering facepiece with exhalation valve.
