Physiological effects of exercising at different intensities wearing surgical or double-layer cotton facemasks compared to not wearing a mask.

Since the beginning of the SARS-CoV-2 pandemic, the community use of facemasks has been widely recommended. However, their use during exercise has raised safety concerns. Thus, we compared the physiological differences between exercising wearing a surgical (SM) or a double-layer-cotton (DLC) facemask and not wearing a mask (NM). Sixteen volunteers underwent 4 bouts of cycling-based exercise, which consisted of two different intensities: light-to-moderate and moderate-to-high. Facemasks were used as follows: bout-1 and 4: NM; bout-2: SM or DLC and bout-3: DLC or SM. Ventilatory, metabolic, pulmonary gas exchange (PGE) and perceptual variables were collected. At both exercise intensities compared to NM, both facemasks induced similar ventilatory adaptations, increasing inspiratory time and tidal volume and decreasing breathing frequency. Effect sizes (ES) were larger for DLC than for SM. At moderate-to-high, both facemasks reduced the minute ventilation, whereas at light-to-moderate, it was only seen with DLC. End tidal and mixed CO 2 pressures, as well as the difference between them, increased with both facemasks. Again, ES was larger for DLC than SM. No relevant oxygen saturation drop was observed with both facemaks and exercise intensities. A small ES increament in VO 2 and VCO 2 were seen with both facemasks. Effort perception increased at moderate-to-high for both exercise intensities, buth larger EF were with DLC than SM . DLC increased facial temperature during both exercise intensities. In conclusion, ventilatory adjustments imposed during facemask exercise influenced PGE and metabolic and perceptual changes. Larger ES were mostly seen for DLC than SM. Abbreviations: B f : Breathing frequency.; CPET: Cardiopulmonary exercise test.; CI: Confidence interval.; DLC: Double-layer cotton.; E T CO 2 : End tidal CO 2 pressure.; ES: Effect size.; ΔE T -PECO 2 : Difference between E T CO 2 and PECO 2. ; FMMT: Facemask microclimate temperature.; H R : Heart rate.; IQR: Interquartile range.; NM: No mask.; PECO 2 : Mixed-expired CO 2 pressure.; RER: Respiratory exchange ratio.; RPE: Rate of perceived effort.; SD: Standard deviation.; SM: Surgical Mask.; SpO 2 : Oxygen saturation.; STP: Subjective thermal perception.; T i /T TOT : Duty cycle.; V E : Minute ventilation.; VCO 2 : Carbon dioxide output.; VO 2 : Oxygen uptake.; V T : Tidal volume.; VT: Ventilatory threshold. HighlightsFacemasks affect the breathing pattern by changing the frequency and amplitude of pulmonary ventilation.The augmented ventilatory work increases VO 2 , VCO 2 , and RPE and promotes nonconcerning drops in SpO 2 and CO 2 retention.Increased inspiratory and expiratory pressure can account for the reduction in pulmonary physiological dead space.