Effects of no mask, a surgical mask and a fabric buff on peripheral oxygenation saturation during moderate intensity exercise: a randomised cross-over study.

Background: Mask-wearing caused significant reductions in coronavirus disease 2019 (COVID-19) transmission. We aimed to determine whether face mask-wearing during exercise caused reductions in peripheral oxygen saturation (SpO) and whether it affected secondary physiological measures [end-tidal carbon dioxide (EtCO), respiratory rate (RR), heart rate (HR), expired breath temperature (EBT)]. Subjective measurements included ratings of perceived exertion (RPE), ratings of perceived breathlessness (RPB), and symptomology.

Methods: A randomised cross-over trial examined no mask (NM), surgical mask (SM) and a buff mask (BM). Thirty participants (30-45 years) cycled at 60% power output for 30 min in three exercise sessions, 24 h apart, within 6 days. Each session recorded all measures at resting baseline (T0), 9 min (T1), 18 min (T2), and 27 min (T3). Dependent statistical tests determined significant differences between masks and time-points.

Results: SpO decreased for SM and BM between T0 compared to T1, T2 and T3 (all P<0.005). BM caused significant reductions at T1 and T2 compared to NM (P<0.001 and P=0.018). Significant changes in EtCO and EBT occurred throughout exercise and between exercise stages for all mask conditions (P<0.001). As expected for moderate intensity exercise, RR and HR were significantly higher during exercise compared to T0 (P<0.001). RPB significantly increased for each condition at each time point (P<0.001). RPE was not significant between mask conditions at any exercise stage.

Conclusions: SM and BM caused a mild but sustained reduction in SpO at commencement of exercise, which did not worsen throughout short (<30 min) moderate intensity exercise. Level of perception was similar, suggesting healthy people can wear masks during moderate exercise and activities of daily living.