Principal findings
CM
In this partially double-blinded randomized cross-over study wearing SM, CM, and FFP2 caused an increase in total airway resistance and specific airway resistance, which was most pronounced for FFP2. The increased breathing resistance led to an increase in work of breathing and respiratory power and thus to a slightly prolonged Ttot. These changes in breathing patterns were observed already at rest and were most pronounced with increasing workload during exercise.With the increasing workload, a decrease was observed in sO