Effects of Using the Surgical Mask and FFP2 during the 6-Min Walking Test. A Randomized Controlled Trial - Cabanillas-Barea, Sara; Rodriguez-Sanz, Jacobo; Carrasco-Uribarren, Andoni; Lopez-de-Celis, Carlos; Gonzalez-Rueda, Vanessa; Zegarra-Chavez, Daniel; Cedeno-Bermudez, Simon; Perez-Bellmunt, Albert (International Journal Of Environmental Research And Public Health, 2021)