Keywords: 6-MWD, 6-minute walk distance; 6-MWT, 6-minute walk test; COVID-19, coronavirus disease-2019; DLCO, diffusing lung capacity for carbon monoxide; FEV1, forced expiratory volume in the first second; FT, pulmonary function tests; FVC, forced vital capacity; HHR, heart rate recovery; IMV, invasive mechanical ventilation; LLN, lower limit of normal; MEP, maximal expiratory pressure; MERS, Middle East respiratory syndrome; MIP, maximal inspiratory pressure; SARS, severe acute respiratory syndrome; SpO2, oxygen blood saturation measured by pulse oximeter.