Assessing Functional Capacity in Directly and Remotely Monitored Home-based Settings: A Protocol for a Multinational Validation Study in Individuals With Chronic Respiratory Diseases

The goal of this validation study is to provide further evidence of the metrological properties of the 6-minute stepper test in individuals with chronic obstructive pulmonary disease (COPD) or interstitial lung disease (ILD). The main questions it aims to answer are: 1. Is the 6-minute stepper test valid when compared to the 6-minute walk test and a maximal cardiopulmonary cycling test? 2. Does the 6-minute stepper test give the same results when conducted through direct (i.e., therapist in person) and remote (i.e., videoconferencing) monitoring? 3. Is the 6-minute stepper test safe when conducted at the home of the individual with direct (i.e., therapist in person) or remote (i.e., videoconferencing) monitoring? Participants will: * Conduct the 6-minute stepper test (several trials on separate days) * Conduct the 6-minute walk test (1 trial on 1 day) * Conduct a maximal cardiopulmonary test on a cycle ergometer (1 trial on 1 day) * Participate in a semi-structured interview to provide their feedback with regards to the 6-minute stepper test

Inclusion Criteria: * Adult ≥ 40 years old * Diagnosis of chronic obstructive pulmonary disease (GOLDa 2 to 4) or of interstitial lung disease (\> 6 months) * Clinically stable for ≥ 4 weeks Exclusion Criteria: * Interstitial lung disease associated with connective tissue disease and sarcoidosis (often accompanied with multisystemic effects) * Unstable or severe cardiac condition * Invalidating rheumatologic or neurologic condition * Weight exceeding maximal limits of exercise equipment (e.g., 130 kg for the stepper) * Any other physical condition limiting or contraindicating exercise testing * Simultaneous participation in another study requiring changes in medication * Recent pulmonary rehabilitation (≤1 year, potential learning bias for the 6-minute walk test and the 6-minute stepper test) * For arm 1 only: Use of oxygen therapy (unable to perform gas analysis with oxygen therapy) * For arm 2 only: Participation in arm 1