Defining Meaningful Change in Cycling Endurance for people with Interstitial lung disease

Exercise testing is fundamental for assessing the effects of pulmonary rehabilitation in people with interstitial lung disease (ILD). Several exercise tests exist, including maximal tests (e.g., peak exercise) and functional tests (e.g., 6-minute walk test), which can be performed either as cycling or walking. However, endurance time during a constant work rate test is considered the most responsive outcome for evaluating exercise-related physiological changes following therapeutic interventions in idiopathic pulmonary fibrosis (IPF), the most severe form of ILD, as well as in chronic obstructive pulmonary disease (COPD). In addition, thresholds that reflect the smallest change perceived as meaningful or important, called the minimal important difference (MID), exist for these exercise tests to determine whether a real improvement or deterioration in function has occurred, beyond random variability or measurement error, as a result of an intervention. While the MID for endurance time on a constant work rate test has been established for people with COPD, it is currently unknown for ILD. The aim of this project is to undertake a secondary analysis of 131 people with ILD who participated in a randomized controlled trial comparing high-intensity interval versus continuous training during pulmonary rehabilitation. Endurance time measured on a constant work rate test was the primary outcome following pulmonary rehabilitation, and this analysis will establish the minimal important difference for cycle endurance time in ILD.