The use of pursed lip breathing (PLB) to improve exercise tolerance in COPD patients has been widely documented. However, its efficacy in patients with interstitial lung disease (ILD) has yet to be confirmed. This study aims to determine if PLB improves perceived exertion and exercise capacity during a six-minute walk test (6MWT) in patients with ILD. To achieve this, a prospective randomized crossover trial will be performed, in which patients with ILD and restrictive ventilatory defect will be recruited via the ILD clinic of Hôpital Notre-Dame. The study will be performed in a single visit, on the day where patients attend a routine physician-prescribed follow-up 6MWT. Patients will be asked to perform a total of two 6MWT. Patients will be randomized to perform the first test with or without using PLB, and the order will be reversed for the second test, with patients serving as their own control. During tests, ventilatory variables will be continuously measured using a portable metabolic cart. The observed parameters will be: perceived exertion using the Modified-Borg Scale, respiratory rate, minute-ventilation, heart rate, peripheral oxygen saturation, and 6-minute walk distance (6MWD). It is expected that the use of PLB will be associated with a decrease of at least one unit on the Modified Borg Scale, which would be clinically significant. Moreover, it is expected that the decrease in dyspnea with PLB will be related to a decrease in respiratory rate minute ventilation during 6MWT. The clinical impact of this study could be significant as therapies allowing the improvement of dyspnea in patients with ILD are scarce.