Responsiveness of the 4 Metre Gait Speed in Patients With Idiopathic Pulmonary Fibrosis and Determination of the Minimum Important Difference

This observational study is investigating a simple test of usual walking speed, measured using the 4 metre gait speed (4MGS) test in patients with a lung disease called Idiopathic Pulmonary Fibrosis (IPF). Drug development for this disease is slow in part because there is a lack of reliable measurements that can assess effectiveness of treatment. Slow walking speed has been shown to relate to poor outcomes in older adults and people with another lung disease called Chronic Obstructive Pulmonary Disease (COPD). The investigators are interested to see whether usual walking speed in IPF patients changes following a treatment called pulmonary rehabilitation (an exercise and education programme for patients with lung disease) and if it changes, what is the smallest change that is meaningful to patients (the minimum important difference - MID). The investigators are also investigating whether the change in walking speed can predict survival, number of hospital admissions and lung disease progression. This will help inform us of the potential use of 4MGS as an outcome measure. To do this, participants who consent to taking part in the study will be timed walking at their usual walking speed over a distance of 4 metres (13.12 feet) before and after a course of pulmonary rehabilitation and follow-up 1 year after completing pulmonary rehabilitation.