Skeletal Muscle Function in Interstitial Lung Disease

Inclusion Criteria for ILD Patients: * Age 40-80 years (inclusive) * A multidisciplinary diagnosis of idiopathic pulmonary fibrosis (IPF), idiopathic fibrotic nonspecific interstitial pneumonia (NSIP), chronic hypersensitivity pneumonitis (HP), or unclassifiable ILD with a differential diagnosis that consists of the above diagnoses * Fibrosis on high resolution computed tomography (HRCT): honeycombing, reticulation, or traction bronchiectasis * Appropriate candidate for pulmonary rehabilitation * 6 minute walk distance 50m or more * Oxygen saturation ≥ 92% by pulse oximetry at rest while breathing room air * Clinically stable for the preceding 6 weeks * Can fluently read and write in English Inclusion Criteria for Healthy Controls: * Age 40-80 (inclusive) * Normal pulmonary function (80-120% predicted) * No lung or cardiovascular disease * Can fluently read and write in English Exclusion Criteria for the ILD patients: * Contraindication to exercise testing (e.g. significant cardiovascular, musculoskeletal, neurological disease) * Other significant extra-pulmonary disease that, based on clinical assessment, could impair exercise capacity and/or oxygenation * Forced vital capacity (FVC) less than 50% or Diffusion capacity for carbon monoxide (DLCO) less than 25% * Concurrent or recent participation (less than 6 months) in a pulmonary rehabilitation program * Use of prednisone greater than 10 mg/day for more than 2 weeks within 3 months of the first study visit * Significant emphysema (less than 10% volume on HRCT or FEV1/FVC less than 0.70) Exclusion Criteria for Healthy Controls: * Currently smoking or previously smoked more than 10 pack-years * Any medical conditions that prevents them for exercising safely * Cardiac pacemaker or any metal or electronic inside the body