1. Contraindication or unable to perform CPET or 6MWT (amputated or paralyzed limb(s), severe lower extremity arthritis, preexisting cardiopulmonary condition precluding exercise including unstable angina or myocardial infarction in last 6 weeks, uncontrolled hypertension, serious cardiac dysrhythmia on resting EKG [severe bradycardia or tachycardia, sick sinus syndrome or multifocal premature ventricular contractions] and syncope)