Functional Incremental Stepping in Place Test (F-IST) Validation

The purpose of this multi-site prospective study is to assess validity of a new step test called Functional-Incremental Stepping-in-place- Test (F-IST) compared to gold-standard cardiopulmonary exercise testing (CPET) and to physical function and health perception, respectively. The investigators will also assess test-retest reliability of the F-IST. The investigators hypothesize that the F-IST will have high validity and test-retest reliability to be used in field testing environments such as the ICU.

Inclusion Criteria: -Currently able to walk with or without a walking aid, such as a cane or walker or rollator Exclusion Criteria: Pregnancy specifically related to cardiopulmonary testing * A recent significant change in resting ECG * Unstable angina * Uncontrolled cardiac dysrhythmias causing symptoms or hemodynamic compromise * Symptomatic severe aortic stenosis * Uncontrolled symptomatic heart failure * Acute pulmonary embolus or pulmonary infarction * Acute myocarditis or pericarditis * Suspected or known dissecting aneurysm * Acute systemic infection accompanied by fever, body aches, or swollen lymph glands * Left Main Coronary Stenosis * Moderate stenotic valvular heart disease * Electrolyte abnormalities * Severe arterial hypertension (\>200 systolic, \>110 diastolic) at rest * Tachydysrhythmia or bradydysrhythmia * Hypertrophic cardiomyopathy and other forms of outflow tract obstruction * Neuromuscular, musculoskeletal, or rheumatic disorders that are exacerbated by exercise * High degree AV block * Ventricular aneurysm * Uncontrolled metabolic disease (diabetes, thyrotoxicosis, or myxedema) * Chronic infectious disease (hepatitis, AIDS, mono) * Mental or physical impairment leading to inability to exercise adequately