Validating a New Machine-Learned Accelerometer Algorithm Using Doubly Labeled Water

Inclusion Criteria: * must be 18+ years of age * be able to ambulate on own, unassisted, on a regular basis * speak and read English * must have access to a working smart phone and a computer with internet access Exclusion Criteria: * wheelchair reliant * assistive walking device reliant (cannot walk for at least 50 feet without an assistive device) * diagnosed uncontrolled hypertension (above 160/100 mgHg) * diagnosed cognitive impairment or inability to follow study procedures such as Alzheimer's disease or dementia * cannot take metabolic altering medications * cannot be pregnant * cannot be breastfeeding * cannot use supplemental oxygen * cannot completed required study activities for any reason * cannot have a resting heart rate \> 100 bpm or a resting blood pressure \> 160 mgHg during Visit 1 * cannot weigh more than 450 lbs