At the time of enrollment, patients will undergo an exercise treadmill test to measure cardiac hemodynamics, including VO2max (measured non-invasively using gas exchange) and maximal heart rate. Average heart rate over 24 hours will also be measured by a 24-hour Holter monitor before and after the exercise program. The maximal exercise testing will be performed on a treadmill using an incremental protocol based on the estimated fitness level established during a warm up.