Exercise Protocol: All exercise testing will occur in the Cardiopulmonary Exercise Physiology Laboratory (CPEP lab). The CPEP lab is located on the 4th floor of the Burrard Building at St. Paul's Hospital (Vancouver, BC). A symptom-limited incremental exercise test will be performed on visit 1 using an electronically braked cycle ergometer (Ergoslect 200P; Ergoline GmbH, Bitz, Germany) according to recommended guidelines. The test will consist of steady-state rest for 6 minutes, a 1 minute warm-up of unloaded pedaling, and 15 watt stepwise increases in work rate every 2 minutes until symptom-limitation. Constant-load exercise tests on visits 2, 3, and 4 will include rest and warm-up periods followed by an immediate increase in work rate to 80% of maximal work (determined on visit 1) until symptom limitation.