This is a case-controlled observational study not involving an intervention. Participants will complete 2 visits approximately 1 week apart, each conducted at the same time of day. Visit 1 will consiste of screening for iligibility, symptom and activity assessments, pulmonary function tests and an incremental cycle cardiopulmonary exercise test (CPET) for familiarization purposes. Visit 2 will include spirometry followed by an incremental cycle CPET with detailed measures of ventilatory, gas exchange, sensory-perceptual and arterial blood gas responses.