Obstructive sleep apnea (OSA) has numerous adverse cardiovascular effects.1 Increased systemic hypertension, nocturnal arrhythmia, and both nonfatal and fatal cardiovascular events have been associated with OSA.2–4 Because cardiopulmonary exercise testing (CPET) aids in prognostic assessment of patients with heart disease,5–7 there is rising interest in the potential utility of CPET for cardiovascular risk stratification in The impact of OSA on exercise capacity remains unclear. Prior studies examining exercise capacity in OSA patients have yielded conflicting results, with some demonstrating reduced exercise capacity11–16 and others suggesting exercise capacity is not impaired.