Obstructive sleep apnea and central sleep apnea are burgeoning sleep-related breathing disorders within the general population. Most of the associated comorbidities and causes of these sleep disorders are known to negatively impact cardiorespiratory fitness; however, little is known about the direct relationships between cardiorespiratory fitness, obstructive sleep apnea and central sleep apnea. This article provides a systematic analysis of existing peerreviewed, published clinical studies pertaining to the relationship between cardiorespiratory fitness and sleep-related breathing disorders in adults. A brief description of each sleep disorder, the pathophysiology, its epidemiology and its implications for cardiorespiratory fitness will be discussed. Conceptual consequences on cardiorespiratory fitness are provided. Finally, we discuss therapy for each disorder and its effect on the cardiovascular system.