The term "Overlap Syndrome" (OS) is used to describe the presence of both chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) in a single patient. Due to premature aging, patients with OS are prone to developing functional decline up to 20 years earlier than the general population. The International Classification of Functioning, Disability and Health (ICF) evaluates functional status in chronic pulmonary disease globally in 5 domains. The investigators propose to study validated outcomes in 3 of these domains: 1) participation in life situations; 2) physical activity; and 3) cardiovascular health. The investigators long-term goal is to develop an exercise strategy tailored to Veterans with OS which will reduce the risk of functional decline through increased PA.

The term "Overlap Syndrome" (OS) is used to describe the presence of both chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA) in a single patient. Veterans with OS who also have excessive daytime sleepiness (EDS-OS) are at highest risk for functional decline yet have the greatest barriers to exercise training. Thus, there is a critical need to identify novel exercise strategies that meet the individual needs and capacities of Veterans with EDS-OS. The investigators propose to test moderate intensity interval training (MIIT), a novel exercise intervention whose translation into durable lifestyle change may be facilitated by the feasibility of short bouts of increased PA. The investigators proposal addresses key knowledge gaps in rehabilitation research by investigating the clinical phenotype of EDS-OS to determine the association with functional outcomes and response to a novel exercise intervention with the goal to reduce functional decline.

Inclusion Criteria:

• Diagnosis of COPD and OSA, i.e., Overlap Syndrome Diagnosis of Overlap Syndrome (both COPD and OSA), confirmed in CPRS from spirometry or pulmonary function test of FEV1/FVC <70 for COPD and a polysomnogram or home-based study for OSA.
• Montreal Cognitive Assessment (MoCA) >20

Exclusion Criteria:

• CAD, as defined by anyone of the following: history of CABG, prior positive stress test for ischemia, infarction or angina or medical problem
• Orthopedic problems as defined by joint pain limiting ambulation
• Fall risk, defined as more than 2 falls in the prior month
• Hospitalization in prior month
• Daytime home oxygen 6. Participation in structured exercise, defined by the Physical Activity Scale for the Elderly (PASE) as more than 1 hour of activity spent in moderate activity and any strenuous activity performed over prior 7 days.