Obstructive sleep apnea syndrome (OSAS) is characterized by repetitive obstruction and collapse of the upper airway resulting in successive episodes of cessation of or decreased respiratory airflow, causing oxygen desaturation, awakening, loud snoring and daytime sleepiness in patients. Sleep apnea is frequently associated with co-morbidity such as obesity, diabetes, hypertension, the metabolic syndrome and cardiovascular disease. Lack of exercise is associated with OSAS severity, independent of body mass. Participation and motivation to exercise is low in OSAS patients, with less that one third of the patients reporting regular exercise routines. We aim to investigate if aerobic interval training improves OSAS in obese subjects.