Obstructive sleep apnea (OSA) is a multi-factorial sleep disorder. Complete collapse or partial collapse in the airway increases the risk of developing cardiovascular and kidney-related disease in OSA patients. Resulting in an increase in medical expenses and workload for the healthcare worker. Multilevel of upper airway muscles especially the genioglossus muscle showed to contribute to airway obstruction as it fatigues easily. The endurance level of OSA patients was shown to be significantly lower. Therefore, the goal of this experimental study is to assess the feasibility and effectiveness of a comprehensive respiratory training exercise program on cardiorespiratory endurance, airway muscle function, and sleep parameters in patients with obstructive sleep apnea (OSA). Aside from exploring the therapeutic effect, the results of the study will be used to explore the mechanism of the treatment in relation to the changes in the OSA severity.