We propose to develop a simple, non-invasive treatment for obstructive sleep apnea (OSA) that uses head and neck exercises to increase oral, pharyngeal, and cervical muscle strength. OSA is a disorder of repeated upper airway obstruction during sleep that is associated with substantial cardiovascular morbidity and mortality, endocrine disturbances, daytime somnolence, decreased quality of life, and motor vehicle crashes. As current therapies have substantial limitations and are not acceptable to many patients, there is an enormous unmet need for effective, well-tolerated, safe, and non-invasive OSA treatments. Oral, pharyngeal, and cervical muscles dilate the upper airway and maintain airway patency during wakefulness; sleep is associated with a decrease in neural input to muscles, leading to a decrease in muscle forces opening the airway. Increasing the strength of these muscles can increase upper airway dilator muscle force from the same neural input. Head and neck exercises for OSA treatment have received attention over the past decade, with multiple placebo-controlled, randomized studies showing improvement but incomplete resolution of OSA. Previous approaches have important limitations. Our strategy is a simplified, effective, safe, and non-invasive head and neck exercise program delivered with the aid of a smartphone app user interface to provide instruction and feedback for proper exercise performance with the aid of simple devices. SleepFlex™ will increase strength of key muscles to increase dilator muscle force during sleep. Our program includes head and neck exercises selected to increase strength of the muscles of the tongue, soft palate, lateral pharyngeal walls, and neck. This Phase I SBIR proposal includes program development and performing a pilot safety and feasibility study. Aim 1: Develop smartphone app user interface. The user interface will be a smartphone app (iOS and Android) that incorporates instructional videos as well as other visual and written information on proper performance of the exercises. The user interface will also include session reminders and tracking of adherence and user feedback. Aim 2: Finalize design and manufacture exercise devices. The exercises will each require a device that enables proper performance with appropriate levels of resistance. Aim 3: Perform pilot safety and feasibility study. We will enroll 10 study participants with previously-diagnosed mild to moderate obstructive sleep apnea who have been unable to tolerate positive airway pressure therapy. All study participants will undergo treatment for 8 weeks with the SleepFlex™ program. Adverse events (pain, dysphagia), usability, and program acceptance and adherence will be measured.