A few, small studies have shown that regular exercise can reduce the severity of obstructive sleep apnea (OSA) as determined by the number of times the upper airway collapses per hour of sleep (AHI). There is an article in the Journal Sleep where researchers studied the effect of a 12 week moderate-intensity exercise program on the AHI in patients with OSA.
There were 43 study participants, ages 18-55 years old with at least moderate severity OSA and who were overweight with a body mass index of >25. The participants also were sedentary, on stable medication dosages, and not being treated for OSA. At baseline, participants had an overnight sleep study, evaluation of body fat composition, pulmonary function tests, and respiratory muscle strength testing. They also wore a home sleep study wrist watch, called an actigraph, for about a week. The participants were then randomized to 12 weeks of exercise training including resistance and aerobic components, or to a stretching only control group. The baseline measurements were than repeated after completion of the 12 weeks.
Results showed that when compared to the stretching only control group, exercise training did moderately improve the AHI. More specifically, 25% were considered a treatment success (based on AHI reduction of at least 50%) and 63% reduced their AHI by at least 20%. And these reductions in OSA severity occurred despite no change in body weight. However, the exercisers did reduce their fat composition by over 1%. Since overweight individuals with OSA can have extra fat in their neck that contributes to upper airway collapse, a reduction in neck fat could explain how the exercisers reduced their OSA severity despite not losing any weight.