TRI Scientists prove better sleeping through exercise

While a person is sitting during the day, fluid accumulates in their legs. This happens because of gravity and because the musculovenous pump in the calves that returns fluid to the rest of the body is not active.

Consequently, when a person lies down at night, gravity redistributes this fluid toward the neck and chest. This fluid shift contributes to two forms of sleep apnea during which breathing repeatedly stops and starts:

  • obstructive sleep apnea (OSA) in which the fluid accumulates in the neck and increases pressure around the throat, reducing its size and increasing its collapsibility;
  • and central sleep apnea (CSA) in which  fluid accumulates in the lungs provoking instability of breathing.
Both forms are associated with increased mortality in people with coronary artery disease or heart failure.

Exercise training has already been shown to reduce the severity of OSA and CSA, yet how this happens is not understood. A recent study led by Toronto Rehab chair holder, Dr. T. Douglas Bradley, sheds light on this phenomenon by studying how it affects fluid retention in the legs.

Dr. Bradley’s team examined the effects of a four week period of exercise training in coronary artery disease patients with OSA or CSA. The team found that the severity of sleep apnea was significantly decreased in patients who underwent exercise training compared to those who did not. This improvement was associated with reduced fluid accumulation in the legs during the daytime, less fluid shift out of the legs overnight and less accumulation of fluid around their neck than those who did not undergo exercise training.

“These findings suggest that reducing fluid shift overnight from the legs to the neck and lungs can reduce the severity of OSA and CSA, even without improving physical fitness or weight loss,” says Dr. Bradley. “Whether the reduction is related solely to fluid shift or to more chronic exercise training requires more study.”

Dr. Bradly is a Senior Scientist at Toronto Rehab and holds the Clifford Nordal Chair in Sleep Apnea and Rehabilitation Research – helping expand and accelerate specialized research, teaching and clinical work to improve diagnosis and develop new treatments surrounding this complex disorder.

Toronto Rehab is the number one rehabilitation research centre in the world and truly Where Incredible Happens. To ensure that the best proven rehabilitation research and technology are available to our patients and the community now and in the future, Toronto Rehab has launched a historic $100-million fundraising campaign. Learn more

Related story: Spotlight on Toronto Rehab at UHN AGM