Fibromyalgia, a condition that affects 11 million to 15 million Americans -- predominantly women -- is characterized by chronic pain and fatigue. Common symptoms include muscle stiffness, sleep disturbances, gastrointestinal discomfort, anxiety and depression.
Previous research has found women with fibromyalgia have lower-than-average cortisol levels, which contributes to pain, fatigue and stress sensitivity.
Lead author Kathryn Curtis, a doctoral student at York University, Professor Joel Katz and colleagues found the study participants' saliva revealed elevated levels of total cortisol following a program of 75 minutes of hatha yoga twice weekly over the course of eight weeks.
"Ideally, our cortisol levels peak about 30-40 minutes after we get up in the morning and decline throughout the day until we're ready to go to sleep," Curtis says in a statement. "The secretion of the hormone cortisol is dysregulated in women with fibromyalgia."
Cortisol is a steroid hormone that is produced and released by the adrenal gland and functions as a component of the hypothalamic-pituitary-adrenal axis in response to stress.
"Hatha yoga promotes physical relaxation by decreasing activity of the sympathetic nervous system, which lowers heart rate and increases breath volume," Curtis says in a statement. "We believe this in turn has a positive effect on the hypothalamic-pituitary-adrenal axis."
The study's results, published in the Journal of Pain Research, mirrored the findings of researchers at Oregon Health & Science University, who reported last November that women who took part in a yoga regimen noticed improvements in both physical and psychological aspects of fibromyalgia, including decreased pain, fatigue, tenderness, anxiety, and better sleep and mood.