An article was published in the April edition of the European Journal of Pain discusing a controlled study that looked that the adrenergic responses to exercise in women with fibromyalgia syndrome (Fibro).
The researchers from the Department of Work-related Musculoskeletal Disorders at the National Institute of Occupational Health, Norway said in the article that “altered responses from the hypothalamus-pituitary-adrenal axis, sympathetic nervous system and muscular system have been suggested as being of importance” in the pathogenesis of widespread pain and fibromyalgia syndrome.
The aim of the study was to determine whether the sympathoadrenal response (i.e. involving the sympathetic nervous system and the adrenal glands) to repetitive muscle contractions against resistance (isometric contractions) until exhaustion is altered in patients with FM, and whether sympathoadrenal responses are associated with muscle fatigue and pain during exercise.
For the study, 19 women with FM, and 19 healthy women matched for age, smoking and self-reported physical activity, participated. The maximal voluntary contraction (MVC) in both quadicep muscles of the participants was measured and then repetitive isometric contractions (6s contraction and 4s resting phases) were performed with both quadriceps muscles at 30% of MVC until exhaustion.
Muscle activity was recorded from the quadriceps muscles by surface electromyography (EMG). Plasma adrenalin, noradrenalin and cortisol were measured and perceived exertion and pain reported during exercise.
The study found that attenuated adrenalin responses with normal plasma noradrenalin and cortisol responses were found during exercise in the Fibro group compared with the control group. Significantly higher EMG amplitude during the contraction phases was found in the Fibro than in the control group, i.e. their muscles were working harder. Perceived exertion and pain responses to exercise were higher in the FM group than in the controls, but without their being a relationship to the sympathoadrenal responses.
The researchers concluded that the exercise was perceived as being more painful and strenuous in the Fibro group and that muscle performance was altered with increased muscle activity during the exercise. Women with Fibro also showed an attenuated adrenalin response to repetitive isometric exercise.
