Influence of Preferred versus Prescribed Exercise on Pain in Fibromyalgia

Fibromyalgia (FM) is a common musculoskeletal pain condition associated with chronic widespread pain as well as stiffness, fatigue, mood disturbances, and other disabling symptoms (47). Currently, there is no cure for FM, and treatment usually requires a multidisciplinary perspective using both pharmacological and nonpharmacological approaches (3,30). Exercise is commonly recommended in the management of FM. The American Pain Society (1), for example, encourages individuals with FM to perform aerobic exercise for therapeutic benefits, and research indicates that exercise training has beneficial effects on global well-being, physical capacity, and physical function (6). Adherence rates to exercise programs, however, are generally low in individuals with FM (6,33,38–40,45). Although not systematically studied, individuals with FM are typically deconditioned (9,28), and there are reports that women with FM experience increased symptoms such as pain and fatigue when they attempt to engage in an exercise session (27,38). Furthermore, pain has been shown to be predictive of poor activity tolerance in FM patients (12) and higher pain self-efficacy has been shown to be a significant discriminator for physical activity participation (11). One study in patients with chronic fatigue syndrome and FM demonstrated that physical activity levels were contingent on current pain and fatigue symptoms but that current activity levels were not predictive of subsequent physical symptoms (23). Thus, there is limited research examining changes in pain after an immediate bout of exercise in women with FM. Normally, in healthy individuals changes in pain sensitivity occur after exercise indicative of an analgesic response (e.g., increases in pain thresholds and tolerances and lower pain ratings). This phenomenon has been termed exercise-induced analgesia (EIA) and has been demonstrated after exercise for several different experimental pain stimuli (for reviews, see Cook and Koltyn (8) and Koltyn (21)). In contrast, there are reports in the literature that FM patients do not experience EIA. Several investigators have reported an increase in pain as a result of exercise (25,32,41,46), whereas other investigators have reported decreases in pain after exercise (17,20,42). Currently, the optimal mode, duration, frequency, and intensity of exercise appropriate for individuals with FM to manage their symptoms are unknown. Also, it is unclear what intensity of exercise is preferred by women with FM to manage pain. Most exercise programs use a prescribed exercise protocol such as the one by the American Pain Society, which recommends exercising at a moderate intensity defined as between 60% and 75% of age-adjusted maximal HR two to three times per week. An alternate approach, however, would be the use of a preferred exertion model in which participants self-select their preferred intensity of exercise (36). It has been suggested that adherence to exercise programs may be increased if exercise prescriptions are based on preferred intensity of exercise because of the inverse association between exercise intensity and adherence rates (14). Furthermore, the incorporation of preferred intensity may also affect pain because self-selection of exercise intensity will allow individuals to change the intensity of exercise as necessary to remain comfortable and to minimize possible exacerbations in pain during the exercise bout. Therefore, the primary purpose of this study was to examine the influence of a preferred- versus a prescribed-intensity exercise session on pain in women with FM.