Perceived exertion, physical fitness, depression and disease severity in women with fibromyalgia

Resumen

ABSTRACT Fibromyalgia is a chronic debilitating disease which represents a heavy burden for the health care system. Identifying factors associated with better symptomatology and lower disease severity is of clinical and public health interest. The major aim of the present International Doctoral Thesis was to provide a comprehensive examination of the association of physical fitness and depression with core fibromyalgia symptoms and disease severity in women with fibromyalgia. In addition, the utility of rating perceived exertion as a tool for monitoring exercise intensity was also studied. To address these aims, seven studies were conducted in the context of two projects. Project I (Studies I and II). During an incremental treadmill test, thirty-three women with fibromyalgia were recorded physiological (oxygen uptake [VO2] and heart rate, among other) and perceptual (rating of perceived exertion [RPE; Borg CR-10 scale] and exercise-induced pain) responses at each workload. Cardiorespiratory fitness [peak VO2], as well pressure pain sensitivity (algometry) and clinical pain intensity (visual analogue scale; VAS) were measured. Project II (Studies III to VII). Physical fitness was assessed with the Senior Fitness Test battery and handgrip dynamometry. Pain was assessed with different tools (including algometry, VAS, and subscales from the revised fibromyalgia impact questionnaire [that assessed fibromyalgia severity] and the SF-36 [that assessed health related quality of life; HRQoL]). Cognitive function was assessed using the Paced Auditory Serial Addition Task and the Rey Auditory Verbal Learning Test, and depression with the Beck Depression Inventory (BDI-II). The main findings of this Doctoral Thesis were: I) The Borg CR-10 scale is a moderately valid and reliable tool for monitoring exercise intensity in women with fibromyalgia. In addition, women with fibromyalgia are able to discriminate between exertion and exercise-induced pain while exercising, especially as exercise intensity increases; II) Higher VO2 peak is associated with lower pressure pain sensitivity but not with clinical pain; III) Higher physical fitness is consistently associated with lower levels of pain (measured with different indicators), lower pain-related catastrophizing and higher chronic pain self-efficacy in women with fibromyalgia. Muscle strength and flexibility are independently associated with pain, while aerobic fitness and flexibility are independently associated with pain-related catastrophizing and chronic pain self-efficacy. There was a combined effect of different fitness components on pain, catastrophizing and self-efficacy; IV) Higher physical fitness is consistently associated with lower fibromyalgia severity in women. The difference in fibromyalgia severity between patients with the lowest and the highest fitness levels surpasses the minimal clinically meaningful difference. The 6-minute walk (aerobic fitness) and back scratch (upper body flexibility) tests are independently associated with fibromyalgia severity, although the variability explained by these fitness tests was rather low (<10%); V) Higher physical fitness is positively and consistently associated with information processing, working memory, delayed recall, verbal learning and delayed recognition in women with fibromyalgia. By contrast, body fatness does not seem to be associated with the studied cognitive tasks. Aerobic fitness seems to be the most important fitness indicator of the cognitive processes evaluated, yet motor agility could also play a relevant role; VI) Higher physical fitness is generally associated with lower symptoms of depression in women with fibromyalgia. However, the observed associations were weak and inconsistent, differing from those previously observed in healthy adults; VII) Higher severity of depressive symptoms is associated with poorer self-reported symptomatology and mental HRQoL, but not with pain sensitivity or physical function in women with fibromyalgia. The results of this Doctoral Thesis enhance our understanding about physical fitness and depression in relation to core fibromyalgia symptomatology and disease severity in women, as well as about the utility of perceived exertion in women with fibromyalgia. These results will lead to future prospective research to understand the predictive value of fitness in this population.