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The results of VHR indices during the supine position and the DBT women with FMS suggest impairment of neurocardiac integrity associated with pain and the impact of FMS on the quality of life.

-The cardiovascular autonomic control and the baroreflex sensitivity (BRS) have been widely studied in fibromyalgia syndrome (FMS) patients through the computation of linear indices of spontaneous heart period (HP) and systolic arterial pressure (SAP) variabilities. However, there are many methodological difficulties regarding the quantification of BRS by the traditional indices especially in relation to the issue of causality. This difficulty has been directly tackled via a model-based approach describing the closed-loop HP-SAP interactions and the exogenous influences of respiration. Therefore, we aimed to assess whether the BRS assessed by the model-based causal closed-loop approach during supine and active standing in patients with FMS could provide complementary information to those obtained by traditional indices based on time and frequency domains. The findings of this study revealed that, at difference with the traditional methods to quantify BRS, the causality analysis applied to the HP, SAP, and respiratory series, through the model-based closed-loop approach, detected lower BRS in supine position, as well as a blunted response to the orthostatic stimulus in patients with FMS compared with healthy control subjects. Also, the strength of the causal relation from SAP to HP (i.e., along the cardiac baroreflex) increased during the active standing only in the control subjects. The model-based closed-loop approach proved to provide important complementary information about the cardiovascular autonomic control in patients with FMS. fibromyalgia; baroreflex; autonomic nervous system; modeling; causality FIBROMYALGIA SYNDROME (FMS) is a noninflammatory syndrome characterized by chronic diffuse musculoskeletal pain, stiffness, and pain hypersensitivity in 18 specific points located in muscles or tendon muscle insertion called tender points (27). Although the painful condition is the main characteristic of this syndrome, advancements regarding the etiology and pathophysiology of FMS have attributed an important role to dysautonomia (i.e., the autonomic nervous system dysfunction) (4,7,11,12,24,25).The dysautonomia has been widely demonstrated in patients with FMS. Thus, it is known that FMS patients present an alteration of the cardiac autonomic modulation characterized by a high cardiac sympathetic modulation and low cardiac parasympathetic modulation even at rest (4,7,11,12,24,25). In addition, despite a normal baroreflex function, a lack of increased sympathetic discharge to vessels and decreased cardiac vagal activity has been reported during the orthostatic stimulus, which may account for the reduced orthostatic tolerance, commonly observed in these patients (7).Traditionally, the baroreflex sensitivity (BRS) in FMS patients has been studied through the computation of indices derived from spontaneous heart period (HP) and systolic arterial pressure (SAP) variabilities (4,7,11,12,24,25). However, these approaches to the quantification of BRS have many methodological drawbacks. The most relevant one is the in...

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Subjects with FMS had lower respiratory muscle endurance, inspiratory muscle strength, and thoracic mobility than healthy subjects. In addition, inspiratory muscle strength was associated with the number of active tender points, fatigue, and axillary mobility.