Fibromyalgia is a common chronic pain condition that exerts a considerable impact on patients' daily activities and quality of life.Objectives: The main objective of the present study was to evaluate kinematic parameters of gait, functional performance, and balance in women with fibromyalgia syndrome.Methods: The study included 26 female patients with fibromyalgia (49.2 ± 8.0 years) according to the criteria of the American College of Rheumatology, as well as 16 pain-free women (43.5 ± 8.5 years). Gait and balance parameters were extracted from video recordings of participants performing several motor tasks. Non-linear dynamic of body sway time series was also analyzed by computing the Hurst exponent. In addition, functional performance and clinical pain were obtained by using standardized motor tests (Berg's balance scale, 6-min walking test, timed up and go task, Romberg's balance test) and self-report questionnaires (Fibromyalgia Impact Questionnaire).Results: Walking speed was significantly diminished (p < 0.001) in FM patients as compared to pain-free controls, probably due to significant reductions in stride length (p < 0.001) and cycle frequency (p < 0.001). Analyses of balance also revealed significant differences between fibromyalgia and pain-free controls on body sway in the medial-lateral and anterior-posterior axes (all ps < 0.01). Several parameters of gait and balance were significantly associated with high levels of pain, depression, stiffness, anxiety, and fatigue in fibromyalgia.Conclusion: Our data revealed that both gait and balance were severely impaired in FM, and that subjective complaints associated with FM could contribute to functional disability in these patients. These findings suggest that optimal rehabilitation and fall prevention in fibromyalgia require a comprehensive assessment of both psychological responses to pain and physical impairments during postural control and gait.

Affective facial expressions are potent social cues that can induce relevant physiological changes, as well as behavioral dispositions in the observer. Previous studies have revealed that angry faces induced significant reductions in body sway as compared with neutral and happy faces, reflecting an avoidance behavioral tendency as freezing. The expression of pain is usually considered an unpleasant stimulus, but also a relevant cue for delivering effective care and social support. Nevertheless, there are few data about behavioral dispositions elicited by the observation of pain expressions in others. The aim of the present research was to evaluate approach–avoidance tendencies by using video recordings of postural body sway when participants were standing and observing facial expressions of pain, happy and neutral. We hypothesized that although pain faces would be rated as more unpleasant than the other faces, they would provoke significant changes in postural body sway as compared to neutral facial expressions. Forty healthy female volunteers (mean age 25) participated in the study. Amplitude of forward movements and backward movements in the anterior-posterior and medial-lateral axes were obtained. Statistical analyses revealed that pain faces were the most unpleasant stimuli, and that both happy and pain faces were more arousing than neutral ones. Happy and pain faces also elicited greater amplitude of body sway in the anterior-posterior axes as compared with neutral faces. In addition, significant positive correlations were found between body sway elicited by pain faces and pleasantness and empathic ratings, suggesting that changes in postural body sway elicited by pain faces might be associated with approach and cooperative behavioral responses.

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