Impact of fatigue on postural control in quiet standing in fibromyalgia.

OBJECTIVE: Fibromyalgia fatigue was described as an overwhelming feeling of tiredness that is not relieved by sleep or rest and is often not in proportion to the effort realized. In fibromyalgia syndrome (FMS), the fatigue has an important functional impact, often limiting the activities of daily living, can induce a state of deconditioning, and causing disturbance of locomotion, whose reasons are not fully understood. The aims of this study was to evaluate the postural performance in quite standing of FMS patients, and to compare them to a control group, and to assess the influence on the posture of a fatigue induced by a short walk.

MATERIAL/PATIENTS AND METHODS: Were included: 11 fibromyalgia patients in fibromyalgia groupe (FMG) and 12 healthy subjects appaired in control group (CG). Foot center of pressure (CP) displacements on a task-force platform under two conditions: eyes opened - i.e. vision and eyes closed - i.e. no-vision, before and after a six-minutes walk test (6MWT) were recorded.

RESULTS: The results showed that subjects with fibromyalgia have a surface displacement of center of pressure more important than healthy subjects. Therefore, before 6MWT, in "No-vision" condition, CP displacement was 200.05±145.31mm(2) (m±SD) in CG vs 397.03±242.82mm(2) in FMG (P<0.05). In "Vision" condition CP displacement were respectively 139.08±61.78mm(2) vs 237.70±136.41mm(2) (P=0.06). The deterioration was more significant in FMG after the 6MWT, only in "No-vision" condition (P<0.05).

DISCUSSION-CONCLUSION: FMG had postural impaired performance compared to healthy subjects, especially in the absence of compensation with visual input. This might be explained by sensory changes induced by chronic painful condition affecting muscles. In addition, the disturbance of postural performance is more important after 6MWT (unlike CG), highlighting the state of fragility of subjects and the risk of falls in fatigue condition. We conclude that the compensation by the vision is important. The walk test induced fatigue property and a possible decrease in sensitivity of proprioceptive system. Thus, this study demonstrates lower postural performance in patients with fibromyalgia and a higher sensitivity to fatigue, but other explanatory factors are to be found, such as the influence of pain.