Fibromyalgia (FM) is a syndrome characterised by chronic diffuse primary pain associated with fatigue, sleep disturbance, cognitive and somatic complaints. Its presence has a significant impact on activities of daily living, affecting the functionality, emotional well-being and quality of life of this population. The wide variety of symptoms reflects dysfunction in multiple body systems, with central nervous system involvement being a central factor. Central sensitisation of pain is considered the most relevant pathophysiological hypothesis in literature, reinforcing the importance of rehabilitation strategies aimed at its modulation. In addition, FM also impairs motor control and the study of muscular activation patterns and the effect of rehabilitation strategies in muscular activation can also contribute to FM management. Movement representation strategies are interventions that neurophysiologically evoke the perceptual and cognitive representation of movement through observation combined, or not, with the actual execution of the movement, which can cause an increase in cortical excitability. Therefore, they have the potential to reverse the inhibition produced by physiological processes associated with chronic pain, such as those presented by patients with FM.

Development of a treatment protocol based on action observation, a movement representation strategy, to evaluate its effectiveness in reducing pain and the impact of fibromyalgia through tools that can measure whether there are changes in cortical excitability and muscle recruitment patterns.

This two-arm parallel randomized controlled clinical trial with a blinded evaluator will include eighty-two patients aged between 20 and 75 years who meet the ACR2016 classification criteria for FM. The subjects will be randomized into two groups: an intervention group (IG-I), that will receive a rehabilitation protocol based on exercises associated with action observation technique, and a control group (CG-I) that will receive a booklet with general guidelines on FM. The primary outcome will be pain intensity, and the secondary variables will be the impact of fibromyalgia, pain sensitivity, fatigue level, level of functionality, level of disability, sleep disturbances, and the patient's global perception of change, kinesiophobia, health-related quality of life, encephalographic (EEG) activity and electromyographic (EMG) activity of the trapezius, vastus lateralis and tibialis anterior muscles. A mediation analysis will also be performed to investigate if increased cortical excitability mediates improvement in pain.

The results of this study will provide important information on the effects of movement representation strategies on cortical activation, motor recruitment, intensity and pain perception in FM patients.

It is expected that this study will contribute to the development of more effective therapeutic approaches for the management of fibromyalgia, improving the quality of life of this population.

This study may clarify whether movement representation techniques can be incorporated into the clinical practice of physical therapists treating patients with fibromyalgia.