All patients performed 10 treatment sessions, lasting 60 to 90 minutes, twice a week, in groups of three to four patients. The gold standard was to choose simple and safe exercises in order to encourage the patient to repeat the schedule at home. The exercises proposed in the MIG have been chosen respecting the following principles: slowness, painlessness, promoting attention, easy to imagine. The main purpose of motor imagery-based exercises was to bring the patient back to "feeling and self-perceiving" the execution of the movement. More than the "quantity" of repetition, the "quality" of the movement, free from pain, was important.

The CG received a conventional rehabilitation protocol, based on ten 1-hour sessions, held twice a week (over a 5-week period), previously investigated as efficient in FM by the authors and published. The exercises included low-to-moderate impact aerobic training, walking in a circle, alternating with periods of going up and down the stairs (3 steps for 10 minutes), for a total of 20 consecutive minutes, posture exercises for the back and proprioceptive exercises for the trunk, to improve axial stability. Each exercise was repeated 10 times (3 sets of 10), with a resting period of at least 3 minutes between sets. All sessions ended with stretching and diaphragmatic breathing exercises.

self-administered instrument to assess the current health status of patients with fibromyalgia

comprehensive measure of outcome in patients with a wide variety of chronic diseases

self-administered index that combines fatigue, sleep disturbances and pain in 16 non-articular sites

Instrument to assess unidimensional measure of pain intensity. VAS was presented in a coloured scale with a middle point, graduations and numbers. Under the scale there was a straight horizontal line of fixed length, 100 mm. The ends were defined as the limits of the parameter to be measured (pain in the last 24 hours), orientated from the left (worst, no pain) to the right (best, worst pain to be imagined). The score is determined by measuring the distance (cm) on the 10 cm line between the "no pain" anchor and the patient's mark, providing a range of scores from 0-10.

Instrument to assess anxiety severity. The HAM-A was one of the first rating scales developed to measure the severity of anxiety symptoms. The scale consists of 14 items, each defined by a series of symptoms, and measures both psychic anxiety (mental agitation and psychological distress) and somatic anxiety (physical complaints related to anxiety). Each item is scored on a scale of 0 (not present) to 4 (severe), with a total score range of 0-56, where <17 indicates mild severity, 18-24 mild to moderate severity and 25-30 moderate to severe. It was administered by a clinician experienced in working with psychiatric patients.