The intervention will consist of performing postural exercises in prone, supine, sitting and standing position, as well as in quadrupedia. Each session will consist of 60 minutes and will be divided into three parts: warm up (15 minutes); postural exercises (30 minutes); and cool down with stretching for 15 minutes.

Grip strength will be measured by a Jamar Analogue Hand Dynamometer with participants seated, their elbow by their side and flexed to right angles, and a neutral wrist position. Subjects were verbally encouraged to produce their maximal grip strength (MGS). Three trials were recorded, consisting of a 3-second maximal contraction, with a 30-second rest period between each trial. The maximal value of the three reproducible trials for each hand was retained for analyses.

Ranges of movement of different joints were evaluated by a goniometer and an inclinometer: Shoulder (flexion, extension, abduction, adduction, internal and external rotation), hip (flexion, extension, abduction, adduction, internal and external rotation), knee (flexion and extension), ankle (flexion, extension, abduction, adduction, internal rotation and external rotation), cervical spine (flexion, extension, rotations and inclinations). For the measurements, subjects were in underwear or wore comfortable clothes.

Evaluated by the McGill Pain Questionnaire (MPQ). The MPQ includes 4 main measures:

1. Pain location. On a drawing of the human body with both anterior and posterior sides, participants indicate the areas of their bodies that have pain. The number of pain sites is summed as in indicator of the sensory pain dimension.
2. Pain intensity. From a list of 6 words, the patient selects the one best word describing the intensity of pain: 0 = none, 1= mild, 2 = discomforting, 3 = distressing, 4 = horrible and 5 = excruciating.
3. Pain quality. Participants respond to the question, "What does your pain feel like?" by selecting from 78 descriptors in 20 subclasses. The quantitative data is summed to form the Pain Rating Index (PRI) (score 0 no pain- 78 worst possible pain).
4. Pain pattern. Participants respond to the question, "How does your pain change with time?" by selecting from 9 words.

Evaluated by the Leisure Time Physical Activity Instrument (LTPAI). It is an instrument assessing the amount of physical activity performed during a typical week. The physical activities are divided into three categories: light, moderate, and heavy activities. The LTPAI total score is the sum of hours in all three categories.

Evaluated by the Fibromyalgia Impact Questionnaire (FIQ). This is a multidimensional self-administered questionnaire with 10 items that evaluates the status of the patient the week before the test is completed, and it assesses the aspects that tend to be more affected in people with FMS. The first item contains 10 sub-items, ranging from four points (from 0= always to 3 = never) and assesses the patient's functional capacity in activities of daily living. The second and third items refer to days of the week and the rest are visual analog scales from 0 to 10. The score ranges from 0 to 100, where 0 represents the maximal functional capacity quality of life and 100 the minimum. This scale was validated in its Spanish version by Salgueiro and García-Leiva in 2013, and it showed an excellent internal consistency (Cronbach's alpha = 0.95).

Assessed by the Hospital Anxiety and Depression Scale (HADS). This is a valid and reliable self-rating scale with 14 items that measures anxiety and depression (7 of the items relate to anxiety and 7 relate to depression). Each item is answered by the patient on a four point (0-3) response category so the possible scores range from 0 to 21 for anxiety and 0 to 21 for depression, with scores categorized as follows: normal 0-7, mild 8-10, moderate 11-14, and severe 15-21. Scores for the entire scale (emotional distress) range from 0 to 42, with higher scores indicating more distress.

Fatigue Severity Scale (FSS). The FSS is a self-administered questionnaire with 9 items (questions) investigating the severity of fatigue in different situations during the past week. Grading of each item ranges from 1 to 7, where 1 indicates strong disagreement and 7 strong agreement, and the final score represents the mean value of the 9 items.

Evaluated by the Pittsburgh Sleep Quality Index (PSQI). It is a self-report questionnaire that assesses sleep quality over a 1-month time interval. The measure consists of 19 individual items, creating 7 components that produce one global score. Each item is weighted on a 0-3 interval scale. The global PSQI score is then calculated by totaling the seven component scores, providing an overall score ranging from 0 to 21, where lower scores denote a healthier sleep quality.