Effectiveness of the Pilates method performed in the equipament or in the mat

INTERVENTION: Both groups will receive a protocol that consists of a specific training of the individual Pilates method exercises. The Mat Pilates group will receive a specific protocol, using a swiss ball, magic circle and elastic bands, while the Equipment Group will work with equipments ‐ Reformer, Step Chair, Ladder Barrel and Cadillac. Each session will last for one hour, twice a week for six weeks. E02.779.483 CONDITION: Low back pain ; M54.5 M00‐M99 PRIMARY OUTCOME: Disability measured by the Roland Morris Disability Questionnaire Pain intensity measured by the Numerical Pain Rating Scale SECONDARY OUTCOME: Function measured by the Patient‐Specific Functional Scale. Global perceived effect measured by the Global Perceived Effect Scale. Kinesiophobia measured by the Tampa Scale of Kinesiophobia. INCLUSION CRITERIA: Patients with low back pain longer than three months, of both gender and aged between 18 and 60 years.