Functioning Disturbance in Chronic Back Pain: Altered Muscle Metabolism

The NSCBP group: * At least 6 patients will be included in this study. * All patients referred to Vestfold Hospital Trust, Kysthospitalet, diagnosed with chronic NSCBP \>3 months duration will be invited to participate in the study. The invitation will be in a written form. Exclusion Criteria: * anamnesis of medical or drug abuse, * surgery on the musculoskeletal system of the trunk, * known congenital malformation of the spine or scoliosis, * body mass index \> 27 kg/m2, * systemic-neurological-degenerative disease, * history of stroke, * psychiatric disorder, * pregnancy and abnormal blood pressure. The subjects will be asked not to use any medications except for paracetamol preparations one week before examination and instructed not to perform any back-straining exercise for 48 h prior to the study, except for ordinary daily working and/or leisure activities.