Functioning disturbance in chronic back pain: Altered muscle activation pattern, muscle metabolism and pain-cognitions.

There is evidence that individuals with chronic non-specific back pain (CNSBP) show altered muscle activation patterns. It is unknown why these alterations in activation pattern occur, which consequences this may have for muscle metabolism and how they ar e linked to pain experience and development of CNSBP. The main objective of this study is to investigate the presence of deviating muscle activation patterns, -metabolism and their interrelationship in CNSBP compared to normals. In this project the foll owing hypotheses will be studied: 1. Muscle activation patterns and metabolism in CNSBP patients differ from asymptomatic controls. 2. Alterations in muscle activation are associated with altered muscle metabolism in CNSBP patients. 3.To assess the clinic al value of assessment of muscle activation patterns and muscle metabolism of sEMG, microdialysis, near infrared spectroscopy, magnetic resonance spectroscopy and ultrasound imaging. All patients referred to Spesialsykehuset for Rehabilitering (SSR) with CNSBP that fulfil the inclusion and the exclusion criterias will be invited to participate in the study (n=30). Age-matched healthy controls (n=30) will be recruited from employees at the hospital. To assess metabolic changes both invasive and non-invasiv e techniques may be used. Microdialysis is an invasive in situ sampling technique, directly assessing chemical changes in the muscle interstitium over time. Near infrared spectroscopy (NIRS) is a non-invasive technique, based on differences in the absorpt ion of near infrared light between oxygenated and non-oxygenated hemoglobin and myoglobin. A 3 Tesla MR enables us to carry out high resolution p-31 MR spectroscopy. Intracellular pH and energy metabolism with ATP, ADP, AMP and PCr can be calculated and g ive a comprehensive status of the muscle during rest and exercise. The voxel size in this MR allow us to specifically measure in mm. multifidii. Muscle blood flow will be evaluated by Ultrasound (US) imaging.