Inclusion Criteria:  Chronic neck pain and/or low back pain longer than 3 month Minimum numeric pain rating scale equal or > 5  Exclusion Criteria:  Change in pain medication within 4 weeks prior or during the enrollment (except intake of rescue medication) Additional pain therapies within 4 weeks prior or during the enrollment Epilepsy Pregnancy Previous experience in TENS Cardiac arrythmia/previous cardiac operation/implanted cardiac devices Infection or malignancies affecting the spinal cord/previous spine operation Severe radicular pain with acute paralysis in the extremities Ongoing pension application