The objectives of this study were to examine the relative efficacy of three active exercise programs for work-related, chronic low back pain, and to observe to what extent the programs affected the mechanical stability of the lumbar region. The subjects were 64 employees who were randomly divided into three groups to match the three active exercise programs which were performed 3 times a week for 6 months. All subjects were assessed with the same measurements at a pre-study examination, and then were reassessed at 2 weeks, 3months and 6 months after the study. The pain intensity didn't show any significant difference among the three groups. However, the Oswestry Disability Index showed significant differences among the three groups at 6 months and the lumbar and thoracic exercise groups showed significant decreases compared to the general physiotherapy group (p<.05). Maximal stretching with both hands in the overhead direction showed a significant difference among the three groups at 3 months and 6 months, and the thoracic exercise group at 6 months showed a significant increase in overhead stretching compared to the lumbar exercise and general physiotherapy groups (p<.05). The group that performed maximal stretching with both hands in the overhead direction showed the most significant among the 3 months and 6 months. At 6 months, the thoracic exercise group showed a significant increase in overhead stretching compared to the lumbar exercise and general physiotherapy groups (p<.05). The lumbar region angle of inclination showed significant differences among the three groups at 2 weeks 3 months, and 6 months, with the thoracic exercise group being decreased more significantly at 6 months than the lumbar exercise and general physiotherapy groups (p<.05). Exercise aimed at increasing thoracic mobility has an effect on lumbar stability. Furthermore, it is far more effective for lumbar stabilization than general physiotherapy and deep muscle strengthening lumbar exercise.