The present study has several limitations, including the small number of patients and their relatively young age; therefore, the results cannot be generalized to all patients with nonspecific chronic LBP. Also, the long-term effects of these exercise protocols cannot be predicted; further studies are needed with larger sample sizes and longer follow-up periods. The strength of the deep lumbar muscles was not monitored directly, using a needle electromyography, ultrasound measurements of deep muscle thickening, or muscle activation using pressure biofeedback [26]. Because we measured only the maximal isometric strength of the lumbar extensors, the results may not reflect the overall strength of the deep lumbar stabilization muscles.
In conclusion, both lumbar stabilization and conventional lumbar dynamic strengthening exercises increased the strength of the lumbar extensor muscles and reduced LBP. However, compared to that of lumbar dynamic strengthening exercises, lumbar stabilization exercises were more effective for strengthening lumbar extensors at small lumbar flexion angle and for improving the functional disability in patients with nonspecific chronic LBP.