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Introduction: Chronic low back pain is a public health problem in view of its functional repercussions and the functional rehabilitation is an integral part of its management.

Aim: To compare the evolution of muscle strentgh of spinal extensors and flexors in chronic low back pain patients after an isokinetic rehabilitation protocol and a conventional rehabilitation one.

Method: This was a prospective and comparative study carried out in the Physical Medicine Department of the Tunis Military Hospital over a period of 7 months. Fifty patients were included, randomly divided into two groups of 25. The first group (G1) benefited from an isokinetic rehabilitation protocol and the second one (G2) from a classic active physiotherapy. We performed a clinical (Sorensen test and Shirado test) and isokinetic evaluation of the trunk muscles before and after rehabilitation.

Results: The mean age of the general population was 42±8.6 years old. Clinical evaluation showed a deficit in the extensor and flexor muscles of the spine, more important in the extensors in both groups. After rehabilitation, there was a significant improvement in clinical tests of muscular endurance in G1 and G2. Isokinetic assessment showed a greater muscle deficit in the extensors in both groups. After isokinetic rehabilitation, peak torque for flexors and extensors increased by 21% and 23% respectively, power was 34% and 37% higher, and total work increased by 26% and 47%. On the other hand, the (F/E) ratios were unchanged for all three speeds. In Group 2, peak torque values for flexors and extensors increased by 22 and 15% respectively, power was higher by 31 and 23% and total work was also up by 29 and 17%, while F/E ratios were also unchanged. Group 1 showed the greatest improvement in extensor strength at 60°/s, and in power at 90°/s for the various muscles.

Conclusion: In our study, we concluded that endurance and muscular strength improved the most after isokinetic rehabilitation.