The purpose of this study were to measured peak torque of lumbar extensor at various degrees and to compare with the choronic low back pain patients and healthy subjects back extensor peak torque. Research subject are fifty choronic low back pain patients and fifty healthy subjects are Dong-a university hospital visited to 2000, January since 1999, august none lumbosacral traumal past history and neurologic disorder that is twenty generation, thirty generation, forty generation, fifty generation, sixty generation in healthy subjects and twenty generation, thirty generation, forty generation, fifty generation, sixty generation in cause choronic low back pain patients. The result were as follows. 1. There were each generation choronic low back pain patients and healthy subjects back extensor peak torque are consideration (p<.05). 2. Twenty generation was all degree of angle in lumbar extention peak torque in choronic low back pain patients back extensor are lower than healthy subjects(p<.05). 3. Thirty generation was all degree of angle in lumbar extention peak torque in choronic low back pain patients back extensor are lower than healthy subjects(p<.05). 4. Forty generation was all degree of angle in lumbar extention peak torque in choronic low back pain patients back extensor are lower than healthy subjects(p<;.05). 5. Fifty generation was all degree of angle in lumbar extention peak torque in choronic low back pain patients back extensor are lower than healthy subjects(p<.05). 6. Sixty generation was all degree of angle in lumbar extention peak torque in choronic low back pain patients back extensor are lower than healthy subjects(p<.05).