Isokinetic exercise is dynamic, but the spped of movement must be regulated so that the resistance is in ratio to the force applied at each point throughout the full range of motion. The purpose of this study is to comparise with trunk flexors & extensors of isokinetic evaluation of pre-exercise and post-exercise in operated laminectomy & disectomy patients. 7 subjects were examined at $120^{circ}$/sec and $60^{circ}$/sec each 15 days. The results were as follows; 1. Peak torque of extensors on $60^{circ}$/sec showed significant difference statistically(p<0.05), but peak torque of flexors on $60^{circ}$/sec showed no significant difference statistically. 2. Trunk flexors/extensors ratio of peak torque of $60^{circ}$/sec showed no significant difference ststistically. 3. Peak torque % B.W of extensors on $60^{circ}$/sec showed significant difference statistically(p<0.05), but peak torque % B.W of flexors on $60^{circ}$/sec showed no significant difference statistically. 4. TAE of extensors on $60^{circ}$/sec showed significant difference statistically (p<0.05), but TAE of flexors on $60^{circ}$/sec showed no significant difference. 5. Total work of flexors & extensors on $60^{circ}$/sec showed significant difference statistically (p<0.05). 6. Average power of flexors & extensors on $120^{circ}$/sec showed significant difference statistically(p<0.05). 7. Endurance ratio of flexors & extensors on $120^{circ}$/sec showed no significant difference statistically. 8. Set total work of flexors & extensors on $120^{circ}$/sec showed significant difference statistically(p<0.05). 9. TAE of extensors on $120^{circ}$/sec showed significant difference statistically(p<0.05), TAE of flexors on $120^{circ}$/sec showed no significant difference statistically. 10. Total work of flexors & extensors on $120^{circ}$/sec showed significant difference statistically (p<0.05).