The purpose of this study were to compare the lumbar extensor strength between pre op patients group and after 6 weeks post op patients group. To evaluate lumbar extensor strength of total 273 patients with HIVD. Lumbar extensor strength was measured in 151 male patients and 122 female patients(Lumbar extensor strength was measured in 91 PELD patients group and 182 OLM group patients) by Medx lumbar extension machine. Maximum voluntary lumbar extension strength was appear $149.36{pm}61.92ft$-lbs in pre op of PELD group, $158.47{pm}54.67ft$-lbs in post op of PELD group and $135.54{pm}54.24ft$-lbs in pre op of OLM group. $147.19{pm}52.42ft$-lbs in post op of OLM group in male. Maximum voluntary lumbar extension strength was appear $83.85{pm}30.22ft$-lbs in pre op of PELD group. $92.99{pm}28.66ft$-lbs in post op of PELD group and $75.16{pm}24.98ft$-lbs in pre op of OLM group, $79.88{pm}25.25ft$-lbs in post op of OLM group in female. Male and female lumbar extension strength was statistically significant difference(P<.05). Lumbar flexion/extension ratio of the two group was 2.14:1 pre op and 2.05:1 post op in lumbar flexion 72 and 0 degree. The ratio of post op group was lesser than pre op group.