This study was an experimental type of study. Sample size was determined by simple non probability sampling method. Sample size was taken to be 36. The persons who were diagnosed with Mechanical low back pain and persons who came under the inclusion criteria are selected for the study. A clear explanation about the study and consent form were given to the patients who are willing to participate. Assessment of the patient included NPRS score, Lumbar flexion and extension measurement. Their evaluation was taken at the start of treatment and after 4 weeks of treatment. Consent was obtained from the subject and the procedure was explained to them. All the subjects in these group were given combination of isometrics technique for posterior oblique sling. This study examined the Numerical pain rating scores (NPRS) and Lumbar flexion measurement before and after the treatment of Mechanical low back pain with combination of isotonics technique on posterior oblique sling and conventional physiotherapy. The mean of NPRS scores pretreatment is 6.35 score out of 10 with standard deviation 1.13. Therefore, mean with standard deviation of pretreatment NPRS scores is 6.35±1.13. The post treatment Mean of NPRS scores with the standard deviation is 3.23±1.03.The mean and standard deviation of Lumbar flexion measurement Pretreatment is 3.94±0.97. The mean and standard deviation of Lumbar flexion measurement Post treatment is 6.82±0.75. Hence, there is significant improvement of lumbar flexion in the patients treated.