The patient will receive 15 sessions of the Global Postural Re-education approach performed 2times/week for 1 hour including patient education. Each treatment will be individualized for every patient and for his/her pain-related limitation. Each session includes only 2-3 postures to increase the standardization of treatment.

The patient will receive the conventional treatment in form of exercise program of(abdominal and pelvic floor strengthening)and (stretching exercise of back and hip flexor muscles)to improve pain and function in chronic low back pain patients.

The GPR involves a series of active gentle movements and postures aimed at realigning joints, stretching shortened muscles, and enhancing the contraction of antagonist's muscles, thus avoiding postural asymmetry.

The GPR method includes eight therapeutic postures, lying, sitting or standing, to be held for 15/20 minutes each. Postures can be variously combined during sessions. Postures are chosen on the basis of some parameters, such as the amount of pain, load capacity and age of the patient, and muscle chains to be stretched. to increase the standardization of treatment, it will be proposed only 2 or 3 postures.

Anterior pelvic tilt will be measured by software application (iHandy Soft, Inc., New York, USA). This application has the capacity to convert the phone into an inclinometer using a built-in sensitive system.It is a tool for assessing angles of slope (or tilt) using all sides of the device plus the camera. A smartphone with the iHandy app can be used in clinical practice and research as an easy and convenient alternative to an inclinometer.

The lumbar lordosis will be measured by flexible ruler. It is commonly used to measure the degree of spinal curvature of the lumbar lordosis in the sagittal plane. Lumbar lateral X-ray radiography is considered as a golden standard method in lumbar lordosis measurement. However, this method has a number of problems such as being time-consuming and expensive. A flexible ruler is a safe, easy-to-use, and inexpensive tool. Validity between lumbar lordosis measurement with the flexible ruler and the x-ray is 0.91 so the flexible ruler can be used effectively for lumbar lordosis measurements and is a valid, assured, portable and non-invasive tool with high reliability and validity.

Flexibility of hip flexors muscles will be measured by modified Thomas test. This test is performed with the patient supine and the thigh is over the edge of the examining table. The patient is told to grasp the thigh of the untested limb and pull it toward the chest. Lumbar spine is flat on the plinth and the pelvis is in posterior rotation. Length of iliopsoas is determined by measuring the angle of hip flexion. Measurements will be taken pre and post treatment

The pain severity level will be measured via the Visual Analogue Scale (VAS). VAS is a pain rating scale, in which scores are based on self-reported measures of symptoms that are recorded with a single handwritten mark placed at one point along the length of a 10 cm line that represents a continuum between the two ends of the scale "no pain" on the left end (0 cm) of the scale and the "worst pain" on the right end of the scale (10 cm). In this scale, zero represents the absence of pain, 1-3 shows mild pain, 4-6 denotes moderate pain, and 7-10 indicates severe pain