In the IKT group before isokinetic training, the subjects were asked to perform five minutes' warm-up followed by slow stretching of back extensors and flexors. The subject was asked to be in an isokinetic dynamometer (Biodex Corporation, New York, USA) in a vertical standing position.

The VRT group received virtual reality training with (Pro-Kin system PK 252 N Techno body, Pelvic Module balance trunk MF, Italy) focusing on the balance of core stability muscles.

The Control group focused on conventional balance training for core muscles. The training includes active isotonic and isometric exercise for abdominal muscles (Internal oblique, external oblique, transverse abdominus and Rectus abdominus) deep abdominal muscles (Psoas major, Psoas minor, Illiacus and Quadratus Lumborum) and back muscles (Erector spinae, Transverses spinalis, inter spinalis and Inter transverse).

The knees were flexed slightly at 15 degrees, and the fixation straps were tied around the popliteus, thigh, pelvis, chest and scapula to prevent the tricky movements.

The pain intensity was measured by visual analog scale (VAS) which consist of a 10 cm horizontal line representing one end with "no pain at all" and the other end with "as bad as possible it could be." Each subject was asked to enter in the line as per his pain perception at rest and the score was measured by the distance on the line. The reliability and validity of VAS in application of musculoskeletal conditions was good.

The pain intensity was measured by visual analog scale (VAS) which consist of a 10 cm horizontal line representing one end with "no pain at all" and the other end with "as bad as possible it could be." Each subject was asked to enter in the line as per his pain perception at rest and the score was measured by the distance on the line. The reliability and validity of VAS in application of musculoskeletal conditions was good.

The trunk flexor and extensor muscles' peak torque was measured by using isokinetic dynamometer. The participant was positioned in standing position and wrapped the lower extremities with Velcro straps to prevent trick movements. Three measurements were taken at 900 per second for trunk flexors and extensors and the average value was considered for data analysis. The reliability and validity of this method of application in low back pain condition was good.

The trunk flexor and extensor muscles' peak torque was measured by using isokinetic dynamometer. The participant was positioned in standing position and wrapped the lower extremities with Velcro straps to prevent trick movements. Three measurements were taken at 900 per second for trunk flexors and extensors and the average value was considered for data analysis. The reliability and validity of this method of application in low back pain condition was good.

Cross sectional area (CSA) is an area exposed by cut through at right angles to an axis. T2 weighted images of para spinal muscles (PM: Psoas Major, QL: Quadratus Lumborum, Mf: Multifidus and ES: Erector Spinae) CSA were taken using a 3-T MRI-scanner (Closed MRI system, Siemens, Hamburg, Germany) with a slice thickness of 5 mm. The subjects were placed in a supine position with a pillow kept under the knees to maintain the normal lordosis of the lumbar spine. The CSA at the level of L3-L4 was selected because of their maximal size at this level.