Validation of a Virtual Reality Timed Up and Go Test in Adults With Chronic Non-Specific Low Back Pain

Inclusion Criteria: * Age 18 to 55 years. * Clinician-diagnosed chronic non-specific low back pain (pain duration ≥ 3 months). * Applied to Selcuk University Medical Faculty Physical Therapy and Rehabilitation outpatient clinic with low back pain complaint. * Able to walk independently and safely perform the Timed Up and Go (TUG) and VR-TUG tests (with or without usual assistive device). * Able to understand and follow instructions; literate in Turkish (at least primary school education). * Willing to participate and able to provide written informed consent. Exclusion Criteria: * Red flag conditions or suspected specific pathology (e.g., fracture, tumor/metastasis, infection such as spondylitis/discitis). * Inflammatory back pain suggestive of conditions such as ankylosing spondylitis or sacroiliitis. * Significant radiculopathy or neurological deficit (dermatomal leg pain, marked weakness, reflex changes, sensory loss), clinically significant lumbar disc herniation, severe spinal stenosis, or spondylolisthesis grade II or higher. * Prior lumbar spine surgery. * Lower-extremity conditions that substantially limit mobility (e.g., severe hip/knee osteoarthritis, hip/knee arthroplasty, amputation, severe deformity). * Neurological disorders affecting gait or balance (e.g., stroke, Parkinson's disease, multiple sclerosis, progressive neuromuscular disease). * Vestibular disorder or recurrent severe vertigo affecting balance. * Severe cardiac or pulmonary disease that may compromise safety during testing. * Pregnancy. * Contraindications to VR use (e.g., photosensitive epilepsy) or history of severe VR intolerance (significant nausea, dizziness, visual discomfort, or migraine triggered by VR). * Severe cognitive impairment, major psychiatric disorder, or communication problems preventing cooperation. * Severe visual or hearing impairment that prevents following instructions or safely using VR.