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

BACKGROUND:

Chronic non-specific low back pain (CNSLBP) is a leading cause of disability worldwide. The Timed Up and Go (TUG) test is a valid and reliable measure of functional mobility in individuals with musculoskeletal conditions, including chronic low back pain, and TUG performance has been shown to correlate with pain intensity and disability. Virtual reality (VR) has increasingly been used as a therapeutic intervention for chronic low back pain, but the use of immersive VR as an assessment tool has not been systematically evaluated in this population.

STUDY DESIGN:

This is a prospective, single-center, observational methodological study designed to assess the validity and test-retest reliability of an immersive virtual reality adaptation of the Timed Up and Go test (VR-TUG) in individuals aged 18-55 years with chronic non-specific low back pain.

PROCEDURES:

• Session 1 (Baseline Assessment):

• Demographic and clinical data collection
• Pain intensity (Visual Analog Scale, VAS)
• Functional disability (Oswestry Disability Index, ODI - validated Turkish version)
• Kinesiophobia (Tampa Scale for Kinesiophobia - Turkish version)
• Classic TUG test performance
• VR-TUG test performance (first measurement)
• Session 2 (7 ± 2 days later):

• VR-TUG test performance (second measurement for test-retest reliability)

VR-TUG PROTOCOL:

Participants will wear a head-mounted display (HMD) that presents an immersive virtual environment replicating the spatial parameters of the classic TUG test. They will perform the same sequence of movements (stand up from a chair, walk 3 meters forward, turn 180°, walk back, and sit down) while immersed in the virtual environment. Time to completion will be recorded. A brief familiarization period (approximately 1-2 minutes) will be provided before testing. Participants will be monitored for any adverse effects (such as dizziness, nausea, or visual discomfort), and the VR-TUG will be stopped immediately if needed.

OUTCOME MEASURES:

• Primary Outcome:

o VR-TUG completion time (seconds), including assessment of test-retest reliability across two sessions.

• Secondary Outcomes:

• Classic TUG completion time (seconds)
• Pain intensity (VAS)
• Functional disability (ODI)
• Kinesiophobia (Tampa Scale for Kinesiophobia)

ANALYSIS PLAN:

• Concurrent validity:

o Correlation between VR-TUG and classic TUG completion times (Pearson or Spearman correlation, depending on data distribution).

• Test-retest reliability:

• Intraclass correlation coefficient (ICC, two-way mixed-effects model, single measure) for VR-TUG completion time between Session 1 and Session 2.
• Estimation of standard error of measurement (SEM) and minimal detectable change (MDC).
• Bland-Altman analysis to evaluate agreement between repeated VR-TUG measurements.
• Construct validity:

• Correlations between VR-TUG completion time and clinical measures (VAS, ODI, Tampa Scale for Kinesiophobia). It is expected that longer VR-TUG times will be associated with higher pain, disability, and kinesiophobia scores.

Statistical significance will be set at p < 0.05.

SAMPLE SIZE:

Based on previous studies reporting excellent reliability of technology-supported functional tests in patients with chronic low back pain (ICC ≥ 0.90), a sample size of approximately 65 participants was calculated to detect a correlation of 0.70 between classic TUG and VR-TUG with 90% power and an alpha of 0.05, allowing for potential dropouts.

SAFETY CONSIDERATIONS:

All testing will be conducted in a safe, obstacle-free environment under the supervision of a trained researcher who can provide physical support if needed. Participants will be screened for contraindications to VR use (for example, photosensitive epilepsy or severe motion sickness). Testing will be stopped immediately if participants experience significant discomfort, dizziness, increased pain, loss of balance, or any other adverse effect. All adverse events and reasons for test discontinuation will be recorded.

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.