Functional mobility encompasses the essential motor skills required for individuals to perform activities of daily living independently and safely. One of the most commonly used methods for assessing this parameter is the Timed Up and Go (TUG) test. The TUG test involves standing up from a chair, walking, turning, walking back three meters, and sitting down, and it is a measurement tool that has demonstrated high sensitivity and reliability in clinical practice for evaluating lower extremity function, mobility, and fall risk.

However, tests conducted in conventional clinical settings have limitations in terms of standardization due to examiner-related variability, environmental influences, and measurement subjectivity. These factors may lead to measurement errors, particularly when detecting small performance differences. Advances in virtual reality (VR) technology offer an innovative approach to the assessment and training of motor performance by recreating real-life scenarios in a three-dimensional and interactive manner. VR-based systems allow simultaneous observation of motor and cognitive processes while enhancing user motivation and engagement, thereby making the assessment process more dynamic. Recent studies have demonstrated that VR applications are effective tools in neurological rehabilitation, particularly in conditions such as multiple sclerosis (MS), for improving balance, walking speed, and functional mobility.

A review of the existing literature reveals that studies evaluating the validity and reliability of VR-based functional tests are limited. Moreover, to date, no study has specifically focused on the validity and reliability of the TUG test in an immersive VR environment for assessing lower extremity functional mobility. Therefore, this study aims to address a significant gap in the literature by being one of the first investigations to examine the validity and reliability of a VR-based version of the TUG test.

This study aims to determine the feasibility, validity, and reliability of the TUG test administered in an immersive VR environment in asymptomatic young adults aged 18-30 years. Additionally, the relationships between VR-based TUG outcomes and the 4-Meter Walk Test, the Four Square Step Test, and lower extremity muscle strength measurements will be examined.

Inclusion Criteria:

• Aged between 18 and 30 years,
• Asymptomatic, with no musculoskeletal, neurological, or cardiovascular symptoms,
• Ability to perform activities of daily living independently,
• Visual, auditory, and vestibular functions suitable for virtual reality applications,
• Ability to understand and follow instructions in Turkish,
• Willingness to participate voluntarily in the study.

Exclusion Criteria:

• History of lower extremity injury, surgical intervention, or serious musculoskeletal condition within the past six months,
• Presence of vestibular disorders, balance impairment, visual or hearing impairments,
• Experiencing symptoms of "VR sickness," such as nausea, dizziness, or spatial disorientation during virtual reality applications,
• History of neurological, cardiovascular, or metabolic diseases,
• Regular participation in heavy exercise or professional sports activities,
• Cognitive impairment that prevents understanding of test instructions,
• Voluntary withdrawal from the study during the research process.

Asymptomatic young adults aged 18-30 years who are able to perform activities of daily living independently and have no musculoskeletal, neurological, or cardiovascular conditions affecting functional mobility.