A single cohort of 74 healthy adult volunteers will undergo an observational test-retest reliability study of four cervical proprioception assessments using computer-vision tracking. No medical interventions will be administered.

Two distinct assessment protocols control for learning effects and follow literature-based retest intervals:

Protocol A (n=37): Cervical Movement Sense Target Tracking at baseline and again after one week to assess longer-term reliability.

Protocol B (n=37): Head Relocation Test in 32 participants at baseline and again after one hour. Cervical Movement Sense Patterned Tracking and Cervical Proprioceptive Function Test in all 37 participants at baseline and again after one hour to minimize short-term learning effects. Separate participant groups prevent cross-test learning, and retest intervals (1 hour vs. 1 week) align with prior studies.

With the help of algorithms, the initial position of the participant's nose tip on the screen will be recorded. Following flexion, extension, or rotation movements, the final position will be obtained, and the difference between the initial and final positions will be calculated in pixels and reported as the error score. While the primary output will be in pixels, this difference can also be expressed in degrees with the necessary conversions. Rotational movements performed during the measurement will be simultaneously recorded using the CROM device, and the values from the screen will be compared with those from the CROM to assess criterion validity, which provides the error magnitude directly in degrees. Measurements performed on the same group at two different time points will be analyzed using the Intraclass Correlation Coefficient (ICC), the Standard Error of Measurement (SEM), and Bland-Altman methods.

During the test, an F8 or ZZ shaped pattern will be displayed on the screen, and the participant will trace the pattern starting from the center using their nose tip. The algorithm will track the nose tip's position in each camera frame throughout the test: if the nose tip remains within the shape, the error score will be 0; if it moves outside, the distance to the nearest point of the shape will be calculated in pixels and recorded as the instantaneous error score. At the end of the test, all instantaneous error scores will be summed to obtain the total error score. The start and finish times of the test will also be recorded to determine the total test duration. Total error scores from measurements performed on the same group at different time points will be analyzed using the Intraclass Correlation Coefficient (ICC), the Standard Error of Measurement (SEM), and Bland-Altman methods.

During the test, a rectangle will appear on the screen and move at a constant speed along the ZZ or F8 paths. The participant will attempt to keep their nose tip inside this moving rectangle. Since the speed is fixed, the test duration is the same for all participants.

Scoring Methods

Time-Based Score: The total time the nose tip remains inside the rectangle is divided by the total test duration. The resulting ratio ranges from 0 to 1:

1 → Best score (nose tip always inside)

0 → Worst score (nose tip never inside)

Distance-Based Score: For each frame, the algorithm calculates the distance from the nose tip to the rectangle:

Inside = 0

Outside = distance in pixels to the nearest edge

At the end, all distances are summed to obtain the total deviation score. Both scores from measurements performed on the same group at different time points will be analyzed using the Intraclass Correlation Coefficient (ICC), the Standard Error of Measurement (SEM), and Bland-Altman methods.