Validation of the HTC VIVE Ultimate Trackers Compared with the Vicon Motion Capture System at Slow, Moderate and Fast Gait Speeds

This study investigated the performance of the HTC VIVE Ultimate Tracker against the Vicon motion capture system during human walking. Ten healthy participants (aged 24–44 years) walked on a treadmill at four speeds (0.5, 1.0, 1.5, and 2.0 m/s) while tracking both feet and the pelvis. Agreement between the two systems was evaluated using a linear mixed model, Bland-Altman plots, and concordance correlation coefficients (CCC). Absolute errors presented the accuracy of Ultimate Trackers ranging from millimetre- to centimetre-level. Linear mixed model [speed (0.5-2.0 m/s) × tracker location (sacrum, left foot, and right foot) × movement direction (vertical, medio-lateral, and anterior-posterior)] indicated the absolute errors increased with higher gait speed. Foot trackers exhibited larger errors than the sacrum location, with greater errors in the medio-lateral and anterior-posterior directions compared to the vertical direction ( p  < 0.001). Bland-Altman analyses revealed widening limits of agreement at different speeds (e.g., left foot, AP direction: -20.29 to 20.20 at 0.5 m/s, -29.97 to 27.80 mm at 2.0 m/s). Ultimate Trackers demonstrated almost perfect agreement (CCC: >0.99) for sacrum tracking across all speeds and directions, and excellent agreement for foot trackers (CCC: >0.98). These findings highlight the Ultimate Trackers’ potential as cost-effective alternatives for the analysis of human movement, demonstrating research- and clinical-grade performance for sacrum and foot tracking during normal gait speeds (≤ 1.5 m/s). However, the finding that accuracy declined at the 2.0 m/s speed, particularly for foot trajectories and in the anterior-posterior direction, indicates the need for further technical refinements for higher speed movements.