Visual Feedback in Augmented Reality to Walk at Predefined Speed Cross-Sectional Study Including Children With Cerebral Palsy

In an augmented reality environment, the range of possible real-time visual feedback is extensive. This study aimed to compare the impact of six
scenarios
in augmented reality combining four visual feedback characteristics on achieving a target walking speed. The six
scenarios
have been developed for Microsoft Hololens augmented reality headset. The four feedback characteristics that we have varied were: Color; Spatial anchoring; Speed of the feedback, and Persistence. Each characteristic could have different values (for example, the color could be unicolor, bicolor, or gradient). Participants had to walk for two consecutive walking trials for each
scenario
: at their maximal speed and an intermediate speed. Mean speed, percentage of time spent above or around target speed, and time to reach target speed were compared between
scenarios
using mixed linear models. A total of 25 children with disabilities have been included. The feasibility and user experience were excellent. Mean speed during
scenario
6, which displayed feedback with gradient color, attached to the world, with a speed relative to the player equal to his speed, and that disappeared over time, was significantly higher than other
scenarios
and control (p =0.003). Participants spent 80.98% of time above target speed during
scenario
6. This
scenario
mixed the best combination of feedback characteristics to exceed the target walking speed (p=0.0058).
Scenarios
5 and 6, which shared the same feedback characteristics for spatial anchoring (world-locked) and feedback speed (equal to the player speed), decreased the time to reach the target speed (p=0.019). Delivering multi-modal feedback has been recognized as more effective for improving motor performance. Therefore, our results showed that not all visual feedback had the same impact on performance. Further studies are required to test the weight of each feedback characteristic and their possible interactions inside each
scenario
. This study was registered in the ClinicalTrials.gov database (NCT04460833).