Accepted for/Published in: JMIR XR and Spatial Computing (JMXR)
Date Submitted: Mar 13, 2026
Date Accepted: Jul 31, 2026
Exploratory Patterns of Task Difficulty and Visual Feedback in VR-Based Upper-Limb Trajectory Training
ABSTRACT
Background:
Virtual reality (VR) is increasingly used in motor rehabilitation because it allows therapy tasks to be gamified and training parameters to be adjusted. However, when training dose is matched, VR-based interventions often show only modest advantages over conventional therapy. Understanding how modifiable VR training elements such as augmented sensory feedback and task difficulty interact may help guide the design of more effective serious games for rehabilitation.
Objective:
The objective of this study was to examine how task difficulty and visual augmented sensory feedback influence motor performance during upper-limb trajectory training in a VR-based task.
Methods:
Nine neurotypical participants completed a VR trajectory-following task using a brace-supported upper-limb interface in which applied forces controlled a cursor in a Unity-based environment. Participants trained under eight modes combining two augmented sensory feedback conditions (visual feedback vs no feedback) and four difficulty levels determined by sinusoidal trajectory amplitude. Motor performance was quantified as the percentage reduction in trajectory-tracking error from pre- to post-training. Paired t tests compared conditions, and linear regression examined the relationship between difficulty and the relative contribution of visual feedback.
Results:
Movement accuracy improved after training across all modes. At higher difficulty levels, visual feedback produced greater improvements than no feedback. Improvements pooled across moderate-to-high difficulty levels were significantly greater with visual feedback (P<.05). The difference between conditions increased with difficulty, with a significant positive association between difficulty and the feedback-related performance benefit (P=.028).
Conclusions:
The benefit of augmented visual feedback during VR-based motor training increases with task difficulty. Coordinating feedback cues with task challenge may improve the design of VR-based serious games and rehabilitation training systems.
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