Sensor-Based Assessment of Upper-Limb Motor Control in Children and Adults Using Two-Dimensional Circular Target Tracking.

Portable sensor-based assessment of human motion is important for monitoring motor development and informing the design of rehabilitation applications. This study investigated upper limb motor characteristics during two-dimensional circular target tracking across different age groups and speeds. Fifty-one participants were divided into three groups: lower-elementary children, upper-elementary children, and adults. Using a tablet- and stylus-based input device suitable for human-computer interaction systems, participants performed the tracking task at three speeds. Each trial included relatively feedback-dominant target-visible segments and relatively feedforward-dominant temporarily target-invisible segments. The latter imposed greater demands on predictive tracking because current target-related visual information was unavailable. A participant-level Tracer Error Ratio was calculated as the target-invisible positional error divided by the target-visible positional error. The two child groups showed similar ratios across all speeds, whereas adults showed lower ratios than either child group. As tracking speed increased, the ratio decreased in all groups, with the adult mean falling below 1 only in the high-speed condition. These findings indicate an adult-child difference in predictive tracking during temporary target disappearance but do not directly identify a specific cerebellar mechanism. This portable tablet-stylus approach may be useful for research on age group differences in upper limb target tracking performance.