Tool length influences reach distance estimation via motor imagery in children with developmental coordination disorder

PURPOSE: Children with developmental coordination disorder (DCD) often have difficulties with planning and generating a precise visuospatial representation of intended actions and using motor imagery to mentally represent motor behavior. Here, we aimed to extend the investigation of motor imagery in children with DCD by exploring its use with an estimation of reach paradigm that combines action representation and extension of space with tools. METHOD: Two groups of 18 children with DCD and typically developing (TD) matched controls were tested with an estimation of reach paradigm using a 20-cm (Experiment 1) and 40-cm (Experiment 2) tool. Conditions involved estimations via motor imagery with their arm, tool, and a switch-block (SB) involving an abrupt change of space with an "extension" from arm to tool and a "retraction" from tool to arm. RESULTS: No significant group differences were found with the 20-cm tool; however, with the 40-cm implement, children with DCD were significantly less accurate than their TD counterparts. CONCLUSIONS: Compared to TD children, those with DCD have more difficulty estimating reach distances using the longer of two tool lengths: 40 cm compared to 20 cm. This finding may be related to differences in quality of motor imagery and in the ability to create an effective internal model for action in this context. Furthermore, our results suggest that tool length may present an additional action processing constraint on children with DCD. Additional studies are necessary to determine other constraints that children with DCD have when integrating tool use with spatial judgments for reach actions, as well as provide rehabilitation insights that involve motor imagery combined with tool use.