Abstract
The end-state comfort (ESC) effect refers to the consistent tendency of healthy adults to end their movements in a comfortable end posture. In children with and without developmental coordination disorder (DCD), the results of studies focusing on ESC planning have been inconclusive, which is likely to be due to differences in task constraints. The present pilot study focused on the question whether children with and without DCD were able to change their planning strategy and were more likely to plan for ESC when demanded by complex object manipulations at the end of a task. To this end, we examined ESC planning in 18 children with and without DCD (aged 5–11years) using the previously used sword-task and the newly developed hammer-task. In the sword-task, children had to insert a sword in a wooden block, which could be relatively easily completed with an uncomfortable end-posture. In the hammer-task, children had to strike down a nail in a wooden pounding bench, which required additional force and speed demands, making it relatively difficult to complete the movement with an uncomfortable end-posture. In line with our hypothesis, the results demonstrated that children with and without DCD were more likely to plan for ESC on the hammer-task compared with the sword-task. Thus, while children with and without DCD show inconsistent ESC planning on many previously used tasks, the present pilot study shows that many of them are able to take into account the end-state of their movements if demanded by task constraints.
Highlights
When selecting a grip in order to perform a grasping movement, several strategies can be used
The main variable of interest was the proportion of end-state comfort (ESC) on the critical trials of the sword-task and the hammertask, which is represented in Figure 2 for children with developmental coordination disorder (DCD) and typically developing (TD) children separately
On the hammer-task, seven TD children ended all trials in ESC, but the other two children still ended less than half of the trials in ESC
Summary
When selecting a grip in order to perform a grasping movement, several strategies can be used. Studies that focused on varying strategies used by children to solve motor planning tasks, found that next to ESC planning, children with and without DCD use planning strategies based on start-state comfort, minimal initial rotation, or repetition of the previous movement (Wilmut and Byrne, 2014b; Bhoyroo et al, 2018) It is, interesting to examine whether children may change their strategy to strive for ESC if the relative weight of the costs and benefits of an uncomfortable start- or end-posture change. If the precision demands of the to-be-performed manipulation at the end of the task are higher, it is expected that it is more beneficial to end the movement in a comfortable posture in order to complete the required task goal Following this reasoning, we developed a hammertask in which children needed to pick up a hammer to strike down a nail in a wooden pounding bench (Figure 1). We hypothesized that this would be true for children with DCD compared with TD children
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