Online control of handwriting in children with Developmental Coordination Disorder
Background : Previous research indicates that children with Developmental Coordination Disorder (DCD) present difficulties in forward modeling and online control. Most of these studies emphasize speeded discrete movements, but controlling movements online is imperative for movement sequences of longer duration such as control necessary in handwriting.
Aim: To examine online planning in children with DCD during a handwriting task. It was hypothesized that children with DCD would present more difficulty adjusting to a change in an ongoing handwriting task, as evidenced by decreased fluency, longer duration of strokes, and greater percentage of time before peak velocity in the stroke immediately after a perturbation. Additionally, it was hypothesized that children with DCD would exhibit greater difficulty when more complex control is required, as shown by decreased fluency, longer stroke duration, and greater percentage of time after peak velocity when performing simple and complex sequences of loops and peaks.
Method : Eleven children with DCD (10 y1.34 years) and 11 typically developing children (10 y1.34 years) performed continuous (loops) and discontinuous (peaks) movement sequences in which complexity was varied (a series of shapes of the same height or of a combination of heights). On some trials children had to increase the size of the loops on cue. Kinematic analysis of movement sequences was performed using NeuroScript and a digitizing tablet.
Results: Children with DCD were more dysfluent and spent more time to peak velocity than the TD but adjusting to the tone by changing their plan online was not different. Discontinuous tasks (peaks) required a greater control from DCD and the TD group, with the simple sequence being the only that captured differences in strategies used to control the movement. Children with DCD spent equal time in the upstroke and downstroke, compared with TD who spent more time in the downstroke. Additionally, children with DCD spent a greater percent of time into peak velocity in contrast with the TD group, who spent a greater percentage after peak velocity.
Conclusion : Children with DCD present different strategies to control their movements that may interfere with their ability to plan online. Further research is needed that include tasks with greater level of complexity.