Coordination of grip force and load force in developmental coordination disorder: A case study

Abstract

In adults, moving an object using precision grip involves anticipatory adjustment of grip force for fluctuations in inertial load force. These adjustments suggest that motion planning is based on an internal model of the effect or system and the environment. In the current study, we evaluate the coordination of grip force with load force in a child with developmental coordination disorder (DCD) and a matched, normally developing, control child. The children completed five tasks: (i) lifting an object; (ii) moving an object upwards; (iii) moving an object downwards; (iv) holding an object subject to unpredictable perturbation; (v) a time production (tapping) task. A number of differences were observed between the children. In particular, compared to the control, the child with DCD showed an earlier rise in grip force when making both upward and downward movements. We discuss this result in relation to the greater variability in explicit timing and longer reflex delays observed in the child with DCD. We conclude that this paradigm offers insight into the motion planning difficulties seen in DCD, providing a useful new methodology for the investigation of the observed coordination difficulties.