Dysfunctional anticipatory and feedback responses
In contrast, feedforward mechanisms such as automatic postural responses (APAs) help maintain postural stability by preventing the perturbation of the center of mass (COM) (Johnston et al., 2002). Johnston et al. (2002) investigated the timing of muscle activity and resultant arm movement during rapid voluntary goal-directed movement. It was observed that the onset of activation of all trunk muscles occurred during the APA period in TD children (Johnston et al., 2002). However, DCD children showed activation of only two out of five trunk muscles at the onset of the APA. To date, most studies on postural muscle functions have focused on maintenance of stability following an external perturbation (Johnston et al., 2002). This study was significant as there is little information on postural muscle function in DCD children. This coincides with Geuze’s (2005) findings, which states that DCD children show inconsistent timing of muscle activation sequences, lack of automation and slowness of response.