Abstract
The purpose of this study was to determine differences in the nature and effectiveness of intra-limb coordination in boys with and without DCD, in one-handed catching. Ten boys, in each group, attempted to catch at ten balls at 7m/s. Two high-speed cameras (100Hz) were used to derive 3D coordinates. The degree of coordination was inferred from the magnitude of correlation coefficient between angular displacement of the relevant joints; higher values indicated tighter coupling. Standard deviation, calculated across five trials, was used to infer stability. Results showed a significant interaction effect (F =10.64, p < .01, ?2 = .39) for the degree of spatial coupling, and subsequent planned comparisons revealed significant differences between the groups for shoulder-elbow (Sh-El) (w/oDCD = .69; DCD = .80) and elbow-wrist (El-Wr) (w/oDCD = .79; DCD = .61) joint pairs. Also, a significant group main effect was found for stability (F (1, 18) = 7.97, p < .05, ?2 = .32) for the El-Wr (w/oDCD = .11; DCD = .21). In terms of effectiveness, boys w/ DCD caught fewer balls (w/oDCD = 85%; DCD = 32%). Contrary to previous work, no universal coordinative tendency emerged for either group confirming that (intra-limb) coordination is dependent on many different constraints. The potential causes of failures exhibited by DCD will be discussed in the context of relevant models of redundancy.
