AIMS
The aim was to examine the theoretical and clinical plausibility of subtypes of movement difficulty, and explore the impact subtypes and/or additional factors would
have on motor development.
BACKGROUND
Developmental Coordination Disorder (DCD) is a chronic, often permanent condition evident from early childhood, characterised by difficulties performing a range of movement tasks that are not explainable by neurological or psychological impairments. The aetiology of the condition is unknown and various theories of motor development and impairment have been used to try and explain the variability in expression, prompting hypotheses over whether homogeneous subgroups can be identified that are consistent across populations and with distinct pathways, the identification of which would increase our understanding of the condition.
HYPOTHESES
i& ii) Distinguishable subtypes of perceptual and motor performance in children with DCD are comparable to those obtained in previous studies with group membership consistent across theoretical models.
iii - v) Subtypes contribute differentially to maturation and treatment response whilst additional factors will also be seen to influence movement skill acquisition.
DESIGN AND METHOD
A mixed experimental design was used. The first study tested for the presence of specific components of motor behaviour; their interaction and influence on motor
performance. A second study involved a subset of children in a cross-over intervention programme of 20 weekly therapy sessions with a 6 monthly review of movement skills and developmental progress, over a period of 2 years. Data analysis consideredw hether distinct subtypes were consistent across theoretical perspectives and, whether these or other factors influenced maturation or treatment response.
RESULTS
Factor and cluster analysis identified five subtypes, differentiating children on perceptual and motor performance, similar to previous sub-typing studies. A majority of children benefited from participation in group intervention. Progress was unrelated to degree of initial motor impairment or subtype although those with perceptual and severe movement problems were more likely to have persistent difficulties.
CONCLUSIONS
Five subtypes of DCD were identified which were not found to influence progress or response to treatment,for a smaller subset. Different theoretical perspectives did not
predict similar group membership confounding nosological classification. An alternative approach to modelling coordination difficulties is recommended.