Movement Skill Performance by Children with Autism Spectrum Disorders: Delays, Deficits, and Developmental Trajectories

Background: The nature of ASD is integrally related to development given characteristic behaviours are evident early in life, pervade nearly every aspect of subsequent development, and continue to change throughout the course of development.  Movement skills play a critical role in development and it is generally accepted that performance of movement skills by children with ASD is impaired compared to peers without ASD, suggesting possible delays in the development of movement skills.  These movement skill differences seemingly become more obvious with increasing age, although ongoing debate exists whether these differences simply reflect delays or if development among children with ASD is in some ways unique and follows a different developmental trajectory than their typically developing peers.
Objectives: This study explored the performance of fundamental movement skills among 9 to 12 year old children with ASD using the Test of Gross Motor Development (TGMD-2), a criterion referenced assessment that provides a developmental framework to examine both locomotor and object control skills.  A longitudinal design with two carefully planned comparison groups afforded a more detailed exploration of movement skill development through the notion of delays, deficits, and developmental trajectories.
Methods: The primary group of 26 children with ASD was individually-matched to two typically developing comparison groups.  The first comparison group was matched on sex and chronological age, while the second group was matched on sex and the raw score from the locomotor portion of the TGMD-2.  To explore trajectories of development, movement skill performance of 12 children with ASD and 15 children in the developmentally-matched comparison group was followed for 3 consecutive years.
Results: Comparison to the age-matched group confirmed expected performance differences on both locomotor and object control subtests of the TGMD-2.  By definition, the developmentally-matched group was younger, ages 4 to 6 years.  Longitudinal comparison between these groups revealed different developmental trajectories.  Despite being much older, children with ASD seemingly reached a plateau in the performance of both locomotor and object control skills, while the younger, typically developing children continued to refine their performance with increasing age.  
Conclusions: The developmentally-matched comparison group clearly demonstrates a delay in the development of fundamental movement skills among children with ASD.  The obvious age differences, extent of impairment resulting from cumulative delays, and increasing differences reflected in the developmental trajectories would suggest that children with ASD develop movement skills differently than their typically developing peers.  Current teaching strategies and intervention approaches therefore need to reflect these unique patterns of development.