Developmental Differences in Movement Planning Among Children with ASD

Background: Children with ASD demonstrate impaired performance of fundamental movement skills early in life, thereby impacting nearly every aspect of subsequent development.  These performance differences may be related to factors underlying skill acquisition, such as movement planning.    

Objectives: To examine how children with ASD plan and execute fundamental movement skills using a developmental framework.

Methods: Twenty-five children (ages 9 to 12 years) with ASD were individually matched to three groups of typically developing children on developmental variables related to movement behaviour: chronological age (CA), locomotor skill (LOC), and mental age equivalence (MA).  Performance on an obstacle course comprised of 8 horizontal barriers (relative to 30, 40, 50, or 60% of each participant’s height) was compared to examine how fundamental locomotor skills are planned and executed.  Each child moved through the obstacle course four times, twice at each of two speeds (self determined and as fast as possible).  Performance was filmed and analyzed at 30 frames per second.  Movement planning was inferred from the frequency of acts of hesitation (ACTS) -- an inference in a change from an initial plan. Movement execution was inferred from execution time (EXEC), movement pattern (over/under), and percentage of successful clearance. 

Results: Mann-Whitney analyses revealed that when compared to children matched on CA, children with ASD had significantly greater frequency of ACTS at all barriers (p < .01) except the one reflecting 60% of their height.  When compared to younger children matched on LOC or MA, children with ASD executed significantly more ACTS when all barrier heights were considered together (p < .01) and at barrier heights reflecting 40% (p < .01) and 50% (p < .05) of their height.  Based on MANOVA, significant differences in EXEC were found demonstrating that children with ASD moved through the obstacle course significantly slower than children matched on CA (p < .01), LOC  (p < .05), and MA (p < .01).  Mann-Whitney analyses were also used to examine the choice of movement pattern and rates of successful clearance.  All children tended to move over barriers at 30% and under at 60% and children with ASD chose to move over the barriers at 40 and 50% with similar frequency as the younger children matched on LOC.  The children with ASD had similar rates of successful clearance as the younger children matched on LOC or MA. 

Conclusions: Despite demonstrating similar movement patterns as younger children matched on LOC or MA, the children with ASD took significantly more time to plan and execute their movements.  Collectively, these results suggest children with ASD have difficulty planning their movements beyond what would be expected for their CA, LOC, or MA.  To explore trajectories of development, the obstacle course performance of 16 children with ASD and 15 children initially matched on LOC was followed for 3 consecutive years and these results will be discussed.

Sponsor: SSHRC, Autism Research Training Program (funded through CIHR, Autism Speaks, FRSQ) and research grants received from McGill University and Special Olympics