Postural Stability and Symmetry in Persons with Autism Spectrum Disorder: Relation Between Symptom Severity and Wii Balance Board Performance

Background: Postural stability and postural symmetry are fundamental aspects of motor ability that allow individuals to navigate an environment. Decreased postural stability has been previously reported in persons with ASD (e.g., Fournier et al., 2010; Minshew et al., 2004; Molloy et al., 2000). Nevertheless, it is unclear how postural stability is related to core ASD symptomatology.  

Objectives: The present study aimed to examine postural stability (i.e., balance time and degree of waiver) and postural symmetry (i.e., center of balance) during standing postures on a Wii balance board. The present sample only included individuals with ASD and typical development with IQs in the average range to minimize the impact of intellectual disability on findings.   

Methods: Twenty-six individuals with ASD and 26 age-and-IQ-matched individuals with typical development (age range 16-30 years) stood on the balance board on one leg or two legs with eyes opened or closed. Participants were timed for how long they could hold each posture. Additionally, postural stability and left-right center of balance were recorded by a Wii balance board connected via Bluetooth to a laptop computer. Balance board data were recorded every 16.7 milliseconds. Past research has demonstrated excellent reliability and validity in using the Wii balance board for research purposes (Clark et al., 2010).  Current ASD symptom severity was assessed using the Repetitive Behavior Scale-Revised (RBS-R), and the Social Responsiveness Scale (SRS). Additionally, self-rated empathy was assessed using the Empathy Quotient (EQ).  

Results: The results indicated significant group differences during one-legged standing in postural stability (balance time, p =.01, and postural drift, p =.02) but no significant group differences during two-legged standing. Degree of waiver during two-legged standing in the group with ASD was significantly related to current repetitive behaviors (RBS-R), r = +.48, social symptoms (SRS), r = +.54, and empathy (EQ), r = -.49 (i.e., decreased postural stability was associated with more severe symptoms and less empathy). Additionally, current repetitive behavior symptoms were significantly related to postural symmetry during two-legged standing, r = +.46 (i.e., decreased postural symmetry was associated with more severe symptoms).  

Conclusions:  The present results suggest that postural stability in adolescents and adults with ASD is impaired during one-legged standing relative to that of persons with typical development. This suggests that diagnostic group differences may emerge during more difficult standing postures, even in average-IQ individuals with ASD. Moreover, this is the first study to find that postural stability is significantly related to ASD symptom severity measures, suggesting that postural stability may be intimately intertwined with key ASD symptoms and may be more central to a diagnosis of ASD than previously thought. The decreased postural stability seen in the group with ASD may be symptomatic of cerebellar or corpus callosum atypicalities, which have been commonly reported in persons with ASD in the past and have been previously linked to symptom severity in ASD.  Understanding how postural stability may contribute to the social, communication, and repetitive behaviors of persons with ASD may be an important avenue for future research and intervention development.