Study of Compensatory Postural Control Strategies in Children with Down Syndrome in Different Sensory Conditions

One of the major early symptoms seen in almost all children with Down syndrome is learning disabilities and developmental delays. Postural control studies using force plates in people with Down syndrome have revealed more information about the differences between these children and normal peers. Given the differences in children with Down syndrome in balance and their delays in developing balance–related skills, they seem to use different compensatory strategies to maintain their balance. Therefore, the present study aimed to determine compensatory postural control strategies in children with Down Syndrome in different sensory situations.

The present study was a causal–comparative study. This study investigated compensatory postural control strategies of children with Down syndrome in different sensory conditions. The sample size for the present study was determined by G*Power software to be 16, which was reduced to 14 due to the absence of 2 subjects. Therefore, the sample size in this study was 14 children with Down syndrome aged 6 to 11 years. They were under the supervision of Ahmadabad Ghaem Rehabilitation Center in Eslamshahr City, Iran, in the academic year 2018–2019. Also, 13 healthy children of the same age from primary schools in Eslamshahr City were included as the control group. The inclusion criteria were children with Down syndrome, with normal vision, no history of fractures and deformities in the lower extremities, and non–athletes. The range of IQs acceptable for children with Down syndrome was 60 to 85. Any participant who was unable to continue the study was excluded from the study. The sensory organization test assesses the performance of the proprioceptive and vestibular visual senses in postural control. The test has 6 different sensory states. According to the defined protocol, each test is performed 3 times. The average indicates the postural control strategy (0 to 100), with 0 representing the hip and 1 for the ankle strategies. The force plate is fixed in the first three positions and moves in the anterior and posterior directions in the other three states. People with bare feet stood on the machine, each attempt lasting 20 seconds with equal rest intervals of 5 minutes between the three defined attempts on the device. Descriptive statistics indices, including frequency, mean, standard deviation, and inferential statistics, including multivariate analysis of variance (MANOVA) and Tukey's post hoc test, were calculated using SPSS 25 at a significant level of 0.05.

The results showed no significant difference between the two groups in the first situation, where all the sensory information was available (p=0.543). Both groups used the ankle strategy. In the second condition, with the deletion of the visual sensory input, and the third condition, with eyes open but the visual environment moving to result in false visual arrays, a significant difference was observed between the two groups (p=0.001). The normal group used the ankle strategy, and the Down syndrome group used the hip strategy. In the fourth situation, where the force plate was mobile and resulted in the manipulation of proprioception information, there was a significant difference between the two groups in the stance control compensatory strategy (p=0.001), and both groups used the hip strategy. There was no significant difference between the two groups in the fifth condition when eyes closed, and the mobile force plate eliminated the proprioceptive but kept the vestibular information (p=0.606). In the sixth situation, where proprioceptive information was removed, and the person was given inappropriate visual information to evaluate vestibular information, there was no significant difference between the two groups (p=0.671). In this situation, both groups used the step strategy.

Based on the findings of this research, when removing a sensory system, especially the sense of vision, children with Down syndrome adopt more cautious strategies compared to healthy children.