Anticipatory Postural Adjustments in Children with Typical Development, Hemiplegia and Diplegia

Anticipatory postural adjustments (APAs) play an important role in the performance of many functional activities that require the maintenance of standing balance. Despite the significance of this postural control mechanism, little is known about the organization of APAs, in children with typical development and children with cerebral palsy (CP), during the performance of arm movements executed while standing. The purpose of this thesis is to determine whether APAs are present in these populations of children. A second purpose is to describe the organization, as well as any similarities and differences, in their APAs. The final purpose is to investigate the association between APAs and functional performance by correlating the APA integrals of the children with CP with their scores on measurement tools commonly administered in clinical settings. Children between the ages of 7 – 18 years were recruited for both studies. APAs were measured by recording electromyographic activity in six muscles of the trunk and legs (R and L sides) and calculating changes in center of pressure (COP) and peak arm acceleration. The first study reports on APAs in children with typical development during the performance of bilateral, reciprocal and unilateral arm movements. The results indicate that typically developing children (n=10) generate patterns of anticipatory muscle activation and suppression and center of pressure changes similar to those reported in healthy adults. They can also produce task specific sequencing of muscle activity and differentiate between symmetrical and asymmetrical perturbations. In the second study, data were collected during arm flexion and extension movements performed by children with hemiplegia (n=9) and diplegia (n=9). We found that children with CP are able to generate anticipatory muscle activity and produce task specific APAs. However, only children with typical development and hemiplegia demonstrate changes in COP similar to those described in healthy adults. The children with diplegia demonstrate higher baseline muscle activity and smaller APA magnitudes than children with typical development and hemiplegia and during bilateral shoulder extension, change in COP is posterior, and peak acceleration of arm movement is reduced. Recommendations for treatment strategies to enhance APAs in children with CP are presented. Finally, correlations between APA EMG integrals and scores on clinical measures of gross motor performance and balance were analyzed to explore relationships between APAs and function, and EMG integrals were quantified using a Symmetry Index (SI). The results of these findings are presented and discussed.