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Abstract
The purpose of this dissertation is to examine the relationships among the brain, muscle and physical activity in children with CP. The aim of the first study was to determine the relationship(s) between physical activity, muscle co-contraction and muscle strength in children with CP. The main finding was that muscle co-contraction did not relate to functional strength in children with CP. However, muscle co-contraction during the more difficult stages of a progressive lateral step-up test was inversely related to physical activity in children with CP. The aim of the second study was to assess the relationships between muscle strength, muscle co-contraction and brain activity in the prefrontal cortex in children with CP. The main finding was that muscle weakness was associated with altered prefrontal cortex hemodynamic activation patterns in children with CP. Additionally, muscle co-contraction did not significantly relate to functional strength in children with CP. In conclusion, children with CP experience increased levels of muscle co-contraction associated, to a greater degree, by increased muscle weakness rather than pathological increases in antagonistic muscle activity. The ability to properly modulate muscle co-contraction could potentially influence physical activity participation in children with CP. Furthermore, the inability to modulate muscle co-contraction in children with CP was related to altered patterns of brain hemodynamic activation compared to typically developing children.