Effect of bimanual task constraint on grip and load force coordination in hemiplegic cerebral palsy
Date
2007
Authors
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Publisher
University of Delaware
Abstract
Introduction. Object manipulation is crucial for functional independence and quality of life, yet children with spastic hemiplegic cerebral palsy (CP) often have difficulty with tasks requiring use of their involved arm or hand. One popular method for evaluating manual control involves measuring the coordination of grip force (G) and load force (L). Evidence suggests that movements of both arms may arise from common bimanual control mechanisms during the execution of symmetrical bimanual tasks; however, little is known about the effect of a bimanual task constraint on G and L coordination for the CP population. Purpose. In this study, I aimed to determine how bimanual execution of a task affects G and L coordination by way of scaling and coupling. To accomplish this, I compared data from the bimanual task constraint with those collected during unimanual execution. I hypothesized that the CP group would show poorer scaling and coupling of G and L for their involved side during unimanual tasks and that the bimanual task constraint would prompt more ideal coordination of G and L for the involved side. Methods . Six CP participants (4 boys, 2 girls; mean age = 11.65 +/- 1.82) and 6 typically-developing (TD; 4 boys, 2 girls; mean age = 11.61 +/- 1.59) control participants matched for age and gender performed simple lifting and force-matching tasks by way of isometric unimanual or bimanual pulling using a device that measures G and L by way of six force transducers across two 4.5-inch handles. To provide a standardized measure of manual function, I also administered the Jebsen-Taylor Test of Hand Function to all participants. Results . Participants in the CP group showed severe involvement on one side through much longer times on the Jebsen-Taylor Test (p <0.05). Times to completion for all but two subtests were also longer for the non-involved side as compared to the dominant side of the TD group (p <0.05). Not all participants with CP were able to complete the ramp and hold task or oscillation tasks, but for the simple lifting task, CP participants showed lower cross-correlation coefficients and higher G/L ratios than their TD counterparts for most segments (p <0.05; lift, hold, drop), and there was no difference between segments within the group. Using both hands together did not bring about significant changes in scaling or coupling for the involved arm (p> 0.05). Discussion. Children with CP showed poorer force coordination by way of scaling (higher G/L ratios) and coupling (lower intra-limb cross-correlation coefficients) when using their involved arm in the tasks employed here. Force coordination of the non-involved arm was also impaired compared to the dominant arm of their TD counterparts. The bimanual task constraint had no effect on force coordination of the involved limb as there was still a disparity present between sides when both arms were used together during simple lifting.