|Institution:||University of Oregon|
|Keywords:||Cerebral palsy; Posture; Reaching; Sitting; Trunk control|
|Full text PDF:||http://hdl.handle.net/1794/19189|
This dissertation aimed to investigate the relationship between posture and reaching in both healthy and pathological conditions, approaching the trunk as a multi-segmented structure. For this purpose, neuromuscular and kinematic profiles were recorded from trunk and arm during seated reaches providing mid-rib vs pelvic levels of trunk support. Healthy adults with mature postural and reaching abilities displayed invariant arm kinematics during the reach. However, participants displayed increased anticipatory control and earlier activation of cervical muscles with mid-rib support. Participants also presented increased compensatory responses of paraspinal muscles when responding to the increased trunk balance demands with pelvic support. Children with moderate/severe cerebral palsy (CP) cannot maintain an upright sitting position and thus cannot create a stable postural frame around which upper limb movements are planned and executed. A second set of studies examined postural and reaching characteristics in these children, while applying axillae, mid-rib or pelvic levels of support. Participants were classified according to their intrinsic level of trunk control as mild, moderate and severe. With higher levels of support children with moderate to severe impairments in trunk control showed improvements of head and trunk control along with enhanced reaching performance. Participants with mild trunk dysfunction were able to sit independently and thus did not demonstrate significant changes in postural and reaching proficiency across levels of external trunk support. Electromyographic profiles were more variable depending on the severity of intrinsic trunk control. Overall, participants in the mild group presented more refined timing mechanisms for both anticipatory (closer to reaching onset) and compensatory (reduced latency) postural adjustments during the reach across all levels of support. Participants in the moderate group displayed earlier muscle onsets and more efficient arm/trunk muscle amplitudes with higher levels of support. Participants in the severe group showed very limited capability of anticipatory control of paraspinal muscles, delayed muscle onsets and variable muscle amplitudes across levels of support. These results emphasize the complex neuro-anatomical nature of trunk control during reaching. Also, they highlight that inefficient postural control while sitting significantly impacts children with CP and trunk dysfunction. This dissertation includes previously unpublished co-authored material. Advisors/Committee Members: Karduna, Andrew (advisor).