Postural control features in performance of Whole Body Reach

• Main Authors: Jen-Suh Chern, 陳貞夙
• Other Authors: Saiwei Yang
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/21825717578807879482

博士 === 國立陽明大學 === 醫學工程研究所 === 94 === Background and Motivation. Postural control training is the focus of stroke rehabilitation and assessment of postural control determines the efficacy of postural control training program. Voluntary movements perturb human postures and the degrees of perturbation depend on the amount of the movement of the center of mass needed. The amount of the movements of the center of mass needed is often context dependent. The clinical tools for assessment of postural control were easy and cost effectiveness but interval scores usually are unable to reveal the underlying mechanism of control and might be biased by subjective judgment. Laboratory assessment quantifies postural control by continuous variables such as center of pressure and ground reaction force. Those variables have been shown to be valid in measuring the postural control. Various approaches were available to improve the postural control of stroke patients and the results suggested that functional based and task oriented program were most effective. Whole Body Reach is a functional daily task and clinicians have been using it as an assessment tool and training program for postural control of stroke patients. Target locations were manipulated to grade the context of the demands of postural control. Rare researches on Whole Body Reach exist. The purpose of this study are to investigate the context effects on postural response, to examine the difference of postural response between stroke patients and normal adults during performance of Whole Body Reach, and to correlate the performance of Whole Body Reach with functional postural control. Methods. 33 stroke patients and 16 normal adults were recruited and under went a series of tests of postural control, including performance of Whole Body Reach, performance of Sit-to-Stand transfer, Berg Balance Scale and Functional Reach Test. The sequences of those tests were randomized. The context during WBR were manipulated with six target locations ( 2 distances x 3 directions) and each subjects have to perform two trials for each context. The foot pressure measurement mat was used to measure the center of pressure data and the AMTI force platform was used to measure the ground reaction data during performance of Whole Body Reach and Sit-to-Stand transfer. The foot pressure mat was able to provide data for calculations of CoP total path excursion, maximum CoP displacement in ML direction, maximum CoP displacement in AP direction, CoP average velocity and CoP maximum velocity for the whole body. The paretic/non-paretic limb weight bearing ration was also calculated by the output of the foot pressure mat. In addition, the footprint from the foot pressure mat was processed for calculation for the CoP initial position, CoP stop position, and the percentage of the MAP in relations to the foot length for individual foot. Finally, the movement time during WBR and STS was determined by the event markers activated by the experimenter. The AMTI force platform was able to provide data for calculation of GRF measures, including force variability, peak force, and force integral. Posturography and pedeography was plotted by the data from foot pressure mat for qualitative analysis of the postural response during Whole Body Reach and plots of the CoP shift direction were made to show the change of CoP direction during dynamic task performance. Results and Conclusions. Both normal adults and stroke patients were found to change their postural response during WBR according to the target locations. The hierarchical order in terms of degrees of the demands on postural control form the least to the greatest were found to be :10M, 30M, 10SS, 10AA, 30SS, 30AA. The effects of targets distance on postural response were prominent and consistent but the effects of target direction on postural response were not as prominent and inconsistent and interact with target distance. The stroke patients and normal adults were found to react to the demands of postural challenges during Whole Body Reach differently as measured by CoP Measures and GRF measures. The CoP measures were more capable of differentiating stroke patients and normal adults. The qualitative data also show different CoP patterns between groups with that in stroke was jerky and fluctuated and that in normal was smooth and straightforward. The correlations between Whole Body Reach and Berg Balance Score and Functional Reach distance were weak to moderate indicating that different aspect of dynamic postural control were measured by different tool but the moderate correlation between WBR for targets in the middle and STS suggested that the postural control demands of those tasks might be similar. The GRF measures turned out to be more sensitive parameter explain the variance of functional performance than the CoP measures. Differences between the involvement of the paretic and non-paretic limb in WBR was found for both groups, although some differences failed to reach statistical significant level. The involvement of the paretic (non-dominant) limb was increased during WBR when the targets were far and in the paretic (non-dominant) side. This result suggested that WBR for targets that were far and in the paretic side had the potential to train the function of the paretic limb of the stroke patients.