This study examined the effectiveness of mental imagery compared to visual feedback of postural sway in reestablishing symmetrical stance stability in hemiplegic patients. Thirty second measurements of stance symmetry were accomplished . through the use of a computerized standing forceplate. This forceplate also has the capacity to provide continuous feedback of changes in weight distribution during a 30 second trial. The imagery technique used was based on the assumptions of ideokinetic facilitation (Sweigard, 1974).
Twenty hemiplegic patients (a year or more post-stroke) were randomly, and equally distributed to one of the two groups; the Imagery Group, to test the effects of imagery, or the Visual Feedback Group, to test the effects of visual feedback from a forceplate. Each individual participated in the study for 5 consecutive days. On each of these days, 30 second pre-and post-test measures were taken. A quasi experimental design was used, with the first test on day 1 serving as each subject's control.
A three-way ANOVA with two repeated factors was used to test the effects of imagery and visual feedback on the ability of stroke patients to center themselves over their base-of-support. The independent variables were: group, day, and test. The dependent variables were: lateral stance symmetry, anterior- posterior symmetry, and sway .
The hypothesis was that imagery would be significantly more effective than feedback from a forceplate for reestablishing lateral stance symmetry. The results, in fact, showed that both groups demonstrated equal ability in reestablishing lateral symmetry. The ANOVA also showed that although the Imagery Group took longer to reestablish symmetry, they may prove to be more symmetrical over time. A longer study is needed to establish this. For anterior-posterior distribution, a curious difference between the groups was noted. The Imagery Group showed a strong shift from an anterior to a posterior weight distribution over the course of the experiment. A posterior shift is seen in individuals when they are able to effectively use imagery. This seems to indicate that as an individual increases in their ability to use imagery they are able to regain control in the motor task of stance symmetry.
It is encouraging to note that individuals in both groups showed a significant degree of learning over the course of this experiment. This would indicate that an individual, one year or more post-stroke still has the possibility to improve their lateral symmetrical postural stability, and functional abilities thereby enhancing their quality of life through additional rehabilitative techniques of Imagery and Visual Feedback from a forceplate. Further studies are needed to explore these techniques and their effects in changing functional gait patterns, and quality of movement for other activities of daily living.
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