Background: Hemiparesis is the most common cause of disability after stroke. The role of concentric exercises has not been recognized in anticipatory postural adjustment due to controversy on the effects of these exercises on upper motor neuron lesions. The purpose of this study was to determine feed forward responses disturbances of postural control mechanism and the effects of concentric exercises of involved lower-extremity muscles on the treatment of these impairments in hemiparetic patients of Kahrizak Charity Foundation in 2003.

Methods and Materials: Thirty four secondary hemiparetic patients to stroke were participated in this clinical trial. All patients were screened to ensure that their time since onset of stroke was at least 12 months. Patients were assigned randomly to either an experimental group or a control one. The isometric strength (kg) of seven muscle groups was measured with a hand-held dynamometer. Feed forward responses (ordinal scale) were assessed using Functional Reach Test (FRT) before and after 12 sessions of intervention. All patients were assessed by two raters who were blinded group allocation. The experimental group received strengthening exercises in addition to functional and balance exercises. The control group received only functional and balance exercises. Independent and paired t-tests, Mann-Whitney and Wilcoxon tests were used to compare the pretreatment and post-treatment results.

Results : The mean age of experimental group and control group was 49.3 ± 7.1 and 55.5 ± 3, respectively. In parallel feet position, anticipatory postural adjustments increased only in the experimental group, significantly from 1.29±0.2 to 2.9±0.17 after intervention (P<0.0001). In this position, the comparison of post-treatment results showed that mean of anticipatory postural adjustments in experimental group (2.9±0.17) was higher that in control that in (1.18±0.18) (P<0.0001). A significant improvement (P<0.0001) was seen in the experimental (1.59±0.21) compared to control group (0.12±0.08) with respect to mean difference of FRT. All muscular groups strength was correlated significantly with the FRT scores in tandem (r=0.483-0.726) and parallel (r=0.401-0.645) feet position.

Conclusion: The results of this study support the effectiveness of muscle strength training of involved lower extremity to improve feed forward responses of postural control mechanism for anticipatory postural adjustment in hemiparetic patients in the chronic stage of rehabilitation following stroke. The results also are in support of using the involved lower extremity muscle strength to evaluate postural anticipatory control.