Effect of Symmetry Improvement in Weight Bearing on Postural Stability of Hemiparetic Patients

Impaired postural control has been known as the main cause of fall in hemiparesis after stroke. Is Asymmetry of weight bearing on lower limb is one of the prominent characteristics of postural imbalance in these patients. The aim of this study was to evaluate the effect of symmetry improvement in weight bearing through therapeutic interventions on postural stability in hemiparetic patients.

In this quasi – experimental study which 27 hemiparetic patients were selected through sample of convenience by simple method from men and women who were referred to neurology clinic of Hazrat-e-Rasool hospital. For postural assessment patients stood quietly with open eyes and close eyes on force plates. Primary assessments included evaluation of asymmetry index (AI), RMS COP displacement (Root Mean Square of Center of Pressure) and RMS COP velocity in both frontal and sagital planes. Then a 10mm lift was inserted under the unaffected limb and primary assessments were repeated. Data were analyzed by repeated measure ANOVA test.

Simple main effect of lift on asymmetry index was significant (P<0/0001). There was no significant interaction between vision and lift. Simple main effect of lift on postural stability variables was also non significant (for RMS COP displacement in frontal and sagital planes P=0.186 and P=0.245, respectively and for RMS COP velocity P=0.259 and P=0.342 respectively).

Inserting a lift can improve symmetry by shifting center of gravity to midline. Since symmetry improvement did not decrease postural instability, asymmetric weight bearing can not be the primary cause of postural instability and may not be the principal target of rehabilitation programs aiming at restoring standing balance after stroke.