| Purpose/Hypothesis. The purpose of this study was to: (1) assess the influence of weakness on asymmetry of lower limb loading, (2) assess the influence of weakness on lower extremity kinetics and (3) assess the associations among asymmetry of lower limb loading, balance, balance confidence and strength with physical function.;Materials/Methods. Twenty seven participants post hip fracture (age; 80.3 +/-7.6 years) and 15 elderly controls (age; 73.2 +/-4.9 years) volunteered for this study. Participants with >80% involved side strength (involved/uninvolved) were assigned to the strong group and participants with <80% involved side strength were assigned to the weak group. Each subject performed two sit to stand tasks wearing a vest; one with no weight (0% BW) and one with 5% body weight (5% BW) added to the vest. During each sit to stand task, ground reaction (vGRF) forces and hip/knee kinetics were determined using an 8 segment biomechanical model of the lower extremities. Self report and performance instruments were used to assess function (Lower Extremity Measure), balance (BERG Balance Scale) and Activities Balance Confidence (ABC scale). Two way mixed effects ANOVA models were used to assess equivalence across groups (Hip Fracture Weak (HFW), Hip Fracture Strong (HFS), and Elderly Controls (EC)). Regression analysis was used to assess which variables (asymmetry, weakness, balance, or balance confidence) best predicted function.;Results. Weakness did not influence asymmetry of lower limb loading. There were no statistical differences between the HFS and HFW groups. The effect of a weighted vest was to increase asymmetry for participants with hip fracture, but not controls. Hip and knee kinetics were lower on the involved side compared to the uninvolved side and controls during a sit to stand task. Asymmetry of lower limb loading (17.5%), BERG Balance Scale (8.6%) and Activities Balance Confidence Scale (29.2%) predicted Lower Extremity Measure, but not strength.;Conclusions. Weakness is not associated with asymmetry of lower limb loading post hip fracture. Lower muscular contributions of the involved limb and higher muscular contributions of the uninvolved limb caused asymmetry of lower limb loading. Asymmetry is an important predictor of physical function post hip fracture.;Clinical significance. Augmenting the focus of rehabilitation protocols to target restoring symmetry and increasing balance confidence may improve function and reduce disability following a hip fracture. |
