Relationship between knee extension force and stand-up performance in community-dwelling elderly women

Objective: To describe the relationship between knee extension force and stand-up performance. Design: Prospective, cross-sectional, descriptive, and correlational. Setting: Community. Participants: Fifty-five community-dwelling women 60 or more years old. Interventions: Information pertaining to stand-up performance was gathered via structured questions. The time to complete 1 sit-to-stand from a bench of known height (16in) was obtained in conjunction with subjects' ratings of perceived exertion (RPEs) relative to the task. Bilateral lower extremity knee extension strength was measured with a hand-held dynamometer and normalized against body weight. Main Outcome Measures: Total knee extension forces (raw and body-weight normalized values) generated by each subject were correlated with 3 measures of stand-up performance. Results: Low to moderate correlations (r = -.323 to -.526) were found between knee extension forces and the stand-up performance measures of bench stand time and stand-up difficulties. Normalized knee extension force had a higher correlation than raw knee extension force with stand-up difficulties and RPE. Correlations were higher when the curvilinear nature of the relationship was taken into account. The highest correlation was between normalized knee extension force and the RPE associated with the bench stand task (r = -.767). Conclusion: Knee extension force offers an important but incomplete explanation of stand-up performance from low surfaces by elderly women. Interventions leading to increased knee extension force may improve stand-up performance.