Reliability and Validity of Measurements of Knee Extension Force Obtained by Hand-held Dynamometry from Community Dwelling Elderly Women

Abstract

Purpose: The purpose of this study was to examine the inter-rater reliability and validity of knee extension force measures obtained from community dwelling elderly women. Subjects: Fifty-five community dwelling women 60 or more years old (mean = 75.3 ± 8.6) participated. Methods: The women were interviewed to obtain anthropometric and demographic data and relevant medical history. The Physical Functioning Scale of the SF-36 was administered. The knee extension force of both the dominant and nondominant lower extremities was measured by either 1 or both of 2 testers using a hand-held dynamometer. The knee extension forces of the 2 lower extremities were combined and normalized against body weight. Inter-rater reliability was assessed using data from the 32 subjects, who were tested by both testers. Correlations were determined between knee extension force measurements and SF-36 scores. The actual knee extension force values obtained from the 25 subjects, who were between 60 and 79 years of age, were compared with previously published norms. Results: The inter-rater reliability of the knee extension forces measured by the 2 testers was a good (intraclass correlation coefficient = .885), but the forces measured by the stronger tester were significantly higher (t = 4.794, p < .001). Physical functioning scores correlated significantly with actual (r = .379) and normalized (r = .521, R = .580) knee extension forces. The knee extension forces of the 25 age appropriate subjects were not significantly different from previously published norms (F = 0.000, p = .989). Conclusion: The measures of knee extension force obtained in this study proved to be both reliable and valid. Hand-held dynamometry may be a legitimate procedure for use with elderly community dwelling women.