Normative Values of Knee Extensor Isokinetic Strength for Older Women and Implications for Physical Function

Abstract

Background and purpose: Lower-limb strength is required for everyday activities and thus its evaluation has been especially emphasized in older adults. Isokinetic testing is a criterion standard method to assess muscle strength; however, lack of reference values limits its usefulness in geriatric evaluation and rehabilitation. The aim of this study was to develop reference values of knee extensor isokinetic strength for older women. As a secondary aim, functional tests were performed for clinical significance validation.

Methods: A total of 453 older women aged 60 to 84 years participated in this study. Knee extensor isokinetic strength was measured using the Biodex System dynamometer at 60° per second. The Timed Up and Go test and the 5 times Sit-to-Stand test were used for functional performance evaluation. Participants were categorized into age groups of 5 years range. The 20th, 40th, 60th, and 80th percentiles were used for stratification purposes.

Results and discussion: As expected, mean strength values significantly decreased with advancing age groups. Isokinetic percentile groups are presented according to age. Individuals in the lower percentile strata showed significantly reduced performance in both the Timed Up and Go and 5 times Sit-to-Stand tests (P < .05).

Conclusion: This study provides normative values of isokinetic knee extensor strength in older women. The association between lower isokinetic knee extensor strength strata and reduced functional capacity supports the potential application of these reference values in clinical and research settings. Future studies should ascertain these findings in different female populations.