Reliability of a device for the knee and ankle isometric and isokinetic strength testing in older adults

Background: Lower extremity muscle mass, strength, power, and physical performance are critical determinants of independent functioning in later life. Isokinetic dynamometers are becoming very common in assessing different features of muscle strength, in both research and clinical practice; however, reliability studies are still needed to support the extended use of those devices. Objective: The purpose of this study is to assess the test-retest reliability of knee and ankle isokinetic and isometric strength testing protocols in a sample of older healthy subjects, using a new and untested isokinetic multi-joint evaluation system. Methods: Sixteen male and fourteen female older adults (mean age 65.2 ± 4.6 years) were assessed in two testing sessions. Each participant performed a randomized testing procedure that includes different isometric and isokinetic tests for knee and ankle joints. Results: All participants concluded the trial safety and no subject reported any discomfort throughout the overall assessment. Coefficients of correlation between measures were calculated showing moderate to strong effects among all testretest assessments and paired-sample t test showed only one significant difference (p<0.05) in the maximal isokinetic bilateral knee flexion torque. Conclusions: The multi-joint evaluation system for the assessment of knee and ankle isokinetic and isometric strength provided reliable testretest measures in healthy older adults. Level of evidence: Ib.