Reliability of an isometric and isokinetic strength testing protocol of the knee and ankle in young adults

Background: Isokinetic dynamometers are becoming very common in assessing muscle strength and pathology, both in research and clinical practice, but for most of those devices reliability studies are still needed to support their extended use. The aim of this study is to assess the test-retest reliability also in health adults. Methods: Thirty adults (13 male and 17 females; mean age 25.4 ± 2.7 years) were recruited among University students. They participated to two testing sessions (7 day apart) in which they performed isokinetic and isometric strength assessment of the knee and ankle flexion and extension. Results: All variable showed an Intra-class correlation coefficient higher than 0.7 (isometric knee extension 0.96; isokinetic knee extension 0.96; isokinetic knee flexion 0.97; isometric ankle right flexion pl and flexion do 0.75-0.96; isometric ankle left flexion pl and flexion do 0.78-0.97; isokinetic ankle right flexion pl and flexion do 0.88-0.73; isokinetic ankle right flexion pl and flexion do 0.88-0.85) and paired-sample t-test showed no significant difference. Moreover, most of the recorded values were included within the upper and lower limits of agreement. Conclusion: Multi-joint evaluation system is a reliable device to assess knee and ankle isokinetic and isometric strength among healthy adults.