The Effects of Isometric Extension at Different Knee Angles on Vastus Medialis Electromyographic Activity in Patients with Knee Joint Osteoarthritis

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[Purpose] The objective of the study was to examine maximum voluntary isometric contraction (MVIC) of the vastus medialis at different knee angles in a knee joint isometric extension exercise for the knee joint osteoarthritis patients, and to identify the most effective extension angle for strengthening the vastus medialis. [Subjects] The subjects of this study were 17 knee joint osteoarthritis patients. [Methods] In order for the knee joint to be fixed at a certain angle, SYSTEM 3Pro isokinetic exercise equipment was used, and comparisons of MVIC forces of the vastus medialis at different angles were made using surface electromyography (sEMG) measurements. [Results] MVIC forces of the rectus femoris, the vastus medialis, and the vastus lateralis were greatest at 15°, followed by 30° and 45°; MVIC force of the vastus medialis significantly increased at 15°. [Conclusion] We consider isometric exercise with the knee joint angle at 15° is conducive to strengthening the vastus medialis of knee joint osteoarthritis patients during their early exercise periods.