Diagnosis and Treatment of Muscle Inhibition of the Extensor Muscles of the Knee in Elderly

Peak torque change

时间窗: Baseline and 9th intervention week

Maximal isometric knee extensor torques were obtained on an isokinetic dynamometer (Biodex System 3; Biodex Medical Systems). Participants were positioned on the dynamometer according to the manufacturer's recommendations. After a warm-up and a familiarization session, each subject executed three maximal isometric knee extensor contractions with the knee fixed at a flexion angle of 60o. Each contraction lasted for 5 s and a 2-min interval was observed between consecutive contractions.

Electromyographic activation change

时间窗: Baseline and 9th intervention week

An eight channel EMG system (AMT-8, Bortec Biomedical Ltd., Canada) connected to a Windaq data acquisition system (Dataq Instruments Inc., USA) was used during the maximal isometric and concentric knee extensor contractions. EMG signals were obtained following the recommendations by Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles with respect to skin preparation and electrode positioning. Passive bipolar electrodes (Meditrace - 100; Ag/AgCl; inter-electrode distance = 2.2 cm) were placed on the skin covering the rectus femoris, vastus lateralis and vastus medialis muscles. A reference electrode was placed on the medial surface of the tibia. EMG signals were digitized with a sampling frequency of 2000 Hz per channel with a 16 bits analogue-to-digital board DI-720 (Dataq Instruments Inc., USA) and stored for further analysis.

Muscle architecture change

时间窗: Baseline and 9th intervention week

An ultrassound system (SSD 4000, 51 Hz, ALOKA Inc., Japan) with a linear array probe (60 mm, 7.5 MHz), was used to determine the thickness, fascicle length, and pennation angle of the vastus lateralis muscle. Ultrassound images were obtained at rest with the subject sitting on the chair of an isokinetic dynamometer (Biodex System 3; Biodex Medical Systems, Shirley, NY) with the hip and knee flexed at 85o and 90o, respectively. All images were captured in the sagittal plane of vastus lateralis (at midway between the lateral condyle of the femur and the greater trochanter). The ultrasound probe was positioned in the approximate direction of the vastus lateralis muscle fibers (long axis with respect to the limb).