Dynamic Frequency Analyses of Lower Extremity Muscles during Sit-To-Stand Motion for the Patients with Knee Osteoarthritis

ObjectiveMuscle activities during the sit-to-stand motion (STS) are characterized by coordinated movements between hip extensors and knee extensors. However, previous reports regarding the STS and lower extremity muscle activities have focused on some quantitative assessment, but little qualitative research. This study aimed to examine the muscle activities of the lower extremity both quantitatively and qualitatively.MethodsStudy participants included 13 patients with knee osteoarthritis (knee OA) and 11 age-matched asymptomatic controls. The task was STS from a chair with a height-adjustable seat. EMG activities were acquired using surface electromyogram. The root mean square signals normalized as a percentage of maximum voluntary isometric contraction values (RMS%MVC) and the mean power frequency (MPF) were calculated.ResultsDuring STS, knee OA patients had increased RMS%MVC of the vastus medialis and raised MPF of the rectus femoris before buttocks-off.ConclusionThese findings suggest that STS of knee OA patients not only increased relative muscle activity of the vastus medialis, but also enlisted the rectus femoris in knee extension to improve muscle contraction force by activating more type II fibers to accomplish buttocks-off.坐站运动（sit-to-stand motion, STS）过程中的肌肉活动，以髋伸肌与膝伸肌的协同运动为核心特征。然而，既往关于STS与下肢肌肉活动的研究多聚焦于定量评估，定性相关研究则较为匮乏。本研究旨在从定量与定性双维度，探究下肢肌肉活动的特征与规律。 方法：本研究共纳入13例膝骨关节炎（knee osteoarthritis, knee OA）患者，以及11名年龄匹配的无症状对照者。实验任务为从高度可调座椅上完成坐站运动。采用表面肌电图采集肌电活动信号，并计算了以最大自主等长收缩值百分比归一化的均方根信号（root mean square percentage of maximum voluntary isometric contraction, RMS%MVC）与平均功率频率（mean power frequency, MPF）。 结果：在坐站运动过程中，膝骨关节炎患者的股内侧肌RMS%MVC显著升高；且在臀部离地阶段前，其股直肌的MPF亦出现上升。 结论：上述研究结果表明，膝骨关节炎患者的坐站运动不仅提升了股内侧肌的相对肌肉活动强度，还额外募集股直肌参与膝关节伸肌活动，通过激活更多Ⅱ型肌纤维以增强肌肉收缩力量，进而完成臀部离地动作。