Kukić Filip, Mrdaković Vladimir, Stanković Aleksandar, Ilić Duško
Police Sports Education Center, Abu Dhabi Police, Abu Dhabi 253, United Arab Emirates.
Faculty of Sport and Physical Education, University of Belgrade, 11030 Belgrade, Serbia.
Biology (Basel). 2022 Oct 12;11(10):1490. doi: 10.3390/biology11101490.
This study investigated the effects of knee joint angle on muscle activation, exerted torque, and whether the knee angle affects the muscle activation−torque ratio. Nine healthy adult male participants participated in the study. They performed maximal voluntary isometric contraction (MVIC) at six (80°, 90°, 100°, 110°, 120°, and 130°) different knee joint angles (i.e., angles between the thigh and shin bones). Their maximal torque was assessed utilizing an isokinetic chair, while their muscle activation (root mean square [RMS]) was assessed using an eight-channel single differential surface EMG sensor. For the purposes of the torque−knee angle relationship and muscle activation−knee angle relationship, the torque and RMS were normalized relative to the maximal value obtained by each participant. To evaluate the muscle activation−torque ratio in function of knee angle, RMS was normalized relative to the corresponding torque obtained at each knee angle. Repeated measure analysis of variance was used to investigate the effects of knee angle on muscle activation, torque, and muscle activation−torque ratio. There was a significant effect of knee joint angle on normalized torque (F = 27.521, p < 0.001), while the activation of vastus lateralis and vastus medialis remained unchanged. The changes in knee angle affected the muscle activation−torque ratio of vastus lateralis (Chi-square = 16.246, p = 0.006) but not the vastus medialis. These results suggest that knee joint angles from 80° to 130° provide a stable milieu for muscle electrification, while mechanical factor such as knee joint angle (i.e., lever arm length) affect the torque output when one needs to contract quadriceps maximally during the isometric contraction.
本研究调查了膝关节角度对肌肉激活、施加扭矩的影响，以及膝关节角度是否会影响肌肉激活-扭矩比。九名健康成年男性参与者参与了该研究。他们在六个（80°、90°、100°、110°、120°和130°）不同的膝关节角度（即大腿骨和胫骨之间的角度）下进行了最大自主等长收缩（MVIC）。利用等速椅评估他们的最大扭矩，同时使用八通道单差分表面肌电图传感器评估他们的肌肉激活（均方根[RMS]）。为了研究扭矩-膝关节角度关系和肌肉激活-膝关节角度关系，将扭矩和RMS相对于每个参与者获得的最大值进行归一化。为了评估膝关节角度对肌肉激活-扭矩比的影响，将RMS相对于每个膝关节角度获得的相应扭矩进行归一化。采用重复测量方差分析来研究膝关节角度对肌肉激活、扭矩和肌肉激活-扭矩比的影响。膝关节角度对归一化扭矩有显著影响（F = 27.521，p < 0.001），而股外侧肌和股内侧肌的激活保持不变。膝关节角度的变化影响了股外侧肌的肌肉激活-扭矩比（卡方 = 16.246，p = 0.006），但对股内侧肌没有影响。这些结果表明，80°至130°的膝关节角度为肌肉起电提供了一个稳定的环境，而在等长收缩期间需要最大程度收缩股四头肌时，诸如膝关节角度（即力臂长度）等机械因素会影响扭矩输出。
