Uncertainty of knee joint, muscle activity during knee joint torque exertion: the significance of controlling adjacent joint torque
Uncertainty of knee joint, muscle activity during knee joint torque exertion: the significance of controlling adjacent joint torque
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DOI：
10.1152/japplphysiol.00365.2005
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发表时间：
2005-09-01
影响因子：
3.3
通讯作者：
Akai, M
中科院分区：
文献类型：
--
作者：
Nozaki, D;Nakazawa, K;Akai, M
在被广泛用于控制肌肉活动的单关节力矩施加任务中，只指定了相应的关节力矩。然而，考虑到我们之前的结果，即使是单关节肌肉活动水平也是不确定的，而没有指定邻近关节的扭矩，忽略邻近关节可能会使手术变得不可靠。在这里，我们研究了膝关节扭矩产生的髋关节扭矩的量及其对膝关节肌肉活动的影响。12名健康受试者被要求施加不同水平的等长膝关节扭矩。膝关节和髋关节扭矩通过使用定制的装置获得。由于没有向受试者提供有关髋关节扭矩的信息，此处测量的髋关节扭矩是与任务相关的次要扭矩。不同受试者髋关节扭矩的大小不同，表明他们采取了不同的策略来完成任务。在一些受试者中，髋关节扭矩有相当大的内部变异性。这种变异性是不可忽视的，因为当受试者被要求改变策略时，由表面肌电(EMG)量化的膝关节肌肉相对于膝关节扭矩的活动水平发生了显著变化。这种变化是以一种非常系统的方式发生的：在伸膝的情况下，随着髋关节屈曲扭矩的增大，单关节和双关节伸膝的活动分别减少和增加。这些结果表明，由于髋关节扭矩的不确定性，单关节和双关节肌肉之间的相对贡献不可避免地存在主体间和/或试验间的变异性，这是传统的单膝关节扭矩用力的缺点。我们讨论了两个关节力矩都需要考虑的观点，将为各种有争议的问题带来见解，如肌电-力关系的形状，有助于决定肌肉力量训练效果的神经因素等。
In the single-joint torque exertion task, which has been widely used to control muscle activity, only the relevant joint torque is specified. However, the neglect of the neighboring joint could make the procedure unreliable, considering our previous result that even monoarticular muscle activity level is indefinite without specifying the adjacent joint torque. Here we examined the amount of hip joint torque generated with knee joint torque and its influence on the activity of the knee joint muscles. Twelve healthy subjects were requested to exert various levels of isometric knee joint torque. The knee and hip joint torques were obtained by using a custom-made device. Because no information about hip joint torque was provided to the subjects, the hip joint torque measured here was a secondary one associated with the task. The amount of hip joint torque varied among subjects, indicating that they adopted various strategies to achieve the task. In some subjects, there, was a considerable internal variability in the hip joint torque. Such variability was not negligible, because the knee joint muscle activity level with respect to the knee joint torque, as quantified by surface electromyography (EMG), changed significantly when the subjects were requested to change the strategy. This change occurred in a very systematic manner: in the case of the knee extension, as the hip flexion torque was larger, the activity of mono- and biarticular knee extensors decreased and increased, respectively. These results indicate that the conventional single knee joint torque exertion has the drawback that the intersubject and/or intertrial variability is inevitable in the relative contribution among mono- and biarticular muscles because of the uncertainty of the hip joint torque. We discuss that the viewpoint that both joint torques need to be considered will, bring insights into various controversial problems such as the shape of the EMG-force relationship, neural factors that help determine the effect of muscle strength training, and so on.