CONTROL OF AN EXTERNAL FORCE IN LEG EXTENSIONS IN HUMANS
CONTROL OF AN EXTERNAL FORCE IN LEG EXTENSIONS IN HUMANS
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DOI：
10.1113/jphysiol.1992.sp019397
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发表时间：
1992-11-01
影响因子：
5.5
通讯作者：
SCHENAU, GJV
中科院分区：
文献类型：
--
作者：
JACOBS, R;SCHENAU, GJV
1.我们研究了单关节和双关节肌肉执行不同功能的假设：前者主要依赖于其机械优势，而后者被认为主要与控制外力的方向有关。七名受试者被要求从三个不同的位置向各个方向施加恒定的外力。对力矢量的幅度（300和600 N）和方向给出反馈。在每次试验期间，记录受试者的位置。地面反作用力和肌肉活动（EMG）从主要的单关节和双关节大腿肌肉记录。连杆段建模用于获得膝关节和髋关节的净力矩。对于每一块肌肉，计算每个力方向上的机械效益。控制地面反作用力的任务是在个体间差异很小的情况下进行的，这反映在不同的力和EMG变量的变异性上。股直肌和腘绳肌的活动度差与膝关节和髋关节周围的净力矩差呈线性关系，相关系数分别为0.96（300 N）和0.97（600 N），且与体位无关。该活动差异与力矢量角度之间的平均相关性也很高：-0.95（300 N）和-0.94（600 N）。单关节和双关节肌肉的活动增加时，可以从他们获得更大的机械优势，除了股二头肌（短头）。结果支持的假设，即双关节肌肉有一个独特的作用，在控制分配的净力矩的关节，因此，在控制施加在环境上的外力的方向。
1. We investigated the hypothesis that mono- and bi-articular muscles perform different functions: the former are chiefly dependent on their mechanical advantage, while the latter are considered to be mainly concerned with controlling the direction of an external force.2. Seven subjects were asked to exert a constant external force in various directions from three different positions. Feedback was given on the amplitude (300 and 600 N) and direction of the force vector.3. During each trial the position of the subject was registered. Ground reaction force and muscle activity (EMG) from the main mono- and bi-articular upper leg muscles were recorded. Link segment modelling was used to obtain net moments about the knee and hip joints. For each muscle the mechanical advantage was calculated in each force direction.4. The task of controlling the ground reaction force was performed with little interindividual variation as reflected by the variability of the different force and EMG variables.5. A linear relationship between the difference in activity of rectus femoris and hamstrings and the difference in net moment around the knee and hip was found. This relationship showed very high correlation coefficients of 0.96 (300 N) and 0.97 (600 N) and was independent of position. Mean correlations between this activity difference and the angle of the force vector were also high: -0.95 (300 N) and -0.94 (600 N).6. The mono- as well as the bi-articular muscles increased in activity when a larger mechanical advantage could be obtained from them, except for the biceps femoris (short head).7. The results support the hypothesis that bi-articular muscles have a unique role in controlling the distribution of net moments about the joints and, as a consequence, in controlling the direction of the external force exerted on the environment.