Toussaint H M, van Baar C E, van Langen P P, de Looze M P, van Dieën J H
Department of Health Science, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
J Biomech. 1992 Nov;25(11):1279-89. doi: 10.1016/0021-9290(92)90283-7.
Net joint moments are often used to quantify the loading of structures (e.g. the intervertebral disc at L5S1) during lifting. This quantification method is also used to evaluate the loading of the knee, for instance, to determine the effect of backlifting as opposed to leglifting. However, the true loading of the joint as derived from net joint moments can be obscured by a possible co-contraction of antagonists. To unravel the mechanisms that determine the net joint moments in the knee, the leglift was compared to the backlift. Although a completely different net knee moment curve was found when comparing the two lifting techniques, it appeared to be closely related to the ground reaction force vector and its orientation with respect to the joint centre of rotation (R > 0.995). This close relation was established by co-contraction of both flexors and extensors of the knee. Furthermore, a close relation appeared to exist between the joint moment difference between hip and knee and the activity difference between rectus femoris muscle and hamstring (R = 0.72 and 0.83 in leglift and backlift, respectively). The knee-ankle joint moment difference and the activity of the gastrocnemius showed a close relation as well (R = -0.89 and 0.96 in leglift and backlift, respectively). These relations can be interpreted as a mechanism to distribute net moments across joints. It is concluded that during lifting tasks the intermuscular coordination is aimed at coupling of joint moments, such that the ground reaction force points in a direction that provides balance during the movement. The use of net joint moments as direct indicators for joint loading (e.g. knee) seems, therefore, questionable.
净关节力矩常用于量化举重过程中结构（如腰5骶1椎间盘）的负荷。这种量化方法也用于评估膝关节的负荷，例如，确定背举与腿举相比的效果。然而，由净关节力矩得出的关节实际负荷可能会因拮抗肌的共同收缩而被掩盖。为了揭示决定膝关节净关节力矩的机制，对腿举和背举进行了比较。尽管比较这两种举重技术时发现了完全不同的净膝关节力矩曲线，但它似乎与地面反作用力矢量及其相对于关节旋转中心的方向密切相关（R>0.995）。这种密切关系是通过膝关节屈伸肌的共同收缩建立的。此外，髋关节和膝关节之间的关节力矩差异与股直肌和腘绳肌之间的活动差异之间似乎也存在密切关系（腿举和背举中R分别为0.72和0.83）。膝关节-踝关节力矩差异与腓肠肌的活动也显示出密切关系（腿举和背举中R分别为-0.89和0.96）。这些关系可以解释为一种在关节间分配净力矩的机制。得出的结论是，在举重任务中，肌肉间协调旨在使关节力矩耦合，以便地面反作用力指向在运动过程中提供平衡的方向。因此，将净关节力矩用作关节负荷（如膝关节）的直接指标似乎是值得怀疑的。
