Cleather Daniel J, Southgate Dominic F L, Bull Anthony M J
School of Sport, Health and Applied Sciences, St. Mary's University, Twickenham, UK.
Department of Bioengineering, Imperial College London, London, UK.
J Theor Biol. 2015 Jan 21;365:217-25. doi: 10.1016/j.jtbi.2014.10.020. Epub 2014 Oct 24.
The role of the biarticular muscles is a topic that has received considerable attention however their function is not well understood. In this paper, we argue that an analysis that is based upon considering the effect of the biarticular muscles on the segments that they span (rather than their effect on joint rotations) can be illuminating. We demonstrate that this understanding is predicated on a consideration of the relative sizes of the moment arms of a biarticular muscle about the two joints that it crosses. The weight of the previous literature suggests that the moment arms of both the biarticular hamstrings and gastrocnemius are smaller at the knee than at the hip or ankle, (respectively). This in turn leads to the conclusion that both biarticular hamstrings and gastrocnemius are extensors of the lower limb. We show that the existence of these biarticular structures lends a degree of flexibility to the motor control strategies available for lower limb extension. In particular, the role of the gastrocnemius and biarticular hamstrings in permitting a large involvement of the quadriceps musculature in closed chain lower limb extension may be more important than is typically portrayed. Finally, the analysis presented in this paper demonstrates the importance of considering the effects of muscles on the body as a whole, not just on the joints they span.
双关节肌的作用是一个备受关注的话题，然而其功能尚未得到充分理解。在本文中，我们认为基于考虑双关节肌对其所跨越节段的影响（而非其对关节旋转的影响）的分析可能具有启发性。我们证明，这种理解基于对双关节肌在其跨越的两个关节处的力臂相对大小的考虑。以往文献表明，双关节的腘绳肌和腓肠肌在膝关节处的力臂分别比在髋关节或踝关节处小。这进而得出结论，双关节的腘绳肌和腓肠肌都是下肢的伸肌。我们表明，这些双关节结构的存在为下肢伸展的运动控制策略提供了一定程度的灵活性。特别是，腓肠肌和双关节腘绳肌在允许股四头肌大量参与闭链下肢伸展中的作用可能比通常所描述的更为重要。最后，本文所呈现的分析表明，考虑肌肉对整个身体的影响，而不仅仅是对其所跨越关节的影响，是很重要的。
