Lieber R L, Fridén J
Department of Orthopaedics, University of California, San Diego, USA.
J Electromyogr Kinesiol. 1998 Apr;8(2):93-100. doi: 10.1016/s1050-6411(97)00025-4.
This review describes a series of experiments in which sarcomere length was measured in human wrist muscles to understand their design. Sarcomere length measurements were combined with studies on cadaveric extremities to generate biomechanical models of human wrist function and to provide insights into the mechanism by which wrist strength balance is achieved. Intraoperative measurements of the human extensor carpi radialis brevis (ECRB) muscle during wrist joint rotation reveal that this muscle appears to be designed to operate on the descending limb of its length-tension curve and generates maximum tension with the wrist fully extended. Interestingly, the synergistic extensor carpi radialis longus (ECRL) also operates on its descending limb but over a much narrower sarcomere length range. This is due to the longer fibers and smaller wrist extension moment arm of the ECRL compared to the ECRB. Sarcomere lengths measured from wrist flexors are shorter compared to the extensors. Using a combination of intrapoperative measurements on the flexor carpi ulnaris (FCU) and mechanical measurements of wrist muscles, joints and tendons, the general design of the prime wrist movers emerges: both muscle groups generate maximum force with the wrist fully extended. As the wrist flexes, force decreases due to extensor lengthening along the descending limb of their length-tension curve and flexor shortening along the ascending limb of their length-tension curve. The net result is a nearly constant ratio of flexor to extensor torque over the wrist range of motion and a wrist that is most stable in full extension. These experiments demonstrate the elegant match between muscle, tendon and joints acting at the wrist. Overall, the wrist torque motors appear to be designed for balance and control rather than maximum torque generating capacity.
本综述描述了一系列实验，在这些实验中测量了人类腕部肌肉的肌节长度以了解其结构。肌节长度测量与对尸体肢体的研究相结合，以生成人类腕部功能的生物力学模型，并深入了解实现腕部力量平衡的机制。在腕关节旋转过程中对人桡侧腕短伸肌（ECRB）进行术中测量发现，该肌肉似乎设计为在其长度 - 张力曲线的下降段运作，并在腕部完全伸展时产生最大张力。有趣的是，协同肌桡侧腕长伸肌（ECRL）也在其下降段运作，但在更窄的肌节长度范围内。这是由于与ECRB相比，ECRL的纤维更长且腕部伸展力矩臂更小。与伸肌相比，从腕部屈肌测量的肌节长度较短。通过对尺侧腕屈肌（FCU）的术中测量以及对腕部肌肉、关节和肌腱的力学测量相结合，主要腕部运动肌的总体结构显现出来：两个肌肉群在腕部完全伸展时产生最大力量。随着腕部弯曲，由于伸肌沿着其长度 - 张力曲线的下降段伸长以及屈肌沿着其长度 - 张力曲线的上升段缩短，力量会减小。最终结果是在腕部运动范围内屈肌与伸肌扭矩的比例几乎恒定，并且腕部在完全伸展时最稳定。这些实验证明了作用于腕部的肌肉、肌腱和关节之间的精妙匹配。总体而言，腕部扭矩产生机制似乎是为了实现平衡和控制而设计，而非最大扭矩产生能力。
