Wong Jeremy D, Bobbert Maarten F, van Soest Arthur J, Gribble Paul L, Kistemaker Dinant A
Brain and Mind Institute, Western University, Ontario, Canada.
MOVE Research Institute, Vrije Universiteit Amsterdam, Nord-Holland, The Netherlands.
PLoS One. 2016 Feb 26;11(2):e0150019. doi: 10.1371/journal.pone.0150019. eCollection 2016.
A goal of biomechanics and motor control is to understand the design of the human musculoskeletal system. Here we investigated human functional morphology by making predictions about the muscle volume distribution that is optimal for a specific motor task. We examined a well-studied and relatively simple human movement, vertical jumping. We investigated how high a human could jump if muscle volume were optimized for jumping, and determined how the optimal parameters improve performance. We used a four-link inverted pendulum model of human vertical jumping actuated by Hill-type muscles, that well-approximates skilled human performance. We optimized muscle volume by allowing the cross-sectional area and muscle fiber optimum length to be changed for each muscle, while maintaining constant total muscle volume. We observed, perhaps surprisingly, that the reference model, based on human anthropometric data, is relatively good for vertical jumping; it achieves 90% of the jump height predicted by a model with muscles designed specifically for jumping. Alteration of cross-sectional areas-which determine the maximum force deliverable by the muscles-constitutes the majority of improvement to jump height. The optimal distribution results in large vastus, gastrocnemius and hamstrings muscles that deliver more work, while producing a kinematic pattern essentially identical to the reference model. Work output is increased by removing muscle from rectus femoris, which cannot do work on the skeleton given its moment arm at the hip and the joint excursions during push-off. The gluteus composes a disproportionate amount of muscle volume and jump height is improved by moving it to other muscles. This approach represents a way to test hypotheses about optimal human functional morphology. Future studies may extend this approach to address other morphological questions in ethological tasks such as locomotion, and feature other sets of parameters such as properties of the skeletal segments.
生物力学和运动控制的一个目标是了解人类肌肉骨骼系统的设计。在此，我们通过对特定运动任务最优的肌肉体积分布进行预测，来研究人类功能形态学。我们研究了一个经过充分研究且相对简单的人类运动——垂直跳跃。我们探究了如果肌肉体积针对跳跃进行优化，人类能跳多高，并确定了最优参数如何提高表现。我们使用了一个由希尔型肌肉驱动的人类垂直跳跃四连杆倒立摆模型，该模型能很好地近似熟练的人类表现。我们通过允许改变每块肌肉的横截面积和肌肉纤维最佳长度，同时保持总肌肉体积不变，来优化肌肉体积。我们观察到，也许令人惊讶的是，基于人体测量数据的参考模型对于垂直跳跃来说相对较好；它达到了专门为跳跃设计肌肉的模型所预测跳跃高度的90%。横截面积的改变——横截面积决定了肌肉可传递的最大力量——构成了跳跃高度提高的主要部分。最优分布导致股四头肌、腓肠肌和腘绳肌体积增大，能产生更多功，同时产生与参考模型基本相同的运动模式。通过减少股直肌的肌肉量来增加功输出，鉴于其在髋关节处的力臂以及蹬地时的关节活动范围，股直肌无法对骨骼做功。臀肌占肌肉体积的比例过大，将其肌肉量转移到其他肌肉可提高跳跃高度。这种方法代表了一种检验关于人类最优功能形态学假设的方式。未来的研究可能会扩展这种方法，以解决诸如运动等行为学任务中的其他形态学问题，并研究其他参数集，如骨骼节段的特性。
