Elastic ankle exoskeletons reduce soleus muscle force but not work in human hopping
Elastic ankle exoskeletons reduce soleus muscle force but not work in human hopping
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DOI：
10.1152/japplphysiol.00253.2013
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发表时间：
2013-09-01
影响因子：
3.3
通讯作者：
Sawicki, Gregory S.
中科院分区：
文献类型：
--
作者：
Farris, Dominic James;Robertson, Benjamin D.;Sawicki, Gregory S.
受人类腿部肌肉-腱单元（MTU）的腱中的弹性能量存储和返回的启发，外骨骼通常将弹簧与MTU平行放置以辅助MTU。然而，这可能会扰乱正常有效的MTU机制，实际上增加了主动肌肉的机械功。本研究测试了弹性并联辅助对MTU力学的影响。参与者在有和没有弹簧加载踝关节外骨骼的情况下跳跃，以辅助跖屈。逆动力学分析，结合在体超声成像的比目鱼肌束和表面肌电图，被用来确定肌肉肌腱力学和激活。从间接量热法获得全身净代谢功率。当用弹簧加载的外骨骼跳跃时，比目鱼肌激活减少（30-70%），比目鱼肌力的大小（峰值力减少30%）和比目鱼肌力产生的平均速率（减少50%）也是如此。虽然力较低，但平均正束功率保持不变，因为束偏移增加（+4-5 mm）。净代谢功率在外骨骼辅助下降低（19%）。这些发现强调，对具有可观的串联弹性的肌肉的并行辅助可能具有一些负面后果，并且与产生力相关的代谢成本可能比为这些肌肉做功的成本更显著。
Inspired by elastic energy storage and return in tendons of human leg muscle-tendon units (MTU), exoskeletons often place a spring in parallel with an MTU to assist the MTU. However, this might perturb the normally efficient MTU mechanics and actually increase active muscle mechanical work. This study tested the effects of elastic parallel assistance on MTU mechanics. Participants hopped with and without spring-loaded ankle exoskeletons that assisted plantar flexion. An inverse dynamics analysis, combined with in vivo ultrasound imaging of soleus fascicles and surface electromyography, was used to determine muscle-tendon mechanics and activations. Whole body net metabolic power was obtained from indirect calorimetry. When hopping with spring-loaded exoskeletons, soleus activation was reduced (30-70%) and so was the magnitude of soleus force (peak force reduced by 30%) and the average rate of soleus force generation (by 50%). Although forces were lower, average positive fascicle power remained unchanged, owing to increased fascicle excursion (+4-5 mm). Net metabolic power was reduced with exoskeleton assistance (19%). These findings highlighted that parallel assistance to a muscle with appreciable series elasticity may have some negative consequences, and that the metabolic cost associated with generating force may be more pronounced than the cost of doing work for these muscles.