Oudenhoven Laura M, Boes Judith M, Hak Laura, Faber Gert S, Houdijk Han
Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Center, P.O. Box 7057, 1007 MB Amsterdam, The Netherlands.
Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
J Biomech. 2017 Jan 25;51:42-48. doi: 10.1016/j.jbiomech.2016.11.058. Epub 2016 Nov 29.
Running specific prostheses (RSP) are designed to replicate the spring-like behaviour of the human leg during running, by incorporating a real physical spring in the prosthesis. Leg stiffness is an important parameter in running as it is strongly related to step frequency and running economy. To be able to select a prosthesis that contributes to the required leg stiffness of the athlete, it needs to be known to what extent the behaviour of the prosthetic leg during running is dominated by the stiffness of the prosthesis or whether it can be regulated by adaptations of the residual joints. The aim of this study was to investigate whether and how athletes with an RSP could regulate leg stiffness during distance running at different step frequencies. Seven endurance runners with an unilateral transtibial amputation performed five running trials on a treadmill at a fixed speed, while different step frequencies were imposed (preferred step frequency (PSF) and -15%, -7.5%, +7.5% and +15% of PSF). Among others, step time, ground contact time, flight time, leg stiffness and joint kinetics were measured for both legs. In the intact leg, increasing step frequency was accompanied by a decrease in both contact and flight time, while in the prosthetic leg contact time remained constant and only flight time decreased. In accordance, leg stiffness increased in the intact leg, but not in the prosthetic leg. Although a substantial contribution of the residual leg to total leg stiffness was observed, this contribution did not change considerably with changing step frequency. Amputee athletes do not seem to be able to alter prosthetic leg stiffness to regulate step frequency during running. This invariant behaviour indicates that RSP stiffness has a large effect on total leg stiffness and therefore can have an important influence on running performance. Nevertheless, since prosthetic leg stiffness was considerably lower than stiffness of the RSP, compliance of the residual leg should not be ignored when selecting RSP stiffness.
跑步专用假肢（RSP）旨在通过在假肢中加入一个真正的物理弹簧，来模拟人类腿部在跑步时类似弹簧的行为。腿部刚度是跑步中的一个重要参数，因为它与步频和跑步经济性密切相关。为了能够选择一种有助于满足运动员所需腿部刚度的假肢，需要了解假肢在跑步过程中的行为在多大程度上受假肢刚度的支配，或者它是否可以通过残肢关节的适应性调整来调节。本研究的目的是调查使用RSP的运动员在不同步频的长跑过程中是否以及如何调节腿部刚度。七名单侧经胫骨截肢的耐力跑运动员在跑步机上以固定速度进行了五次跑步试验，同时施加不同的步频（首选步频（PSF）以及PSF的-15%、-7.5%、+7.5%和+15%）。除其他外，还测量了双腿的步幅时间、地面接触时间、腾空时间、腿部刚度和关节动力学。在健全的腿部，步频增加伴随着接触时间和腾空时间的减少，而在假肢腿部，接触时间保持不变，只有腾空时间减少。相应地，健全腿部的腿部刚度增加，而假肢腿部则没有。尽管观察到残肢对总腿部刚度有很大贡献，但随着步频的变化，这一贡献并没有显著变化。截肢运动员在跑步过程中似乎无法改变假肢腿部的刚度来调节步频。这种不变的行为表明RSP刚度对总腿部刚度有很大影响，因此可能对跑步表现有重要影响。然而，由于假肢腿部的刚度明显低于RSP的刚度，在选择RSP刚度时，不应忽视残肢的顺应性。
