Ogaya Shinya, Okita Yusuke, Fuchioka Satoshi
Course of Physical Therapy, School of Comprehensive Rehabilitation, Osaka Prefecture University, 3-7-30, Habikino, Habikino-shi, Osaka 583-8555, Japan.
Physical Medicine and Rehabilitation Unit, Istituto Ortopedico Rizzoli via G. C. Pupilli 1 (ospedale), Bologna 40136, Italy.
J Biomech. 2016 Oct 3;49(14):3381-3386. doi: 10.1016/j.jbiomech.2016.08.028. Epub 2016 Aug 25.
Humans employ two distinct strategies to maintain balance during standing: the ankle and hip strategies. People with a high fall risk tend to alter their motion patterns during forward body tilting from a hip to an ankle strategy. Improved knowledge regarding how muscles control the center of mass (COM) during balancing would facilitate clinical assessment. The present study aimed to investigate individual muscle contributions to COM motion during forward body tilting with both ankle and hip strategies in 16 healthy adults. While standing, participants were instructed to oscillate their bodies and touch anterior and posterior targets at 0.5Hz. The anterior target was positioned at the sternum height level in a HIGH and 5% lower in a LOW condition to induce ankle and hip strategies, respectively. The muscle tension force was calculated from measured angle data using a two-dimensional, muscle-driven forward simulation model. Muscle contributions to COM acceleration during forward body tilting were calculated via induced acceleration analysis. Long hamstrings were found to increase upward-contributing action and forward COM acceleration in the LOW condition during forward tilting. In contrast, the contribution of the soleus to backward COM acceleration was reduced. These results imply that the contribution of hamstrings to forward COM acceleration is disadvantageous to fore-aft COM control and balance recovery during forward body tilting.
踝关节策略和髋关节策略。跌倒风险高的人在身体向前倾斜时往往会从髋关节策略转变为踝关节策略，从而改变他们的运动模式。深入了解肌肉在平衡过程中如何控制重心（COM）将有助于临床评估。本研究旨在调查16名健康成年人在采用踝关节和髋关节策略进行身体向前倾斜时，各个肌肉对重心运动的贡献。站立时，参与者被要求以0.5Hz的频率摆动身体并触碰前后目标。前目标在“高”条件下位于胸骨高度水平，在“低”条件下低5%，分别诱导踝关节和髋关节策略。使用二维肌肉驱动的正向模拟模型，根据测量的角度数据计算肌肉张力。通过诱导加速度分析计算身体向前倾斜时肌肉对重心加速度的贡献。研究发现，在向前倾斜的“低”条件下，股二头肌增加了向上的作用和重心向前的加速度。相比之下，比目鱼肌对重心向后加速度的贡献减少。这些结果表明，在身体向前倾斜时，股二头肌对重心向前加速度的贡献不利于前后重心控制和平衡恢复。
