Choi Hwan, Peters Keshia M, MacConnell Michael B, Ly Katie K, Eckert Eric S, Steele Katherine M
Mechanical Engineering, University of Washington, 3900E Stevens Way NE, Box 352600, Seattle, WA 98195, USA.
Department of Physics, University of Washington, 3910 15th Ave NE, Box 351560, Seattle, WA 98195, USA.
J Biomech. 2017 Nov 7;64:145-152. doi: 10.1016/j.jbiomech.2017.09.015. Epub 2017 Sep 23.
Ankle foot orthoses (AFOs) are designed to improve gait for individuals with neuromuscular conditions and have also been used to reduce energy costs of walking for unimpaired individuals. AFOs influence joint motion and metabolic cost, but how they impact muscle function remains unclear. This study investigated the impact of different stiffness AFOs on medial gastrocnemius muscle (MG) and Achilles tendon (AT) function during two walking speeds. We performed gait analyses for eight unimpaired individuals. Each individual walked at slow and very slow speeds with a 3D printed AFO with no resistance (free hinge condition) and four levels of ankle dorsiflexion stiffness: 0.25Nm/°, 1Nm/°, 2Nm/°, and 3.7Nm/°. Motion capture, ultrasound, and musculoskeletal modeling were used to quantify MG and AT lengths with each AFO condition. Increasing AFO stiffness increased peak AFO dorsiflexion moment with decreased peak knee extension and peak ankle dorsiflexion angles. Overall musculotendon length and peak AT length decreased, while peak MG length increased with increasing AFO stiffness. Peak MG activity, length, and velocity significantly decreased with slower walking speed. This study provides experimental evidence of the impact of AFO stiffness and walking speed on joint kinematics and musculotendon function. These methods can provide insight to improve AFO designs and optimize musculotendon function for rehabilitation, performance, or other goals.
踝足矫形器（AFO）旨在改善患有神经肌肉疾病个体的步态，也被用于降低未受损个体的行走能量消耗。AFO会影响关节运动和代谢成本，但它们如何影响肌肉功能仍不清楚。本研究调查了不同刚度的AFO在两种步行速度下对腓肠肌内侧头（MG）和跟腱（AT）功能的影响。我们对八名未受损个体进行了步态分析。每个个体以慢速和非常慢速行走，使用无阻力的3D打印AFO（自由铰链状态）以及四种踝关节背屈刚度水平：0.25Nm/°、1Nm/°、2Nm/°和3.7Nm/°。使用运动捕捉、超声和肌肉骨骼建模来量化每种AFO状态下MG和AT的长度。随着AFO刚度增加，AFO背屈峰值力矩增加，同时膝关节伸展峰值和踝关节背屈峰值角度减小。随着AFO刚度增加，整体肌腱长度和AT峰值长度减小，而MG峰值长度增加。随着步行速度减慢，MG峰值活动、长度和速度显著降低。本研究提供了AFO刚度和步行速度对关节运动学和肌腱功能影响的实验证据。这些方法可为改进AFO设计以及为康复、运动表现或其他目标优化肌腱功能提供见解。
