Journal
JOURNAL OF BIOMECHANICS
Volume 64, Issue -, Pages 145-152Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jbiomech.2017.09.015
Keywords
Ankle foot orthoses; Ultrasound; Musculoskeletal modeling; Stiffness; Achilles tendon; Gastrocnemius; Gait
Categories
Funding
- National Science Foundation [CBET 1452646]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1452646] Funding Source: National Science Foundation
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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: 0.25 Nm/degrees, 1 Nm/degrees, 2 Nm/degrees, and 3.7 Nm/degrees. 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. (C) 2017 Elsevier Ltd. All rights reserved.
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