Impact of ankle foot orthosis stiffness on Achilles tendon and gastrocnemius function during unimpaired gait |
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| Affiliation: | 1. Mechanical Engineering, University of Washington, 3900E Stevens Way NE, Box 352600, Seattle, WA 98195, USA;2. Department of Physics, University of Washington, 3910 15th Ave NE, Box 351560, Seattle, WA 98195, USA;3. Human Centered Design & Engineering, University of Washington, 3900E Stevens Way NE, Box 352315, Seattle, WA 98195, USA;1. Department of Mechanical & Industrial Engineering, Montana State University, United States;2. Department of Cell Biology & Neurosciences, Montana State University, United States;3. Department of Orthopaedics & Sports Medicine, University of Washington, United States;1. Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA;2. PERCRO Laboratory, TeCIP Institute, Scuola Superiore Sant’Anna, via Alamanni 13b, 56010 Ghezzano, San Giuliano Terme, Pisa, Italy;3. Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA, USA;1. Department of Mechanical Engineering, College of Engineering, Michigan State University, East Lansing, MI, USA;2. MSU Center for Orthopedic Research, College of Osteopathic Medicine, Michigan State University, Lansing, MI, USA;3. Department of Osteopathic Surgical Specialties, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, USA;4. School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea;1. Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan;2. Division of Dental Informatics, Osaka University Dental Hospital, 1-8 Yamadaoka, Suita, Osaka 565-0871, Japan;1. School of Engineering and Applied Science, University of Virginia, Charlottesville, VA 22904, USA;2. Department of Mechanical Engineering, Dublin City University, Glasnevin, Dublin 9, Ireland |
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| Abstract: | 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/°, 1 Nm/°, 2 Nm/°, and 3.7 Nm/°. 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. |
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| Keywords: | Ankle foot orthoses Ultrasound Musculoskeletal modeling Stiffness Achilles tendon Gastrocnemius Gait |
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