College of Health
39 Effects of Different Thickness of Carbon Fiber Insoles on Foot Motion using X-Rays
Megan Weaver; Kota Takahashi; and Amy Lenz
Faculty Mentor: Kota Takahashi (Health, Kinesiology, and Recreation, University of Utah)
Abstract
Carbon fiber has been incorporated into high performance running shoes and found to reduce energy expenditure during running because of carbon fiber’s ability to act as an energy storage and release material. Outside of high-performance settings, the energy storage and return capacity of carbon fiber has many other clinical applications, including assistance with locomotion and foot mechanical limitations in the elderly, those with limited walking abilities, and everyday use, as carbon fiber may reduce the work done by the foot during locomotion. However, whether the energy storage and return capability of carbon fiber plates results in changes to the foot mechanics is largely unknown, as due to data collection limitations, the in-shoe foot mechanics when ambulating with carbon fiber insole has not been studied. Therefore, the purpose of this study was to determine how different thicknesses of carbon fiber changed foot joint angles during a typical walking gait cycle. We hypothesized that increasing shoe stiffness via carbon fiber insoles would cause the: 1) toe joint to decrease dorsiflexion [toe will bend less] 2) arch to decrease plantarflexion [arch will be flatter] 3) ankle to increase peak dorsiflexion [foot will increase forward lean]. Through the use of a biplane fluoroscopy (i.e., x-ray) system, bone motion was captured inside of the shoe to analyze foot joint angles. One participant (N=1, F, 21) walked across the biplane fluoroscopy under four different conditions: barefoot, shoe, shoe with 1.6 mm carbon fiber, and shoe with 3.2 mm carbon fiber.
Analysis of the joint angles for the metatarsophalangeal joint (i.e., toe), midtarsal joint (i.e., arch), and ankle were conducted through use of the Kinovea software. Overall, the results found comparing baseline Shoe vs Carbon 3.2 mm supported the hypothesis: 1) toe decreased dorsiflexion by 16.28° 2) arch decreased plantarflexion by 2.3° 3) ankle increased dorsiflexion by 2.96°. These results indicate that, at toe off, increasing the CF plate thickness resulted in a flatter foot at the toe and arch, but greater ankle dorsiflexion, potentially reducing work/energy requirements of foot through energy storage and release capability of the CF plate. The research utilized a novel state-of-the-art method via high-speed X-rays to analyze foot motion inside of the shoe during walking. This data is meaningful in helping further the development of footwear for people of all ages with the goal to reach new athletic records, walk with less energy requirement, and wear a more comfortable shoe.
Introduction
In recent years, carbon fiber (CF) has been slowly incorporated into many high-performance running shoes, e.g., Alphyflys, Vaporflys, and Carbon X. Many athletic