Evaluation of biomechanical environment of foot within different shoes

Pao Yue-kong Library Electronic Theses Database

Evaluation of biomechanical environment of foot within different shoes

 

Author: Cong, Yan
Title: Evaluation of biomechanical environment of foot within different shoes
Degree: Ph.D.
Year: 2012
Subject: Foot -- Mechanical properties.
Shoes -- Design.
Hong Kong Polytechnic University -- Dissertations
Department: Interdisciplinary Division of Biomedical Engineering
Pages: xiii, 188 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2530104
URI: http://theses.lib.polyu.edu.hk/handle/200/6716
Abstract: The increasing popularity of high-heeled shoes can be attributed to modern fashion, job requirement and common belief in enhancing aesthetic appeal. Wearing high-heeled shoes would change the body alignment and muscle activities, redistribute the plantar stresses and ground reaction force. The changes may induce clinical problems, such as forefoot pain, hallux valgus deformity, ankle sprain and foot callus. This study aimed to evaluate the effect of high-heeled shoe on the biomechanical environment of foot, including in-shoe plantar pressures and shear stresses, ground reaction force and foot motion patterns, when frictional properties of foot-insole interface and walking cadence changed. Results from this study were expected to provide more information to improve better high-heeled shoes and alleviate high-heeled foot problems. Ten healthy female subjects volunteered in this study. Five in-shoe triaxial force transducers were used to measure the plantar contact pressure and shear at five major weightbearing regions, including the hallux, heel, first, second and fourth metatarsal heads. A multi-segment foot model, comprised of 8 segments, was constructed to analyze the high-heeled gait kinematics. The segments included arch angle, hallux, the first and fifth metatarsal, calcaneus, tibia, thigh and pelvis. The experiments were carried out with 3 heel heights (30, 50 and 70 mm), 3 interfacial conditions (barefoot, nylon and cotton socks) under 3 cadences (90, 110, 130 steps/min). The influences of heel heights, interfacial properties and walking cadences on in-shoe triaxial stresses and foot kinematics were investigated. For mechanical stresses, as the heel height increased from 30 to 70 mm, the peak pressure and shear stress shifted from the lateral to medial forefoot in either balanced standing or walking. Heel height elevation had a greater influence on peak shear than peak pressure during walking. The ratios of resultant shear to pressure ranged from 0.1 to 0.5 and increased over the heel, hallux, first and second metatarsal heads. An increased peak posterolateral shear over the hallux was noted, while the peak pressure in this region decreased. It was also found that there were differences in the location and time of occurrence between in-shoe peak pressure and peak shear. In addition, there were significant differences in time of occurrence for the double-peak loading pattern between the resultant horizontal ground reaction force peaks and in-shoe localized peak shears. Plantar shear stresses could be of particular importance with an inclined supporting surface of high-heeled shoe and shear dominant effect should be considered in predicting foot complaints. Fast walking cadence generated larger peak pressure over all targeted foot regions except for the fourth metatarsal head, in which the peak pressure had no differences among different walking cadences. The walking cadence had a more pronounced influence on the peak resultant shear over hallux, second metatarsal head and heel especially walking with socks, while it slightly changed the shear stress without Effects of walking cadence were more important on a low friction surface.
Sock material altered the frictional characteristics at the foot-shoe interface, which further changed the plantar stresses. Compared with the condition without socks, nylon socks reduced the shear stresses over the first, second and fourth metatarsal heads, while they increased the shear stress over heel. A deep insight into the characteristic of plantar stresses should consider the interface frictional properties combined with shoe construction and subjects' activities. The kinematic results showed that the heel height had a dominant influence on the motion patterns of the lower extremity, compared with the sock material and walking cadence. The arch height, ankle plantarflexion, rearfoot inversion and hallux dosiflexion increased with the elevation of heel height. When the heel height increased to 70 mm, the foot had the permanent ankle plantarflexion and rearfoot inversion during the whole stance phase. For most of subjects, the hallux had a more abducted motion wearing high-heeled shoes. For motions of hip and knee joints, the effects of heel height were not obvious. The motions in all three planes were not significantly different. However, a prolonged midstance maximal knee flexion was noted. The movements of medial forefoot and lateral forefoot in frontal plane were different. As the heel height increased, the medial forefoot eversion increased, while the lateral forefoot inversion increased. The walking cadence mainly affected the motion of rearfoot in sagittal plane and the sock material mainly changed the motion of the medial forefoot in frontal plane. As the walking cadence increased, the peak ankle plantarflexion decreased. Walking with nylon socks, the range of motion for the medial forefoot in frontal plane was larger than that walking with cotton socks and without socks. Redistribution of plantar stresses was associated with the movement of lower extremity. The increased hallux dorsiflexion and the first metatarsal plantarflexion were consistent with the inspected arch height increased. These changes together with increased ankle plantarflexion and the medial forefoot pronation in midstance could possibly contribute to the high pressure and shear stress over the medial forefoot region wearing high-heeled shoes. These factors explained 34.1% and 50.8% of variance in peak pressures over the first and second metatarsal heads, respectively, while they explained 30.5% and 49.1% of variance in peak resultant shear stresses over these regions, respectively. Current studies inspected the relationship between shoe construction and foot biomechanics, which could be useful in understanding foot function changes in high-heeled shoes. The information is essential to improve shoe designs and manage the high-heeled pathologies.

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