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DYNAMIC ARCH DEFORMATION AND ITS CONSEQUENCE ON SHOE DESIGN

P.Freychat and N. BoucheAdvanced Research Department, Decathlon Production, Villeneuve dAscq, France, 59 650

INTRODUCTION

Functional footwear aims to protect the human foot from injury and to facilitate performance.

In order to accomplish this, a shoe must be comfortable. One mode of thinking is that

matching the dynamic changes in foot shape and dimensions is the appropriate constructionfor a comfortable shoe. The purpose of this study was to evaluate a three-dimensions flexible

footwear in order to match the normal function of the foot during hiking.

REVIEW AND THEORY

Discomfort, skin blisters or black nails as well as premature shoe damages are often

suffered during sustained walking situations. Freychat et al.(1996) suggested that such

conflicts between the shoe and the foot may find their origin in relative forefoot ab/adductionthat occur during the ground contact. By means of 3D motion analysis during walking,

running and shuffling, Lee (1997) quantified forefoot ab/adduction, arch height flatteningand arch elongation (Table 1). Bojsen-Moeller (1978) considered that movement of the

forefoot with respect to the rearfoot occur at the the transverse tarsal joint, with rotation in

the horizontal plane occurring about the calcaneo-cuboid joint. Because of the slightly lateral

location of the calcaneo-cuboid joint relative to the foot axis, forefoot ab/adduction is

combined with medial arch elongation and flattening (Figure 1).

VARIABLE

Forefoot Ab/adduction (deg) 9.3 (3.4)Arch flattening (mm) 7.0 (2.6)

Arch augmentation (mm) 10.8 (3.6)

Arch elongation (mm) 6.4 (3.1)

Arch shortening (mm) 15.0 (4.3)

Table 1:Mean (SD) values for foot deformation Figure 1:Rotation about the

during walking, running and shuffling (n=20) calcaneo-cuboid joint (CCJ)

PROCEDURES

5 young male subjects (26.2 years, 1.71 m, 65.2 kg ) walked on an incline and decline

walkway at 4 slope while wearing a backpack (mass 20 kg), to simulate the loading

conditions which might be expected to be encountered while hiking.

Two pairs of hiking shoes were provided: one pair of conventional design and one of

prototype incorporating an accordion-like articulation located within the outsole at the

midfoot (Figure 2). Its position was slightly lateral to centre, and its shape was slightly

asymmetrical. The intent of this technology was to allow for relative forefoot abduction,medial foot length elongation and arch height flattening. A thermoplastic rigid bone was

encapsulated at the bottom of the midsole to minimize torsion between the rearfoot and the

forefoot and a piece of extensible neoprene allowed medial arch elongation on the upper part.

Reflective markers were affixed to the left conventionnal shoe and prototype at locations

CCJ

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