The Foot Feature Measurement System and Its Application to

Postural Stability of Healthy Subjects

Kyung-Ryoul Mun

, Sungkuk Chun

, Hyungan Oh

, Yunjung Kang

, Junggi Hong

and Jinwook Kim

Imaging Media Research Center, Korea Institute of Science and Technology, 136791 Seoul, Republic of Korea

Department of Physical Education, Kookmin Univeristy, Seoul, Republic of Korea

Keywords: Foot Feature Measurement System, Medial Longitudinal Arch, Lateral Longitudinal Arch.

Abstract: In this study we aimed to develop a foot feature measurement system (FFMS) being able to simultaneously

extract foot feature parameters in both static and dynamic condition. In addition, we investigated how these

foot features are associated to the postural stability through human experiments as this is one of the most

important requirements for natural and aesthetic gait pattern. From all thirteen subjects participated in this

study, this foot arch mechanism were clearly observed. It indicates that observation of LLA and area of MLA

curves is important to investigate postural stability in accordance with the different type of foot arches. For

the conclusion, foot anatomical characteristics such as height and the area of each arch curves can be observed

in both static and dynamic condition using the FFMS. In addition, it can be concluded that the FFMS can

provide more precise and various foot information by considering the LLA during both static and dynamic

condition.

1 INTRODUCTION

Recently, studies on designing subject-specific shoes

and insoles have been actively proceeded, to decrease

an impact force and stress applied at foot and to

increase a performance of the sports related

movements. Especially, a foot mechanism which is

static and dynamic changes of foot arch is the most

important factor to determine the performance of gait

and other activities. Thus, identifying this mechanism

is necessary for establishing the design of

personalized shoe insole. The foot arch, comprised of

medial longitudinal arch (MLA), lateral longitudinal

arch (LLA), and transverse arch, significantly

contributes to the body weight support, shock

absorption, body propulsion, and postural control

during walking and running (Wright et al., 2012,

Daentzer et al., 1997, Chang et al., 2014). However,

most of currently available personalized insoles are

generally manufactured by contemplating the

structure of MLA in static condition without

considering the LLA structure and dynamic

circumstances (Shirmohammadi and Ferrero, 2014,

Uhm et al., 2015, Coudert et al., 2006).

Therefore in this study we aimed to develop a foot

feature measurement system (FFMS) being able to

simultaneously extract foot feature parameters such

as foot length, foot width, the height of MLA and

LLA in both static and dynamic condition. In

addition, we investigated how these foot features are

associated to the postural stability through human

experiments as this is one of the most important

requirements for natural and aesthetic gait pattern.

2 METHODS

The FFMS system is shown in Fig 1. Overall FFMS

is composed of a measurement system and analysis

modules. The measurement system is comprised of a

runway and a scanning stage. The runway is a

wooden structure of 200cm (length) x 70cm (width)

x 45cm (height), and the scanning stage is composed

of a depth camera embedded underneath the

transparent acrylic panel and four uni-axial force

sensors at corners of the panel. The depth camera is

built in to measure morphological characteristics of

foot and geometric structure of the foot arch, while

the force sensors are set up to investigate the stability

of movements which is a center of pressure (CoP) of

the foot (Fig. 1B). All the obtained images and CoP

data were stored in an in-house developed software.

Mun, K-R., Chun, S., Oh, H., Kang, Y., Hong, J. and Kim, J.

The Foot Feature Measurement System and Its Application to Postural Stability of Healthy Subjects.

In Extended Abstracts (icSPORTS 2016), pages 23-26

Analysis modules then can be used to extract the foot

features from the images obtained by the FFMS.

To evaluate the feasibility of the FFMS and to

investigate relation of foot features and postural

stability, thirteen healthy young subjects were

participated in the experiment. The experiment is

comprised of sitting (static condition), walking

(dynamic condition), and one leg standing (OLS).

The foot features such as the curves and heights of

MLA and LLA were extracted in both static and

dynamic conditions. In addition, temporal trajectory

of center of pressure (CoP) were obtained and

anterior-posterior (AP) CoP distance was calculated

during OLS condition. For the dynamic condition, the

foot parameters were calculated in the mid-stance,

where the ground reaction force acting on the foot

was the maximum. The MLA curve is defined along

a foot skin surface by connecting a representative

point on the calcaneus and the 1st

metatarsophalangeal (MTP) joint. Similarly the LLA

curve is defined by connecting a point on the

calcaneus and the 4th MTP joint. Correlations

between foot features and CoP distance were

calculated to investigate relations of the parameters.

Figure 1: System installation of FFMS, A) scanning stage

of the proposed system, B) Depth camera beneath the

transparent acrylic board, and C) an example of a depth

image of a foot.

Table 1: Mean and standard deviation of foot arch

parameters in both static and dynamic conditions.

Foot Parameters Mean (mm) SD (mm)

Height MLA

Static 11.45 1.40

Dynamic 9.55 1.56

Height LLA

Static 4.78 1.13

Dynamic 3.93 1.11

Area MLA

Static 5818.10 916.54

Dynamic 4972.65 927.45

Area LLA

Static 1495.74 415.88

Dynamic 1254.20 365.60

3 RESULTS

The curves of MLA and LLA during both static and

dynamic conditions were shown in Figure 2, and

calculated maximum heights and curve areas which

are the integral of the arch curves were presented in

Table 1. The heights and areas decreased significantly

in dynamic condition at both MLA and LLA. Table 2

shows the correlation coefficients between arch

parameters and CoP distance in AP direction. The

maximum height of LLA curves and area of MLA

curves are moderately correlated with the CoP

distance.

4 DISCUSSION

In this study, we were able to extract geometric

changes of the medial and lateral longitudinal arch

curves as well as their height and area from the static

and dynamic conditions using newly developed

FFMS. The MLA height is lowered in weight bearing

condition compared to non-weight bearing condition.

It is because once entire foot is on the ground, the foot

has to endure downward force caused by body weight

(Stolwijk et al., 2014, Fukano and Fukubayashi,

2009). From all thirteen subjects participated in this

study, this foot arch mechanism were clearly

observed.

In addition, the height of LLA in dynamic condition

as well as the area of MLA in both static and dynamic

conditions had positively moderate correlations with

CoP distance in AP direction. It indicates that

observation of LLA and area of MLA curves is

icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support

Figure 2: MLA and LLA curves and their standard deviations in static and dynamic conditions. Black line shows the averaged

arch curves of thirteen subjects, and blue line shows the standard deviations (mm).

important to investigate postural stability in

accordance with the different type of foot arches since

each longitudinal arch has a different respective

function (Fukano and Fukubayashi, 2009).

For the conclusion, foot anatomical characteristics

such as height and the area of each arch curves can be

observed in both static and dynamic condition using

the FFMS. In addition, it can be concluded that the

FFMS can provide more precise and various foot

information by considering the LLA during both

static and dynamic condition. Therefore we expect

that foot shape related studies for various sports

activities, and studies establishing protocols to

prevent injuries caused by the foot deformity will be

actively performed by quantitatively measuring and

analysing the foot parameters using the FFMS.

Table 2: Correlation coefficient between foot arch

parameters and CoP distance in AP direction.

AP CoP distance

r p

Height MLA

Static

0.361 0.108

Dynamic

0.432 0.051

Height LLA

Static

0.255 0.265

Dynamic

.519* 0.016

Area MLA

Static

.471* 0.031

Dynamic

.439* 0.047

Area LLA

Static

0.308 0.174

Dynamic

0.41 0.065

ACKNOWLEDGEMENTS

This research project was supported by the Sports

Promotion Fund of Seoul Olympic Sports Promotion

Foundation from Ministry of Culture, Sports and

Tourism, Korea.

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icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support