Influence of Wearing Shoes on the Impact Force during Drop-jump

Keiji Koyama

, Reo Kurisu

, Huka Shibata

and Junichiro Yamauchi

2,3,4

Department of Sport Technology, Toin University of Yokohama, Yokohama-shi, Kanagawa, Japan

Graduate School of Human Health Sciences, Tokyo Metropolitan University, 1-1, Tokyo, Japan

Future Institute for Sport Sciences, Tokyo, Japan

Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand

Keywords: Running Shoes, Shock Absorption, Vertical Ground Reaction Force.

Abstract: The purpose of this study was to investigate the vertical ground reaction force during drop-jumping in bare

and shod conditions. Seven healthy men participated and performed the drop-jump from the box of the

45cm-height in barefoot (BARE) and shod (SHOD) conditions. The force variables at the contact were

measured on the force plate. The maximum vertical ground reaction forces (MGRF), contact time (CT) and

jump height (JH) were used. MGRF, CT and JH were not significantly different between BARE and SHOD

conditions.

1 INTRODUCTION

In modern life style most of people living in

developed countries wear shoes when they have

walking, jogging, running and daily activities.

Shock absorption of shoes can be achieved by

thickness, stiffness, cushioning properties of midsole

and insoles. Impact stress and calcaneal loading

rates were significantly reduced by material

moderation during the landing phase of the jump

(Gross and Bunch, 1989). Insoles play a more

important role in cushioning properties and the

percentage of impact absorbed was different by

properties of insole (Chiu and Shiang, 2007). Peak

vertical GRF during landing activities was

significantly greater for the normal and hard

midsoles compared to soft midsoles (Zhang et al.,

2005). Also, EMG studies show that muscle activity

of plantar flexors is higher when wearing with

unstable shoes as compared normal walking shoes

during standing (Nigg et al., 2006) and walking

(Koyama et al., 2012).

It seems that different shoe conditions affect the

lower leg and foot at the contact phase of ground

during the running movement. However, only a

small number of studies have been compared

between barefoot and shod conditions during high

impact force activities other than running. The

influence of wearing shoes as compared with

barefoot condition on the impact force during high

GRF landing movements has not been clear yet.

Therefore, the purpose of this study was to

investigate the shock absorption function and force

enhancement of the foot during the drop jump

performance in shod and barefoot condition.

2 METHODS

Seven healthy men (age, 21.3±0.8 years; height,

1.72±0.05 m; body mass, 63.1±10.2 kg; mean±SD)

volunteered to participate in this study. No

participants were taking medications nor did they

have any injuries in feet and legs within a year.

They drop-jumped from the box of 45cm-height

in barefoot (BARE) and shod (SHOD) conditions.

The drop jump was performed as stepping off from a

height of the box to the ground, then quickly

jumping up as high as possible. Participants were

instructed to naturally contact with the both feet

within the area of the force plate.

The force variables at the contact during the

drop-jump were measured on the force plate. The

sample frequency of the force platform was set at 1

kHz. The maximum vertical ground reaction force

(MGRF), contact time (CT) and jump height (JH)

were analysed. By measuring the FT from the force

record on the force plate, the vertical take-off

velocity (Vv) of the centre of gravity was calculated

with the following equation:

Koyama K., Kurisu R., Shibata H. and Yamauchi J..

Inﬂuence of Wearing Shoes on the Impact Force during Drop-jump.

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

Vv = 1/2FTg,

where g is the acceleration of gravity (9.81

m/s2). Then, jump height (JH) was calculated with

the following equation:

JH = Vv2(2g)

-1

MGRF was normalized by body weight. The

mean of the 3 measurements was used for further

analysis.

3 RESULTS

The representative GRF curves during the drop-

jump at both foot contacts were compared between

BARE and SHOD conditions. Figure X shows two

typical GRF time series data in two conditions.

MGRF, CT and JH were not significantly

different between BARE (MGRF; 60.2±12.5 N/kg,

CT; 0.24±0.04 s, JH; 22.4±4.42 cm) and SHOD

(MGRF; 58.4±11.7 N/kg, CT; 0.24±0.04 s, JH;

21.7±4.93 cm).

4 DISCUSSIONS

This study showed that the drop-jump performance

in BARE and SHOD conditions was similar in the

landing impact force, contact time and jump height.

The drop jump movement is known as the typical

single action of stretch-shortening cycle (SSC)

exercise.

When compared with shod and barefoot

condition, the impact force in shod running was

higher than that of barefoot running (Lieberman et

al., 2010). This is because the foot was contacted

with rearfoot in shod condition, but with forefoot in

barefoot condition. In case of the drop-jump, the

foot contact was similar in both conditions. During

the drop jump, the force production in a concentric

contraction phase of the jump should be stronger

when it immediately proceeds with an eccentric

contraction of the same muscle. This pre-stretch

conditioning of lower limb muscles occur in

particular knee extensors and ankle plantar flexors

during the drop jump (Dvir, 1985a). The stretch

reflex elicited during eccentric phase of muscle

contraction may play an important role in controlling

subsequent muscle stiffness and elastic energy store,

and thus enhancing concentric muscle mechanical

power production during SSC muscle performance.

High muscle activity during the eccentric phase on

the contact plays an important role in storing elastic

energy, and this stored elastic energy can be

reutilized for production of high power during the

concentric phase on the contact (Viitasalo et al.,

1998). In the barefoot condition the foot may

naturally use these SSC functions in lower limb and

foot joints, while in shod condition elastic material

of the shoes may help to enhance the performance.

This result suggests that in order to improve the

SSC functions, exercises with barefoot may be

effective. However, exercises with barefoot should

be carefully planed because they can be very easy to

overcome the limited functions of the foot and leg

muscles.

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