Influence of Fatigue on Balance and Lower Limb Muscles Activity in

Flatfoot Children

Riza Adriyani

, Tommy Apriantono

, and Suprijanto Suprijanto

Sports Science Department, Postgraduate Programs, Institut Teknologi Bandung, Indonesia

Instrumentation and Control Research Group, Institut Teknologi Bandung, Indonesia

ariyaniriza@gmail.com

Keywords: Fatigue, foot posture, median frequency, static balance.

Abstract: Fatigue could lead to excessive eversion and affect static balance. This study was aimed to find out the

influence of foot posture and jumping fatiguing effect on static balance and muscle activity of lower limb

muscles. Methods: 19 elementary school children aged 9 to 11 years took part in this study. Of these all

children, 10 had normal foot and 9 had flatfoot which was classified by their foot posture. Foot posture was

measured based on arch index of footprint by a foot scanner. Surface electromyography (EMG) activity was

recorded from tibialis anterior, gastrocnemius medialis and peroneus longus muscles while participants were

standing on one leg barefoot with opened eyes. Results: Normal foot had arch index 0.25±0.01 whereas

flatfoot had 0.36±0.01. Statistical analysis showed that fatigue could influence static balance in flatfoot

children (p < 0.05). Based on electromiographic data, there were no significant differences on median

frequency of lower limb muscles between both groups. After fatigue, median frequency (MF) timing was

significantly different (p < 0.05) on tibialis anterior and peroneus longus. MF timing showed earlier in

flatfoot. Conclusion: Fatigue influenced static balance and tended to appear earlier on lower limb muscles in

flatfoot children.

1 INTRODUCTION

Plantar arch development is observed before the age

of six and then children will had characteristics

features of adult feet (Hennig et al., 1994). This

development affected by various factors such as

internal (age, sex, genetic) and external factors (age

at which closed shoe wearing begins, body

composition and physical activity level) (Halabachi

et al., 2013; Mortazavi et al., 2007). Most of the

flatfoot are flexible, asymptomatic and physiologic.

Early closed shoes wearing in children may lead to

flatfoot because it could influence foot motion and

ligament laxity which lead to lowering the arch

height (Abolarin et al., 2011). Furthermore, excessed

body weight on children also lead to the impairment

of foot functional status (Krul et al., 2009).

High impact sports need an efficient foot posture

for shock absorption, generating and transfering the

energy. Variations of foot posture could be at high

risk for overuse injuries after doing repetitive

athletic tasks (Queen et al., 2007). Flatfoot is at high

risk of ankle injury while participating in high

impact sports because of its high intensity and

frequent foot contacts with hard surface (Cain et al.,

2007). Flatfoot children will get muscle fatigue and

pain earlier on their lower extremity compared to

normal foot children because higher muscle activity

is needed to stabilize tarsal transversal and subtalar

joint to reduce load on medial longitudinal arch. If

muscles become fatigue, the injury risk may increase

due to increased strains and bending moments

because muscles cannot absorb high impact and fail

to protect bones from tension (Mosca V. S., 2010).

There is still controversy about physical

performances in flatfoot. Tudor et al found that static

balance performances was similar between flatfoot

and normal foot children (Tudor et al., 2009), but

another studies found poorer physical performances

in flatfoot compared to normal foot (Marginson et

al., 2005; Roohi et al., 2013). Several researches

have shown correlations between flatfoot and their

functional limitation while running and walking

mostly on adults. There has been no study to find out

fatigue’s effect on static balance and lower limb

muscles activity in children. Therefore, we would

like to know whether fatigue was the one factor that

influenced physical performances in flatfoot

Adriyani, R., Apriantono, T. and Suprijanto, S.

Inﬂuence of Fatigue on Balance and Lower Limb Muscles Activity in Flatfoot Children.

In Proceedings of the 2nd International Conference on Sports Science, Health and Physical Education (ICSSHPE 2017) - Volume 1, pages 5-11

ISBN: 978-989-758-317-9

children. We have hypothesized that fatigue will

influence static balance and lower limb muscles

activity in flatfoot compared to normal foot children.

2 METHODS

2.1 Participants

19 elementary school children aged 9 to 11 years

took part in this study. Of these all children, 10 had

normal foot (8 males and 2 females) and 9 had

flatfoot (5 males and 4 females) with unknown

pathologies were recruited to take part in this study

(Table 1).

Ethics approval was obtained from the

Polytechnic of Health, Ministry of Health, Research

Ethics Committee (ID:LB.02.1/3.1/0260/2015).

Details of the study procedure were presented, and

consent was obtained from parents before children

participated in the study.

2.2 Screening Protocol

Foot scanner was used to categorize foot posture.

Foot posture was classified using arch index as a

clinical measurement from footprint analysis with

AUTOCAD 2013 software. Each foot was placed on

foot scanner while participants were standing. Only

one foot from was included in the data analysis

where we categorized the “the flatter foot” into the

flatfoot group

To qualify for the flatfoot group, participants had

arch index greater than two standard deviations from

the mean values obtained for the normal foot group.

Figure 1 represents the arch index measurements

from the footprint. Based on the arch index, we

divided participants into flatfoot and normal foot

group.

Figure 1(a) Figure 1(b)

Figure 1: Footprint of flatfoot child where the length of the

foot (excluding the toes) is divided into equal thirds to

give three regions: A -- forefoot; B -- midfoot; and C --

heel. Arch index is then calculated by dividing the midfoot

region (B) by the entire footprint area (Arch index =

B/[A+B+C] (Figure.1a). We used AUTOCAD 2013

software to calculate the arch index (Figure.1b).

2.3 Experimental Protocol

All participants completed the entire protocol in a

single session. Pre fatigue data collection consisted

of measurements of body mass index, body fat

percentage, vertical jump test, static balance test,

and electromyographic (EMG) activity while

performing static balance test. Post fatigue data

collection consisted of vertical jump test, static

balance test, EMG activity while performing static

balance test. During trials, the participants were

instructed to perform static balance test and

electromyographic data was collected. Each test was

performed two times and separated by a 3 minutes

rest period. Only the best result will be included in

the statistical analysis.

2.3.1 Body Mass Index

Body height and body weight were measured using

ZT 120 health scale. The weight was recorded to the

nearest 0,1 kg and the height was also recorded to

the nearest 0,01 m. Body mass index was calculated

for each subject by dividing the weight by the square

of the height. We used WHO AnthroPlus software to

assess body mass index.

2.3.2 Body Fat Percentage

The measurement site was on triceps and calf at the

right part of the body using skinfold calliper. Test

was performed two times. The result was an average

ICSSHPE 2017 - 2nd International Conference on Sports Science, Health and Physical Education

values of these two trials. Slaughter Lohman

Formula was used to calculate body fat percentage.

Figure 2 (a) Figure 2 (b)

Figure 2: Measurement site of body fat percentage on

triceps (Figure. 2a) and calf (Figure. 2b).

2.3.3 Vertical Jump Test

This test was performed on vertical jump meter. The

task was to perform two maximal eccentric-

concentric jumps with hands held at the hips along

the test. A single jump started with straight legs

performing a natural flexion before the take off

phase. We only took the best results from two trials.

2.3.4 Static Balance Test

Participants performed single limb standing test

barefoot for 30 seconds with opened eyes. The non

support limb was held flexed 90

at the knee but not

contacting the supporting limb muscles while their

hands were placed on the hips. The goal of the test is

to stand on static position for maximum 30 seconds.

Weight shifting and/or equilibrium reactions in the

feet are acceptable. These timed trials should be

stopped if the supporting limb moves in a space or

the non support limb touches the support limb. The

result was the best performed of these two trials.

2.3.5 Electromyographic Activity

Tibialis anterior, gastrocnemius medialis and

peroneus longus muscles activity were recorded

using bioamplifier with the use of pediatric soft-

cloth electrodes which was more comfortable for

child skin. An inter-electrode distance was 10 mm.

The placement of surface electrodes followed the

recommendation of SENIAM (www.seniam.org).

Reference electrodes for tibialis anterior and

gastrocnemius medialis were placed on malleolus

medial and reference electrode for peroneus longus

was placed on malleolus lateral (Figure 3).

Figure 3(a) Figure 3(b) Figure 3(c)

Figure 3: The placement of electrodes on tibialis anterior

(a) gastrocnemius medialis (b) and peroneus longus (c).

2.3.6 Fatigue Protocol

Participants completed plyometric jumping fatiguing

protocols (Marginson et al., 2005). Before testing,

each participant followed a standardized warm-up. It

consisted of five submaximal and five maximal

continuous jumps. After warming up, the

participants performed eight sets of 10 continuous

maximal plyometric jumps.

The participants stood with feet shoulder width

apart and hands on hips. They were asked to jump as

high as possible and each jump was performed as

fast as possible.

Each set of the 10 jumps was separated by one

minute rest period, in which the participant was still

walking around to reach fatigue’s effect.

2.3.7 EMG Data Processing

During the static balance test, raw EMG signal was

passed through a differential amplifier at a gain of

1000 with the sampling frequency of 2 kHz. A band

passed filter of 512 Hz for the surface electrodes.We

used three channels of 2048 samples/seconds for

each muscle recording.

Encoder samples the incoming signals, digitizes,

encodes, and transmits the sampled data to the TT-

USB interface unit.

A fiber optic cable was used for transmission to

the TT-USB, providing maximum freedom of

movement and electrical isolation. Myoscan sensor

connected each electrode set to EMG encoder.

The raw EMG signal of the selected lower limb

muscles between pre fatigue and post fatigue were

analysed every 2 seconds to get power spectrum

profile. Median frequency was used as a parameter

for muscle fatigue which divided power spectrum

Inﬂuence of Fatigue on Balance and Lower Limb Muscles Activity in Flatfoot Children

into two equal parts. Median frequency timing was

also analysed for each muscle.

2.3.8 Statistical Analysis

Shapiro wilk test was used for data distribution. The

statistical analysis was chosen based on

compatibility with the measure scale. We used a

parametric test or non parametric test which was

based on data distribution.

To show differences between pre fatigue and

post fatigue t-dependent tests were used, where

independent samples t-tests were used to show

differences between flatfoot and normal foot with p

value less than 0.05 considered significant.

3 RESULTS

Table 1: Participants Anthropometric and Foot Posture

Characteristics.

General

Anthopometric

Flatfoot

N=9

Normal

Foot

N=10

value

Gender Ratio

5/4

8/2

(Male/Female)

Age (Mean±SD)

Years

9.89 ±

0.60

10.10 ±

0.88

0.538

Height (Mean±SD)

134.06 ±

6.32

140.50 ±

9.7

0.108

Weight (Mean±SD)

33.11 ±

7.25

34.00 ±

8.46

0.810

BMI (Mean±SD)

Kg/m

18.26 ±

2.94

17.26 ±

4.48

0.579

Body Fat Percentage

(Mean±SD) %

28.38 ±

6.52

27.85±

6.12

0.855

Foot Posture

Characteristics

Arch Index

(Mean±SD)

0.36 ±

0.01

0.25 ±

0.01

0.000*

*Significantly different p value < 0.001

There were no significant differences for

anthropometric characteristics between flatfoot and

normal foot groups. Body composition (body mass

index and body fat percentage) between flatfoot and

normal foot was almost equal. However, foot

posture was shown significantly different (p < 0.05)

in both groups (Table 1).

Table 2: Physical Fitness Profile between Flatfoot and Normal Foot.

Physical fitness

Pre fatigue

p value

Post fatigue

p value

Flatfoot

Normal foot

Flatfoot

Normal foot

Static balance

(mean±SD) seconds

27.44 ± 4.61

29.80 ± 0.63

0.188

21.67 ± 8.66

29.10 ± 2.23

0.020*

Vertical Jump

(mean ± SD) cm

34.00 ± 6.8

29.00 ± 5.68

0.873

33.60 ± 3.59

29.60 ± 3.02

0.774

*Significantly different p value < 0.05

Based on physical fitness profile, there were

significant differences on static balance

performances between both groups at post fatigue

condition (p< 0.05) (Table 2).

Table 3: Median Frequency (MF) of Selected Lower Limb Muscles between Flatfoot and Normal Foot.

Lower limb muscles

Pre fatigue

p valueP

Post fatigue

p value

Flatfoot

Normal foot

Flatfoot

Normal foot

MF tibialis anterior

(Hz)

78.71 ± 23.31

90.77 ± 37.38

0.902

88.86± 45.50

99.86 ± 50.64

0.806

MF gastrocnemius

medialis (Hz)

90.12 ± 35.88

90.90 ± 23.09

0.327

91.35 ± 37.83

85.18 ± 30.16

0.870

MF peroneus longus

(Hz)

120.52 ± 38.60

98.57 ± 44.28

0.221

104.62 ± 39.83

110.73 ± 78.98

0.806

*Significantly different p value < 0.05

Decreased median frequency of lower limb

muscles (tibialis anterior, gastrocnemius medialis

and peroneus longus muscles) showed no

differences between both groups (Table 3).

ICSSHPE 2017 - 2nd International Conference on Sports Science, Health and Physical Education

Table 4: Median Frequency (MF) Timing of Selected Lower Limb Muscles between Flatfoot and Normal Foot.

Lower limb

muscles

Pre fatigue

p valueP

Post fatigue

p value

Flatfoot

Normal foot

Flatfoot

Normal foot

MF timing of

tibialis anterior

(seconds)

16.44 ± 10.52

10.8 ± 8.12

0.234

6.89 ± 5.57

14.0 ± 9.04

0.054*

MF timing of

gastrocnemius

medialis (seconds)

10.44 ± 8.11

17.2 ± 6.47

0.060

9.33 ± 7.07

14.2 ± 8.66

0.201

MF timing of

peroneus longus

(seconds)

14.44 ± 10.76

13.2 ± 9.24

0.790

5.78 ± 4.17

12.4 ± 7.7

0.033*

*Significantly different p value < 0.05

Median frequency timing of tibialis anterior,

gastrocnemius medialis and peroneus longus were

appeared earlier (at 6,9,5 seconds) in flatfoot

compared to normal foot children (at 14,14,12

seconds) at post fatigue. It showed significant

differences on median frequency timing of tibialis

anterior and peroneus longus (p<0.05) in flatfoot

compared to normal foot, but there were no

significant differences for gastrocnemius medialis

(Table 4).

4 DISCUSSION

Anthropometric characteristics were almost equal in

both groups. Flatfoot children were shorter than

normal foot children. We found that body mass

index and also body fat percentage had no

differences in both groups. These findings is in

contrast to another studies (Chang et al., 2010; Cetin

et al., 2011). In this study, there was no body size

effect on physical performances in both groups.

Prevalence of flatfoot is higher in males than in

females (Abolarin et al., 2011; Chang et al., 2010;

Ezema et al., 2014; Mickle et al., 2011; Wozniacka

et al., 2013), and it is also similar to findings of our

study.

Arch index of the participants was determined

with inclusion value for clinical measurements

(Murley et al., 2009). Arch index is most repeatable

and have a high correlation with arch height value

(Queen et al., 2007).

The arch index value of children was higher than

young adults in a previous study conducted by

Murley et.al (Murley et al., 2009). In this study, we

chose the “flatter foot” for flatfoot group to get the

best comparison with normal foot.

This study would like to find out the influence of

foot posture and fatigue on static balance and EMG

activity of selected lower limb muscles. At pre

fatigue condition, our findings were similar to Tudor

et.al (Tudor et al., 2009) which showed no

differences on physical performances such as static

balance and vertical jump between flatfoot and

normal foot children. In the other hand, several

researches (Roohi et al., 2013; Marginson et al.,

2005) showed poorer performances in flatfoot

children.

Our findings gave an explaination about the

controversial findings in static balance performances

between flatfoot and normal foot in previous studies.

We investigated the effect of fatigue on physical

performances in both groups. The results revealed

that fatigue was one factor which influenced static

balance in flatfoot children. Lack of stability in

flatfoot was in agreement with Tsai et.al (Tsai et al.,

2005) where flatfoot had greater displacement in

anterior posterior direction as a mechanism to their

poorer postural stability.

The fatigue protocol using plyometric jumping

fatiguing protocols (Marginson et al., 2005) could of

reach fatigue’s effect in both groups. It was shown

on significantly decreased vertical jump

performances between pre fatigue and post fatigue.

Muscle fatigue are measured through EMG

signal. Decreased median frequency and greater

percentage of maximum amplitude are the parameter

of fatigue condition on muscles. During static

balance trials, decreased median frequency of lower

limb muscles showed no differences between pre

fatigue and post fatigue in both groups. These

findings are in contrast to Murley et.al (Murley et

al., 2009) which showed a greater percentage of

maximum amplitude for tibialis anterior in flatfoot

compared to normal foot. This might be caused to

the fact that mean aged of these children were 10

years which were less competent at the task of

balancing on one limb (Mickle et al., 2011), so both

groups can’t maintain their balance well.

Inﬂuence of Fatigue on Balance and Lower Limb Muscles Activity in Flatfoot Children

However, median frequency timing of the

selected lower limb muscles were showed earlier in

flatfoot children. It gave the facts that flatfoot

children experienced fatigue earlier compared to

normal foot children. It seemed significant for

median frequency timing of tibialis anterior and

peroneus longus because they worked harder to

stabilize the subtalar joint. These findings is similar

with Neptune et al (Neptune et al., 1999) where

tibialis anterior and peroneus longus had to work

harder to limit excessive subtalar joint rotation in

order to prevent ankle injuries. Everted and

dorsiflexed foot will stretch the invertor muscles

(tibialis anterior) and plantarfleksor groups

(peroneus longus) during weight bearing position.

This study may have implications when choosing

an appropriate sport type for flatfoot children in

order to prevent earlier fatigue in flatfoot children

that might lead to injury because of the impairment

of static balance. These findings are in agreement

with the importance of strengthening exercise on

inversion muscles (tibialis anterior) and peroneus

longus in flatfoot children.

5 CONCLUSION

Fatigue influenced static balance and tended to

appear earlier on lower limb muscles in flatfoot

children. It should take into consideration when

flatfoot children get involved in high impact sports.

Further research might needed to investigate the

influence of foot posture and fatigue on static

balance in children over 11 years to get better

comparison because balance slowly improves until

10 years of age.

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Inﬂuence of Fatigue on Balance and Lower Limb Muscles Activity in Flatfoot Children