Vol.2, No.2, 57-64 (2013) Advances in Aging Research
http://dx.doi.org/10.4236/aar.2013.22008
Relationships between gait properties on soft
surfaces, physical function, and fall risk for the
elderly
Shinichi Demura1, Sohee Shin2, Shinji Takahashi3, Shunsuke Yamaji4*
1Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
2School of Medicine, Gifu University, Gifu, Japan
3Teikyo Heisei University, Chiba, Japan
4Faculty of Medical Sciences, Morphological and Physiological Sciences, Sports Medicine, University of Fukui, Fukui, Japan;
*Corresponding Author:
Received 5 December 2012; revised 20 January 2013; accepted 27 January 2013
Copyright © 2013 Shinichi Demura et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The plantar aspect change caused by contact
with soft surfaces creates and unstable gait and
increases the risk of falling, especially in the
elderly. This study aimed to analyze gait prop-
erty by three-dimensional motion analysis on
soft and normal surfaces and to clarify the rela-
tionship with physical function and fall risk.
Twenty-four older people aged 65 - 88 years old
and living independently without any assistive
device (7 men, 17 women) performed 5 m of
walking with own maximal speed on normal and
soft surface walkways. The soft surface walkway
used was a low rebound urethane foam mattress.
The three-dimensional kinematic gait analysis
by sixteen anatomic points was used to evaluate
gait property on both walkways. The gait prop-
erty on soft surfaces tended to be swinging up
and down in each joint and to largely lean left
and right as compared with the normal surface.
Moreover, it tended to decrease in a step length
and to increase in a step width. All gait parame-
ters on soft surfaces correlated significantly
with functional reach. On the other hand, that on
normal surface correlated significantly with leg
strength. Gait properties on soft surfaces which
changes in plantar aspect during foot contact
differs from those on normal surfaces. Walking
on soft surfaces may cause an unanticipated
inverted pendulum sway supporting a foot con-
tact point because of the disturbance by a sag-
ging walkway; in short, requiring more effort to
keep a body balanced. In conclusion, gait on the
soft surfaces requires balance ability (functional
reach) rather than leg strength.
Keywords: Three-Dimensional Kinematic Analysis;
Leg Strength; Balance
1. INTRODUCTION
Prolongation of independent life for the elderly and
control of the marked increased rate of medical expenses
are key tasks in Japan, which has become a super aging
society. Mobility is one of the most basic skills necessary
to keep an independent daily life. Their falls bring about
serious problems related to the decline of quality of life,
such as the bedridden state caused by bone fractures, and
the decline of activity range and volume due to the fear
of falling. It was reported that more than one third of the
elderly over 70 years of age living independently in com-
munities experience a fall at least once a year, and their
fall occur chiefly during walking or transfer movement
[1].
A fall is the result of exceeding the limit of one’s own
postural control from any cause. Age-related decline in
the physical functioning of visual, locomotion, and ner-
vous system makes stability during walking difficult.
However, a fall during walking rarely occurs without
some sort of trigger, except for those who fall due to
dizziness or syncopy. Most falls involve a trigger such as
a misstep or slip. The risk of falling increases when a
person lacks the ability to adapt to surface environment
changes (e.g. tilt, difference in floor height, slipperiness,
and hardness change) [2-4].
Many mobility tests that evaluate fall-related physical
fitness have been proposed in the previous studies: 10-m

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64
58
Walking Test [5], Figure Eight Track Walking Test [6],
Timed Up and Go Test [7], and Tandem Gait Test [8].
These tests are useful to evaluate the independence of
daily living. However, mobility on stationary surfaces
may not reflect the ability to avoid a fall, because the fall
risk relates to the adaptability to variations in walking
environments, as previously stated.
On the other hand, an obstacle walk test has been
proposed as an irregular surface condition [9,10]. It is a
useful test to evaluate avoiding a stumble that induces a
fall. However, the participants can see the obstacles
placed in test walkways before they begin to walk, and
are therefore more likely to maintain stability.
There has been little research on the gait of elderly
people on varied surfaces. Therefore, a soft surface, such
as a mattress, is considered to be adequate for the gait
analysis of elderly individuals because the change of
plantar aspect when contacting the surface increases the
risk of falling. When an elderly person walks on soft
surfaces, the plantar aspect changes and they are required
to control the sway of their body by using somatosensory
input through plantar and postural reflexes. It is much
more difficult for an individual to maintain their balance
when walking on a softer surface compared to a normal
walkway.
Considering a fall process, it will be important to ex-
amine the body’s stability during walking in the above
walkway condition. It was hypothesized that gait pro-
perty on soft surfaces differs from that under normal con-
ditions, and is related to different physical functions,
adding that walking on soft surfaces reflects more the
degree of fall risk and independence of daily living. If
physical functions related to gait properties on both
walkway conditions differ, it is necessary to review the
exercise and physical functions to prevent falls.
This study aimed to analyze gait property by three-
dimensional motion analysis on soft and normal surfaces
and to clarify the relationship between physical function
and fall risk.
2. METHODS
2.1. Participants
Seven older men (Age: 72.4 ± 5.2 years, Height: 162.6
± 6.2 cm, Body mass: 65.7 ± 13.0 kg) and seventeen
women (Age: 74.6 ± 7.5 years, Height: 148.9 ± 7.3 cm,
Body mass: 52.2 ± 9.8 kg) living independently without
any assistive devices in the community dwelling partici-
pated in this study. There was no significant difference in
the mean ages of the sexes (t(22) = 0.670, p = 0.510).
Informed consent was obtained from each participant
after a full explanation of the experimental project and its
procedure. This study was approved by the Ethics Com-
mittee on Human Experimentation of Faculty of Educa-
tion, Kanazawa University.
2.2. Experimental Device
For the three-dimensional kinematic gait analysis, si-
xteen passive markers (15-mm diameter reflective, adhe-
sive styrofoam) were attached bilaterally to the following
anatomic landmarkers; acromion, olecranon, ulnar head,
anterior iliac crest, greater trochanter, knee, ankle and
fifth metatarsal. Marker trajectories were recorded two
strides after one stride from onset of walking at 60 Hz by
six digital camcorders (MA-2000, Anima, Japan). Tridi-
mensional reconstruction of the marker trajectories was
performed by means of a reference system (leveling
wires with equally spaced markers, forming a cube 3.0 m
in length, 1.70 m in height, and 1.30 m in width) in order
to calibrate the experimental set.
Gait parameters were selected as follows: mean walk
velocity, standard deviations of the movement distance
of joint points (acromion, knee, and ankle) in the frontal
and sagittal directions [11]. Further analysis was per-
formed on only the right joint points because the move-
ment distance between the right and left joints had a 0.95
correlation.
2.3. Procedure
Using within-subjects design, the participants perfor-
med a 5-m walk at their own maximal speed on normal
and soft surface walkways. The trial order on both
walkway conditions was allocated randomly, and the rest
among the trials was set 10 minutes. The participants
walked on a low rebound urethane foam mattress (Blan-
ce mattress, Achiless, Japan; width: 970 mm, depth: 603
mm, thickness: 80 mm) spread on the soft surface walk-
way. The toughness of mattress was 75 N and the ratio of
renaturation was 92%.
2.4. Falls Risk Assessment Score and
Independent of Daily Living Score
Fall risk was estimated using a fall risk assessment
questionnaire [4-12]. This consisted of eight risk factors
(gait deficit, balance deficit, muscle weakness, disease,
medication use, environment, visual and hearing deficit,
and fall fears: 15 items). Participants answered all ques-
tions with a dichotomous scale (yes or no). The response
with a high risk category for each question was consid-
ered to be a “high-risk response”, and persons scoring
over five points were judged to have a high fall risk.
Independence of daily living was estimated from the
view point of physical function level by falls efficacy
scale [13] and activity of daily living (ADL) test [14].
The former consists of 13 items common to daily living,
and participants were evaluated regarding their confi-
dence with these items on a scale of one to ten. The ADL

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64 59
test consisted of 12 items representing ADL domains of
walking ability, changing and holding posture, balance,
and muscular strength and dexterity (manual activity).
2.5. Tests of Leg Function
Tests of leg function were selected from leg strength
and dynamic balance ability which related to mobility/
transfer movement and posture control ability: isometric
muscle strength tests of toe flexion, knee extension, and
hip flexion joints in the former, and a functional reach
test in the latter. Isometric muscle strength tests were
performed twice for both legs using a hand held dyna-
mometer (μTAS F-1, ANIMA, JAPAN). A mean of a
higher value in both legs was used as maximal strength
in each joint. Plantar flexion was measured in long sit-
ting position, and the others were measured in sitting
position. Functional reach was measured by using an
elastic stick [15]. Each participant maximally extended
the dominant hand from an upright posture while touch-
ing the top of an elastic stick fixed at dominant acromion
height on the wall. They pushed and shortened the elastic
stick by extending the dominant hand and the shortened
distance of the elastic stick was measured.
2.6. Data Analysis
An unpaired t-test was used to reveal sex differences
in the fall risk assessment score and independence of
daily living score. Two-way ANOVA (sex × walkway
condition) was use to reveal the difference of gait para-
meters between both surface conditions. Pearson’s cor-
relation coefficient was calculated to clarify the rela-
tionships between gait parameters under both walkway
conditions, fall risk score, independence of daily living
score, and leg function. A probability level of 0.05 was
indicative of statistical significance.
3. RESULTS
Table 1 shows sex differences of fall risk scores, in-
dependence of daily living scores, and leg function.
There were no significant sex differences in all parame-
ters. All effect sizes by Cohen’s d were less than mode-
rate values (d < 0.68).
Figure 1 shows exemplification of the gait pattern
analyzed by joint point trajectories in the frontal and sa-
gittal directions. The gait properties on a soft surface
tended to swing up and down in each joint and to lean to
the right and left directions significantly as compared
with the normal surface. Moreover, it tended to decrease
with a step length and to increase with step width.
Table 2 shows the result of two-way ANOVA (sex ×
walkway condition) regarding gait parameters. There
were significant walkway condition effects in all para-
meters. Walk velocity on soft surface significantly de-
creased, and body sway in the right-left and up-down
directions significantly increased. Effect sizes between
walkway conditions by sexes were over 0.5 in all pa-
rameters. In particular, the effect of the magnitude of the
standard deviation of movement distance in the sagittal
direction was relatively high (1.2 - 5.2).
Table 3 shows the correlation coefficients among gait
parameters, fall risk score, and independence of daily
living score by sexes. Walk velocity on the soft surface
correlated significantly with fall efficacy scale and ADL
score in both sexes.
Table 4 shows the correlation coefficients between
gait parameters and leg functions by sexes. All gait pa-
rameters, except for standard deviation of movement
distance in frontal direction at acromion and knee in
males, on soft surface correlated significantly with func-
tional reach in both sexes. On the other hand, those on
normal surfaces tended to correlate significantly with leg
strength.
4. DISCUSSION
This study examined whether the gait properties and
their relationship with the fall risk score and leg func-
tions differ between those on the soft surface which
changes the plantar aspect during foot contact and on the
normal surface.
Takenaka and Uechi [16] reported that sex differences
were not found in walking velocity and fall self-efficacy
scale for people 61 - 91 years of age. In previous studies,
the findings of sex difference on fall incidence were not
always agreement. Some researchers reported that they
were higher in women than in men [4,17,18], but others
reported that there was no significant difference [19,20].
Physical fitness level varies among individuals because it
does not only relate to sex and aging, but also relates to
various factors such as chronic disease, physical activity
and cognition function. There were no significant sex
differences in age, fall risk score, independence of daily
living score, and leg strength in this study. The effect
sizes by Cohen’s d in fall risk and ADL score, and leg
strengths were moderate (0.40 - 0.68), and the sex dif-
ference in these parameters will be found in studies with
a larger sample size.
The standard deviations of movement distance in
frontal and sagittal directions in this study evaluate the
degree of a joint sway. Walking velocity and body stabi-
lity on soft surface decrease because the walkway sinks
down during foot contact. Body sway of acromion in the
frontal direction on soft surface was larger than that of
knee and ankle joints. It is inferred that walking on a soft
surface causes an unanticipated inverted pendulum sway
supporting a foot contact point because of the distur-
bance by the sagging walkway. That is, walking on the
soft surface required to keep the body in balance. On the
other hand, body sway in the sagittal direction was larger

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64
60
Table 1. Sex differences of fall risk score, independence of daily living score, and leg muscle functions.
Male (n = 7) Female (n = 17)
M SD M SD
t ES
Fall risk score point 3.9 2.6 2.9 2.2 0.9 0.40
Fall efficacy scale point 122.1 12.3 122.5 10.4 0.1 0.04
ADL score point 29.7 4.6 26.6 6.0 1.2 0.55
Toe flexion strength kg 5.6 3.0 4.1 2.0 1.5 0.68
Knee extension strength kg 17.0 7.3 14.1 3.7 1.3 0.57
Hip Flexion strength kg 23.1 11.3 19.1 6.4 1.1 0.50
Functional reach cm 32.3 6.6 32.2 5.6 0.0 0.00
There were no significant sex differences in any parameters.
0
20
40
60
80
100
120
140
0.00.81.21.62.02.42.9
movement distance in sagittaldirection(cm)
(sec)
‐60
‐55
‐50
‐45
‐40
‐35
‐30
‐25
‐20
0.00.81.21.62.02.42.9
movement distance in frontal direction (cm)
(sec)
‐60
‐55
‐50
‐45
‐40
‐35
‐30
‐25
‐20
0.00.61.01.41.92.32.73.13.5
movement distance in frontal direction (cm)
(sec)
0
20
40
60
80
100
120
140
0.00.61.0 1.41.92.32.73.13.5
acromion
knee
ankle
movement distance in sagittaldirection(cm)
(sec)
Gaitonnormalsurfacewalkway
Gaitonsoftsurfacewalkway
Figure 1. Exemplification of gait pattern analyzed by movement distance of 8 joint points (only right side) on the both surface
conditions. Upper panel: normal surface walkway, Lower panel: soft surface walkway.
to be small as compared with that at knee and ankle
joints. It is inferred that walking on soft surface required
igher elevation of the foot during the swing phase.
in the knee and ankle joints than in acromion. A sagging
walkway by a foot contact makes the whole body sway
to downward. However, body sway at acromion tended h

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64 61
Table 2. Two-way ANOVA of gait parameters between the both walkway conditions by sexes.
Soft surface Normal surface Two-way ANOVA
Effect size
between both
walkway
conditions
Male Female Male Female sex
walkway
condition inter-action
M SD M SD M SD M SD Ｆ Ｆ Ｆ Male Female
Walk
velocity
(cm/s)
67.3 18.1 72.0 19.6 93.517.890.4 38.5 0.0 11.0* 0.3 1.6 0.6
Standard deviation of movement distance in frontal
direction (cm)
acromion 4.1 1.9 3.4 1.7 2.6 0.7 2.1 0.8 2.3 14.8* 1.3 1.1 1.0
knee 2.9 1.0 2.6 1.8 1.7 0.7 1.8 0.9 0.2 5.8* 0.2 1.5 0.6
ankle 3.9 1.3 2.9 2.0 2.1 0.7 2.1 1.0 1.1 7.8* 1.2 1.8 0.5
Standard deviation of movement distance in sagittal
direction (cm)
acromion 1.9 0.5 1.7 0.7 1.3 0.4 1.0 0.2 1.7 14.7* 0.0 1.5 1.2
knee 3.3 0.5 3.4 0.7 1.4 0.2 1.3 0.3 1.0 337.1* 2.2 5.2 4.2
ankle 6.5 1.1 6.3 0.9 4.9 0.9 4.1 0.7 2.1 105.0* 1.8 1.8 2.8
*p < 0.05.
Table 3. Correlation coefficients among gait parameters, fall risk score, and independence of daily living score.
Male Female
Soft surface Normal surface Soft surface Normal surface
Fall risk
score
Fall efficacy
scale ADL Fall risk score
Fall
efficacy
scale
ADL Fall risk
score
Fall
efficacy
scale
ADL Fall risk
score
Fall efficacy
scale ADL
Walk
velocity
(cm/s)
−0.43 0.78* 0.76* −0.13 −0.09 0.24 −0.33 −0.65* 0.58* 0.08 0.14 0.33
Standard deviation of movement distance in frontal
direction (cm)
acromion −0.16 0.13 0.51 0.40 −0.45 −0.43 0.19 0.16 −0.16 0.07 −0.34 −0.35
knee −0.27 0.16 0.49 0.22 0.02 0.12 −0.26 0.21 0.02 0.01 0.03 0.02
ankle −0.10 0.64 0.22 −0.32 −0.38 0.22 0.06 0.23 0.10 −0.04 0.07 −0.03
Standard deviation of movement distance in sagittal
direction (cm)
acromion 0.72 −0.17 −0.42 0.52 0.03 0.14 −0.01 0.26 −0.01 0.04 0.19 0.51*
knee 0.74 0.14 −0.39 0.19 0.34 −0.11 −0.21 0.19 0.08 −0.35 0.40 0.13
ankle 0.35 −0.13 0.18 0.30 0.45 0.11 −0.23 0.49* 0.41 −0.43 0.65* 0.74*
*p < 0.05.
Moreover, all correlations of gait parameters between
both walkways were not high. Thus, walking properties
on both walkways may be affected by different physical
functions.
Significant correlations were not found between gait
parameters and fall risk score. However, the indepen-
dence score of daily living correlated significantly with
walking velocity on a soft surface in both sexes and the
sagittal direction sway of the ankle joint on a normal
surface in females. Nine participants in this study were
identified to have a high fall risk by cut-off score (5
points) (37.5%), and the others were lower than 3 points.
Fall risk scores involve not only physical function such
as walking ability, leg strength, and balance ability, but
also the other factors such as medicine, environment,
personality, visual and hearing problems, and fear of
falling [4,12]. From the present results, gait parameters
may reflect mainly physical function factors. Meanwhile,

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64
62
Table 4. Correlation coefficients between gait parameters and leg muscle functions.
Male Female
Soft surface Normal surface Soft surface Normal surface
Toe
flexion
Hip
flexion
Knee
extension FR Toe flexion
Hip
flexion
Knee
extension FR Toe flexion
Hip
flexion
Knee
extension FR Toe flexion
Hip
flexion
Knee
extension FR
Walk velocity (cm/s) 0.02 0.18 0.32 0.76* 0.540.730.59 0.690.420.020.05 0.49* 0.48* 0.26 0.07 0.35
Standard deviation of movement distance in frontal direction (cm)
acromion −0.26 −0.11 0.30 −0.45 0.240.320.300.30−0.45 −0.35 −0.35 −0.64* 0.18 −0.02 −0.15 0.34
knee −0.47 −0.45 −0.05 −0.49 0.490.81*0.720.23 −0.31 −0.13 −0.05 −0.48* 0.49* −0.21 −0.15 0.27
ankle −0.52 −0.39 −0.20 −0.81* 0.350.530.48−0.12 −0.26 −0.02 −0.06 −0.48* 0.49* −0.37 −0.29 0.11
Standard deviation of movement distance in sagittal direction (cm)
acromion −0.08 0.19 0.30 −0.76* 0.44 0.84*0.83*0.73 −0.31 −0.15 −0.19 −0.50* 0.64* −0.12 −0.20 0.17
knee −0.07 0.14 0.13 −0.77* −0.11 −0.41 −0.370.22 0.15 0.18 −0.22 −0.52* −0.37 −0.07 −0.22−0.50
ankle −0.08 0.22 0.28 −0.78* 0.08 0.240.120.350.430.13−0.10 −0.50* 0.48* −0.06 0.48*0.18
*p < 0.05, FR: functional reach.
the independence score of daily living was composed of
item groups related closely to physical function factors
[16,21]. Hence, it may have shown relationships with
gait parameters on both surfaces. However, it is noted
that the gait parameters with significant correlations dif-
fered between both walkway conditions. Potter et al. [21]
reported that a relationship was found between Barthel
ADL score and walking speed. However, this relation-
ship depends largely on the physical fitness level of the
older population. Because walking five meters on a nor-
mal surface was an easy task for the elderly in this study,
it is hard to attribute individual differences in gait by
their physical fitness level. Therefore, it may have shown
a poor relationship with the independence score of daily
living.
Conversely, because walking on soft surface poses
high difficulty, a significant relationship with walking
velocity may have been found. Means [9] and Means and
O’Sullivan [22] reported that walking at a high difficulty
level such as navigating an obstacle is superior in the
improvement ratio of physical function to walking nor-
mally for older people living in community-dwelling.
Therefore, walking on a soft surface walkway may be
effective as exercise for fall prevention. In addition,
those displaying greater ankle movements in the sagittal
direction on a normal surface tended to have a higher
independence score of daily living. Foot height during
the swing phase decreases with age and physical function
decline [23]. In this study, the ankle movement of the
sagittal and frontal directions in the normal surface cor-
related with toe flexion strength in females, thus it may
important to improve toe flexion strength for the inde-
pendence of daily living. Moreover, gait parameters on
the normal surface in females, as compared with that on
the soft surface, correlated with leg strength. This sug-
gests that the greater movement of joint points during
normal walking is affected by leg strength. These results
may mean that persons with superior leg strengths walk
forcefully on a normal surface.
On the other hand, almost gait parameters on soft sur-
faces correlated with a functional reach test in both sexes.
This test was proposed to evaluate dynamic balance for
older people [24]. As stated above, walking on a soft
surface which prolonged the swing phase (the one-leg
support phase) requires better balance ability. Walking
on a low rebound urethane foam mattress makes it diffi-
cult to kick the ground when beginning walking and to
elevate a leg due to soft surface. In case of normal walk-
ing, forcefully kicking the ground contributes to gain
rapid and forceful movement. However, forcefully kick-
ing the ground on the soft surface is needed large balance
ability. Because the ankle movement in the sagittal di-
rection on a soft surface correlated positively with func-
tional reach, persons with superior functional reach may
be able to elevate foot during swing phase. In fall pre-
vention exercise schools, it is recommended to improve
iliopsoas and femoral muscles to avoid stumbling over
an obstacle [25,26]. However, it will also be important to
propose exercise to positively move the center gravity of
the body. Such exercises include the functional reach
action which helps to keep body stable while walking on
an irregular surface.
Further studies will be examined to clarify motion
properties using kinematic analysis of other fall trigger

S. Demura et al. / Advances in Aging Research 2 (2013) 57-64 63
actions such as slips and missteps which require a step-
ping strategy.
5. CONCLUSION
In conclusion, gait properties on soft surfaces which
change the plantar aspect during foot contact differ from
those on a normal surface. Body sway of the acromion in
the frontal direction on a soft surface is larger than that
of knee and ankle joints. Walking on a soft surface may
cause an unanticipated inverted pendulum sway support-
ing a foot contact point because of the disturbance by the
sagging walkway. Gait on the soft surface requires bal-
ance ability (functional reach) rather than leg strength.
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