Proceedings of the 2021 IEEE International
Conference on Intelligence and Safety for Robotics
Nagoya, Japan, March 4-6, 2021

Identiﬁcation of healthy elderly’s gait characteristics
by analyzing gait parameters
Takuya Mayumi1 , Yasuhiro Akiyama1 , Shogo Okamoto1 , and Yoji Yamada1
Abstract— For the elderly, the deterioration in the qualityof life owing to the decline in walking function causes various
problems like tripping and falling. Thus, it is important toimprove the walking function by gait characteristics. In thisstudy, Some gait parameters based on gait data were introduced, and gait characteristics of the elderly were analyzed bycomparing with those of the young. The gait data publishedby the National Institute of Advanced Industrial Science andTechnology were used. Data from 103 young (27 ± 6 years) and
107 elderly (69 ± 3 years) subjects were used. The following
points characterize gait of the elderly in comparison with the
gait of young adults. (1) The elderly’s center of mass is locatedin a forward position in the area of the base of the support
when walking. (2) A longer step length is correlated to thesteeper inclination of lower limb axis on heel contact timing.
(3) On the toe-off timing, steeper foot angle is less accompaniedby the ﬂexion of knee, unlike in young adults. (4) The increasein minimum foot clearance is accompanied by knee ﬂexion atheel contact and backward swing of the lower leg at the toe-off
timing. These ﬁndings are useful to develop walking assist suitsthat improve walking function in the elderly.

I. INTRODUCTION
Nowadays, the population is aging rapidly in advanced
countries. The gait ability of the elderly decreases owing toaging effects such as the deterioration of muscle strengthand balance ability. The limitation of gait ability may decrease the quality of life by limiting daily living activities.
Therefore, maintaining walking function is important for
improving the quality of life.
Thus, it is important to understand the characteristics ofthe gait of the elderly in order to maintain walking function.
Furthermore, the elderly’s gait analysis is considered to
be extremely useful for determining the elderly’s fallingmechanism and the developing walking assist suits basedon the gait characteristics.
Thus, in this study, the gait motion of the elderly andyoung adults recorded in a database were analyzed. Parameters representing gait motion were calculated and compared.
Furthermore, characteristics of elderly’s gait useful for thedevelopment of walking assist suits, were revealed.
II. METHODSIn this study, parameters representing gait characteristics
were calculated. To compare and evaluate the gait motionof the elderly, data from sufﬁcient number of samples werecollected from people with various attributes. Therefore, the1 Takuya Mayumi, Yasuhiro Akiyama, Shogo Okamoto and Yoji Yamada
are with Department of Mechanical Systems Engineering, Nagoya University, Japan. akiyama-yasuhiro@mech.nagoya-u.ac.jp

978-0-7381-4674-4/21/$31.00 ©2021 IEEEAIST gait database published by the National Institute ofAdvanced Industrial Science and Technology (AIST) wasused [1].
The AIST gait database contains the gait data of 300
healthy adults. For one subject, 10 gait cycles, which are
determined as the interval between heel contact (HC) andsuccessive HC, starting from both legs, were recorded [1].
A motion capture system was used to measure gait data, andthe sampling frequency was 200 Hz. The joint angle andcenter of mass were obtained from the motion capture datausing Visual 3D (C-motion, Inc., MD). The ground reaction
force was measured by force plates at the sampling frequencyof 1 kHz.
A. Gait Parameter
The data of eight out of 111 subjects aged 20-40 years
and four out of 111 subjects aged 65 and above years did
not ﬁt the model. In the two excluded cases, subjects didn’t
put their feet correctly on the force plate. In nine excluded
cases, the data at HC was not obtained. In one excluded case,the data of the left toe marker was not obtained. Thus, thedata of 103 subjects aged 20-40 years and 107 subjects aged
65 and above years were used, except for abnormal results.
A gait event was detected from the force plates, anda single stride was extracted from each trial. Sixteen parameters were introduced for characterization of the gait.
These parameters were calculated from the joint angles,
marker positions, and center of gravity (COG) positions
using the following method. The t-test was used to compare
the parameters between the elderly and young adults..
The correlation value was calculated to compare the trendof the distribution of each parameter. It was calculated forthe young and elderly respectively. The parameters whoes
correlation value clearly differed between the young andelderly were further analyzed. In addition, the variables thatshow a correlation value exceeding 0.2 or below -0.2 werechosen.
1) Step length: Step length is deﬁned as the distance inthe forward direction between the position of the heel marker
at the HC of the leading leg and the position of the heelmarker at the HC of the opposite leg.
2) Step width: Step width is deﬁned as the lateral distance
between the right heel marker at the right HC and the left
heel marker at the left HC.
3) Pelvis angle: Pelvis angle is deﬁned as the inclinationof the plane around the lateral axis created by the markersof the left and right anterior superior iliac spines and themarkers of the sacral point.

2204) Minimum foot clearance: Minimum foot clearance(MFC) is deﬁned as the distance from the ﬂoor to the solewhen the foot is horizontal to the ground during the swing
phase. The heel marker and toe marker are used to estimate
the MFC. Fig. 1 shows a geometric model for calculating
the MFC.
As shown in Fig 1(a), the timing when the entire solecontacts the ground is estimated. The vector α is deﬁned
as the vector from the heel to toe marker. The entire soleis considered to contact with the ground when the rate ofchange in the slope of this vector α is close to 0. The angle
between the vector α and the ground at this time is θhorizon ,and the height from the ground to the heel marker is hheel .
After toe-off (TO), as shown in Fig 1(c), the angle between
the vector α and the ground again becomes θhorizon . Whenθ equals to θhorizon , the foot is assumed to be horizontal
and h is deﬁned as the height from the ground to the heelmarker. MFC is calculated by the difference between h andhheel .
5) Thigh tilt: Thigh tilt is deﬁned as the angle between
the thigh and horizontal axis in the sagittal plane. Thigh isdeﬁned as the vector from the hip joint point to the midpoint
between the lateral epicondyle and the medial epicondyle ofthe femur. Thigh tilt was calculated at HC and TO. Fig. 2
shows the thigh tilt.
6) Knee angle: Knee angle is deﬁned as the angle between the thigh and the lower thigh. The thigh is deﬁned
above. the distal end of the shank is deﬁned as the midpoint
between the lateral malleolus and medial malleolus. The
proximal end is deﬁned as the midpoint between the lateralepicondyle and the medial epicondyle of the femur. The
lower thigh is deﬁned as the vector from the proximal end
to the distal end. The knee angle was calculated at HC and
TO. Fig. 2 shows the knee angle.
7) Lower thigh tilt: Lower thigh tilt is deﬁned as the angle
between the lower and the horizontal direction. The deﬁnitionof the lower thigh is as described above. The lower thigh tilt
was calculated at HC and TO. Fig. 2 shows the lower thightilt.

Fig. 1.

8) Foot angle: Foot angle was introduced as a representative parameter of the strength of kicking at TO. The
distal end is deﬁned as the midpoint between the ﬁrst andﬁfth metatarsal heads. The proximal end is deﬁned as the
midpoint between the lateral and medial malleolus. Foot
angle is deﬁned as the angle which the vector from the distal
end to proximal end, makes with the horizontal direction. The
foot angle is offset to 0 when the entire sole contacts theground. The foot angle was calculated at TO. Fig. 3 shows
the foot angle.
9) Upper body tilt: Upper body tilt is deﬁned as theinclination of the line connecting the midpoint between C7
and the upper margin of the sternum with the midpoint
between the xiphold process and the point directly behind
it. The backward tilt direction is deﬁned as the positive
direction.
10) Ratio of center of gravity position: Ratio of centerof gravity (COG) position is deﬁned as the ratio of COG
positions on the area of the base of support (BOS), which
is a rectangle consisting of the heel positions of both thefeet at the time of HC. The ratio of the COG position in
the lateral direction (COGr lateral ) against forward direction
and the ratio of COG position in the forward direction(COGr f orward ) were calculated following formulas, using
distance between left heel and COG position in lateral
direction (COGp lateral ), distance between right heel and
COG position in the forward direction (COGp f orward ),right step length (RS), and step width (SW). Ratio of COG
position was calculated at the right HC. Fig. 4 shows theratio of COG position.
COGp lateral
SW
COGp f orward
COGr f orward =RS

COGr lateral =III. RESULTS
The values of gait parameters between the young andthe elderly that showed a p-value are given in Table I.
The values of step length, knee angle at HC, lower thightilt at HC, and foot angle were signiﬁcantly smaller inGeometric model for calculation of minimum foot clearance
Fig. 3.

Fig. 2.

The deﬁnition of lower leg angle

Fig. 4.

221

The deﬁnition of foot angle

Ratio of center of gravity positionelderly subjects than in young subjects. Regarding step lengthnormalized with height, p-value is less than 0.01, and thevalue is signiﬁcantly smaller in elderly subjects than in young
subjects. In addition, the ratio of the COG position in theforward direction was signiﬁcantly higher in elderly subjects
than in young subjects. The correlation coefﬁcient of thightilt at TO, knee angle at TO, lower thigh tilt at HC and TO,
and foot angle with respect to right step length are given in
Table II. Knee angle at TO, lower thigh tilt at HC, and footangle showed a positive correlation with right step length inboth young and elderly subjects. Thigh tilt and lower thightilt at TO showed a negative correlation with right step length
in both young and elderly subjects.
The correlation values of thigh tilt and lower thigh tilt at
HC with respect to the ratio of COG position in the forward
direction are given in Table III. Thigh tilt and lower thigh tilt
at HC showed a negative correlation with the ratio of COG
position in the forward direction.
The correlation values of thigh tilt and knee angle at TOwith respect to foot angle are given in Table IV. There
was a slight correlation between foot angle and thigh tilt
at TO in young subjects. In contrast, foot angle showed anegative correlation with thigh tilt at TO in elderly subjects.
In addition, foot angle showed a negative correlation withknee angle at TO in young subjects. On the contrary, there
was no correlation between foot angle and knee angle at TO
in elderly subjects.
The correlation values of right step length, knee angle
at HC, foot angle, and lower thigh tilt at TO with respect
to MFC are given in Table V. MFC showed a positive
correlation with step length in elderly subjects. MFC showeda negative correlation with knee angle at HC and lower thightilt at TO in both elderly and young subjects. There was nocorrelation between MFC and foot angle in elderly subjects.
In contrast, MFC showed a positive correlation with footangle in young subjects.
IV. DISCUSSION
In this study, gait parameters were calculated based on
AIST gait data to elucidate the characteristics of the elderly’s

gait to develop the countermeasures such as a gait assist device for the elderly against fall. We compared the distributionof gait parameters between the young and elderly.
A. Characteristics of gait regarding to step length
From the results in Table I, step length of the elderly
was approximately 4 cm smaller than that of the young.
The walking speed of the young and elderly was 1.36 ±0.03 m/s and 1.31 ± 0.15 m/s, respectively, expressed byaverage and standard deviation. The p-value was 0.03, andthe walking speed was signiﬁcantly higher in young subjects.
The correlation coefﬁcient between the walking speed andstep length was 0.77 in young subjects and 0.74 in elderly
subjects. The decrease in walking speed is considered to be
one of the causes of the elderly’s decrease in step length.
This is consistent with the report [2][3] that the higher thewalking speed, the larger the step length.
From the results in Table II, the step length showed apositive correlation with knee angle TO, the lower thigh tilt
at HC, and foot angle in both young and elderly subjects. In
addition, step length showed a negative correlation with thethigh tilt at TO and the lower thigh tilt at TO in both young
and elderly subjects. The hip extension, the knee extension at
TO, forward swing of the lower leg at HC, backward swingof the lower leg at TO, and the foot angle accompanied theincrease in step length and walking speed. It is consideredthat the smaller lower thigh tilt at HC and foot angle of theelderly corresponds to a smaller step length.
B. Characteristics of gait regarding to ratio of COG position
From the results in Table I, the ratio of COG position in
the forward direction is located forward in the elderly thanin the young. There is a possibility that the tilt of upper bodyaffects COG. However, there was no signiﬁcant difference inthe tilt of the upper body between the young and the elderly.
In addition, the correlation value was very small in both ofthem, which showed no correlation. Thus, it is consideredthat the ratio of COG position in the forward direction isaffected by the posture and motion of the lower limbs.
According to Table III, the ratio of COG position in theforward direction showed a negative correlation with thightilt at HC and lower thigh tilt at HC. This indicates that

TABLE IT HE COMPARISON OF PARAMETER VALUE BETWEEN YOUNG SUBJECTSTABLE II
T HE CORRELATION COEFFICIENT VALUE ABOUT STEP LENGTH

AND ELDERLY SUBJECTS

Right step length (m)Left step length (m)Step width (m)Pelvis angle (IC)Pelvis angle (TO)
MFC
Thigh tilt (HC) (deg)Thigh tilt (TO) (deg)Knee angle (HC) (deg)Knee angle (TO) (deg)Lower thigh tilt (HC) (deg)Lower thigh tilt (TO) (deg)Foot angle (deg)Tilt of upper body (deg)Ratio of COG position (lateral)
Ratio of COG position (forward)

young (n = 103)
mean
SD
0.684
0.049
0.683
0.054
0.065
0.024
12.0
6.3
11.4
6.3
0.023
0.004
117.8
3.5
79.6
3.5
172.7
3.9
139.8
4.6
110.8
2.1
38.6
3.0
70.4
8.2
17.2
7.6
0.445
0.194
0.644
0.023

elderly (n = 107)
mean
SD
0.645
0.059
0.649
0.058
0.069
0.028
11.5
6.2
11.5
6.2
0.023
0.005
117.7
3.3
80.2
4.7
171.1
4.2
138.7
5.7
109.3
2.8
38.1
2.7
67.1
8.7
16.1
8.1
0.528
0.470
0.658
0.025

p value
<.01
<.01
>.10
>.10
>.10
>.10
>.10
>.10
<.01
>.10
<.01
>.10
<.01
>.10
>.10
<.01

Thigh tilt (TO)Knee angle (TO)
Lower thigh tilt (HC)
Lower thigh tilt (TO)Foot angle

Right step length
young (n = 103)
elderly (n = 107)
-0.47
-0.57
0.20
0.32
0.32
0.45
-0.27
-0.29
0.41
0.48

TABLE IIIT HE CORRELATION COEFFICIENT VALUE ABOUT RATIO OF COG
POSITION IN FORWARD DIRECTION

Thigh tilt (HC)
Lower thigh tilt (HC)222

Ratio of COG position (forward)
young (n = 103)
elderly (n = 107)
-0.21
-0.34
-0.54
-0.53

the ratio of COG position is located forward in the BOS if
the foot is not placed well in the forward position at HC.
According to Table I, lower thigh tilt at HC is smaller in theelderly than in the young, so the step length is small, and
BOS did not expand. As a result, ratio of COG position is
located relatively forward in the elderly.
The correlation value between the ratio of COG in theforward direction and thigh tilt at HC was smaller in theelderly than in the young. This is because the elderly’s ratioof COG position in the forward direction was originallyforward than in that of the young.
C. Characteristics of gait regarding to foot angle
From the results in Table IV, foot angle showed a negative
correlation with knee angle at TO in the young. In contrast,in the elderly, foot angle showed a negative correlation withthigh tilt at TO. The difference in the correlation between
young and elderly individuals suggests a difference in the
motion mechanism, which determines their foot angle.
D. Characteristics of gait regarding to MFC
From the results in Table I, there was no signiﬁcantdifference in MFC between the young and the elderly. Rezaul[4] reported that there was no signiﬁcant difference in MFC.
However, it seems important to analyze MFC because manystudies [5][6][7][8] reported that trip and fall occur owing to
the decrease of MFC in the elderly.
According to Table V, MFC showed a positive correlation
with right step length in the elderly. Thus, it is consideredthat the increase in MFC is accompanied by an increase instep length in elderly subjects. In addition, MFC showed anegative correlation with knee angle at HC and the lower
thigh tilt at TO in both young and elderly subjects. Thus,
it is considered that the increase in MFC is accompanied
by knee ﬂexion at HC and backward swing of the lower
leg at TO. Additionally, MFC showed a positive correlation
with foot angle in young subjects. In contrast, there was nocorrelation between MFC and foot angle in elderly subjects.
The difference in the correlation between young and elderly
individuals suggests a difference in the motion mechanism,
which determines their MFC.
TABLE IV
T HE CORRELATION COEFFICIENT VALUE ABOUT FOOT ANGLE
Thigh tilt (TO)Knee angle (TO)Foot angle
young (n = 103)
elderly (n = 107)
-0.17
-0.30
-0.48
0.04

TABLE VT HE CORRELATION COEFFICIENT VALUE ABOUT MFC
Right step length
Knee angle (HC)Foot angle
Lower thigh tilt (TO)

MFC
young (n = 103)
elderly (n = 107)
0.19
0.28
-0.20
-0.26
0.23
0.004
-0.20
-0.26

V. CONCLUSIONSIn this study, we calculated some gait parameters thatcharacterize gait from the AIST Gait Database. In addition,
we investigated the gait characteristics of the elderly bycomparing these parameters between the young and theelderly.
From the analysis results, it was found that the elderly
have a smaller step length because the lower leg swing at HC
and foot angle, which affects the increase in step length, aresmall. Furthermore, the ratio of COG position was relatively
forward in BOS. In terms of foot angle, the increase in footangle is accompanied by knee ﬂexion in the young and withhip extension in the elderly. With respect to MFC, there wasno signiﬁcant difference between the young and the elderly.
However, as a result of comparing correlation, the increasein MFC is accompanied by an increase in step length in theelderly. The increase in MFC is accompanied by knee ﬂexion
at TO and the motion of increasing the tilt angle of the lower
thigh at TO in both the young and the elderly.
The results of this study are considered to be usefulfor deciding effective walking strategies to improve gait in
the elderly, and to develop walking assist suits. However,the number of parameters that lead to ﬁndings was small.
Therefore, it is necessary to select and introduce appropriate
parameters such as the parameters at MFC timing to explain
gait characteristics.
ACKNOWLEDGMENT
The authors would like to express their gratitude to
Dr. Tetsuya Nemoto in National Center for Geriatrics andGerontology, and Mr. Tomohito Umeshita in MATSUMOTO
Prosthetics & Orthotics Manufacturing CO. LTD., for useful
discussions.
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