Pedometer-determined physical activity among youth in the Tokyo Metropolitan area: a cross-sectional study
Fukushima et al. BMC Public Health
Pedometer-determined physical activity among youth in the Tokyo Metropolitan area: a cross-sectional study
Noritoshi Fukushima 0
Shigeru Inoue 0
Hiroyuki Kikuchi 0
Hiroki Sato 0
0 Department of Preventive Medicine and Public Health, Tokyo Medical University , 6-1-1 Shinjuku Shinjuku-ku, Tokyo 160-8402 , Japan
Background: Providing large-scale descriptive data of objectively measured physical activity in youth is informative for practitioners, epidemiologists, and researchers. The purpose of this study was to present the pedometer-determined physical activity among Japanese youth using the Tokyo Metropolitan Survey of Physical Fitness, Physical Activity and Lifestyle 2011. Methods: This study used a school-based survey. The Tokyo Metropolitan Board of Education originally collected pedometer-determined steps per day in the fall of 2011. Data were collected from 15,471 youth aged 6 to 18 years living in Tokyo. Participants were asked to wear pedometers for 14 consecutive days, and daily steps logged in the final 7 days were selected for this analysis. Results: At the primary and junior high school levels, boys (12,483 and 9476, respectively) had a significantly higher mean number of steps per day than did girls (10,053 and 8408, respectively). There was no significant difference in the mean number of steps per day between the sexes at the high school level. Mean steps per day decreased consistently with age and grade level; the lowest overall steps per day was observed in the last year of junior high school, although there was a slight increase in the subsequent year, the first year of high school. Conclusions: This study demonstrates a trend toward reduced physical activity with age in Japanese youth and a substantial difference in the number of steps per day between boys and girls in Tokyo. The age-related reduction in steps per day was greater in boys because they attained a higher peak value prior to this reduction, and sex-related differences in the step count disappeared in high school students.
Survey; Steps; Children; Adolescents; Cross-sectional study; Descriptive epidemiology
Lack of physical activity (PA) in childhood and
adolescence is associated with adverse health problems such as
obesity and increased cardiovascular and diabetes risk
[1, 2]. Childhood PA patterns often extend into
adulthood; insufficient PA during this developmental period
is therefore a great public health threat . To improve
health outcomes, the World Health Organization
recommends that children and adolescents (hereafter
collectively termed “youth”) aged 5 to 17 years participate in a
daily minimum of 60 min of moderate to vigorous PA
. Despite these recommendations, physical activity
levels among youth remain low worldwide [5, 6].
Previous studies that evaluated PA levels primarily
used standardized self-report questionnaires [2, 5, 6].
Although self-reporting is reasonable for large-scale
epidemiological investigations, it may be less appropriate
for measuring PA in children and adolescents. For
example, recall bias may affect the accuracy of child data
more than adult data . Additionally, children may be
unable to accurately summarize the sporadic and
complex nature of their PA when responding to questions
about habitual behavior [8, 9]. Further, cross-national
comparisons of self-reported PA are affected by language
and cultural differences [10–12]. Collectively, these
concerns indicate a substantial need for objectively
measured youth PA .
Pedometers and accelerometers are commonly used to
objectively measure PA and are increasingly used as
research tools. It has also been reported that these devices
are valid and feasible in assessing PA in youth .
Moreover, pedometers are more cost-effective than
accelerometers; the number of steps per day provides
simple and practical information about PA volume for
researchers, practitioners, and the lay public. There are a
few examples of national surveys of young people’s
objectively determined steps per day: the Canadian Physical
Activity Levels among Youth (CANPLAY) survey used
pedometers [15, 16], the U.S. National Health and
Nutrition Examination Survey used accelerometers , and
the European Youth Heart Study also used
accelerometers . Still, evidence regarding objectively measured
PA among Asian youth are quite limited .
We aimed to examine descriptive epidemiological data
for children’s and adolescents’ pedometer-determined PA
levels using the Tokyo Metropolitan Survey of
Physical Fitness, Physical Activity and Lifestyle 2011.
Specifically, we provide descriptive epidemiological data
on the number of steps per day, stratified by sex and
A schematic depicting the sampling and data assessment
methodology used in this study is shown in Fig. 1.
The Tokyo Metropolitan Board of Education (TMBE)
performed a cross-sectional survey to investigate PA in
youth living in Tokyo by examining the number of
pedometer-recorded steps per day during the 2011 fall
academic term. The TMBE authority and the Tokyo
Metropolitan Government approved the secondary use
of these data for research purposes, and all provided
data were stripped of personal identifiers.
Fig. 1 Participant sampling flow chart and strategy for data assessment
Participants and data collection
Primary school and junior high school are compulsory
in Japan. Children are admitted to primary school at
6 years of age. They spend 6 years in primary school,
followed by 3 years in junior high school. After
graduation from public junior high school in 2011, 97.6 % of
students in Tokyo attended high school for 3 years .
In Tokyo in June 2011, there were 561,329 students
registered in 1308 public primary schools, 229,483 students
in 626 public junior high schools, and 134,864 students
in 191 public high schools. Geographically, the Tokyo
metropolitan comprises 2 areas and 2 islands containing
62 municipalities: 23 Ku-Area (23 wards), Tama-Area
(26 cities, 3 towns, and 1 village), and Izu and Ogasawara
Islands (2 towns and 7 villages). This is a secondary
analysis of a TMBE survey that did not employ random
sampling. Instead each of the 62 municipalities of Tokyo were
asked, at their own discretion to designate one public
primary school and one public junior high school from their
jurisdiction for targeted measurement. Thus, the data
came from 62 primary schools and 62 junior high schools
throughout Tokyo. One class per grade in each of these
schools participated in this survey. The TMBE sampled
high school students from the 11 school districts of the
Data were collected from 10,087 students from 62
primary schools (372 classes), 5164 students from 62 junior
high schools (186 classes), and 1137 students from 11
public high schools (33 classes). Participants were aged 6
to 18 years. Each school held an orientation meeting for
this survey for participants and their parents or
guardians in August 2011. Data were collected using
pedometers and questionnaires during the fall term of 2011
(September to November).
TMBE members chose the pedometer used in the survey
(EX-200; Yamasa Co., Ltd., Tokyo, Japan; approximately
$US 23); Yamasa is the Japanese generic name for
Yamax, and this brand has been commonly used among
PA researchers [20, 21]. In addition, our previous study
reported acceptable comparability of the EX-200
compared with the SW-200 (Yamax Co., Ltd., Tokyo, Japan),
the Kenz Lifecorder (Suzuken Corp., Nagoya, Japan),
and the Active style Pro HJA-350IT (Omron Healthcare,
Kyoto, Japan) among Japanese children . Pedometers
were placed in participants’ pockets for data collection
in the present study. The EX-200 can store up to 7 days
of memory data, and students recorded their step counts
daily using the memory function at school under the
guidance of trained teachers. Participants were asked to
wear an unsealed pedometer during waking hours for 14
consecutive days; they were allowed to remove the
device for water-based activities and while engaging in
fullcontact sports (e.g., judo). The number of steps per day
during the first 7 days of monitoring was not recorded
in accordance with the original TMBE survey protocol.
Therefore, the data for the remaining 7 days were used
in these analyses.
Data treatment and statistical analyses
Step data were treated similarly to those of the
CANPLAY survey  to enable comparison of both sets of
results. Because a single day of pedometer data can be
used to accurately estimate PA levels for surveillance
purposes, participants aged 6 to 18 years with at least 1
valid day of pedometer data were included in this
analysis [23, 24]. Records of <1,000 or >30,000 steps per day
were considered outliers and excluded from further
analyses [15, 20, 23]. Valid days were thus defined as any
day with recorded data between these two thresholds.
Descriptive data (means, 95 % confidence intervals [CI])
for the number of steps per day were calculated based
on the number of valid days for each grade level and sex
(combined and separately). Ranges and percentile values
were calculated for each grade level by sex. In Japan, an
evidence-based recommendation for steps per day for
youth aged 6 to 18 years has not yet been established.
Therefore, we used criteria applied in past studies to
describe the proportion of participants taking ≥10,000,
≥12,000, and 15,000 steps per day [15, 25, 26].
Specifically, these criteria were a separate body mass
indexreferenced criteria for boys and girls (15,000 and 12,000
steps/day, respectively) [15, 26] and a step count related
to 60 min of moderate to vigorous PA for adolescent
boys and girls (10,000 steps per day) . Moreover,
15,000 steps per day is the target recommended by the
Tokyo Metropolitan Government for boys and girls aged
6 to 18 years  and <7000 steps per day is a potential
candidate for the lower threshold in children, which
indicates a sedentary lifestyle . Finally, an accumulated
<5000 steps per day (originally considered to indicate a
sedentary lifestyle for adults) was used as an alternative
marker of a sedentary lifestyle . Student’s t-test was
used to test for sex differences, stratified for each grade
level. Cohen’s d effect size index was used to assess the
magnitude of intergroup differences and statistical
significance . All statistical procedures and calculations
of p-values were conducted using two-tailed t-tests.
Differences were considered statistically significant at
p < 0.05. Statistical analyses were performed using
IBM SPSS software, version 21.0 (IBM, Armonk, NY, USA).
A total of 16,388 students participated in this survey.
We excluded 261 students whose sex was unspecified in
the data set, 605 students without any pedometer data
recorded during the final 7 days of the monitoring
period, and 51 students with no pedometer data after
truncation to <1000 or >30,000 steps per day as data
outliers. Thus, step-defined PA was successfully
measured for 15,471 students, each with at least 1 valid day
of data. Overall, 3.1 % of boys and 1.6 % of girls had only
1 valid day of pedometer data; 86.2 % of boys and 90.7 %
of girls had ≥4 valid days of pedometer data (Table 1).
Table 2 shows the mean number of steps per day and
95 % CI, stratified by sex and grade level. The highest
mean number of steps per day (11,659) was found
among first-grade students in primary school (6–7 years
old) and consistently decreased with age. The lowest
mean number of steps per day (7887) was observed in
students in the last year of junior high school (14–
15 years old). Beyond junior high school, the mean step
count modestly increased to 8485 steps per day in the
first year of high school (15–16 years old), but declined
as students advanced through high school (8032 steps
per day at 17–18 years old). For boys, the mean number
of steps per day increased from 12,575 in the first grade
of primary school, peaked at 12,736 in the third grade of
primary school, and subsequently ranged from 8337 to
10,218 in junior high school and from 7935 to 8583 in
high school. For girls, the mean number of steps per day
followed the same trend seen for both sexes combined:
the highest mean number of steps per day was observed
in the first grade of primary school (10,694) and
consistently declined through junior high school (7437–9104),
with a slight increase in the minimum value of the range
in high school (8025–8398).
During primary and junior high school, the step count
was significantly higher among boys by 2000 and 1000
Junior high school
Differences of steps
per day between
boys and girls
95 % CI
steps per day, respectively, compared with girls at the
same grade level. However, during the high school
years, there was no significant sex difference in
numbers of daily steps (p = 0.592 for high school level 1
[15–16 years], p = 0.373 for level 2 [16–17 years], and
p = 0.574 for level 3 [17–18 years]), with boys taking
an absolute average of only 200 steps per day more
than girls (Table 2). Table 3 shows the minimum,
maximum, and percentile values for the number of
steps per day in each school grade, stratified by sex.
Table 4 compares the results of this study, which used
Yamasa EX-200 pedometers, and those of the CANPLAY
survey, which used Yamax Digiwalker SW-200
pedometers . The mean number of daily steps taken by boys
in primary school was similar for the two surveys.
However, at the higher-grade levels, pedometer-determined
PA levels were lower for boys living in Tokyo than for
their Canadian counterparts by approximately 1000 to
2000 steps per day. Similarly, the number of steps taken
per day by girls living in Tokyo was lower by
approximately 1000 steps per day than that of Canadian girls
across all grades.
The proportion of students taking ≥10,000, ≥12,000,
and ≥15,000 steps per day was 60.5, 41.2, and 17.4 %,
respectively, for boys and 39.1, 17.6, and 3.9 %,
respectively, for girls (Fig. 2). Boys showed a distinct decrease
in the number of steps per day between the sixth
primary school grade and the first junior high school grade.
Girls showed a gradual decline in the number of steps
per day from the start to the finish of primary school,
with a slight increase during the first year of junior high
The proportion of students taking <7000 and <5000
steps per day was 14.1 and 4.7 %, respectively, for boys
and 20.7 and 5.0 %, respectively, for girls (Fig. 3). The
proportion of boys taking <7000 and <5000 steps per
day rapidly increased between the sixth grade of primary
school and the first grade of junior high school, and
continued to increase toward high school. The proportion
of girls taking <7000 steps per day gradually increased
from the first grade level to the last year of junior high
school. There was a moderate relative decrease in the
proportion of girls taking <7000 steps per day in the first
year of high school, but a subsequent steady increase in
Using a representative sample of the Tokyo metropolitan
area, this is one of the largest surveys worldwide to
investigate pedometer-determined PA levels in children
and adolescents. The results indicate that in primary
school (age 6–12 years), junior high (age 12–15 years),
and high school (age 15–18 years), boys took an average
of 12,483, 9476, and 8294 steps per day, respectively,
while girls took an average of 10,053, 8408, and 8184
steps per day, respectively. The mean number of daily
steps was significantly higher for boys than for girls
through 6 to 15 years, with an overall decreasing
agerelated trend for both sexes. Boys tend to be more active
than girls at most ages, although this difference
disappears in high school, and a reduction in PA levels from
childhood to adolescence has been previously reported
[17, 18, 25]. Until now, there has been limited objective
data for large-scale evaluations of PA levels in Japanese
children and adolescents . The step patterns of our
Tokyo students are similar to those reported in a review
of pedometer data from 43 studies of young people in 13
Although high school is not compulsory in Japan,
more than 95 % of students in Tokyo attend high school
after passing their entrance examination . Generally,
Japanese students in the third year of junior high school
spend substantial time studying for this examination.
Therefore, students in their final junior high school year
may focus more on studying than on PA, which may
explain why this group has the lowest overall mean step
count and the highest proportion of youth accumulating
fewer steps per day relative to the two indices of a
The differences in PA levels between children in
Tokyo and those in Canada can be interpreted in four
ways. First, Canadian and Japanese children may actually
have different PA levels. Second, this difference may
result from variations in the survey-specific pedometers
used and their positioning. The EX-200 (used in this
survey) is an in-pocket pedometer and the SW-200 (used in
the CANPLAY survey) is worn on a belt. The EX-200 is
a triaxial accelerometer with a filter function that
monitors continuous walking activity to recognize actual
steps; it is programmed to count steps when an
individual takes ≥10 steps without pausing for <2 s (e.g., if a
subject moves <10 steps and pauses for ≥2 s, the
previous steps will not be counted). Silcott et al.  reported
that pedometers with a filter function might
underestimate step counts compared with pedometers without a
filter function. Although there is no data directly
comparing steps measured by the EX200 and the SW-200,
Tanaka et al. reported that the EX-200 underestimated
step counts by 7.9 % compared with the Kenz Lifecorder
among children aged 6 to 12 years  (additionally,
Schneider et al. reported no significant difference in step
count values between the Kenz Lifecorder and the
SW200 ). These findings suggest that the EX-200 step
counts may be lower than those obtained by the SW-200.
Thus, differences among devices should be considered.
Third, the sampling method in this TMBE-administered
survey was different from the CANPLAY which employed
random sampling and collected data through the mail. In
Junior high school
Junior high school
Junior high school
Junior high school
Steps per day
Steps per day
Steps per day
Steps per day
contrast, the Tokyo survey asked each municipality to
choose one primary and one junior high school from its
district. All geographical areas throughout Tokyo were
covered by this method. However, it is uncertain whether
this sampling method lead to underestimation or
overestimation of the step counts. Finally, children’s activity levels
may be affected by seasonal variation . Craig et al. 
reported that Canadian children’s PA is lower in the fall
and winter than in the spring and summer. Because this
survey was conducted in the fall in Tokyo, further study is
needed to determine the effect of seasonal changes on PA
levels in Japanese children and adolescents.
Vincent et al.  assessed pedometer-determined daily
step counts in a convenience sample of children aged 6 to
12 years in the U.S. (n = 711), Sweden (n = 680), and
Australia (n = 563). Although there are potential issues
with the sample size, sampling bias, and the different
pedometers used in the present survey, the Tokyo survey
reported approximately 3000 and 1000 fewer steps for boys
per day than Swedish and Australian boys, respectively,
but a similar level of activity to American boys. We
observed a similar pattern for girls, who took approximately
2000 and 1000 fewer steps per day than Swedish and
Australian girls, respectively, but accumulated a
similar mean number of steps per day as American girls.
There are no clear guideline recommendations for
number of steps per day for children and adolescents.
However, we interpreted the present data in the context of
previously published step-defined criteria. Certainly, it is
optimal to use criteria that have been established based on
health-related values. However, practical effectiveness
should also be taken into consideration when setting any
single criterion. For example, if almost all (or very
few) people meet a specified value, then its practical
effectiveness for educational and public health
purposes is questionable. The present results include
implications regarding the practical effectiveness of
various criteria. We found that the proportion of boys
and girls meeting specific criteria (i.e., 10,000, 12,000,
and 15,000 steps per day) decreased with age.
Additionally, distinct sex-specific patterns were observed.
The Tokyo Metropolitan Government has
recommended ≥15,000 steps per day for children and
adolescents, regardless of age or sex . However, our
findings reveal that many children and adolescents
(except primary school boys) do not meet this target.
Therefore, a criterion of ≥15,000 steps per day seems
very high and thus not practically effective, especially
for girls. Two courses of action might improve the
situation. First, appropriate age- and sex-specific
targets may be set. Second, a graduated scale of values
might describe PA distribution better than a single
target value and may encourage less active children to
improve their PA level. Although it seems too low as
an optimal value for health, a criterion of ≥10,000
steps per day showed dynamic patterns across age
and sex in this survey. This suggests that ≥10,000
steps per day is a practically effective criterion for
evaluating lifestyle changes/differences across age and
sex for education and public health purposes. For
children, <7000 steps per day has been suggested as
an appropriate sedentary lifestyle index [15, 28]. In
this survey, the proportion of students meeting this
criterion increased with age as anticipated. However,
Fig. 2 Proportion of students taking ≥10,000, ≥12,000, or ≥15,000
steps per day by sex and school grade
its practical effectiveness was limited for primary
school boys, who accumulated a higher average
number of steps per day than this value, suggesting the
need for age- and sex-specific values on a graduated
scale for youth.
In the present study, the use of unsealed pedometers
meant that participants were aware of their step counts,
potentially leading to reactivity bias. Because TMBE
did not record the steps per day for the first 7 days,
our ability to test for reactivity was hampered.
However, Craig et al.  showed no evidence of reactivity
in a population sample of 5- to 19-year-olds wearing
unsealed pedometers for 7 days. Other studies have
reported no evidence of reactivity bias and have
generally concluded that this is not a problem when
evaluating children . Additionally, Clemes and
Deans  reported that the reactivity effect
diminishes after the first week of monitoring, returning to
normal levels in the second week. Therefore, the data
Fig. 3 Proportion of students taking <7,000 or <5,000 steps per day
by sex and school grade
obtained in the second week of our 2-week
surveillance were probably not systematically affected by
Study strengths and limitations
This study has several strengths. Because the
participants were sampled throughout Tokyo, their mean
number of steps per day is representative of PA levels in
Tokyo youth. Using the same adjusted treatment
methods for pedometer data as used in the CANPLAY
study enabled between-study comparisons. Finally, in
this study, more than 86 and 90 % of boys and girls,
respectively, wore their pedometers for a minimum of
4 days; it has been reported that 4 or more valid days of
data in youth enhances data reliability .
Study limitations must be acknowledged. First, this
was that was a secondary analysis of a survey conducted
by an education authority and we had no input
regarding the original study design. Despite this, the survey
represents an important source of objectively monitored
data on children. Although this is the largest study of
inpocket pedometer-determined PA in youth (and is thus a
useful reference data source for others using this type of
device), these pedometers do tend to underestimate
absolute step-defined PA levels. Regardless, it is reasonable to
assume that the observed data trends are valid. Second,
the lack of private school students in the sample may
influence the results. In 2011, the proportion of students in
the Tokyo metropolitan area attending private primary,
junior high, and high schools was 4.5, 25.5, and 55.9 %,
respectively . The difference in tuition costs for private
schools may indicate differences in familial socioeconomic
status. If socioeconomic status affects youth PA levels, the
present data may not accurately reflect PA in the larger
Tokyo youth population. Third, the TMBE survey
complied with the organization’s safety policy, thus allowing
students to remove their pedometers during vigorous
fullcontact activity (unfortunately, this was not tracked); this
may have underestimated the overall number of steps per
day. Finally, the issue of wearing compliance should be
considered. Students recorded their step counts at school
under the guidance of trained teachers. However, no other
methods were employed to confirm whether they actually
wore the pedometers as directed.
This study demonstrates that children’s
pedometerdetermined PA generally decreases with age and that
there is a substantial difference in the number of steps
taken per day between boys and girls in Tokyo. The PA
decrease was greater in boys because they achieved
initial higher peak values; once the students reached high
school, the sex difference in the number of steps per day
disappeared. These findings contribute to our current
understanding of the PA levels of youth living in Tokyo
and will be useful for surveillance, screening, and
comparison purposes, as well as planning strategies.
CANPLAY: Canadian physical activity levels among youth; CI: Confidence
interval; PA: Physical activity; TMBE: Tokyo Metropolitan board of education
We thank all the study participants and data collectors for their willingness
to participate in this survey. We also thank all members of the Tokyo
Metropolitan Board of Education and the Tokyo Metropolitan Government
who helped make this study possible.
Availability of data and materials
The data described herein come from a secondary use of dataset collected
by the Tokyo Metropolitan Board of Education with their permission. The
data is not permitted to be opened for public use.
SI conceived the study. NF carried out the analysis, and drafted the
manuscript. SI, CTL, and ST interpreted results and critically edited the
manuscript. HS and HK provided statistical expertise, and contributed to
discussion. YH advised on and reviewed data analysis, and contributed
to discussion. All authors read and approved the final manuscript.
The author declares that they have no competing interests.
Consent for publication
Ethics approval and consent to participate
Ethical approval was obtained from the Tokyo Medical University Ethics
Committee (No. 2762). Data were collected as administrative data by the
Tokyo Metropolitan Board of Education and the Tokyo Metropolitan
Government. The Tokyo Metropolitan Board of Education and the Tokyo
Metropolitan Government approved the secondary use of these data for
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