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PHYSICAL FITNESS DIFFERENCES BETWEEN
PREPUBESCENT BOYS AND GIRLS
CARLOS C. MARTA,
1,2
DANIEL A. MARINHO,
2,3
TIAGO M. BARBOSA,
2,4
MIKEL IZQUIERDO,
5
AND
MA
´RIO C. MARQUES
2,3
1
Department of Sport Sciences, Polytechnic Institute of Guarda, Education, Communication, and Sport School, IPG, Guarda,
Portugal;
2
Research Center in Sports, Health and Human Development, CIDESD, Portugal;
3
Department of Sport Sciences,
University of Beira Interior, Covilha˜, Portugal;
4
Department of Sport Sciences, Polytechnic Institute of Braganc¸a, Braganc¸a,
Portugal; and
5
Department of Health Sciences, Public University of Navarre, Navarre, Spain
ABSTRACT
Marta, CC, Marinho, DA, Barbosa, TM, Izquierdo, M, and
Marques, MC. Physical fitness differences between pre-
pubescent boys and girls. J Strength Cond Res 26(7):
1756–1766, 2012—The purpose of this study was to analyze
in which physical capabilities boys and girls are closer or
distant. An additional objective was to find which of the body
fat, physical activity, and somatotype factors have a greater
effect on prepubescent children’s physical fitness. This was
a cross-sectional study involving 312 children (10.8 60.4
years). The physical fitness assessment employed sets of
aerobic fitness, strength, flexibility, speed, agility, and bal-
ance. The boys presented higher values in all selected tests,
except tests of balance and flexibility, in which girls scored
better. Gender differences in the physical fitness were great-
est in the explosive strength of upper (p#0.01, h2
p¼0:09)
and lower limbs (p#0.01, h2
p¼0:08), although with
a medium-size effect of gender, and smaller in the abdominal
(p.0.05, h2
p¼0:007) and upper limbs (p.0.05,
h2
p¼0:003) muscular endurance, and trunk extensor strength
and flexibility (p.0.05, h2
p¼0:001). The endomorphic (p#
0.01, h2
p¼0:26) in the girls, and the ectomorphic (p#0.01,
h2
p¼0:31) and mesomorphic (p#0.01, h2
p0:26)intheboys,
had the high-sized effect on the physical fitness. The physical
activity in the girls, and the endomorphic and body fat in the
boys, did not have a significant effect. These findings can
help in the planning of activities that take into account the
success and motivation of both boys and girls and thus
increase levels of physical activity and physical fitness at
school. However, in prepubescent children, one cannot
neglect the influence of genetic determinism, observed from
the morphoconstitutional point of view.
KEY WORDS gender difference, somatotype, motor
performance, school
INTRODUCTION
Physical fitness has been recognized as a key
determinant in healthy lifestyles based increasingly
on criteria referenced to general health and not
merely to motor performance (30). It has posi-
tively been related, among others, with benefits to cardio-
vascular, total and abdominal adiposity, skeletal health,
depression, anxiety, self-esteem, and higher academic perfor-
mance (19,30). However, many children and adolescents are
only exposed to vigorous physical activity during school-
based physical education classes (9). That way, schools seem
to provide an excellent setting to enhance physical activity
and physical fitness levels.
Unfortunately, it has been observed that there is an
apparent avoidance of children of the physical education
classes and regular physical activity practice at school (33).
This decrease in the interest of children in physical educa-
tion is partly because of the lack of planning that takes into
account the interest, motivation, and success of children in
the execution of the exercises, respecting the differences
among students, including boys and girls (14). Physical
education classes or extracurricular activities commonly
include children of both sexes. This requires teachers to
establish a match between the goals they want to achieve
and the means and resources available, taking into account
the various constraints that may arise, such as reduced prac-
tice time per session, number of weekly sessions, lack of
material resources and facilities, high numbers of students
and athletes by class, and variety of content to be taught,
often involving the same activities for boys and girls alike.
In this respect, beyond the duty of the teacher to maximize
the opportunities for practice, it is necessary to program the
exercises in school to make them appealing and motivating for
both boys and girls (29). The psychological saturation and
Address correspondence to Dr. Mikel Izquierdo, mikel.izquierdo@
gmail.com.
26(7)/1756–1766
Journal of Strength and Conditioning Research
Ó2012 National Strength and Conditioning Association
1756
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physiological enervation that may attend on attempts to match
results close to those achieved by opposite-sex colleagues in
the same exercise can be alleviated when there is knowledge
about which exercises and the respective capabilities they
deploy can be best performed concurrently by boys and girls.
One of the major reasons why many children drop out of sport
and physical activity is that they feel they do not have the
necessary skills to be involved. Both girls and boys tend to
be reluctant to participate if their perceived level of skill is
low. The proof of this is that the female students reported more
positive and adaptive perceptions in same-sex classes (22).
Thus, the knowledge, not only of the physical capabilities in
which boys and girls are higher but also the magnitude of the
differences between them, can help teachers in the planning
and organizing of activities at school, increasing the motiva-
tional levels in the exercises and thus, increasing levels of phys-
ical activity and physical fitness of their students. Also, at the
level of assessment, this knowledge may add value in allowing
the teacher to better analyze and understand the results
obtained in general.
On the other hand, for a better understanding of gender
differences in physical fitness, it will be important to
understand the interaction of several factors referred in the
literature with the motor performance, in both boys and girls.
There is much evidence pointing to significant differences
between boys and girls in motor performance (8,15). These
differences are largely because of gender differences in levels of
habitual physical activity (37) and body fat (8,20). Although
body fat is associated negatively with several motor tasks, par-
ticularly those related to the propulsion and lift movements of
the body (11), higher levels of physical activity represent a gain
in motor performance in general (36). However, there is a rel-
ative paucity of reports focused on the differences in the phys-
ical fitness between prepubertal boys and girls regarding his or
her somatotype. Most studies in this context refer to the
influence of body mass index in the motor performance in
youth, but somatotype has been found to be inherited to
a greater extent than body mass index (32). The values of
relative adiposity, relative muscle-skeletal magnitude, (robust-
ness) or relative thinness of the subjects (23), allow perform-
ances to vary depending on the type of motor tasks (17). One
cannot exceed the limits imposed by what is a manifestation of
genetic determinism, observed from the morphoconstitutional
point of view, and there is evidence that by prepuberty there
already exists a fairly stable somatotype, pointing to 8 years as
the age by which somatotype stability becomes manifest
(23,24). Hence, it seems relevant to examine, in this age group,
the effect of the presence or absence of certain physical traits
on the motor performance and compare it with the effect of
body fat and physical activity, often referenced in the literature.
The aim of this investigation was to analyze in which
physical capabilities boys and girls are closer or distant. An
additional objective was to find which of the body fat,
physical activity, and somatotype factor is more interactive
with prepubescent children’s physical fitness level. It was
considered the hypothesis that there is a set of exercises
and physical capabilities inherent to them, in which the per-
formance of boys and girls is very similar or divergent. We
also hypothesized that, despite the age group considered,
somatotype already plays a determinant role on the perfor-
mance of selected exercises, in both boys and girls.
METHODS
Experimental Approach to the Problem
It has been observed that there is an apparent decrease in the
interest of children in physical education partly because of
the lack of planning that takes into account the success of
children in the execution of the exercises respecting the
differences among students, including boys and girls. The
knowledge of the magnitude of the differences between boys
and girls in physical fitness can help the planning of activities
that promote the success and motivation of both boys and
girls and thus improve levels of physical activity and physical
fitness at school. On the other hand, the knowledge of the
effect of the somatotype on the performance in the pre-
puberty (comparing it with the effect of body fat and
physical activity, often referenced in the literature) may also
allow a better understanding of gender differences.
Three hundred and twelve students were recruited from
a Portuguese public basic school (from fifth and sixth grades)
to perform this study. In Portugal, a physical education class
has a set of 45 minutes and another of 90 minutes twice
a week. Typical physical education classes include various
activities, in which participate simultaneously boys and girls,
with a clear pedagogical focus, but mainly for the purpose of
promoting levels of physical activity and physical fitness of
students. Usually, these classes start with jogging run during
10 minutes to general warm-up, proceed to joint mobiliza-
tion and general stretches. After that, the class is divided into
2 or 3 proficiency level groups to start the main activities and
sports of the class.
The required data were collected (from January 4 to
February 25, 2011) from self-assessed of maturity level,
anthropometric measurements, questionnaire about habitual
physical activity, and application of a battery of previously
selected tests. All anthropometric measurements were car-
ried out before any physical performance test. All the
participants were familiarized with physical fitness tests,
and the measurements were performed after a 10-minute
warm-up period (7-minute running with an intensity suffi-
cient to raise breath rate, 3-minute stretching and joint-
specific warm-up). All measurements were made by the
same investigator, in the first periods in the morning, and the
testing assessment procedures were always conducted in
the same indoor sportive facility (with temperature between
15 and 188C). In the course of conducting testing, there was
a constant concern to ensure the necessary security and
maintenance of safe hydration levels and to encourage all
the children to achieve the best results. Clear instructions
about the importance of adequate nutrition for physical
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activity were also given. The fol-
lowing exclusion criteria were
used: subjects with a chronic
pediatric disease or with an
orthopedic limitation. Subse-
quently, to minimize the effects
of growth, only the subjects who
were self-assessed in Tanner
stages 1–2 were selected (12).
Subjects
The sample, cross-sectional in
type, consisted of 312 prepubes-
cent children (160 girls, 152
boys) all of whom volunteered
for this study. The age, height,
and weight of the whole sample
were 10.8 60.4 years, 1.45 6
0.08 m, 40.0 68.7 kg, respec-
tively (girls: 10.8 60.4 years,
1.44 60.07 m, 38.9 68.5 kg;
boys: 10.8 60.4 years, 1.45 6
0.09 m, 41.2 68.8 kg). Both
boys and girls were in Tanner
stages 1–2 (girls: stage 1, 53.1%
and stage 2, 46.9%; boys: stage 1,
81.6% and stage 2, 18.4%). This
study was approved by the insti-
tutional review boards of the
University of Beira Interior
(UBI) and Research Centre in Sports, Health and Human
Development (CIDESD), Portugal. An informed consent
was obtained from all of the children and their parents/
guardians before testing.
Procedures
Parameters of body fat, somatotype, level of physical activity,
and physical fitness were evaluated for all the subjects
participating in the study (Table 1).
Anthropometric Measurements. All anthropometric measure-
ments were assessed according to international standards for
anthropometric assessment (25). The participants were bare-
foot and wore only underwear. Body weight (kilograms) was
measured to the nearest 0.1 kg using a standard digital floor
scale (Seca, model 841, Germany). To evaluate body height
(centimeters), a precision stadiometer with a range scale of
0.10 cm was used (Seca, model 214). For perimeter measure-
ment, a circumference tape was used (Seca 200). The bicon-
dyle femoral and humeral diameters were assessed
(Campbell, 20, Ross Craft, Canada). The percentage body
fat (%FAT) from skinfold anthropometry was calculated fol-
lowing the method of Slaughter et al. (35). As such, triceps
and subscapular skinfolds were determined by internation-
ally recommended methods (25). The definition of morpho-
logical typology (TYPE) used the method described by
Heath-Carter (16), expressed quantitatively by a score of 3
components: endomorphy (ENDO), mesomorphy (MESO),
and ectomorphy (ECTO). Maturity level based on Tanner
stages was self-assessed (12). The students were asked to
answer to an image with corresponding legend question-
naire, in an individual booth, without interference from their
teachers or friends.
Physical Activity Assessment and Physical Fitness Tests. The
habitual physical activity level was measured using the
Baecke et al. (5) questionnaire expressed quantitatively by
a score of 3 indexes: physical activity in school, sport during
leisure time, and physical activity during leisure time exclud-
ing sport.
For the assessment of physical fitness, motor tests were
chosen to include the assessment of aerobic capability (20-m
multistage shuttle run), flexibility of the lower back and
hamstrings (left and right sit-and-reach), trunk extensor
strength and flexibility (trunk lift), speed (20-m sprint),
agility and coordination (9.14-m shuttle run), general
stability (flamingo balance), muscle strength and endurance
(curl-ups and push-ups), explosive strength (standing broad
jump and medicine-ball throw), maximum isometric
strength (handgrip strength), and anaerobic muscular power
TABLE 1. Descriptive data of anthropometric and morphological parameters,
physical activity indexes, and physical performance measures: Overall sample.*
Min Max Mean SD
Fat mass (%) 8.54 50.92 22.75 7.84
Endomorphic 1.05 8.23 3.79 1.66
Mesomorphic 1.57 8.14 4.17 1.23
Ectomorphic 0.10 6.61 2.67 1.46
School index 2.00 3.75 2.72 0.28
Sport index 1.25 4.50 2.87 0.61
Leisure-time index 1.50 4.25 3.02 0.47
Total index 3.25 11.25 8.60 1.02
20-m Multistage shuttle run (a.u.) 7.00 74.00 27.81 14.03
20-m Sprint (s) 3.41 5.75 4.45 0.46
9.14-m Shuttle run (s) 10.62 16.78 13.25 1.31
Flamingo balance (faults) 0.00 35.00 8.49 5.81
Sit-and-reach R (cm) 3.00 30.00 21.48 5.81
Sit-and-reach L (cm) 6.00 30.00 20.81 6.09
Trunk lift (cm) 8.00 30.00 23.50 4.92
Curl-ups (a.u.) 0.00 75.00 29.00 17.71
Push-ups (a.u.) 0.00 39.00 10.45 7.77
Standing broad jump (cm) 64.00 197.00 126.90 23.97
Medicine-ball throw (cm) 138.00 315.00 231.94 39.35
Handgrip strength R (kg) 8.00 30.00 17.52 4.29
Handgrip strength L (kg) 6.00 28.00 16.24 4.07
M-K power stair test 14.96 89.19 38.58 13.45
*School index = index of physical activity in school; sport index = sport during leisure time;
leisure-time index = physical activity during leisure time excluding sport; total index = habitual
physical activity index.
Predictors of Gender Differences in Physical Fitness
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(Margaria-Kalamen power stair test). Curl-ups, push-ups,
20-m multistage shuttle run, sit-and-reach, and trunk lift
were evaluated using field tests from the FITNESSGRAM
test battery (27). Standing broad jump, hand grip strength
and flamingo balance were assessed using EUROFIT test
battery (1). Shuttle run agility test was evaluated using the
AAHPERD test battery (3). In the Margaria-Kalamen power
stair test, the protocol was used as described by George et al.
(13). Medicine-ball throw was evaluated using the protocol
described by Mayhew et al. (26).
Twenty-m multistage shuttle run: This test involved
continuous running between 2 lines 20 m apart in time to
recorded beeps. The subjects ran between the 2 lines, turning
when signaled by the recorded beeps. After about 1 minute,
a sound indicated an increase in speed, and the beep rhythm
accelerated. This pattern was continued at intervals of
1 minute per rhythm level. When the participants failed to
reach the line on 2 con-
secutive occasions, they
were stopped and the
number of completed
20-m laps was recorded.
The 20-m multistage
shuttle run has shown an
intraclass correlation
coefficient (ICC) of 0.98.
Left and right sit-and-
reach: The subjects were
seated with their legs
joined and outstretched.
The soles of their feet
were supported on a stan-
dardized wooden box
(Well Box). By means of
a trunk inflection, the
subjects were required to
reach with the index fin-
ger (arms joined and
hands superimposed) the
maximum attainable dis-
tance as marked on the
box. The participant was
asked to stretch 4 times
and hold the position for
1 second during the
fourth attempt. The fur-
thest distance the subject
was able to reach was
recorded in centimeters.
The ICC of data for left
and right sit-and-reach
was 0.96 and 0.97,
respectively.
Trunk lift: The subjects
raised the torso as high as
possible from the floor from a prone position, while keeping
the eyes on an object placed on the floor in line with the
eyes. This position was held while the distance from the
floor to the chin was measured. Two trials were given, and
the furthest distance was measured in centimeters. The trunk
lift has shown an ICC of 0.94.
Twenty-m sprint running: In a track measuring 20 m in
length, the subjects were required to cover the distance in
the shortest time they could. Time to run 20 m was obtained
using photocells (Brower Timing System, Fairlee, VT, USA).
Three trials were performed, and the best time scored
(seconds and hundredth) was registered. The sprint running
(time) has shown an ICC of 0.96.
Shuttle run agility test: The subjects were asked to tack
and shift, at the fastest pace they were capable of, within an
area delimited by 2 lines (9.14 m apart each other). Two
blocks were placed on the line opposite the starting line. On
TABLE 2. Gender difference in physical performance: Adjusted means after
MANCOVA.
Gender Mean SE
95% CI
p*LB UB
20-m Shuttle run (a.u.) Female 25.38 1.05 23.32 27.44 0.001z
Male 31.05 1.19 28.71 33.39
20-m Sprint (s) Female 4.52 0.04 4.45 4.60 0.047†
Male 4.40 0.04 4.31 4.48
9.14-m Shuttle run (s) Female 13.56 0.10 13.36 13.77 ,0.001z
Male 12.89 0.12 12.65 13.12
Flamingo balance (faults) Female 7.55 0.50 6.56 8.53 0.011†
Male 9.70 0.57 8.58 10.82
Sit-and-reach R (cm) Female 22.95 0.50 21.96 23.93 0.001z
Male 20.07 0.57 18.95 21.18
Sit-and-reach L (cm) Female 23.03 0.52 22.01 24.04 ,0.001z
Male 18.62 0.59 17.47 19.78
Trunk lift (cm) Female 23.75 0.44 22.87 24.62 0.583
Male 23.34 0.50 22.35 24.33
Curl-ups (a.u.) Female 26.61 1.50 23.67 29.55 0.145
Male 30.27 1.70 26.93 33.62
Push-ups (a.u.) Female 9.95 0.61 8.75 11.15 0.362
Male 10.89 0.70 9.52 12.25
Standing broad jump (cm) Female 119.30 1.83 115.70 122.90 ,0.001z
Male 135.42 2.08 131.33 139.51
Medicine-ball throw (cm) Female 218.28 3.29 211.80 224.75 ,0.001z
Male 248.91 3.74 241.56 256.27
Handgrip strength R (kg) Female 16.88 0.36 16.17 17.58 0.006z
Male 18.53 0.41 17.72 19.33
Handgrip strength L (kg) Female 15.54 0.35 14.86 16.22 0.003z
Male 17.27 0.39 16.50 18.04
M-K power stair test Female 34.62 1.16 32.35 36.90 ,0.001z
Male 43.88 1.31 41.29 46.46
*Bonferroni’s test; SE = standard error; CI = confidence interval; LB = lower bound; UB = upper
bound; MANCOVA = multivariate analysis of covariance.
†p#0.05;
zp#0.01.
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a given signal, the participant sprinted to the opposite line,
picked up a block of wood, ran back, and placed it on or
beyond the starting line. Then, turning without pause, they
ran back to retrieve the second block carrying it back across
the finishing line. Three trials were performed, and the best
time scored (seconds and hundredths) was registered. This
test has shown an ICC of 0.98.
Flamingo balance: Balancing on a preferred leg, the
subject was required to flex the free leg at the knee with
the foot of this leg held close to the buttocks. The stopwatch
was stopped each time the participants lost balance (either
by falling off the beam or letting go of the foot being held).
The exercise was then recommenced and again timed until
balance was lost. The number
of such falls occurring over 60
seconds was then counted. The
Flamingo balance has shown
an ICC of 0.93.
Standing long jump: The
participants stood feet slightly
apart (toes behind a starting
line) and jumped as far forward
as possible. Three trials were
given, and the furthest distance
was measured in centimeters
from the starting line to the
heel of the foot nearest to this
line. The standing long jump
has shown an ICC of 0.97.
Curl-ups: The participants
were required to bend their
knees at approximately 1408,
feet flat on the floor, arms straight and parallel to the trunk
with palms of hands resting on the mat. The fingers were
fully extended and the head placed in contact with the mat.
One measuring strip was placed on the mat under the legs.
The participant then curled up slowly, sliding the fingers
across the measuring strip until the fingertips reached the
other side, then curled back down until the head touched the
mat. The number of correct curl-ups performed in a caden-
ce of 20 curl-ups per minute (1 curl-up every 3 seconds) was
then scored. This test has shown an ICC of 0.97.
Push-ups: The participants were positioned with hands and
toes touching the floor, body and legs in a straight line, feet
slightly apart, arms at shoulder-width apart, extended and at right
angles to the body. Keeping
the back and knees
straight, the subject then
lowered the body to the
point at which there was
a908angle at the elbows,
with the upper arms paral-
lel to the floor. The total
number of correct push-
ups was recorded during
a cadence of 20 complete
push-ups per minute
(1 complete push-up every
3 seconds). This test has
shown an ICC of 0.97.
Medicine-ball throw:
The subjects were seated
with the backside of
the trunk in touch with
a wall. They were re-
quired to hold a medicine
ball (Bhalla International,
Vinex Sports, Meerut,
TABLE 3. Effect of the somatotype, physical activity, and body fat factors on the
physical performance of boys and girls: MANCOVA.
Effect FpPartial eta squared Observed power
Male Fat mass (%) 0.599 0.862 0.060 0.359
Physical activity 2.217 0.010* 0.190 0.960
Endomorphic 1.196 0.286 0.113 0.705
Mesomorphic 3.379 ,0.001* 0.264 0.998
Ectomorphic 4.314 ,0.001* 0.314 1,000
Female Fat mass (%) 2.585 0.002* 0.205 0.984
Physical activity 1.554 0.100 0.135 0.843
Endomorphic 3.444 ,0.001* 0.256 0.998
Mesomorphic 2.131 0.013†0.176 0.952
Ectomorphic 2.422 0.005* 0.195 0.976
*p#0.01;
†p#0.05.
TABLE 4. Statistical significance and effect size of sex on the physical performance
variables: Analysis of covariance.
Dependent variable Fp
Partial eta
squared
Observed
power
20-m Multistage shuttle run (a.u.) 10.490 0.001* 0.033 0.898
20-m Sprint (s) 3.966 0.047†0.013 0.510
9.14-m Shuttle run (s) 14.927 ,0.001* 0.047 0.971
Flamingo balance (faults) 6.558 0.011†0.021 0.723
Sit-and-reach R (cm) 11.869 0.001* 0.038 0.930
Sit-and-reach L (cm) 25.937 ,0.001* 0.071 0.999
Trunk lift (cm) 0.302 0.583 0.001 0.085
Curl-ups (a.u.) 2.138 0.145 0.007 0.308
Push-ups (a.u.) 0.834 0.362 0.003 0.149
Standing broad jump (cm) 27.710 ,0.001* 0.084 0.999
Medicine-ball throw (cm) 30.933 ,0.001* 0.092 1,000
Handgrip strength R (kg) 7.529 0.006* 0.024 0.781
Handgrip strength L (kg) 8.928 0.003* 0.029 0.846
M-K power stair test 22.827 ,0.001* 0.070 0.997
*p,0.01;
†p,0.05.
Predictors of Gender Differences in Physical Fitness
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India) weighing 2 kg (Vinex, model VMB-002R) with their
hands (abreast of chest) and throw it forward over the
maximum distance possible. Hip inflection was not allowed
nor withdrawal of the trunk away from the wall. Three trials
were given, and the furthest throw was measured in
centimeters from the wall to the first point at which the
ball made contact with floor. The medicine-ball throw has
shown an ICC of 0.97.
Left and right hand grip strength: This was measured by the
Jamar (0–200 lb) hydraulic hand dynamometer. Each partici-
pant stood erect in the 908elbow flexion position. The handle
of the dynamometer was adjusted if required. The subjects
were then instructed to exert maximal grip (for about 3 sec-
onds), interrupted by brief pauses (of about 1 minute). No
other body movement was allowed. Three trials were given
for each hand separately and the best score recorded in
kilograms was chosen for analysis. The ICC of data for left
and right hand grip strength was 0.99 and 0.96, respectively.
Margaria-Kalamen power stair: The participant was placed
ready at the starting line 6 m in front of the first step. On
command, the subject sprinted to and up the flight of steps,
taking preferably 3 steps at a time in the attempt to mount the
steps as fast as possible. The time taken to get from the third
step to the ninth step was
then recorded. The test
was repeated thrice and
the fastest time recorded
in hundredths of seconds.
Power (kilograms per
meter per second) was
calculated as follows:
Power = body mass (kilo-
grams) 3vertical distance
between steps (meters)/
time (seconds). The Mar-
garia-Kalamen power stair
has shown an ICC of 0.97.
Statistical Analyses
Standard statistical meth-
ods were used for the cal-
culation of the means and
SDs. Intraclass correlation
coefficient was used to
determine between-subject
reliability of selected tests.
Independent samples t-test
was used to check gender
differences in anthropomet-
ric and morphological
parameters and physical ac-
tivity indexes. For the anal-
ysis of statistical differences
between boys and girls on
physical performance varia-
bles, a multivariate analysis of covariance (MANCOVA) was
used, having as factors, in addition to sex, the maturation, and
the fat mass, physical activity, endomorphic, mesomorphic and
ectomorphic as covariates. The normality of the residuals of
MANCOVA was checked by applying the Kolmogorov-
Smirnov test and the homogeneity of variance-covariance ma-
trix, was tested by the Box M test (M= 435.60, F[315, 36950.5] =
1.22, p#0.05). Because it was not verified, this assumption we
used the Pillai’s Trace test statistics. It should be noted that the
correlations between the dependent variables ranged between
0.006 and 0.647. When statistically significant differences were
observed between boys and girls, an analysis of covariance
(ANCOVA) was estimated for each dependent variable, followed
by Bonferroni’s post hoc comparison tests. By ANCOVA, it was
also possible to analyze the statistical significance and effect size
of gender in the physical performance variables. To determine
which of the somatotype, physical activity, and body fat factor
had a greater influence on the motor performance of both boys
and girls, a MANCOVA was estimated for each gender, with the
maturation as a factor and the fat mass, physical activity, and
somatotype as covariates. The normality of the residuals was
validated by the Kolmogorov-Smirnov univariate and the homo-
geneity of variance-covariance matrix was validated by the Box
TABLE 5. Correlations between canonical coefficients and variables.
Canonical dimensions*
123
Performance variables 20-m Shuttle run (a.u.) 0.708 20.224 0.035
20-m Sprint (s) 20.465 0.142 20.515
9.14-m Shuttle run (s) 20.491 0.049 20.507
Flamingo balance (faults) 20.262 0.373 0.114
Sit-and-reach R (cm) 0.139 20.349 20.318
Sit-and-reach L (cm) 20.004 20.374 20.262
Trunk lift (cm) 20.109 20.121 20.337
Curl-ups (a.u.) 0.494 20.010 0.024
Push- ups (a.u.) 0.274 20.026 0.031
Standing broad jump (cm) 0.555 20.148 0.459
Medicine-ball throw (cm) 20.034 0.333 0.332
Handgrip strength R (kg) 20.201 0.308 0.519
Handgrip strength L (kg) 20.202 0.303 0.412
M-K power stair test 0.082 0.243 0.099
Eigenvalue and
variance
Eigenvalue 1.417 0.780 0.377
% of Variance 52.2 28.7 13.9
% of Cumulative variance 52.2 80.9 94.8
Canonical correlations 0.766 0.662 0.523
Wilks lambda 0.147 0.355 0.632
Multivariate tests F7.420 4.839 2.748
DF 1 90.0 70.0 52.0
DF 2 1643.1 1394.3 1136.9
p,0.001†,0.001†,0.001†
*Significant canonical dimensions; DF 1 = hypothesis degrees of freedom; DF 2 = error degrees
of freedom.
†p,0.01.
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Mtest(Girls:M=190.47,F[105, 4664.4] = 1.12, p.0.05; Boys:
M= 385.41, F[210, 5606.2] = 1.14, p.0.05), so we used Wilk
Lambda test. The reliability of physical performance was ana-
lyzed with Cronbach’s alpha.
We also carried out a canonical correlation to understand
which of the performance variables explained the data
variability more. We first found how many dimensions were
required to understand the existing associations. The tests of
dimensionality indicated the existence of 3 canonical dimen-
sions statistically significant. The first dimension had a canon-
ical correlation of 0.766, with an eigenvalue of 1.42 and an
explained variance of 52.2%. The second dimension showed
a canonical correlation of 0.662, representing an eigenvalue of
0.78 and an explained variance of 28.7%. The third dimension
had a canonical correlation of 0.523, an eigenvalue of 0.377 and
an explained variance of 13.9%. Together 97.7% of variance
was explained. Then, we calculated the correlation coefficients
between the canonical dimensions and the physical perfor-
mance variables, and the standardized scores for each
dimension were represented graphically. Data were analyzed
using SPSS 15.0. The statistical significance was set at p#0.05.
RESULTS
Regarding gender differences in anthropometric and mor-
phological parameters and physical activity indexes, we can
observe that girls registered
higher mean values of % FAT,
ENDO, and ECTO. On the
other hand, boys showed
higher values in the MESO
component and in all levels of
physical activity (school, sport,
leisure time, and total physical
activity indexes). However,
these differences were only
significant in the MESO (t=
27.897, p#0.001) and ECTO
(t= 2.161, p#0.05) compo-
nents, and school (t=22.392,
p#0.05), sport (t=25.594,
p#0.001) and total (t=
24.330, p#0.001) physical
activity indexes. In %FAT,
ENDO and leisure-time index,
gender differences were not
statistically significant.
In the analysis of gender
differences in physical perfor-
mance, the MANCOVA
showed that physical fitness
variables had a Cronbach’s
Alpha of 0.705, which indicates
that they have a reasonable
reliability for the physical per-
formance measurement. We
observed a significant and high-sized effect of gender in all
physical performance measures (Pillai’s Trace = 0.28, F[14,
291] = 8.13, p#0.01, h2
p¼0:28, Power = 1.00). However,
we found that the effect of Tanner’s stage was not significant
(Pillai’s Trace = 0.44, F[14, 291] = 0.97, p.0.05, h2
p¼0:44,
Power = 0.61). Through the ANCOVA, estimated for each
dependent variable when statistically significant differences
were observed between boys and girls, it was observed that
the boys were superior to the girls on tests of aerobic capabil-
ity, speed, agility, explosive strength, and maximum isometric
strength. The girls were superior in flexibility of the lower back
and hamstrings and balance (Table 2).
Regarding MANCOVA estimated for the girls, we
observed a significant and high-sized effect of endormophic
in all physical performance measures, followed by body
fat, Ectomorphic and Mesomorphic, with significant but
medium-sized effect. The physical activity did not have,
for girls, a statistically significant effect on physical perfor-
mance variables. In the boys, there was a significant and
high-sized effect of Ectomorphic and Mesomorphic in all
physical performance measures, followed by physical activ-
ity with significant but medium-sized effect. The variables
body fat and endomorphic did not have, for boys, a statisti-
cally significant effect on physical performance variables
(Table 3).
Figure 1. Scatterplot between dimension 1 and dimension 2 by sex.
Predictors of Gender Differences in Physical Fitness
1762
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Through the ANCOVA, we observed that gender differ-
ences in physical fitness were greater in the explosive
strength of upper and lower limbs (medicine-ball throw
and standing broad jump), although with a medium-size
effect of gender. In the opposite direction, gender differences
were smaller in the muscle strength and endurance (curl-ups
and push-ups) and trunk extensor strength and flexibility
(trunk lift), followed by speed (20-m run) and balance
(flamingo balance) (Table 4).
Table 5 shows the correlation coefficients between the
canonical dimensions and physical performance variables.
The performance variables with the greatest effect on the
first dimension were the endurance (0.708), explosive
strength of lower limbs (0555), abdominal muscular endur-
ance (0.494), agility (20.491), and speed (20.465). In the
second dimension, the variables flexibility of the lower back
and hamstrings (right: 20.349, and left: 20.374) and balance
(0.373) were the ones that had a stronger correlation with
this dimension. In the third dimension the speed (20.515)
and agility (20.507) were the variables with the highest cor-
relation with this dimension. (Table 5)
Figure 1 shows the standardized scores for the first
dimension (it has the variables with the greatest positive
effect the endurance, explosive strength of lower limbs and
abdominal muscular endur-
ance, in which boys have
greater values than the average,
and the greatest negative effect
the speed and agility, where
the boys have smaller values
than the average), and the sec-
ond dimension (it has the vari-
able with the greatest positive
effect the balance, where the
boys have a number of faults
greater than the average, and
greatest negative effect the
flexibility of the lower back
and hamstrings, where the
boys have smaller values than
the average). We observed that
the scores of the boys are more
concentrated in the fourth
quadrant (values above the
average in the first dimension
and below the average in the
second dimension), whereas
in the girls, the values are more
concentrated in the first quad-
rant (values above the average
in the second dimension and
below the average in the first
dimension).
Figure 2 shows the standard-
ized scores for the second and
third dimensions. The third dimension has the variables with
the greatest positive effect the maximum isometric strength
and explosive strength of lower limbs, in which the boys
have greater values than the average, and the greatest neg-
ative effect the speed and agility, where the boys have
smaller values than the average. It is observed that the scores
of the boys are more concentrated in the second quadrant
(values below the average in the second dimension, and
above the average in the third dimension), whereas in the
girls, the values are more concentrated in the fourth quad-
rant (values above the average in the second dimension and
below the average in the third dimension).
DISCUSSION
The purpose of this study was to analyze in which physical
capabilities boys and girls are closer or divergent. An
additional objective was to find which of the body fat,
physical activity, and somatotype factor is more interactive
with prepubescent children’s physical fitness level. The main
results suggested that the somatotype had the greatest
influence on the motor performance of both boys and girls
(ectomorphic and mesomorphic in the boys and endomor-
phic in the girls). The physical activity in the girls, and the
endomorphic and body fat in the boys, had no significant
Figure 2. Scatterplot between dimension 2 and dimension 3 by sex.
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effect. The difference between boys and girls in the physical
fitness was greater in the explosive strength of upper and
lower limbs, and smaller in the abdominal and upper limbs
muscular endurance, and trunk extensor strength and flexi-
bility, followed by speed and balance.
The girls studied showed higher values of %FAT, ENDO,
and ECTO compared with that shown by the boys. The
higher percentage values of body fat in girls are consistent
with the findings of several studies in the literature that
report higher such values for women in general (8,20,37).
ENDO expresses the degree of adiposity development (23)
being a variable close to % FAT, either in terms of definition
or the way they are both calculated so that values here also
show higher for girls than for boys (23). This body fat rep-
resents an inert noncontributory load and thus an increased
metabolic cost for children, making them less efficient in
terms of cardiorespiratory response and performance on
tests that require lifting and propulsion tasks (4,11,39). The
ECTO represents the relative thinness of the subject (23)
and therefore associates negatively with strength (23). At
the chronological ages under discussion, it seems that the
weighting index, that is, the quotient of height by the cube
root of body weight, which is based on the ECTO (23), is in
favor of girls. This becomes more noticeable if we consider
that the height growth curves in boys and girls intersect for
a time, referred to as “crossing over,” when girls overtake
boys in stature, a stage that coincides with prepuberty (23).
The boys showed higher values in the MESO component
and in all levels of physical activity (school index, sport
index, leisure-time index, and total index) relative to the girls.
The main literature also refers to higher MESO values
(23,24) and higher levels of physical activity (15,20,37) in
male subjects. The MESO represents the relative skeletal-
muscle magnitude (robustness) and therefore associates pos-
itively with strength and motor performance in general (23).
Similarly, higher levels of physical activity are associated
with a better physical fitness of children (15,20,31,39).
The curiousity in this study is that the variables with no
significant effect on the physical fitness of boys are the ones
that had the greatest effect on the performance of girls
(endomorphic and body fat). The greater robustness (23)
and higher levels of physical activity (37) of the boys,
including the higher levels of body fat (8,20) and a more
sedentary lifestyle (37) of the girls, seem to have influenced
the effect of each of these factors on the physical fitness of
boys and girls. No less interesting is that the primary com-
ponents of the somatotype had the greatest influence on the
motor performance of both boys and girls (ectomorphic and
mesomorphic in the boys and endomorphic in the girls), and
therefore, the relative skeletal-muscle magnitude of the boys
and the degree of adiposity development of the girls seems
to have reduced the dependence of the other factors on the
motor performance. This fact highlights the importance of
the morphological typology in the prepubescent children’s
physical fitness level and seems to suggest that one cannot
neglect the limits imposed by what is a manifestation of
genetic determinism, observed from the morphoconstitu-
tional point of view, because the presence or absence of
certain physical traits seems to be determinant on the phys-
ical performance of both boys and girls.
In terms of gender differences in motor performance, the
results confirm those of other studies that report the
superiority of boys in tests of aerobic fitness and muscular
strength and of girls in tests of balance and flexibility
(8,15,20). Additionally, our findings indicate that the differ-
ence between boys and girls in physical fitness was greater in
the explosive strength of upper and lower limbs, although
with a medium-size effect of gender. In the opposite direc-
tion, gender differences were smaller in the muscle strength
and endurance (curl-ups and push-ups) and trunk extensor
strength and flexibility, followed by speed, and balance.
Looking for the canonical correlation, the physical perfor-
mance variables that most explain the variability of the data
were the endurance, speed, agility, hand grip strength,
abdominal muscular endurance, and explosive strength of
lower limbs, in which boys are better, and flexibility of the
lower back and hamstrings and balance, in which girls
scored better. According to several studies in the literature,
the boys are superior to girls in aerobic fitness because,
among other factors such as higher levels of physical activity
(15,20,39) and lower fat mass (4,11,30), to other factors
mainly linked to the cardiac size and oxygen-carrying capac-
ity (i.e., left ventricular inner diastolic diameter, maximal
heart rate, and maximal stroke volume) (10). These factors
seem to determine the difference found between boys and
girls in cardiorespiratory fitness. In the same way, the fat-free
mass or lean body mass statistically higher in boys and
higher levels of physical activity permits a better muscular
strength (20,39). However, the absence of statistically signif-
icant differences between boys and girls in the muscular
endurance tests (curl-ups and push-ups) corroborates the
results of previous studies with children of similar age (7)
and may be because the weight of the boys, close to the
weight of girls in prepubertal stage (23), is an extra load to
be moved during weight-bearing tasks, added to the fact that
the boys still present a reduced muscle mass in prepubertal
ages, because the effects of circulating androgens, particu-
larly testosterone, only manifest themselves at puberty
(23). Also, the lower values for body fat recorded by boys
give them an advantage on tests of speed (11) and agility
(4,11), and the higher levels of physical activity permits bet-
ter performance in the same capabilities (31,36). Some
approximation found in speed between boys and girls, may
be because speed is a specific capability, highly dependent
on the influence of genetic factors such as neuromuscular
components and muscle fiber quality (i.e., fiber type propor-
tion), and the high degree of gene transfer implied in this
aptitude is today recognized (21). Regarding the flexibility,
there are many reports that girls have larger range of motion.
Some of the factors presented are the difference of
Predictors of Gender Differences in Physical Fitness
1764
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extensibility of muscle and tendon tissues, the greater passive
dorsiflexion angle of girls, because boys have a higher muscle
volume, and dynamic property of tendon tissues (18). There
are also studies in the literature referring to the absence of
significant associations of this capability with physical activ-
ity levels (15), and skeletal-muscle magnitude (robustness),
favorable to boys (34). There are even studies that report
a negative association between the physical activity levels
with performance on tests of flexibility (20). However, in this
capability, the difference by gender there occupies a place
emphasized during periods of rapid growth (28), which may
explain in part the proximity between boys and girls in the
trunk lift, associated to the fact that this capability is also
very dependent of the upper body strength (27). The study
of Monyeki et al. (28) showed that boys at this age can be
more flexible than girls. Also in the balance boys and girls
showed some proximity. These results may be obtained
because in the prepubertal period the difference in stature
between boys and girls gradually decreases, as a result of the
growth velocity of girls at this stage that is higher than for
boys, reaching the peak height velocity earlier (23). A greater
stature leads to a high body’s center of mass, in turn respon-
sible for increased postural instability on balance exercises
(2). However, other factors absent from this study may
account for the approximation or divergence of boys and
girls in physical fitness. Such factors may include, among
others, different practice opportunities (38) or the preference
for activities that require more endurance, strength, and
speed or balance and flexibility (6).
PRACTICAL APPLICATIONS
It has been observed that there is an apparent decrease in the
interest of children in physical education classes and regular
physical activity practice at school. This seems to be partly
because of the lack of planning that takes into account the
success of children in the execution of the exercises
respecting the differences among students, including boys
and girls. The knowledge of the magnitude of the differences
between boys and girls in physical fitness (greater in the
explosive strength of upper and lower limbs, and smaller in
the abdominal and upper limbs muscular endurance and
trunk extensor strength and flexibility, balance and speed),
can help in the planning of activities that take into account
the success of both boys and girls, and thus, increase levels of
physical activity and physical fitness at school. However, the
results seem to suggest that one cannot neglect the influence
of genetic determinism, observed from the morpho-consti-
tutional point of view, because the presence of certain
physical traits (ectomorphic and mesomorphic in the boys
and endomorphic in the girls) have shown to be determinant
in prepubescent children’s physical fitness level.
ACKNOWLEDGMENTS
The authors would like to thank all the children who
participated in this research. They would also like to
graciously thank the reviewers that took the time to critique
this manuscript. The authors have no professional relation-
ships with any companies or manufacturers identified in this
study. The results of this study do not constitute endorse-
ment of the product either by the authors or by the National
Strength and Conditioning Association.
REFERENCES
1. Adam, C, Klissouras, V, Ravassolo, M, Renson, R, Tuxworth, W,
Kemper, H, Van Mechelen, W, Hlobil, H, Beunen, G, Levarlet-
Joye, H, and Van Lierde, A. Eurofit. Handbook for the Eurofit Test of
Physical Fitness. Rome, Italy: Council of Europe. Committee for the
Development of Sport, 1988.
2. Allard, P, Nault, M, Hinse, S, Leblawc, R, and Labelle, H.
Relationship between morphologic somatotypes and standing
posture equilibrium. Ann Hum Biol 28: 624–633, 2001.
3. American Alliance for Health, Physical Education, Recreation and
Dance. Youth Fitness Test Manual. Washington, DC: AAHPERD, 1976.
4. Artero, EG, Espan
˜a-Romero, V, Ortega, FB, Jime
´nez-Pavo
´n, D,
Ruiz, JR, Vicente-Rodrı
´guez, G, Bueno, M, Marcos, A, Go
´mez-
Martı
´nez, S, Urzanqui, A, Gonza
´lez-Gross, M, Moreno, L,
Gutie
´rrez, A, and Castillo, MJ. Health-related fitness in adolescents:
underweight, and not only overweight, as an influencing factor. The
AVENA study. Scand J Med Sci Sport 20: 418–427, 2010.
5. Baecke, JA, Burema, J, and Frijiters, JE. A short questionnaire for the
measurement of habitual physical activity in epidemiological
studies. Am J Clin Nutr 36: 936–942, 1982.
6. Branta, C, Haubenstricker, J, and Seefeldt, V. Age changes in motor
skills during childhood and adolescence. Exercise Sport Sci Rev 12:
467–520, 1984.
7. Castro-Pin
˜ero, J, Gonza
´lez-Montesinos, JL, Mora, J, Keating, XD,
Girela-Rejo
´n, MJ, Sjo
¨stro
¨m, M, and Ruiz, JR. Percentile values
for muscular strength field tests in children aged 6 to 17 years:
Influence of weight status. J Strength Cond Res 23: 2295–2310, 2009.
8. Cepero, MR, Lo
´pez, R, Sua
´rez-Llorca, C, Andreu-cabrera, E, and
Rojas, FJ. Fitness test profiles in children aged 8–12 years old in
Granada (Spain). J Hum Sport Exerc 6: 135–146, 2011.
9. Coleman, KJ, Heath, EM, and Alcala, IS. Overweight and aerobic
fitness in children in the United States/Mexico border region. Rev
Panam Salud Pu
´bl/Pan Am J Public Health 15: 262–271, 2004.
10. Dencker, M, Thorsson, O, Karlsson, M, Linde
´n, C, Eiberg, S,
Wollmer, P, and Andersen, B. Gender differences and determinants
of aerobic fitness in children aged 8–11 years. Eur J Appl Physiol 99:
19–26, 2007.
11. Dumith, SC, Ramires, VV, Souza, MA, Moraes, DS, Petry, FG,
Oliveira, ES, Ramires, SV, and Hallal, PC. Overweight/obesity and
physical fitness among children and adolescents. J Phys Act Health 7:
641–648, 2010.
12. Faigenbaum, AD, Westcott, WL, Micheli, LJ, Outerbridge, AR,
Long, CJ, LaRosa-Loud, R, and Zaichkowsky, LD. The effects of
strength training and detraining on children. J Strength Cond Res 10:
109–114, 1996.
13. George, JD, Fisher, AG, and Vehrs, PR. Laboratory Experiences in
Exercise Science. Boston, MA: Jones & Bartlett Publishers, Inc, 1994.
14. Haff, GG. Roundtable discussion: Youth resistance training. Strength
Cond J 25: 49–64, 2003.
15. Hands, B, Larkin, D, Parker, H, Straker, L, and Perry, M. The
relationship among physical activity, motor competence and health-
related fitness in 14-year-old adolescents. Scand J Med Sci Sports 19:
655–663, 2009.
16. Heath, BH and Carter, JE. Growth and somatotype patterns of
Manus children, territory of Papua and New Guinea: Application of
a modified somatotype method to the study of growth patterns. Am
J Phys Anthropol 35: 49–67, 1971.
Journal of Strength and Conditioning Research
the
TM
|
www.nsca.com
VOLUME 26 | NUMBER 7 | JULY 2012 | 1765
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
17. Jak
si
c, D and Cvetkovi
c, M. Neural network analysis of somatotype
differences among males related to the manifestation of motor
abilities. Acta Kinesiologica 3: 107–113, 2009.
18. Kato, E, Oda, T, Chino, K, Kurihara, T, Nagayoshi, T, Fukunaga, T,
and Kawakami, Y. Musculotendinous factors influencing difference
in ankle joint flexibility between women and men. Int J Sport Health
Sci 3: 218–225, 2005.
19. Kvaavik, E, Klepp, KI, Tell, GS, Meyer, HE, and Batty, GD. Physical
fitness and physical activity at age 13 years as predictors of
cardiovascular disease risk factors at ages 15, 25, 33, and 40 years:
Extended follow-up of the Oslo Youth Study. Pediatrics 123: e80–
e86, 2009.
20. Lennox, A, Pienaar, AE, and Wilders, C. Physical fitness and the
physical activity status of 15-year-old adolescents in a semi-urban
community. S Afr J Res Sport Phys Educ Recreation 30: 59–73, 2008.
21. Little, T and Williams, AG. Specificity of acceleration, maximum
speed, and agility in professional soccer players. J Strength Cond Res
19:76–78, 2005.
22. Lyu, M and Gill, D. Perceived physical competence, enjoyment and
effort in same-sex and coeducational physical education classes. J
Educ Psychol 31: 247–260, 2011
23. Malina, RM and Bouchard, C. Growth Maturation and Physical
Activity. Champaign, IL: Human Kinetics, 1991.
24. Malina, RM, Bouchard, C, and Bar-Or, O. Growth, Maturation and
Physical Activity. Champaign, IL: Human Kinetics, 2004.
25. Marfell-Jones, M, Olds, T, Stewart, A, and Carter, L. International
Standards for Anthropometric Assessment. Potchefstroom, South
Africa: ISAK, 2006.
26. Mayhew, JL, Ware, JS, Johns, RA, and Bemben, MG. Changes in
upper body power following heavy-resistance strength training in
college men. Int J Sports Med 18: 516–520, 1997.
27. Meredith, MD and Welk, GJ. Fitnessgram/Activitygram Test
Administration Manual (4thed.).Champaign,IL:HumanKinetics,2007.
28. Monyeki, MA, Koppes, LJ, Kemper, HG, Monyeki, KD, Toriola, AL,
Pienaar, AE, and Twisk, JW. Body composition and physical fitness
of undernourished South African rural primary school children. Eur
J Clin Nutr 59:877–883, 2005.
29. Physical activity and cardiovascular health. NIH Consensus
Development Panel on Physical Activity and Cardiovascular Health.
J Am Med Assoc 276: 241–246, 1996.
30. Ortega, FB, Tresaco, B, Ruiz, JR, Moreno, LA, Matillas, M, Mesa, JL,
Warnberg, J, Bueno, M, Tercedor, P, Gutie
´rrez, A, and Castillo, MJ.
Cardiorespiratory fitness and sedentary activities are associated with
adiposity in adolescents. Obesity 15: 1589–1599, 2007.
31. Reed, JA and Metzker, A. Relationships between physical activity
and motor skills in middle school children. Percept Motor Skill 99:
483–494, 2004.
32. Reis, VM, Machado, JV, Fortes, MS, Fernandes, PR, Silva, AJ,
Dantas, PS, and Filho, JF. Evidence for higher heritability of
somatotype compared to body mass index in female twins. J Physiol
Anthropol 26: 9–14, 2007.
33. Roetert, EP. The lack of childhood activity in the United States.
Strength Cond J 26: 22–23, 2004.
34. Shukla, M, Venugopal, R, and Mitra, M. A cross sectional study of
body composition somatotype and motor quality of rural and urban
boys of Chhattisgarh. Int J Fitness 5: 1–7, 2009.
35. Slaughter, MH, Lohman, TG, Boileau, RA, Horswill, CA,
Stillman, RJ, VanLoan, MD, and Bemben, DA. Skinfold equations
for estimation of body fatness in children and youth. Hum Biol 60:
709–723, 1988.
36. Sola,K,Brekke,N,andBrekke,M.Anactivity-based
intervention for obese and physically inactive children
organized in primary care: Feasibility and impact on fitness and
BMI a one-year follow-up study. Scand J Prim Health 28: 199–
204, 2010.
37. Sveinsson, T, Arngrimsson, SA, and Johannsson, E. Association
between aerobic fitness, body composition, and physical activity in
9- and 15-year-olds. Eur J Sport Sci 9: 141–150, 2009.
38. Thomas, JR and French, KE. Gender differences across age in motor
performance: A meta-analyses. Psychol Bull 98: 260–282, 1985.
39. Tovar, G, Poveda, JG, Pinilla, MI, and Lobelo, F. Relationship
between overweight, physical activity and physical fitness in school-
aged boys in Bogota
´Colombia. Arch Latinoam Nutr 58: 265–273,
2008.
Predictors of Gender Differences in Physical Fitness
1766
Journal of Strength and Conditioning Research
the
TM
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.