Advances in Physical Education
2012. Vol.2, No.4, 187-196
Published Online November 2012 in SciRes (http://www.SciRP.org/journal/ape) http://dx.doi.org/10.4236/ape.2012.24032
Do Anthropometric Measures Influence Torso Muscle Endurance
Profiles of Children Aged 7 to 14?
Aleksandar Dejanovic1, Erin Harvey2, Jordan Andersen3, Stuart McGill3
1Department of Biochemical and Medicine Science, University of Novi Pazar, Novi Sad, Serbia
2Department of Statistics and Actuarial Science, Faculty of Mathematics, University of Waterloo,
Waterloo, Canada
3Department of Kinesiology, Faculty of Applied Health Sciences, University of Waterloo,
Waterloo, Canada
Received August 1st, 2012; revised September 4th, 2012; accepted September 16th, 2012
The aim of this study was to investigate whether torso endurance scores were linked with anthropometric
variables in children and to develop a normative scale of anthropometric measures in children in both
genders for clinical assessment, rehabilitation, physical education targets and young athletic training pur-
poses. It was hypothesized that changes in anthropometric measures through ages 7 to 14 influence en-
durance scores in both subsets. It was also hypothesized that boys and girls differ in the relationships be-
tween torso muscle endurance and anthropometric measures. Reduced torso muscle endurance has been
identified as a potential personal risk factor for developing low back pain and decreased athletic perfor-
mance. However, torso muscle endurance data in children is lacking. Further, given that endurance tests
require postures where the body is supported horizontally, it makes sense that anthropometric variables
would influence endurance. Isometric torso muscle endurance scores established through four tests were
performed in random order by healthy children. These were correlated with anthropometric dimensions.
Seven hundred and fifty-three children from one elementary school (394 boys and 359 girls) were
grouped into 8 age strata (7 to 14). Each age stratum had different number of participants for boys and
girls. Four tests established isometric torso muscle endurance: Biering-Sorensen test for extensor endu-
rance, flexor endurance test and right and left side bridge tests. The mean, standard deviation of the en-
durance tests and anthropometric measures were determined for each gender/age strata. The Pearson
product-moment correlation coefficients were determined between the anthropometric dimensions and
isometric torso endurance scores for each gender/age strata. Variance in endurance scores were not well
explained by anthropometric measures. Variables other than segment length and circumference influence
torso endurance as children grow and develop. Given links to future back pain and athletic performance,
more investigation would be justified.
Keywords: Anthropometric Measures; Torso Muscle Endurance Tests; Correlation; Children
Introduction
Isometric muscle endurance of the torso has been reported in
children (Dejanovic, 2006), adolescents (Salminen et al., 1992)
and adults (Biering-Sorensen, 1984; McGill et al., 1999). These
values are important as they have been identified as potential
risk factors for developing low back pain and decreased athletic
performance. Given that endurance test postures require the
body to be supported horizontally, it makes sense that anthro-
pometrics would influence endurance.
It has been shown that correlations between some anthro-
pometric measures and fitness variables, such as strength, are
important. Evidence indicates that body weight and height,
among children, are correlated with grip strength across several
populations (Everett & Sills, 1952; Johnson, 1925; Metheny,
1941). Further, there is general agreement that strength and
endurance are also important for motor development in children.
For example, Rarick and Dobbins (1975) emphasized strength
and its relationship to body size as major factors in physical
performance and that excess of body fat decreased motor per-
formances in children aged 6 - 9. Gabbard and Patterson (1980),
however, noted low correlations between muscular endurance,
body weight and height among children aged 3 - 5. Specifically,
a several reports suggested that endurance scores were lower in
tall and high body mass children (Docherty & Gaul, 1991;
Slaughter et al., 1977). Furthermore, Jürimäe and Jürimäe
(2000) found no correlation between Eurofit test results and
body height in boys while there was a relationship in girls. In
fact, longitudinal body dimensions in pre-pubertal girls had
more influences on motor ability tests when compared with
boys.
The current study was conducted to investigate the links be-
tween selected anthropometric measures and isometric torso
muscle endurance in boys and girls aged 7 to 14. Another goal
of this study was to develop a database of these measures for
children. It was hypothesized that changes in torso endurance
scores are associated with anthropometric measures. It was also
hypothesized that boys and girls differ in the relationship be-
tween torso muscle endurance and anthropometric measures.
Methods
Anthropometric measurements and torso muscle endurance
were obtained from boys and girls at an elementary school us-

A. DEJANOVIC ET AL.
ing previously established protocols (Dejanovic et al., 2012)
but which are repeated here. First, confirm that you have the
correct template for your paper size. This template has been
tailored for output on the custom paper size (21 cm * 28.5 cm).
Subjects
Seven hundred and fifty-three children (394 boys and 359
girls) aged 7 - 14 years from a Serbian elementary school took
part. The testing and data collection methods were presented to,
and approved by, the Parents’ Committee of the elementary
school, City of Novi Sad, Republic of Serbia, as well as from
the Teaching and Scientific Council, Faculty of Sport and
Physical Education in Nis, Department for Applied Kinesiology,
University of Nis, Republic of Serbia. All parents signed in-
formed consent documents prior to data collection. To reduce
risk of injury and psychological distress, each test was ex-
plained and demonstrated in front of the children. The inclusion
criteria for participants were: aged from 7 to 14 years; no cur-
rent or previous history of neurological or orthopaedic pro-
blems of the spine and hips; no upper or lower musculoskeletal
disorders or injuries; prior to testing, all subjects needed to feel
healthy, which was confirmed verbally before the testing ses-
sion.
Instrumentation
For the anthropometric measurements, the following stan-
dard instruments were used: Segment lengths were measured
using the Martin anthropometer, scaled 0 - 200 cm with a read-
ing accuracy of 0.1 cm. A balance beam scale, accurate to 0.1
kg, measured participants’ weight. Measuring tape 150 cm in
length was used to measure segment circumferences, accurate
to 0.1 cm. Finally, Martin sliding calipers with ranges of 0 - 40
cm and 0 - 20 cm were used for segment girth measurements,
also accurate to 0.1 cm.
Data Collection
Torso Muscle Endurance Tests
Four tests were used to measure isometric torso muscle en-
durance after McGill et al. (1999): Biering-Sorensen test, torso
flexor endurance test and right and left lateral torso test. McGill
et al. found these tests to be reliable with a reliability coeffi-
cient >0.97 when tested consecutively over a five-day period.
Evans and colleagues (2007) documented high reliability of the
lateral endurance tests.
Back Extension Test (BET): The Biering-Sorensen test was
used to measure back torso muscle endurance. Participants lay
on their front with their hips (anterior superior iliac spine
(ASIS)) in-line with the edge of a test bench (150 × 110 × 50
cm) so that the upper body was cantilevered out over the end,
holding their arms across the chest. To keep the participant in
place, the pelvis, knees and hips were secured with padded
straps or a research assistant held both ankles. The test ended
when the participant could no longer maintain a horizontal
position or when they reached 300 seconds. During the test,
participants were allowed to be verbally corrected twice to
maintain a horizontal position and the test ended on the third
correction.
Flexor Endurance Test (FET): Participants adopted a sit-up
position with arms placed across the chest. The feet were se-
cured under toe straps or by a researcher and the back began
resting against a jig angled 50˚ from the floor with knees and
hips flexed at 90˚. To begin, the jig was pulled back 10 cm
while the subject held this position for as long as possible. The
test was stopped when the participants’ back touched the jig or
when a maximum time of 300 seconds was reached.
Left and Right Side Bridge Tests (LS & RS): Lateral torso
muscle endurance was tested with the subject lying in the full
side-bridge position. Legs were extended, the top foot was
placed in the front of the lower foot for support and the partici-
pant was asked to bridge up with the elbow while holding their
hips off the floor. The test was terminated when the subject lost
a straight back posture or when a maximum time of 300 se-
conds was reached.
Anthropometric Measures
The following parameters were used to evaluate the anthro-
pometric measurements: 1) longitudinal dimensions—body
height, sitting height, upper arm length, arm length and leg
length; 2) transversal dimensions—shoulder diameter (bia-
cromial diameter), pelvic width (bicristal diameter) and knee
diameter; 3) circumferential dimensions—upper arm, forearm,
chest, waist, hips, upper leg and calf; and 4) body weight. Body
weight was measured to the closest 0.5 kg. All other measure-
ments were taken to the closest 0.1 cm. Anthropometric mea-
surements were carried out in accordance with the guidelines of
the International Biological Program (Lohman et al., 1988).
Body height was measured with participants standing bare-
foot in an upright position. A measurement was taken from the
floor to the top of the participant’s head in a neutral position.
Sitting height was done with participants in a flat-seated chair
with his or her back in a neutral position. A measurement was
taken from the seat of the chair to the top of the participants’
head. For the upper arm, a measurement was taken from the
acromion to the olecranon with the elbow flexed at 90˚ and the
palm facing up. Arm length was taken from the acromion to the
tip of the middle finger when the arm was in front of the par-
ticipant parallel to the ground with the palm facing up. Leg
length was taken from the floor to the ASIS when the partici-
pant was standing upright.
Shoulder and pelvic diameter were measured with the Martin
sliding caliper. With the participant in an upright standing posi-
tion, the anthropometer was placed on the outer part of both
acromia for the shoulders and at the top of the iliac crest for the
pelvis. Knee diameter was taken around the level of the epi-
condyles of the femur with the participant in a seated position
and the knee bent to 90˚.
All circumference measurements were carried out with the
participants in an upright standing posture, except for the calf
that was done in a seated position. The upper arm measurement
was taken midway between the acromion and the olecranon.
The forearm, upper leg and calf measurements were taken at
the level of greatest circumference of the segment. Circumfer-
ence of the chest was taken from between the attachment of the
3rd and 4th ribs around to the sternum. A measurement was
taken at the end of a normal exhalation. Waist circumference
was taken at the level of the umbilicus and hip circumference
was measured at the greatest circumference of the gluteal mus-
cles.
Body weight was measured with the participant in a quiet,
upright standing posture.
188

A. DEJANOVIC ET AL.
Boys Statistical Analysis
Torso endurance test scores were not normally distributed for
boys or girls, determined by the Kolmogorov-Smirnov test in
SPSS Statistics 20.0. Stem-and-leaf plots suggested that this
was likely due to a ceiling effect of endurance scores (i.e. nu-
merous children reached the 300 s time limit for each test).
Spearman rank-order correlation was used to determine the
strength of relationships between torso endurance scores and
anthropometric measurements for each gender. The participants
were then separated into 8 age groups (ages 7 through 14). For
boys, the numbers of participants in each age group were: 7 (n = 30),
8 (n = 35), 9 (n = 58), 10 (n = 42), 11 (n = 59), 12 (n = 49), 13
(n = 63) and 14 (n = 58). For girls, the numbers of participants
were: 7 (n = 41), 8 (n = 38), 9 (n = 50), 10 (n = 42), 11 (n = 58),
12 (n = 43), 13 (n = 45) and 14 (n = 42). This division was done
to determine whether there were any differences in torso en-
durance scores and anthropometric measures at different ages
between genders. Spearman correlations were determined be-
tween endurance times and anthropometrics for each age group
of both genders.
Examining the relationships between endurance variables
and anthropometric variables, independent of age, Spearman
correlations were strongest between BET and longitudinal an-
thropometric measures; however, while statistically significant,
the highest R value was 0.28, meaning that very little variance
was explained. Figure 1 illustrates this notion with an example
plotting all endurance scores with height. Among each torso
endurance test, the highest correlations were also in the longi-
tudinal dimension; however, relationships between FET, LS
and RS and anthropometrics, though significant, were also very
low (Table 2(a)).
When examining each age group as a cluster, Spearman cor-
relations showed a different trend. Of all the anthropometric
measurements, circumferential dimensions were most corre-
lated with the torso endurance scores for boys. Knee diameter
was correlated with the greatest number of endurance tests and
across the highest number of age groups (the largest being r =
0.53). The next most correlated anthropometric variables were
forearm circumference, upper leg circumference and body
weight. Most of the correlations, especially those that were
significant, were negative; however, correlations between the
BET test for 14 year old boys and these 4 body measurements
were all positive (Table 3(a)).
Means and standard deviations were calculated for each in-
dividual age group by gender for all of the torso endurance and
anthropometric measures. The Kruskal-Wallis test was used to
determine whether there was a significant effect of gender on
the 4 torso endurance scores (α = 0.0125 with Bonferroni cor-
rection). The Mann-Whitney U statistic was then used to de-
termine the loci of these differences, with the alpha value Bon-
ferroni corrected to 0.007.
Changes in all anthropometric variables followed a linear
trend when plotted against age; however, torso endurance test
scores did not as there were several inflection points. For ex-
ample, BET showed an initial peak at 9 years then a second
peak at 13 years (Figure 2). FET, on the other hand, increased
almost twofold from ages 7 to 8 in boys before it leveled off at
age 9. A slight drop in abdominal torso endurance occurred at
age 12 before it increased in ages 13 and 14. A similar trend
exists in both lateral torso endurance tests, except the dips in
Results
Means and standard deviations of torso endurance scores and
anthropometric measures are presented in Tables 1(a)-(d) for
the 8 separate age groups of boys and girls.
Figure 1.
A scatter plot of all endurance scores for boys and height illustrating no obvious links.

A. DEJANOVIC ET AL.
Table 1.
(a) Mean and standard deviation of torso endurance tests for boys and girls of all age groups; (b) Mean and standard deviation of anthropometric
longitudinal dimensions for boys and girls of all age groups; (c) Mean and standard deviation of anthropometric transversal dimensions and body
weight for boys and girls of all age groups; (d) Mean and standard deviation of anthropometric circumferential dimensions for boys and girls of all
age groups.
(a)
Torso Endurance
BET FET LS RS
Sex Age N
Mean SD Mean SD Mean SD Mean SD
7 30 110.8 59.7 76.0 51.2 62.4 32.0 66.1 27.6
8 35 126.1 67.9 140.6 87.2 60.0 26.4 60.0 24.6
9 58 150.7 63.3 147.9 91.5 74.5 40.7 84.6 54.7
10 42 165.1 68.7 138.0 74.7 82.0 44.6 88.5 42.5
11 59 160.2 67.5 129.3 78.9 72.4 30.8 76.8 31.0
12 49 169.1 64.2 124.4 69.3 71.9 36.2 79.9 38.2
13 63 183.0 70.2 138.7 71.6 84.4 32.5 88.9 31.2
Male
14 58 181.4 59.7 155.0 75.7 95.0 43.9 97.7 38.4
7 41 111.0 44.5 96.6 75.9 56.9 21.5 59.1 22.1
8 38 137.0 64.6 100.7 81.0 44.7 24.7 53.9 24.6
9 50 191.7 62.9 168.6 95.3 84.5 38.9 77.6 43.0
10 42 202.1 65.6 149.1 81.4 85.9 38.9 96.0 46.8
11 58 182.0 67.8 111.0 69.3 77.5 39.1 76.1 27.9
12 43 210.4 56.9 126.2 64.2 68.5 32.1 64.9 24.9
13 45 206.3 57.9 148.2 79.2 75.7 29.3 80.3 34.0
Female
14 42 197.6 72.7 140.8 72.3 86.0 32.2 86.0 35.3
Average difference between
genders across all age groups
†−23.9 †14.9 †1.1 †21.3 †2.8 †8.5 †6.1 †6.9
Note: †Positive values denote greater value from male population; Negative values show bias towards females; Torso endurance scores measured in seconds; BET—back
extension test (Biering-Sorensen); FET—flexor endurance test (sit-up posture); LS—left side bridge; RS—right side bridge.
(b)
Longitudinal Dimensions
Body Height Sitting Height Leg Length Arm Length Upper Arm Length
Sex Age N
Mean SD Mean SD Mean SD Mean SD Mean SD
7 30 127.1 5.5 68.9 2.9 71.1 3.8 53.1 3.2 24.2 1.7
8 35 132.1 4.6 69.5 2.5 75.3 3.3 55.1 2.1 26.1 10.0
9 58 139.2 5.7 72.5 2.9 80.1 4.5 57.1 4.3 25.3 1.8
10 42 144.2 6.5 75.8 3.3 84.1 4.9 62.9 3.9 28.3 2.2
11 59 150.5 7.1 77.9 4.0 88.4 5.0 64.1 3.7 29.2 2.5
12 49 157.1 6.9 81.2 3.3 92.2 6.4 68.2 4.2 31.5 2.7
13 63 165.0 8.4 84.4 4.7 96.8 6.0 72.3 4.8 33.6 6.8
Male
14 58 169.7 8.0 88.1 4.5 99.1 5.0 74.3 4.1 34.1 2.1
7 41 126.8 5.1 68.9 2.7 70.9 3.9 52.7 3.2 23.8 1.6
8 38 132.0 6.4 69.5 3.0 75.3 4.5 54.2 6.4 25.2 2.0
9 50 138.0 6.2 72.2 3.1 78.6 4.4 56.8 3.2 25.6 1.9
10 42 144.7 8.4 76.2 4.3 84.5 5.8 62.9 4.2 29.1 2.1
11 58 151.2 7.9 79.0 4.2 87.8 5.3 65.3 4.1 30.3 2.1
12 43 158.5 7.0 82.5 3.8 91.2 5.4 69.3 3.8 32.0 2.1
13 45 162.6 6.0 84.5 3.9 94.6 4.6 70.6 3.8 32.6 1.9
Female
14 42 165.0 7.0 86.9 3.7 94.5 4.8 71.8 3.6 33.4 1.7
Average difference between
genders across all age groups
†0.8 †2.0 †−0.1 †0.8 †1.2 †1.6 †0.4 †1.3 †0.04 †0.8
Note: †Positive values denote greater value from male population; Negative values show bias towards females; Longitudinal dimensions measured in centimetres.
190

A. DEJANOVIC ET AL.
(c)
Transversal Dimensions Body Weight
Shoulder Diameter Pelvis Diameter Knee Diameter
Sex Age N
Mean SD Mean SD Mean SD Mean SD
7 30 27.6 1.5 19.2 1.1 8.3 0.7 26.4 4.5
8 35 28.7 1.5 19.7 1.1 8.5 0.7 30.1 4.7
9 58 30.0 1.5 20.6 1.3 8.8 0.7 35.1 6.4
10 42 30.5 3.8 21.6 1.7 8.7 0.9 39.0 9.1
11 59 32.2 2.1 21.7 1.8 9.8 1.0 44.7 10.9
12 49 34.0 2.0 23.4 1.7 9.6 0.9 48.4 10.3
13 63 35.3 2.3 23.6 1.7 9.9 0.9 54.4 12.1
Male
14 58 35.6 2.5 24.7 2.5 10.0 0.8 57.0 9.1
7 41 26.9 1.3 18.9 1.1 8.0 0.7 26.2 4.1
8 38 28.7 1.5 19.8 1.3 8.2 0.7 29.3 5.3
9 50 29.3 1.6 20.6 1.5 8.6 0.8 33.0 7.5
10 42 29.7 2.3 21.4 1.8 8.3 0.9 37.2 8.3
11 58 31.8 2.0 22.6 2.0 9.2 0.8 42.9 9.2
12 43 33.0 2.6 24.2 3.7 9.0 0.9 47.0 8.6
13 45 34.6 1.6 24.6 1.6 9.5 1.0 53.1 10.1
Female
14 42 34.2 2.2 24.9 1.7 9.2 0.7 54.6 8.8
Average difference between genders
across all age groups
†0.7 †0.4 †−0.3 †0.5 †0.5 †0.2 †1.5 †0.7
Note: †Positive values denote greater value from male population; Negative values show bias towards females; Transversal dimensions measured in centimeters; Body
weight measured in kilograms.
(d)
Circumferential Dimensions
Chest
Circumference Upper Arm Circumference Forearm Circumference Hip Circumference Waist Circumference Upper Leg Circumference Calf Circumference
Sex Age N
Mean SD Mean SD Mean SD Mean SD MeanSD Mean SD MeanSD
7 30 61.6 4.2 18.1 2.1 17.91.8 65.7 5.3 55.7 5.1 37.2 3.6 25.4 2.5
8 35 64.4 4.8 19.4 1.9 19.11.5 69.1 5.2 59.1 4.9 39.7 4.1 26.9 1.9
9 58 68.8 5.6 20.0 2.1 19.51.4 73.2 6.3 62.3 6.9 43.6 4.9 28.6 2.5
10 42 72.0 7.9 21.1 2.8 20.52.0 75.4 8.3 65.2 9.5 43.0 6.7 28.9 3.1
11 59 74.3 7.6 22.1 3.1 20.62.0 81.1 8.6 67.1 8.7 48.0 6.7 31.0 3.3
12 49 76.7 7.0 22.9 3.2 21.82.0 81.1 9.2 67.3 7.6 47.7 8.8 31.1 3.4
13 63 78.8 7.9 23.7 3.2 22.42.2 86.6 8.4 69.6 7.5 51.0 8.6 33.3 3.8
Male
14 58 80.6 7.2 24.0 2.4 23.21.9 86.0 7.4 69.1 5.1 48.4 5.3 33.3 2.9
7 41 60.9 4.1 18.8 1.9 17.81.3 66.6 4.9 54.8 4.3 39.0 3.8 25.9 1.9
8 38 63.6 4.8 19.1 2.1 18.31.6 69.8 5.6 57.2 5.4 40.3 4.2 26.9 2.2
9 50 66.0 6.4 19.6 2.8 18.91.9 72.9 7.6 57.5 7.0 42.8 5.5 27.9 2.7
10 42 70.0 6.9 20.6 2.5 19.82.0 75.8 7.3 60.5 6.7 43.7 5.1 28.4 3.1
11 58 74.3 7.9 22.4 3.1 20.92.0 80.5 8.1 63.4 8.4 46.1 6.4 30.9 3.3
12 43 78.2 7.0 23.2 3.0 21.52.1 83.1 6.9 64.1 5.6 48.8 5.3 31.9 3.3
13 45 80.4 6.8 23.4 3.1 21.52.1 89.1 8.3 66.0 6.5 51.5 6.0 33.3 2.9
Female
14 42 84.2 5.7 23.5 2.4 22.11.9 85.2 7.9 67.3 6.7 53.4 5.1 32.7 3.4
Average difference
between genders across
all age groups
†−0.1 †2.1 †0.1 †0.5 †0.5 †0.4 †−0.6 †1.2 †3.1 †1.4 †−0.9 †2.0 †0.1 †0.5
Note: †Positive values denote greater value from male population; Negative values show bias towards females; Circumferential dimensions measured in centi-
metres.

A. DEJANOVIC ET AL.
Table 2.
(a) Correlation values between torso endurance scores and anthropometric measurements for boys; (b) Correlation values between torso endurance
scores and anthropometric measurements for girls.
(a)
Longitudinal Dimensions Transversal Dimensions
Boys Body HeightSitting Height Leg LengthArm LengthUpper Arm
Length
Shoulder
Diameter
Pelvis
Diameter
Knee
Diameter
R 0.27** 0.25** 0.26** 0.28** 0.27** 0.26** 0.23** 0.09
BET alpha <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.09
R 0.09 0.10 0.09 0.08 0.08 0.06 0.03 −0.04
FET alpha 0.08 0.06 0.07 0.12 0.13 0.23 0.55 0.40
R 0.16** 0.18** 0.13** 0.15** 0.16** 0.15** 0.10* −0.05
LS alpha <0.001 <0.001 0.01 <0.001 <0.001 <0.001 0.04 0.35
R 0.13** 0.14** 0.11* 0.13* 0.10* 0.12* 0.05 −0.09
RS alpha <0.001 <0.001 0.03 0.01 0.04 0.02 0.29 0.09
Circumferential Dimensions
Boys Chest
Circumference
Upper Arm
Circumference
Forearm
Circumference
Hip
Circumference
Waist
Circumference
Upper Leg
Circumference
Calf
Circumference
Body Weight
R 0.12* 0.04 0.06 0.11* 0.05 0.06 0.11* 0.16**
BET alpha 0.01 0.46 0.24 0.03 0.37 0.25 0.04 <0.001
R 0.00 −0.03 −0.04 0.00 −0.03 −0.01 −0.03 0.01
FET alpha 0.98 0.51 0.47 0.96 0.56 0.80 0.57 0.77
R 0.05 −0.04 0.04 −0.01 −0.07 −0.06 0.02 0.03
LS alpha 0.37 0.40 0.45 0.87 0.15 0.23 0.76 0.50
R −0.01 −0.10* −0.03 −0.05 −0.12* −0.09 −0.04 −0.02
RS alpha 0.91 0.05 0.60 0.35 0.01 0.08 0.42 0.74
Note: Statistically significant (*p < 0.05, **p < 0.01); BET—back extension test (Biering-Sorensen); FET—flexor endurance test (sit-up posture); LS—left side bridge;
RS—right side bridge.
(b)
Longitudinal Dimensions Transversal Dimensions
Girls Body Height Sitting Height Leg Length Arm Length Upper Arm
Length
Shoulder
Diameter
Pelvis
Diameter
Knee
Diameter
R 0.35** 0.32** 0.37** 0.35** 0.34** 0.30** 0.26** 0.17**
BET alpha <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.001
R 0.16** 0.14** 0.17** 0.13* 0.15** 0.101 0.090 0.048
FET alpha 0.002 0.007 0.002 0.012 0.004 0.055 0.088 0.363
R 0.19** 0.20** 0.15** 0.18** 0.18** 0.12* 0.12* −0.049
LS alpha <0.001 <0.001 0.004 0.001 0.001 0.019 0.026 0.357
R 0.17** 0.19** 0.14** 0.17** 0.16** 0.092 0.12* −0.063
RS alpha 0.001 <0.001 0.008 0.001 0.003 0.081 0.028 0.237
Circumferential Dimensions
Girls Chest
Circumference
Upper Arm
Circumference
Forearm
Circumference
Hip
Circumference
Waist
Circumference
Upper Leg
Circumference
Calf
Circumference
Body Weight
R 0.24** 0.17** 0.22** 0.26** 0.17** 0.24** 0.22** 0.27**
BET alpha <0.001 0.002 <0.001 <0.001 0.002 <0.001 <0.001 <0.001
R 0.064 0.065 0.042 0.097 0.040 0.086 0.062 0.11*
FET alpha 0.229 0.217 0.430 0.066 0.448 0.105 0.245 0.043
R 0.071 −0.013 0.052 0.018 −0.061 0.013 0.033 0.072
LS alpha 0.182 0.800 0.322 0.739 0.252 0.809 0.527 0.176
R 0.061 −0.015 0.040 0.018 −0.049 <0.001 0.040 0.062
RS alpha 0.250 0.779 0.449 0.728 0.351 0.996 0.449 0.238
Note: Statistically significant (*p < 0.05, **p < 0.01); BET—back extension test (Biering-Sorensen); FET—flexor endurance test (sit-up posture); LS—left side
bridge; RS—right side bridge.
192

A. DEJANOVIC ET AL.
Table 3.
(a) Correlation values for boys of the 4 most correlated anthropometric variables with the 4 torso endurance tests; (b) Correlation values for girls of the
4 most correlated anthropometric variables with the 4 torso endurance tests.
(a)
Knee Diameter Forearm Circumference
Age 7 8 9 10 11 12 13 14 7 8 9 10 11 12 13 14
R −0.21 −0.16 0.00−0.32* −0.25 −0.03 −0.25*0.13 −0.25 −0.12 −0.25 −0.30* −0.27* −0.35* −0.28*0.17
BET
Sig. 0.27 0.35 0.98 0.04 0.06 0.82 0.05 0.340.180.480.05 0.05 0.04 0.02 0.03 0.20
R 0.14 −0.24 0.12−0.39* −0.11 −0.32*−0.28*−0.16 −0.01−0.23 −0.03 −0.39* −0.27* −0.25 −0.24 −0.27*
FET
Sig. 0.47 0.17 0.35 0.01 0.39 0.03 0.03 0.240.960.180.82 0.01 0.04 0.08 0.06 0.04
R −0.28 −0.19 −0.03 −0.31* −0.33** −0.12 −0.27*−0.26*−0.04 −0.02 −0.21 −0.44** −0.22 −0.10 −0.12 −0.07
LS Sig. 0.14 0.27 0.81 0.04 0.01 0.41 0.03 0.050.820.910.11 0.00 0.10 0.48 0.33 0.62
R −0.07 −0.39* −0.07 −0.51** −0.53** −0.23 −0.41** −0.140.06 −0.11 −0.28*−0.50** −0.53** −0.19 −0.28*0.06
RS
Sig. 0.70 0.02 0.58 0.00 0.00 0.12 0.00 0.290.740.540.03 0.00 0.00 0.20 0.03 0.64
Upper Leg Circumference Body Weight
Age 7 8 9 10 11 12 13 14 7 8 9 10 11 12 13 14
R −0.03 −0.09 −0.18 −0.31* −0.29* −0.12 −0.31*0.15 −0.20 −0.14 −0.09 −0.32* −0.22 −0.22 −0.26*0.19
BET
Sig. 0.88 0.63 0.18 0.04 0.03 0.40 0.01 0.260.280.440.51 0.04 0.09 0.12 0.04 0.16
R −0.11 −0.20 0.06−0.42** −0.14 −0.25 −0.12 −0.240.01 −0.220.04 −0.46** −0.17 −0.34* −0.15 −0.27*
FET
Sig. 0.56 0.24 0.64 0.01 0.28 0.09 0.36 0.070.980.210.75 0.00 0.21 0.02 0.23 0.04
R 0.11 −0.08 −0.26* −0.54** −0.34** −0.14 −0.18 −0.26*−0.11 −0.06 −0.21 −0.53** −0.36** −0.20 −0.22 −0.23
LS Sig. 0.57 0.66 0.05 0.00 0.01 0.34 0.16 0.050.560.720.12 0.00 0.01 0.18 0.09 0.09
R 0.24 −0.20 −0.38** −0.68** −0.51** −0.20 −0.30*0.040.05 −0.17 −0.30*−0.70** −0.55** −0.33* −0.40** −0.08
RS
Sig. 0.21 0.25 0.00 0.00 0.00 0.17 0.02 0.780.800.320.02 0.00 0.00 0.02 0.00 0.54
Note: Significant correlations (*p < 0.05, **p < 0.01); BET—back extension test (Biering-Sorensen); FET—flexor endurance test (sit-up posture); LS—left side bridge;
RS—right side bridge.
(b)
Body Height Sitting Hei ght
Age 7 8 9 10 11 12 13 14 7 8 9 10 11 12 13 14
R 0.35* 0.38* −0.12 0.21 0.08 0.05−0.04 −0.16 0.290.40*−0.100.12 0.03 −0.19 −0.13 −0.19
BET
Sig. 0.02 0.02 0.420.19 0.53 0.770.800.300.060.010.47 0.47 0.85 0.23 0.400.23
R 0.47** 0.15 −0.27 −0.13 0.06 0.02 −0.150.130.413** 0.17 −0.296*−0.15 −0.01 −0.08 −0.23 0.10
FET
Sig. 0.00 0.37 0.050.40 0.66 0.910.320.410.010.290.04 0.34 0.97 0.62 0.130.52
R −0.10 0.07 −0.35* 0.04 −0.03 0.07−0.12−0.270.080.17 −0.34*0.00 0.03 −0.03 −0.06 −0.44**
LS
Sig. 0.53 0.69 0.010.81 0.82 0.640.450.090.620.310.02 0.99 0.84 0.86 0.690.00
R −0.06 0.38* −0.44** −0.02 0.00 0.100.00−0.32*0.08 0.50**−0.38** −0.05 0.07 0.14 0.01−0.43**
RS Sig. 0.72 0.02 0.000.89 0.97 0.530.980.040.640.000.01 0.77 0.62 0.36 0.920.00
Leg Length Pelvic Diameter
Age 7 8 9 10 11 12 13 14 7 8 9 10 11 12 13 14
R 0.35* 0.34* −0.11 0.22 0.09 0.29−0.02 −0.160.210.06 −0.28*0.17 −0.03 −0.15 −0.17 −0.34*
BET Sig. 0.03 0.04 0.430.15 0.48 0.060.880.320.180.700.05 0.29 0.84 0.35 0.280.03
R 0.41** 0.10 −0.31* −0.04 −0.01 0.21−0.09 0.050.38*−0.05 −0.17 −0.14 −0.36** 0.06 −0.19 −0.07
FET
Sig. 0.01 0.54 0.030.81 0.97 0.180.570.760.020.750.25 0.36 0.01 0.71 0.220.68
R −0.17 −0.06 −0.31* 0.04 −0.19 0.03−0.17 −0.33*0.03 −0.04−0.54** −0.12 −0.20 −0.08 −0.02−0.26
LS Sig. 0.29 0.70 0.030.79 0.16 0.850.270.030.880.810.00 0.43 0.14 0.63 0.890.10
R −0.11 0.19 −0.43** −0.03 −0.10 0.02−0.15 −0.40** −0.040.14 −0.40** −0.12 −0.16 0.27 −0.10 −0.32*
RS
Sig. 0.48 0.26 0.000.85 0.48 0.920.320.010.810.420.00 0.47 0.22 0.08 0.530.04
Note: Significant correlations (*p < 0.05, **p < 0.01); BET—back extension test (Biering-Sorensen); FET—flexor endurance test (sit-up posture); LS—left side bridge;
RS—right side bridges.

A. DEJANOVIC ET AL.
194
Figure 2.
Torso extensor and flexor endurance and anthropometric changes with age in boys illustrating progressive
increase in anthropometric variables with age while endurance scores showed inflection points.
performance for these tests occurred at age 8 and between ages
11 and 12 before increases were seen. Figures 2 and 3 show the
non-linear changes in torso extensor/flexor endurance and la-
teral torso endurance, respectively, along with the year by year
systematic increase in the 4 anthropometric variables that were
most correlated with the torso endurance tests (knee diameter,
forearm circumference, upper leg circumference and body
weight).
Girls
Similar to the boys, correlations were strongest between BET
and longitudinal measures for the girls when taken across all
ages; however, the girls showed higher correlations than the
boys. The girls followed the same pattern of significant, but
weak, correlations between FET, LS and RS and anthropome-
trics (Table 2(b)).
While transversal and circumferential dimensions and body
weight were most correlated with torso endurance scores within
each age group for the boys, the longitudinal dimensions
dominated these correlations in the girls. Body height, followed
by sitting height, leg length and pelvic diameter were the high-
est correlated anthropometric measures with BET, FET, RS and
LS (Table 3(b)).
There were also similarities in the changes in anthropometric
variables and torso endurance scores between the boys and girls;
however, there were differences in the torso endurance inflec-
tion peaks and valleys. BET scores demonstrated the first peak
at age 10 before dropping at age 11 and increasing to age 12,
leveling out for ages 13 and 14. FET times increased a year
later in girls than they did in boys and did not increase as dra-
matically; an increase in scores of 74% was seen from age 8 to
9. There was a drop from age 9 to 10 and then even more sub-
stantial from 10 to 11 before an increase was seen through age
13. Lateral torso endurance scores in girls changed most simi-
larly to boys; there was, however, an initial peak in RS and LS
at age 10. Figures 4 and 5 show these changes along with the
linear changes in the anthropometric variables that were most
correlated with the 4 torso endurance tests (body height, sitting
height, leg length and pelvic diameter).
Boys vs. Girls
Girls had better BET scores than boys with an average dif-
ference of 23.9s across all age groups. Though boys had higher
scores in the other 3 endurance tests, the greatest difference
between the genders was only 6.1s (LS) (Table 1).
The Kruskal-Wallis test determined there was a significant
effect of gender on BET (H(1) = 17.675, p < 0.001) and RS
(H(1) = 9.366, p = 0.002), but not FET (p = 0.216) and LS (p =
0.111) scores. The Mann-Whitney U statistic showed that girls
had significantly greater BET scores than the boys at ages 9 (U =
929.5, p = 0.001) and 12 (U = 628, p = 0.001). There were no
significant differences between the genders in RS scores (p >
0.047).
Discussion
The most surprising result of this study was that torso en-
durance scores seem to change independently of age. When all
individuals were considered together regardless of age, the only
pattern that was detected existed between longitudinal dimen-
sions and endurance times. Though significant correlations
existed between several anthropometric variables and torso
endurance times, the magnitudes were very low. Despite the
wide range of body measurements taken in multiple dimensions,
there were no notable trends in the correlations. There are other
factors in children, less related to body size, which must influ-
ence torso muscle endurance. Perhaps hormonal changes asso-
ciated with puberty or other variables that affect one’s effort
during physical exertions may have more of an impact on torso
endurance testing than the length of their legs. Thus, the first
hypothesis must be rejected that anthropometric features influ-
ence endurance times. The second hypothesis suggesting boys
and girls differ both in endurance profiles and their links to
anthropometric variables is accepted.
There are divided opinions regarding gender differences for
back muscle endurance in the literature. Some authors found
significantly higher endurance scores in females (Kankaanpää

A. DEJANOVIC ET AL.
Figure 3.
Lateraltorso endurance and anthropometric changes with age in boys illustrating progressive increase in
anthropometric variables with age while endurance scores showed inflection points.
Figure 4.
Torso extensor and flexor endurance and anthropometric changes with age in girls illustrating progres-
sive increase in anthropometric variables with age while endurance scores showed inflection points.
Figure 5.
Lateraltorso endurance and anthropometric changes with age in girls illustrating progressive increase in
anthropometric variables with age while endurance scores showed inflection points.

A. DEJANOVIC ET AL.
196
et al., 1998), while other studies claim the opposite (Alaranta et
al., 1994). Another factor related to gender that contributes to
back muscle endurance may be differences in body segment
proportions, as suggested by the data from the current study.
Tichauer et al. (1978) reported that females had longer torsos
and shorter legs than males, suggesting they can achieve better
endurance times in back endurance tests because of it; however,
similar to the findings of Xiao et al. (2005), the results from the
current study failed to support this notion with any clear pattern
between segment length and torso endurance.
One of the problems in this controversy is that some back
muscle endurance scores were achieved in healthy populations
while the others were collected from low back pain (LBP) sub-
jects. Our study was limited to healthy children aged 7 to 14
and results showed that girls are able to maintain longer back
extension. One of the reasons for this may be due to greater
lumbar lordosis in girls, allowing for higher mechanical advan-
tage of the spinal erector muscles, as suggested by Tviet et al.
(1994) and McIntosh et al. (1993). The different geometry of
the female torso from the male torso (Marras et al., 2001), as
well as a presence of a greater number of type I fibers in lumbar
region (Mannion et al., 1997) could potentially influence spine
loading. Some limitations have to be considered for interpreting
the data of this study. We have found no data sets with which to
directly compare these results. The literature focuses on corre-
lations between BMI, body height and body weight with torso
endurance or grip strength. Another limitation arises from the
fact that results were obtained from Serbian children from one
elementary school aged 7 - 14. Personal factors (motivation, for
example) may have influenced performance on torso endurance
tests, which may complicate the interpretation of the results. In
an effort to protect against this, however, the children were
encouraged during all torso endurance testing.
Conclusion
Boys and girls aged 7 to 14 have different relationships be-
tween torso muscle endurance scores and anthropometric
measures. However anthropometric variables appear to have
little influence on torso endurance and appear to be influenced
by other factors that were not measured in this study. This
eventually may lead to gender specific prevention and ma-
nagement of LBP and exercise program development.
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