Effects of a Circuit Training Program on Muscular and Cardiovascular Endurance and their Maintenance in Schoolchildren

Abstract

The purpose of this study was to evaluate the effects of a circuit training program along with a maintenance program on muscular and cardiovascular endurance in children in a physical education setting. Seventy two children 10-12 years old from four different classes were randomly grouped into either an experimental group (n = 35) or a control group (n = 37) (two classes for each group). After an eight-week development program carried out twice a week and a four-week detraining period, the experimental group performed a four-week maintenance program once a week. The program included one circuit of eight stations of 15/45 to 35/25 seconds of work/rest performed twice. Abdominal muscular endurance (sit-ups in 30 seconds test), upper-limbs muscular endurance (bent arm hang test), and cardiovascular endurance (20-m endurance shuttle run test) were measured at the beginning and at the end of the development program, and at the end of the maintenance program. After the development program, muscular and cardiovascular endurance increased significantly in the experimental group (p < 0.05). The gains obtained remained after the maintenance program. The respective values did not change in the control group (p > 0.05). The results showed that the circuit training program was effective to increase and maintain both muscular and cardiovascular endurance among schoolchildren. This could help physical education teachers design programs that permit students to maintain fit muscular and cardiovascular endurance levels.

Full text

Journal of Human Kinetics volume 37/2013, 153-160 DOI:10.2478/hukin-2013-0036 153
Section III – Sports Training
1 - Department of Physical Education and Sport, University of Granada, Spain.
2 - Department of Physical Education and Sport, University of Granada, Spain.
3 - Department of Physical Education and Sport, University of Granada, Spain.
.
Authors submitted their contribution of the article to the editorial board.
Accepted for printing in Journal of Human Kinetics vol. 37/2013 on June 2013.
Effects of a Circuit Training Program on Muscular and
Cardiovascular Endurance and their Maintenance
in Schoolchildren
by
Daniel Mayorga-Vega1, Jesús Viciana2, Armando Cocca3
The purpose of this study was to evaluate the effects of a circuit training program along with a maintenance
program on muscular and cardiovascular endurance in children in a physical education setting. Seventy two children
10-12 years old from four different classes were randomly grouped into either an experimental group (n = 35) or a
control group (n = 37) (two classes for each group). After an eight-week development program carried out twice a week
and a four-week detraining period, the experimental group performed a four-week maintenance program once a week.
The program included one circuit of eight stations of 15/45 to 35/25 seconds of work/rest performed twice. Abdominal
muscular endurance (sit-ups in 30 seconds test), upper-limbs muscular endurance (bent arm hang test), and
cardiovascular endurance (20-m endurance shuttle run test) were measured at the beginning and at the end of the
development program, and at the end of the maintenance program. After the development program, muscular and
cardiovascular endurance increased significantly in the experimental group (p < 0.05). The gains obtained remained
after the maintenance program. The respective values did not change in the control group (p > 0.05). The results showed
that the circuit training program was effective to increase and maintain both muscular and cardiovascular endurance
among schoolchildren. This could help physical education teachers design programs that permit students to maintain fit
muscular and cardiovascular endurance levels.
Key words: physical fitness program, health-related physical fitness, muscular strength, cardiorespiratory fitness,
school-based program, physical education.
Introduction
Physical fitness is nowadays considered
as one of the most important health markers in
childhood (Ortega et al., 2008). Consequently, in
the last decades several countries have been
promoting physical fitness improvement among
young people in different ways (Department of
Health and Human Services, 1990). In many
circumstances, schools have been considered the
best setting in which children with low fitness
levels can be identified and a healthy lifestyle can
be promoted (Ortega et al., 2008). Therefore, one
of the main Spanish government strategies was
focused on modifying school legislations in order
to give health a more important role in the
Educational System (Ministerio de Educación y
Ciencia, 2006). Schools are mainly attempting to
increase the pupils’ health level by using
measures such as the improvement of their
physical fitness through physical education (PE)
(Ministerio de Educación y Ciencia, 2006). It has
been concluded that the health promotion policies
and physical activity programs should be

154 Effects of a circuit training program on muscular and cardiovascular endurance
Journal of Human Kinetics volume 37/2013 http://www.johk.pl
designed to improve physical fitness, where
strength and cardiovascular endurance are the
most important health-related physical fitness
components (Ortega et al., 2008).
It is known that planning long-term fitness
programs is the best way to improve these
components (Donnelly et al., 2009). Nonetheless,
in the PE setting these programs cannot last the
whole course or a large part of it since many
curricular contents must be developed in a school
year (Ministerio de Educación y Ciencia, 2006).
Consequently, in the PE setting we need to find
short-term programs that could be also effective
for the increment of fitness. One of the
methodologies that meet these criteria could be
the circuit training (Dorgo et al., 2009; Granacher
et al., 2011a; Granacher et al., 2011b). The circuit
training effectively reduces the time devoted to
training while allowing an adequate training
volume to be achieved (Alcaraz Ramón et al.,
2008). Moreover, it permits a greater motor
engagement time (Lozano et al., 2009), which is a
very important requirement for the success of a
PE program. In addition, this methodology has
multilevel effects on fitness, especially in
beginners (Alcaraz Ramón et al., 2008; Dorgo et
al., 2009; Wong et al., 2008).
Other problem related to physical fitness is
its expected decrease after a period of detraining.
Several authors confirm that after 8 to 12 weeks of
detraining children lose a significant part of the
physical fitness gains obtained (Da Fontoura et al.,
2004; Faigenbaum et al., 1996; Ingle et al., 2006;
Isaacs et al., 1994; Tsolakis et al., 2004). A possible
solution for this problem could be the periodical
introduction of short maintaining programs
throughout the academic course. During these
intervals, PE teachers would be able to develop
other curricular contents and at the same time
they could be improving the previous physical
fitness gains. These programs could permit to
keep the physical fitness level achieved without
interfering in the normal course of the PE
planning. Unfortunately, to our knowledge there
are no studies addressing the effect of a physical
fitness maintenance program in a PE setting.
Consequently, the purpose of this study was to
evaluate the effects of a circuit training program
and its maintenance on muscular and
cardiovascular endurance levels in children in a
PE setting.
Material and Methods
Participants
Seventy two apparently healthy Spanish
children (boys, n = 40; girls, n = 32) 10-12 years old
(age 11.10 ± 0.38 years; body mass 43.29 ± 10.45
kg; body height 1.43 ± 0.07 m; body mass index
19.39 ± 3.90 kg/m2) from four different PE classes
of a public primary school participated in this
study. For practical reasons and the nature of the
present study (the intervention was focused on
natural groups in a school context) a cluster
randomized controlled trial was used. General
profiles were assigned randomly to form one of
the study groups (two classes for each group):
experimental group (EG, n = 35), or control group
(CG, n = 37). EG and CG consisted of two gender
balanced groups (47% and 43% of girls,
respectively).
All participants were urged to maintain
their normal levels of physical activity outside of
the supervised setting. Twenty-seven children in
the EG (77%) and 27 children in the CG (73%)
regularly participated (at least twice per week) in
organized sports programs. Children and their
legal guardians were fully informed about all the
features of the study and were required to sign an
informed consent form. The Ethical Committee of
the University of Granada approved the study
protocol.
Measures
The participants were evaluated using the
muscular and cardiovascular endurance tests
included in the EUROFIT battery (Council of
Europe Committee for the Development of Sport,
1988), validated and standardized by the Council
of Europe. The test sessions were carried out
during the PE classes at the beginning and at the
end of the development circuit training program
(pretest and posttest), in order to see the changes
that were produced. Subsequently, after a period
of detraining and the application of the
maintenance circuit training program, the
participants were evaluated again (retest).
The tests were administered in an indoor
sports center court with a non-slip floor, under
the same environmental conditions, on the same
day and at the same time for each student. A blind
evaluation was carried out by two researchers
following the standard protocol for each test. Each
researcher assessed physical fitness with the same
tests using identical equipment. Prior to the

by Mayorga-Vega D. et al. 155
© Editorial Committee of Journal of Human Kinetics
evaluation, the participants completed a
standardized warm-up consisting of five minutes
of running from low to moderate intensity. The
order and a brief description of the test protocol
are as follows:
Sit-ups in 30 seconds test (SUP). This test
was used to measure abdominal muscular
endurance. The participants laid supine on the
mat with their knees flexed at an angle of 90
degrees and their feet flat on the floor, stabilized
by a researcher. The participant´s fingers were to
be interlocked behind their head. On the
command 'Go', the participants´ elbows had to
contact the knees and return to the starting
position as many times as possible in 30 s. Each
participant was allowed to perform the test once.
The total number of sit-ups performed in 30 s was
recorded.
Bent arm hang test (BAH). This test was
used to measure upper-limbs muscular
endurance. The participants had to maintain a
bent arm position while hanging from a bar with
hands in a pronated grip and at shoulder width.
The participants’ chin had to be above the bar and
held in this position as long as possible. The test
ended when the participants’ eyes went below the
bar. Each participant was allowed to perform the
test once. The total time in seconds was retained.
20-m endurance shuttle run test (ESR). This
test was used to assess cardiovascular endurance.
All students ran between two parallel lines put 20
m apart, in the rhythm marked by a recorded
beep. A researcher ran alongside the children to
help them keep the desired pace. The starting
speed was 8.5 km/h; and it increased 0.5 km/h
every minute. The test ended when the child
stopped running due to fatigue or failed to reach
the line before the next signal for two consecutive
times. Each participant was allowed to perform
the test once. The last completed lap (timed in
seconds) was recorded.
Procedures
A circuit training program was applied to
the EG during the PE classes under the
supervision of a researcher. Firstly, the EG
participants performed a development circuit
training program twice a week on nonconsecutive
days for eight weeks. They completed a total of 14
training sessions, since two classes coincided with
festivals and could not be used. Then, after a
period of detraining (four weeks) coinciding with
Christmas holiday, the EG participants completed
a maintenance circuit training program one
session per week during four weeks. During the
period of maintenance program, each session of
maintenance was alternated with a normal class
of PE according to the course planning designed
by the teacher.
Each session lasted 50 minutes and
consisted of a five-minute warm up during which
children had to play a racing game, 40-minute
circuit training, and two series of a 15-30 second
cool-down of static stretching, primarily for the
hamstrings and lumbar region (Table 1). All
exercises were fully explained and previously
demonstrated by the researcher, and children
were asked to try them during a few minutes
before starting the first session of the intervention.
According to previous studies carried out in the
PE setting (Dorgo et al., 2009; Granacher et al.,
2011a; Granacher et al., 2011b), the intervention
was organized in a circuit program. One circuit of
eight stations was developed, and then repeated
twice in each session. Each station consisted of an
exercise lasting from 15 to 35 seconds (extended
progressively from the first session to the last),
and the rest time between them was of 45-25
seconds (gradually reduced during the program).
The increase of the work time and the decrease of
the rest time along the intervention were based on
the training load progression principle.
During the work time the students should
complete as many repetitions as possible in a
controlled manner. As other studies show, the last
repetition of each set represents the momentary
muscular fatigue (Faigenbaum et al., 2002;
Faigenbaum et al., 2005). In order to achieve it, the
children were offered three levels of difficulty in
each station (Table 1), so that the intensity of
exercise was best suited to each student. All
participants began at the first level of difficulty,
and when a student could perform more than one
repetition per second, he/she was allowed to
advance to the next level. With the aim of
developing cardiovascular endurance, at the end
of each circuit all students simultaneously
executed an additional stage consisting of a five-
minute endurance racing game. The researcher
gave positive feedback to motivate participants in
achieving it (Badami et al., 2011).

156 Effects of a circuit training program on muscular and cardiovascular endurance
Journal of Human Kinetics volume 37/2013 http://www.johk.pl
Table 1
Circuit training session
Phase (time)/ Exercises Intensive progression (level 1/ 2/ 3)a Material
Warm-up (5 min)
Racing games
Main part (40 min)
Circuit training stations
a. Throwing from chest 1kg/ 1.5kg/ 2kg MB
b. Rowing Low/ medium/ high resistance Elastic band
c. Going up-down Body weight/ +1kg/ +2kg Swedish bench, MB
d. Triceps extension Low/ medium/ high resistance Elastic band
e. Biceps curl Low/ medium/ high resistance Elastic band
f. Skipping rope Micropause/ with/ without rebound Rope
g. Crunches Arms stretched forward/ chest/ backward Mat
h. Bridging Body weight/ +1kg/ +2kg Mat, MB
Additional station
i. Racing games
Cold-down (5 min)
Static stretching
MB = Medicine ball; a All participants began at the first level of difficulty.
When a student could perform more than one repetition
per second was allowed to advance to next level.
During the development and maintenance
programs the EG executed the circuit
training,while the CG participated in traditional
games, basketball and volleyball activities.
However, during the maintenance program the
EG alternated one session of physical fitness
maintenance with other activities such as
basketball and volleyball. No participant was
allowed to carry out any physical fitness training
outside of the supervised setting.
Analysis
Descriptive statistics (means and standard
deviations) for age, body height, body mass index,
and muscular and cardiovascular endurance
results were calculated. The Student´s t test for
independent samples was used to study the
differences of the general characteristics between
groups. As the BAH variable did not follow a
normal distribution, the data was transformed
using a logarithm (Bland and Altman, 1996).
Because a higher precision was required for ESR
test performance, the final time spent in the test
was expressed in seconds, instead of stages or half
stages, and it was used for statistical analysis
(Ruiz et al., 2011). A two-way analysis of variance
(ANOVA) was applied over the dependent
variables (SUP, BAH, ESR) using groups (EG, CG)
and time factors (pretest, posttest, retest). For the
post-hoc analyses, α values were corrected using
the Bonferroni adjustment. The Hedges´ g effect
size was used to determine the magnitude of
treatment effects (Hedges, 2007). The test-retest
reliability for muscular and cardiovascular
endurance tests was estimated using the intraclass
correlation coefficient from two-way ANOVA
(ICC3,k) (Shrout and Fleiss, 1979). Furthermore,
95% interval of confidence was calculated. All
statistical analyses were performed using the
SPSS version 15.0 for Windows (SPSS® Inc.,
Chicago, IL). The statistical significance level was
set at p < 0.05.
Results
All students completed the development
training program and 67 the maintenance training
program according to previously established
norms (no more than two classes were missed in
the development training program, and none
were missed in the maintenance training). Retest

by Mayorga-Vega D. et al. 157
© Editorial Committee of Journal of Human Kinetics
data of four participants from the EG and one
from the CG were excluded due to missed classes
in the maintenance training program and absence
in the retest session test, respectively. The EG
participants finally considered for analysis
obtained an average attendance of 94% and 100%
in the development and maintenance training
program, respectively. The Student´s t for
independent samples results did not show
statistically significant differences in the general
characteristics between EG and CG.
Sit-ups in 30 seconds test. The EG had
significantly greater gains in SUP compared to the
CG [F(2, 63) = 4.636; p = 0.011; η2p = 0.069; P =
0.773] (Table 2). The ANOVA with Bonferroni
adjustment showed that the EG increased
significantly from pretest to posttest (p = 0.026)
and from pretest to retest (p = 0.004).
Nevertheless, the difference from the posttest to
the retest for the EG was not statistically
significant (p = 0.105). No significant differences
were found for the CG (p = 1.000). The test-retest
reliability for the SUP was 0.86 (0.73-0.93).
Bent arm hang test. Significantly greater
gains were found for the EG compared to CG [F(2,
63) = 5.994; p = 0.003; η2p = 0.087; P = 0.875]. The
EG participants significantly increased FAH from
pretest to posttest (p = 0.009) and from pretest to
retest (p < 0.001). For the EG, the improvement
from the posttest to the retest approached
statistical significance (p = 0.065). No differences
were found for the CG (p ≥ 0.324). The test-retest
reliability for the BAH was 0.95 (0.90-0.97).
20-m endurance shuttle run test. The EG had
significantly greater gains in ESR compared to the
CG [F(2, 64) = 5.230; p = 0.007; η2p = 0.076; P =
0.824]. The ANOVA with Bonferroni adjustment
showed that the EG increased significantly from
pretest to posttest (p = 0.015) though
improvement from the pretest to the retest
approached statistical significance (p = 0.088). No
significant differences were found from posttest to
retest for the EG (p = 0.210). No differences were
found for CG (p ≥ 0.975). The test-retest reliability
for the ESR was 0.90 (0.81-0.95).
Discussion
The results of the present study show that it
is possible to develop both muscular and
cardiovascular endurance by means of an eight-
week circuit training program in the PE setting.
Previous studies in which children performed an
extra-curricular circuit training program
confirmed a significant improvement on both
muscular and cardiorespiratory fitness (Annesi et
al., 2005; Ignico and Mahon, 1995; Wong et al.,
2008).
Previous studies in which children
performed an extra-curricular circuit training
program confirmed a significant improvement on
both muscular and cardiorespiratory fitness
(Annesi et al., 2005; Ignico and Mahon, 1995;
Wong et al., 2008). Nevertheless, the design and
the procedure of the present study depended on
many aspects related to the school context as
previously discussed in this manuscript. Likewise,
due to the lack of special machines in a PE setting,
in the present study body weight, elastic band
and ball exercises (Annesi et al., 2005;
Faigenbaum and Mediate, 2008; Flanagan et al.,
2002) were used instead of specific strength
equipment (Granacher et al., 2011a; Granacher et
al., 2011b).
One of the main objectives of the PE
teachers at these educational levels is to make the
pupils active as long as possible during the
classes. With the circuits method the pupils can
easily reach the minimum motor engagement
time (Lozano et al., 2009) at the same time they
execute many types of exercises. This is the best
way to make the most of the time at a PE teacher’s
disposal, especially when classes are few and
short-lasting and there are many contents to
develop (Ministerio de Educación y Ciencia,
2006). Thus, the present results indicate that the
design proposed in this research could be
effective for PE classes. In this line, Dorgo et al.
(2009) carried out a circuit training program with
adolescents in the PE setting. These authors found
a statistically significant improvement for both
muscular strength and cardiovascular endurance
when the circuit training was complemented with
endurance training.
One of the most important outcomes of this
study was that a maintenance program carried
out once a week in four weeks could be effective
to maintain the gains previously obtained. As
explained before, the majority of studies coincide
in eight weeks setting as the period of inactivity
determining the complete loss of previous
physical fitness gains (Faigenbaum et al., 1996;
Isaacs et al., 1994; Tsolakis et al., 2004).

158 Effects of a circuit training program on muscular and cardiovascular endurance
Journal of Human Kinetics volume 37/2013 http://www.johk.pl
Table 2
Muscular and cardiovascular endurance performance
for the development and maintenance circuit training program
Group Pretest (1)
(M ± SD)
Posttest (2)
(M ± SD)
Retest (2)
(M ± SD) p Effect size
1-2 2-3 1-3
SUP (nº)
Experimental
Control group
20.37 ± 4.21
17.95 ± 4.94
22.09 ± 3.70*
17.64 ± 5.89
23.10 ± 3.88††
17.57 ± 5.76 <0.05 0.44 0.22 0.68
BAHa (s)
Experimental
Control group
11.63 ± 9.93
16.87 ± 18.84
14.65 ± 12.75**
14.13 ± 14.09
20.80 ± 19.07†††
16.11 ± 15.95 <0.01 0.38 0.31 0.65
ESR (s)
Experimental
Control group
160.71 ± 94.33
191.78 ± 96.66
198.71 ± 98.43*
184.06 ± 96.12
186.00 ± 84.76
181.78 ± 100.22 <0.01 0.48 -0.11 0.37
M = Mean; SD = Standard deviation; SUP = Sit-ups in 30 seconds test;
BAH = Bent arm hang test; ESR = 20-m endurance shuttle run test; BAHa = for statistical
analysis the raw data were transformed by the logarithm; p = significance level from two-way
analysis of variance; Effect size = Hedges´g effect size.
Post-hoc analyses with Bonferroni adjustment:
Change statistically significant from pretest to posttest (*p < 0.05, **p < 0.01);
Change statistically significant from pretest to retest (††p < 0.01, †††p < 0.001)
In the present study the sum of the periods
of detraining and maintenance was eight weeks,
thus an unsatisfactory design of the maintenance
program should have matched a decrease (or the
complete dissipation) of the physical fitness
profits. Nevertheless, results were positive since
the muscular and cardiovascular endurance was
maintained after these weeks.
In line with the present study, DeRenne et
al. (1996) found out that a maintenance program
carried out once a week in pubescent basketball
players was efficient to retain strength. However,
Blimkie et al. (1989) found that a maintenance
program carried out once a week in pre-pubescent
children was not efficient to retain strength.
Unfortunately, previous studies that examined the
maintenance of cardiovascular endurance in
youth were not found. In addition, the previous
studies were carried out in an extra-curricular
period and not in a PE setting. Furthermore, the
researchers applied the maintenance program just
after the training program, that is, without a
period of inactivity between development and
maintenance. In the present study, a maintenance
program was applied after a period of detraining
because it is the most common situation in normal
PE planning (due to the typical alternation of
holidays, academic periods and the need to teach
other curricular contents in the PE classes).
Consequently, the design of the present study
seems to be suitable for the school environment as
it respects all the features and norms established
in it. Moreover, it should be effective for
increasing the strength and cardiovascular
endurance values and then maintaining them
during larger periods.
In conclusion, the present study suggests
that it is possible to develop and maintain
muscular and cardiovascular endurance through
a short-term program in the PE setting.
Maintenance programs appear to be necessary in
the school context to make the physical fitness
training effective and feasible within a school
plan, permitting at the same time the regular
development of other curricular contents. Their
utilization could permit the PE teacher to design
programs that guarantee the maintenance of
previous muscular and cardiovascular endurance
gains in a few sessions. Even though more
research is needed to confirm these results, the
maintenance program could become a principal
element to normal PE planning in the future. A

by Mayorga-Vega D. et al. 159
© Editorial Committee of Journal of Human Kinetics
limitation of the present study was the fact that
the intervention program did not include many
playful tasks. At these ages in PE classes it is
important to develop contents mainly through
ludic activities. Future interventions should focus
on physical fitness programs based on stations
with games, as well as the effect of the
combination of different frequencies and
durations of maintenance training.
Acknowledgements
We thank Anna Szczesniak for the English revision. Daniel Mayorga-Vega is supported by a
research grant from the Spanish Ministry of Education (AP2010-5905).
References
Alcaraz Ramón PE, Sánchez-Lorente J, Blazevich AJ. Physical performance and cardiovascular responses to
an acute bout of heavy resistance circuit training versus traditional strength training. J Strength Cond
Res, 2008; 22: 667-671
Annesi J, Westcott W, Faigenbaum A, Unruh J. Effects of a 12 week physical activity protocol delivered by
YMCA after-school counsellors (Youth Fit for Life) on fitness and self-efficacy changes in 5-12 year old
boys and girls. Research Q Exercise Sport, 2005; 76: 468-476
Badami R, VaezMousavi M, Wulf G, Namazizadeh M. Feedback after good versus poor trials affects intrinsic
motivation. Research Q Exercise Sport, 2011; 82: 360-364
Bland JM, Altman D. Transforming data. Brit Med J, 1996; 312: 770
Blimkie CJ, Martin J, Ramsay J, Sale D, MacDougall D. The effects of detraining and maintenance weight
training on strength development in prepubertal boys. Can J Appl Sport Sci, 1989; 14: S102
Council of Europe Committee for the Development of Sport. Eurofit: Handbook for the EUROFIT tests of
physical fitness. Italy: Edigraf editorial grafica; 1988
Da Fontoura AS, Schneider P, Meyer F. Effect of the muscular strength detraining in prepubertal boys. Rev
Bras Med Esporte, 2004; 10: 285-288
Department of Health and Human Services. Healthy people 2000: National health promotion and disease
prevention objectives. Washington, DC: DHHS Publ No (PHS), 91-50212; 1990
DeRenne C, Hetzler RK, Buxton BP, Ho KW. Effects of training frequency on strength maintenance in
pubescent baseball players. J Strength Cond Res, 1996; 10: 8-14
Donnelly J, Greene J, Gibson C, Smith B, Washburn R, Sullivan D, DuBose K, Mayo MS, Schmelzle KH, Ryan
JJ, Jacobsen DJ, Williams SL. Physical activity across the curriculum (PAAC): A randomized controlled
trial to promote physical activity and diminish overweight and obesity in elementary school children.
Prev Med, 2009; 49: 336-341
Dorgo S, King GA, Candelaria NG, Bader JO, Brickey GD, Adams CE. Effects of manual resistance training
on fitness in adolescents. J Strength Cond Res, 2009; 23: 2287-2294
Faigenbaum AD, Mediate P. Medicine ball training for kids. Health Fit J, 2008; 12: 7-12
Faigenbaum AD, Milliken LA, LaRosa-Loud R, Burak BT, Doherty CL, Westcott WL. Comparison of 1 and 2
days per week of strength training in children. Research Q Exercise Sport, 2002; 73: 416-424
Faigenbaum AD, Milliken LA, Moulton L, Westcott WL. Early muscular fitness adaptations in children in
response to two different resistance training regimens. Pediatr Exerc Sci, 2005; 17: 237-248
Faigenbaum AD, Westcott WL, Micheli LJ, Outerbridge AR, Long CJ, LaRosa-Loud R, Zaichkowsky LD. The
effects of strength training and detraining on children. J Strength Cond Res, 1996; 10: 109-114

160 Effects of a circuit training program on muscular and cardiovascular endurance
Journal of Human Kinetics volume 37/2013 http://www.johk.pl
Flanagan SP, Laubach LL, De Marco GM, Alvarez C, Borchers S, Dressman E, Gorka C, Lauer M, Mckelvy A,
Metzler M, Poeppelman J, Redmond C, Riggenbach M, Tichar S, Wallis K, Weseli D. Effects of two
different strength training modes on motor performance in children. Research Q Exercise Sport, 2002;
73: 340-344
Granacher U, Goesele A, Roggo K, Wischer T, Fischer S, Zuerny C, Gollhofer A, Kriemler S. Effects and
mechanisms of strength training in children. Int J Sports Med, 2011a; 32: 357-364
Granacher U, Muehlbauer T, Doerflinger B, Strohmeier R, Gollhofer A. Promoting strength and balance in
adolescents during physical education: Effects of a short-term resistance training. J Strength Cond Res,
2011b; 25: 940-949
Hedges LV. Effect sizes in cluster-randomized designs. J Educ Behav Stat, 2007; 32: 341-370
Ignico AA, Mahon AD. The effects of a physical fitness program on low-fit children. Research Q Exercise
Sport, 1995; 66: 85-90
Ingle L, Sleap M, Tolfrey K. The effect of a complex training and detraining programme on selected strength
and power variables in early pubertal boys. J Sport Sci, 2006; 24: 987-997
Isaacs L, Pohlman R, Craig B. Effects of resistance training on strength development in prepubescent
females. Med Sci Sport Exer, 1994; 26: S210
Lozano L, Viciana J, Martínez JC, Cocca A, Jiménez R. Influence of classroom environment and motor
engagement time. Rev Mex Psicol, 2009; 26: 675-676
Ministerio de Educación y Ciencia. Royal decree 1513/2006, the 7th December, laying down the Curriculum
for Primary Education. Madrid, Spain: Government Gazette, 43053-43102; 2006
Ortega FB, Ruiz JR, Castillo MJ, Sjöström M. Physical fitness in childhood and adolescence: A powerful
marker of health. Int J Obesity, 2008; 32: 1-11
Ruiz JR, España Romero V, Castro Piñero J, Artero EG, Ortega FB, Cuenca García M, Jiménez Pavón D,
Chillón P, Girela Rejón MJ, Mora J, Gutiérrez A, Suni J, Sjöstrom M, Castillo MJ. APHA-Fitness
battery: Field test for assessing health-related fitness among children and adolescents. Appendix. Nutr
Hosp, 2011; 26: 1210-1214
Shrout PE, Fleiss JL. Intraclass correlations: Uses in assessing rater reliability. Psychol Bull, 1979; 86; 420-428
Tsolakis CK, Vagenas GK, Dessypris AG. Strength adaptations and hormonal responses to resistance
training and detraining in preadolescent males. J Strength Cond Res, 2004; 18: 625-629
Wong PCH, Chia MYH, Tsou IYY, Wansaicheong GKL, Tan B, Wang JCK, Tan J, Kim C, Boh G, Lim D.
Effects of a 12-week exercise training programme on aerobic fitness, body composition, blood lipids
and C-reactive protein in adolescents with obesity. Ann Acad Med Singapore, 2008; 37: 286-293
Corresponding author:
Daniel Mayorga-Vega
Department of Physical Education and Sport, University of Granada
Alfacar street, 18011, Granada (Spain)
Phone: 0034-958-24-6641
Fax r: 0034-958-24-43-69
E-mail: dmayorgavega@gmail.com