Pediatric Exercise Science, 1996, 8, 48-56
0 1996 Human Kinetics Publishers, Inc.
The Effects of Resistance and Martial Arts
Training in 6- to 8-Year-Old Boys
Bareket Falk and Guy Mor
The purpose of the present study was to determine the effect of a 12-week
training program on the motor performance of 6- to 8-year-old prepubertal
boys (n = 14). Each subject participated in a 40-min session twice a week,
which included three sets of upper body strength exercises (1 to 15 repetitions1
set), unregimented lower body strength exercises, coordination, balance, and
martial arts skills. The control group included 15 prepubertal boys in the
same age range. All subjects were pre- and posttested on 20-s sit-ups, seated
ball put, standing broad jump, sit-and-reach flexibility, 6 x 4-m shuttle run,
and a coordination task. The experimental group improved significantly (p
< .05) more than the control group in the sit-ups and in the long jump. Both
groups improved (p < .05) in the coordination task. No significant changes
were observed in body weight, seated ball put, flexibility, and shuttle run.
A twice-weekly training program seems to improve performance in selected
motor tasks in 6- to 8-year-old boys.
Resistance exercise training among adults is accepted as an effective method
to improve certain components of physical fitness. Recently, resistance training
has become popular among children and adolescents (12). Numerous studies
have demonstrated that a strength/resistance program can effectively increase
muscle strength among prepubertal children (3, 6, 16, 17, 18, 20, 22, 24). In
fact, de Oliveira and Gallagher (4) recently presented a meta-analysis of
21 studies that demonstrate that the greatest gain in strength due to training is
in the preadolescent child. Strength training can result in an improvement of
motor performance among adults (7). However, the results with prepubertal
children have been inconsistent (6, 22, 24). Most investigators contend that if
the program is well supervised and properly prescribed using youth strengthtraining guides, there is a relatively low risk of injury (8, 19, 24). In fact, Hamill
(8) recently concluded that weight training and weightlifting appear to be safer
than other sports among school-age children.
Most studies involving children have employed a training frequency of
3 sessions per week. The recent guidelines of the American College of Sports
Medicine (1) for adults suggest a training frequency of at least twice a week for
muscular fitness. Faigenbaum et al. (6) have recently demonstrated that a twicea-week strength training program can also effectively increase strength among
Medicine Sciences at t
Resistance and Martial Arts Training - 49
8- to 12-year-old boys and girls. The participants in this study trained and were
tested on child-size weight training equipment. However, Siege1 et al. (22) point
out that most schools and clubs do not have weight-training equipment that is
appropriate for children. Therefore, the conclusions of most resistance training
studies that employ weight-training machines are not easily applied in places
where the equipment cannot be modified for young children. However, resistance
training can also involve the body weight as resistance, as well as inexpensive
barbells or dumbbells. Due to the limited availability and the expense of youth
training equipment, it is desirable to explore the effects of inexpensive forms of
training.
Most studies that have described training-induced improvement in strength
among prepubertal children investigated children older than 8 years. Mersch and
Stoboy (14) cite two studies involving 7- to 9-year-old children who trained for
4 weeks (5, 15). Although no details are provided regarding the type of training,
strength increases were observed in the training group, although no significant
changes were observed in a group that practiced only the skill of weight lifting,
as cited in Mersch and Stoboy (14). To our knowledge, no study has investigated
the effect of resistance training in children younger than 7 years.
Thus, the purpose of this study was to investigate the effect of a 12-week,
twice-weekly training program on motor performance among 6- to 8-year-old
boys. The program emphasized strength and martial arts skills and utilized body
weight as the resistance in the strength exercises.
Methods
Subjects
Following an explanation of the training program, 32 boys, ages 6-8 years,
volunteered to participate in this study. Subjects were students in two local schools
(Grades 1-2) and were not involved in any organized martial arts programs within
the past year. In a previous year, 2 of the control subjects reported participating
in a general gymnastics program. Children underwent a medical examination at
the beginning of the school year, 3-4 months prior to the study. Both the children
and their parents were informed about the purpose and the nature of the study,
and gave their written consent to participate.
The experimental group consisted of 17 boys, age 6.4 0.4 years (range =
6-7 years), who enrolled in the after-school training program that emphasized
strength and martial arts. The control group consisted of 15 boys, age 7.1
0.7 years (range = 6-8 years), who studied at a nearby school, representing a
similar socioeconomic stratum. Some of the control subjects participated in
noncompetitive after-school activities other than the strengthlmartial arts training
program (1 in tennis, 1 in gymnastics, 2 in basketball, and 2 in judo).
All boys were prepubertal according to stages classified by Tanner (23),
as rated by their parents (based on Matsudo and Matsudo [13]). The Tanner
stages rely on secondary sex characteristics such as the extent of pubic hair
growth and the size and shape of the penis and gonads. The control group was
8 months older than the experimental group (p < .01). There were no significant
differences in pretraining body weight (23.3 k 2.6 and 24.5 f 6.0 kg for the
experimental and control groups, respectively), or height (120.3 It 5 and 121.3
+
+
50 - Falk and Mor
+ 4.8 cm for the experimental and control groups, respectively) between the two
groups. Stature was measured only at the beginning of the program.
Testing Procedures
Before and following the 12-week training program, a variety of tests were
administered that reflected muscle strength and endurance, motor performance,
and flexibility. Most children were familiar with the tested tasks. All children
had a chance to practice the tasks once and were acquainted with the tasks (except
the coordination task) before actual measurements were made. Subjects did not
practice the coordination task because, according to the grading system (described
below), a maximal score was awarded for success on the first try. Previous
practice would have interfered with this scoring system. For each task, the proper
technique was explained before and following a demonstration of the task. All
tests were performed at the same time of day.
Abdominal muscle endurance was evaluated by the number of sit-ups in
20 s. During the task, the knees were bent, and the feet were held on the floor.
Upper body explosive power was evaluated using a seated two-handed medicineball (1 kg) put. Subjects sat on a straight-back chair, feet on the floor, and put
the ball, using two hands, as far as they could. The best of three trials was
recorded. Lower body explosive power was evaluated using the standing long
jump. The best of three trials was recorded. Both the medicine-ball put and the
standing long jump are strength-related tests with a distinct strength component,
although they are not strength tests per se.
Lower back and hamstring flexibility was evaluated by the sit-and-reach
test (1 1). The best of three trials was recorded. Agility was evaluated using a 6
x 4 m shuttle run. From a standing position, subjects ran a distance of 4 m,
picked up one of three rubber rings, ran back, and placed it beyond the starting
line. This procedure was repeated three times (i.e., subjects picked up three rings).
The best of two trials (with at least 5 min of rest between trials) was recorded.
The reliability for these tests was examined in a separate sample of seventeen 7.3 0.75-year-old prepubertal boys. Test-retest correlation coefficients
were .91-.95, and there were no differences between the first and second tests.
The two tests were performed one week apart.
Arm coordination was evaluated using two tests. Test A consisted of simultaneous full arm circles in opposite directions. Test B consisted of a vertical
motion with both arms simultaneously: one arm in the sagittal plane and the
other arm in the frontal plane. When one arm was in the "up" position, the
other arm was in the "down" position. All subjects performed both tests, but
the order was reversed for half the subjects in each group. Half the subjects in
each group performed Test A at the start of the program and Test B at the end
of the program, and the other half of the subjects performed the tests in the
reverse order. Subjects received a score of 3 if they could perform the task on
the first try, a score of 2 if they could perform on the second try, a score of 1
if they could perform on the third try, and a score of zero if they could not
perform the task in the three tries. In view of this scoring system, subjects did
not practice the task prior to testing. For the same reason, subjects were not
retested on the same task. Tasks were assumed to be of equivalent difficulty.
liable test that
+
Resistance and Martial Arts Training - 51
could be applied to children of this age range. All subjects were evaluated by
the same investigator.
Training Program
The experimental group participated in the training program twice a week on
Mondays and Thursdays, for 12 weeks. Each session lasted 40 min. A 5-min
warm-up consisted of jogging, jumping, skipping, and various tasks of coordination and balance. Upper body and abdominal strength exercises were practiced
for 10 min. Upper body strength exercises included several variations of pushups with graded difficulty (e.g., push-ups off a ladder with feet on the floor and
hands on the ladder at graded heights, push-ups off a ladder with hands on the
floor and feet on the ladder at graded heights). The starting point for the pushups was straight arms (180") and the ending point was several cm from the floor
or until subjects could touch the floor with their forehead. Abdominal strength
exercises included several variations of sit-ups with graded difficulty (e.g., situps in the forward and diagonal direction, hands on the chest or behind the head).
The starting point for the sit-ups was both scapulae on the floor and the ending
point was touching the elbows to the knees. Subjects performed three sets of
upper body strength exercises and of abdominal strength exercises, with 2-3 min
rest between sets. The lowest number of repetitions in any exercise that could
initially be performed was one (one subject). Once subjects could perform 15
repetitions of a particular exercise, they performed the maximal number of repetitions in another variation of the same exercise with a greater resistance (e.g., in
push-ups, moved hands one stage lower on the ladder). No external resistance
was used in any of the strength exercises.
Lower body strength exercises were incorporated into the martial arts skills
and were unstructured. These included the different martial arts stances (front,
back, "horse"), various kicks (full, half, side), and leg raises (to the front, side,
and around). Flexibility exercises, such as arm circles, side stretches, wrist circles,
front split, as well as flexibility exercises for the lower back and hamstrings,
such as "sit and reach" with legs spread or in the hurdle position, were practiced
for 5 min. General and specific martial arts skills were practiced for 15 min. A
5-min game (e.g., variations of tag) concluded each session.
Statistical Analysis
A two-way (Group x Time) analysis of variance for repeated measures was used
to determine the effect of the training program on the various dependent variables.
Pair-wise post hoc analysis was performed using a t test with a Bonferroni
correction (9). The level of significance was determined at a < .05. Data are
presented as mean plus or minus standard deviation (M +_ SD).
Results
Attendance rate in the experimental group was 90%. The criterion for elimination
was three missed sessions during the 12-week period. None of the subjects were
eliminated by this criterion. Due to social or technical reasons (dislike of other
group members, inability to make practice hours), three subjects voluntarily
52 - Falk and Mor
dropped out of the program. Their characteristics and initial performance were
within one standard deviation of the group mean on all variables. All of the boys
in the control group completed the study.
Body weight did not change significantly in the experimental (23.3 f 2.6
and 22.9 2.5 kg before and after, respectively), or in the control group (24.5
6.0 and 24.5 6.1 kg before and after, respectively) during the training program.
Table 1 presents the changes in motor performance during the 12-week
training program. There were no differences between groups in pretraining measures of motor performance. A significant Group x Time interaction was found
in the number of sit-ups and the long-jump results, indicating that the training
program improved abdominal muscle endurance and standing long jump in the
experimental group. Although the scores in the seated ball put improved in both
groups, the improvement did not reach significance. Additionally, there was no
difference between groups.
Flexibility, as indicated by the sit-and-reach test, improved somewhat in
the experimental group, but decreased in the control group. The variability in
the flexibility test was quite high, and the above changes did not reach significance
(p = .07). Agility, as indicated by the 6 x 4 m shuttle run, did not change
significantly during the training program. The experimental group tended to be
more agile; however, the group main effect was not significant (p = .08). Finally,
arm coordination improved with time in both groups, with no significant differences between groups.
It should be noted that no injuries were sustained during the training
program. Injury was defined as an incident that required medical or paramedical
attention or that caused a participant to miss any part of the training.
+
+
*
Table 1 Changes in Motor Performance Following the 12-Week Training Program
Experimental group (n = 14)
Control group (n = 15)
Pretest Posttest Change % change Pretest Posttest Change % change
Sit-ups
9.1
(4.9)
Ball put (cm) 233
(28)
Long jump
101
(cm)
(13)
Sit & reach 0.78
(cm)
(3.90)
6x4m(s)
12.5
(1.0)
Coordination 1.36
(0.63)
Note. Standard deviations are in parentheses.
Significant Group x Time interaction. That is, significant effect of the training
Resistance and Martial Arts Training - 53
Discussion
This study demonstrates that a group-training program that emphasizes strength
and martial arts can effectively improve performance in tasks requiring lower
body muscle strength (long jump) and abdominal muscle endurance (sit-ups)
among 6- to 8-year-old boys. Motor performance requiring arm strength (seated
ball put), agility (shuttle run), flexibility (sit and reach), and coordination also
improved; however, the difference in improvement compared to the control group
did not reach statistical significance.
The improvement in some of the motor performance tasks found in this
study agrees with several previous resistance-training studies (22, 24), but not
all (6). Early improvements in strength are attributed mainly to neural adaptations,
such as enhanced motor unit recruitment and motor unit synchronization (20).
Thus, some of the improvement in motor performance observed in this and other
studies can be attributed to neural adaptations, as well as to a possible increase
in muscle strength. It should also be noted that some of the gain may be due to
a learning effect, especially in the early stages. No midtraining evaluation was
performed in this study. Therefore, it cannot be determined how much of the
gain in performance is due to a learning effect, neural adaptations, or increased
muscle strength.
Due to the specificity of training principle, it was expected that performance
would especially improve in those tasks in which subjects trained specifically
(i.e., sit-ups). 1ndeed; a marked improvement in the number of sit-ups performed
in 20 s was observed in the experimental group compared to the control group.
Additionally, upper body exercises included in the training program may partly
explain the improvement seen in the seated ball-put test. However, no specific
training was performed for the seated ball-put. Therefore, in line with the specificity of training principle, no difference was observed in the improvement in this
task between the two groups. On the other hand, it is noted that a significant
improvement was observed-in the standing long-jump in the experimental group
compared to the control group. This improvement was seen even though lower
body strength was incorporated only in an unregimented manner into the martial
arts skills, and specific long-jump, hopping, or jump training were not part of
the program. Indeed, many of the lower body strength exercises were isometric
(e.g., front stance, "horse" stance). Thus, the results of the present study only
partly support the specificity of training principle.
Faigenbaum et al. (6) trained 8- to 12-year-old boys and girls using childsized weight-training machines and found no improvement in motor performance
tasks (seated ball-put, vertical jump) that were not specifically trained. On the
other hand, Weltman et al. (24), who used hydraulic machines to train 6- to 11year-old boys (M f SD = 8.2 k 1.3 years), observed no improvement in the
standing long-jump, but found significant improvement in the vertical jump. In
the latter study, specific sit-up training was performed, but unfortunately no
pre-post results were provided for this task. Siege1 et al. (22), who trained
8.4 (fl.5)-year-old boys and 8.6 (k0.5)-year-old girls emphasizing upper body
resistance exercises, found training-induced improvements in hand grip strength
and in the number of chin-ups performed-both requiring upper-body strength.
However, no improvement was observed in the number of sit-ups performed in
1 min. Thus, in the latter two studies, in which 6- to 11-year-old children were
54 - Falk and Mor
trained, training-induced improvement was observed in some of the tasks for
which no specific training was performed.
In the present study, in which mostly younger children (6-8 years) were
trained, improvement was observed in a specifically trained, as well as in a
non-specifically trained task (sit-ups and long jump, respectively). Therefore, it
is possible that in younger children, even general training can lead to neural
adaptations that can be transferred to non-specifically trained tasks. Indeed,
subjects in this study (and their parents) reported better performance (and more
self-confidence) in sport and in other everyday activities. Nevertheless, as previously mentioned, a learning effect cannot be ruled out.
The apparent decrease in performance in the sit-ups and long jump in the
control subjects is perplexing. The investigators who tested the subjects did not
have access to the previous results, and thus, investigator bias is not likely.
Additionally, subjects appeared to be highly motivated. It is possible that the
warm-up they performed prior to testing was not sufficient. The beneficial effect
of warming-up on muscle power produced over 30 s has been previously demonstrated (lo), although the effects of warming-up on muscle power produced over
shorter periods such as in the present study, especially in young children, are
uncertain. Nevertheless, in view of the 1-cm decrease in the flexibility scores on
the sit-and-reach rest, where warming-up can indeed be beneficial, a suboptimal
warm-up may have contributed to and can partly explain the decrease in tests
reflecting abdominal and lower leg power. The apparent improvement in the
seated ball-put in the control group may be explained by the effect of growth
and a possible increase in muscle mass, although no change in body mass was
observed. Additionally, the involvement of some of the control subjects in activities that resemble those of the exercise group may also partly explain the improvement in the seated ball-put.
The difference in lower back and hamstring flexibility between the two
groups did not reach statistical significance, possibly due in part to the large
variability (SD = 3.90-6.78 cm) among the two groups. Additionally, it is unknown if the control group performed any stretching exercises during the period
of the study. Nevertheless, the fact that the experimental group did not get any
tighter is an important finding and supports previous studies that found maintenance or an improvement in flexibility as a result of resistance training among
children, when stretching exercises were incorporated into the training program
(6, 20, 21, 23).
Both groups demonstrated improvement in the coordination tasks. Although
the improvement among the experimental group appears more impressive compared to the control group (68.3% vs. 22.2%), the difference was not statistically
significant. The experimental group's initial scores were somewhat lower than
the control group, which might have contributed to their greater improvement
in coordination. It should be noted that many tasks and martial arts skills that
involve arm coordination were emphasized during the training session. However,
the specific tasks tested were not included in the training sessions. It is unclear
whether coordinated motor unit recruitment can be carried over from one task
to another. Additionally, coordination was evaluated on a four-point scale. This
low sensitivity may have contributed to the fact that the difference in the improvement in coordination did not reach statistical significance.
--
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Resistance and Martial Arts Training - 55
In summary, the present study demonstrates that 6- to 8-year-old boys who
participate in a twice-weekly training program that emphasizes strength exercises
and martial arts skills can improve in selected motor performance skills. This
improvement can be seen in specifically trained tasks, as well as in nonspecifically trained tasks. Because of the positive effects of resistance training
on strength and power (2), and because many of the sports in which children
participate have a substantial strength or power component, it appears reasonable
to recommend resistance training as part of training to improve sports performance
in young boys. However, the effects of resistance training on sports performance
needs to be substantiated in future studies.
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Acknowledgments
We would like to thank the children and their parents and teachers for their participation and cooperation in this study.