Journal of Strength and Conditioning Research, 2006, 20(2), 441–445
q2006 National Strength & Conditioning Association
Human Performance and Coaching Laboratory, Department of Physical Education and Sport Sciences, Aristotle
University of Thessaloniki, Thessaloniki, Greece.
.Kotzamanidis, C. Effect of plyometric training on
running performance and vertical jumping in prepubertal boys.
J. Strength Cond. Res. 20(2):441–445. 2006.—The purpose of this
study was to investigate the effect of plyometric training on run-
ning velocity (RV) and squat jump (SJ) in prepubescent boys.
Fifteen boys (11.1 60.5 years) followed a 10-week plyometric
program (JUMP group). Another group of 15 boys (10.9 60.7
years) followed only the physical education program in primary
school and was used as the control group (CONT group). Run-
ning distances (0–10 m, 10–20 m, 20–30 m, and 0–30 m), were
selected as testing variables to evaluate the training program.
The total number of jumps was initially 60 per session, which
was gradually increased over a period of 10 weeks to 100 per
session. Results revealed signiﬁcant differences between CONT
and JUMP groups in RV and SJ. In JUMP group the velocity
for the running distances 0–30, 10–20, and 20–30 m increased
(p,0.05), but not for the distance 0–10 m (p.0.05). Addition-
ally, the SJ performance of the JUMP group increased signiﬁ-
cantly, as well (p,0.05). There was no change in either RV or
SJ for the CONT group. These results indicate that plyometric
exercises can improve SJ and RV in prepubertal boys. More spe-
ciﬁcally, this program selectively inﬂuenced the maximum ve-
locity phase, but not the acceleration phase.
. running velocity, squat jump, plyometric program
It has been reported that, when myotendinous
tissue is stretched, energy is stored and then
released during muscle shortening (1, 5). This
type of exercise (plyometric or jumping) causes
higher muscle tension compared to convention-
al resistance training (1). For this reason, plyometric
(jumping) exercises are widely recommended for power
enhancement in jumping and running velocity (RV) (32).
Relevant studies with jumping training reported that
plyometric training increased vertical jumping perfor-
mance both for adult (2, 12, 33, 35) and pubertal popu-
lations (10, 21). However, to our knowledge there are no
studies that have examined the inﬂuence of plyometric
training on squat jump (SJ) in a preadolescent popula-
In regard to sprint training, a variety of methods have
been used to improve RV, such as speed training, sprint-
ing against resistances, combined resistance and speed
training, and plyometric training (8, 9, 20, 27). However,
the existing information concerning the effectiveness of
plyometric training on RV in adults is conﬂicting. Some
studies have found that plyometric training had a signif-
icant effect on RV (10), whereas others have reported no
signiﬁcant improvements (13). Additionally, positive re-
sults were obtained for RV when resistance training was
combined with plyometric training on consecutive days
Although a number of speed training studies have
dealt with adults, there is limited information concerning
the effect of these methods on RV performance in the de-
velopmental ages. Mero (22) mentioned that a general
type of training positively affected prepubertal and pu-
bertal boys’ RV. More speciﬁc studies reported that
plyometric (10) and sprint (18) training positively affected
the RV of pubertal and prepubertal boys, respectively.
It seems that there is a lack of information concerning
the inﬂuence of plyometric training on prepubertal pop-
ulation power performance. It is well known that there
are distinctive differences between prepubertal, pubertal,
and adult performance in strength output, muscle mass,
muscle ﬁber distribution, neuromuscular activity (30),
and muscle tendon complex compliance (19). Despite the
mentioned differences between adults and preadoles-
cents, certain studies (11, 20) reported that the prepu-
bertal population demonstrated a high adaptability to re-
sistance training, similar to adults. From this point of
view, it would be interesting to examine preadolescents’
adaptability to plyometric training.
Thus, the main purpose of this study was to investi-
gate the inﬂuence of plyometric training on running per-
formance and jumping ability in a preadolescent popula-
tion. Taking into consideration that applied training pro-
grams in adult (14) and prepubertal populations (18) had
a selective effect on the different running phases, a sec-
ondary purpose of this study was to examine to what ex-
tent the plyometric training would affect selectively the
Experimental Approach to the Problem
This study was designed to prove whether plyometric
training can be applied in a prepubertal population and
to what extent it affects RV and jumping performance.
For this reason, 2 groups of prepubertal boys followed 2
different training programs, 1 consisting of plyometric ex-
ercises and the other comprising the physical education
program. The effectiveness of the applied training pro-
gram was evaluated with pre- and posttesting of RV and
vertical jump. In the pretraining testing period, partici-
pants initially visited the laboratory to be familiarized
with and to practice all testing procedures. They per-
formed all the selected tests during a second visit.
1. Chronological and anthropometrical characteristics of experimental (JUMP) and control (CONT) groups.
Group Mean age (y)
mass 6SD (kg)
2. Total sum of jumps per training session.
Number 60 60 70 80 70 80 80 90 100 100
Thirty healthy, nonathletic boys volunteered to partici-
pate in this study. Boys were divided into an experimen-
tal (JUMP) group (n515) and a control (CONT) group
(n515; Table 1). Children and their parents were in-
formed in detail about the experimental procedure. Par-
ents were asked to complete a written informed consent
for the participation of their children. All children were
examined by a physician and they were found to be at the
ﬁrst stage of maturation according to Tanner’s criteria
(31). No history of chronic diseases and injuries of the
lower limbs in any of the participants was reported before
training. Taking into consideration the strain caused by
plyometric exercises on muscle-tendon tissue, partici-
pants also were under constant medical monitoring in
case of injury and discomfort. The study was conducted
following the principles of the Ethics Committee of Aris-
totle University of Thessaloniki.
Testing and Procedure
All participants performed a standardized warm-up prior
to testing. They jogged for l0 minutes and then performed
a few submaximal runs and jumps. No stretching exer-
cises were included in the warm-up.
The testing procedure was performed in 2 phases. In
the ﬁrst phase participants visited the testing area in or-
der to familiarize themselves with the procedure and to
perform the tests. In the second phase of the experiment,
which took place 5 days later, they visited the same place
and retested again.
Sprint Testing. A 30-m distance was selected to eval-
uate running performance. The intermediate phases 0–
10, 10–20, and 20–30 m were assessed, as well. Partici-
pants performed 2 maximal sprint efforts over the dis-
tance of 30 m in an indoor sport hall with a 3-minute
interval between trials. The best (the lowest time) of the
2 sprints was used for further analyses. Boys were en-
couraged to sprint as fast as possible. Sprint times were
recorded to 0.001 second accuracy by an electronic chro-
nometer (Omega system) that was connected to 4 pairs of
opto-reﬂective switches (TAG HEUER) located at the
start and then at 10-, 20-, and 30-m marks of the 30-m
distance. The system was connected to a printer, which
automatically printed the times for each separate dis-
Jump Test. SJs were recorded using the Ergojump
Bosco-System (4). In this instrument, 2 switch mats for
the timer were placed side by side and connected by an
adapter to the timer (‘‘start on break contact input’’). The
timer was triggered by the feet of the subject at the mo-
ment of the release from the platform, and stopped at the
moment of touching down. Thus, the ﬂight time of the
subject during the jump was recorded. This method of
ﬂight time calculation assumes that the positions of the
jumper on the platform were the same at takeoff and
landing. The vertical displacement of the body was cal-
culated by the ﬂight time. Participants from a standing
point smoothly ﬂexed their knees at 908, with their feet
on the mat. The subjects were instructed to keep their
hands on their hips throughout the jump. After that they
extended their knees completely and executed SJ. Three
trials were executed and the best one was recorded.
The training program lasted 10 weeks and included var-
ious types of jumps. The intensity of the selected exercises
was adjusted according to Chu (7). Exercises speciﬁc to
RV (speed-bound) and vertical jumps were included in the
selected exercises, performed with 1 or 2 legs, based on
Diallo et al. (10). The height of the selected vertical
jumps, which were performed with 2 legs, was initially
10–20 cm and gradually increased to 30 cm. The initial
number of jumps per session was 60 and gradually in-
creased up to 100 by the end of the training period (Table
2). The program was performed twice per week. The sets
consisted of 10 jumps each, separated by a 3-minute in-
A 4-week training program that included running en-
durance, ﬂexibility, coordination, and strength endurance
preceded the speciﬁc training program to prevent inju-
ries, as suggested by previous studies (15). All tests were
performed in a closed sport hall area with a stable tem-
perature of 288C.
Means and standard deviations were determined for the
following variables: SJ, running speed of 0–10, 10–20, 20–
30, and 0–30 m. For each dependent variable, a 2-way
analysis of variance (group 3time) with repeated mea-
sures on time was used. When a main or interaction effect
was detected, a paired t-test was performed to determine
speciﬁc differences. The level of signiﬁcance was set at p
Pearson correlation was used in order to detect any
correlations among sprint, anthropometrical, and jump
variables. Pearson correlation also was used to test the
reliability of the selected tests.
The test-retest reliability coefﬁcients concerning RV var-
iables ranged from 0.901–0.962 (p,0.05), whereas the
relevant value for SJ was r50.911 (p,0.05). At the
3. Pre- and posttraining mean 6SD time (s) in speed tests.*
* CONT 5control group; JUMP 5experimental group.
† Signiﬁcant difference between groups.
‡ Signiﬁcant difference within groups.
4. Pre- and posttraining mean 6SD of vertical jump.*
Group Pretraining Posttraining
* CONT 5control group; JUMP 5experimental group.
† Signiﬁcant difference between and within groups.
5. Correlations between different running phases and
Running phase Squat jump*
beginning of the intervention, there were no signiﬁcant
differences between the 2 groups.
Intergroup Comparisons of Running Performance
The JUMP group (Table 3) showed signiﬁcantly better
performances after the training program in the interme-
diate distances of 0–10, 10–20, and 20–30 m, and 0–30 m
Intragroup Comparisons of Running Performance
Intragroup comparisons (Table 3) revealed an improve-
ment of performance of JUMP group in distances of 10–
20 and 20–30 m (p,0.05), but not for the distance of 0–
10 m. CONT group did not show any improvement in any
of the tested variables (p.0.05).
Intra- and Intergroup Comparisons of SJ
The JUMP group (Table 4) increased signiﬁcantly the SJ
after the training program (p,0.01) and had better per-
formance than the CONT group (p,0.05).
No signiﬁcant correlations were found between height or
body mass and the performance over sprints of 0–10, 10–
20, and 20–30 m (p.0.05) or the height of squat jump.
However, signiﬁcant correlations were found between all
tested RV variables and jump tests varying from 0.612–
0.737 (Table 5).
The main ﬁnding of this study is that the applied ply-
ometric training program resulted in an improvement of
the 30-m RV and the vertical jump in preadolescents.
Speciﬁcally, this type of training positively affected sprint
performance in the intermediate distances of 10–20 and
20–30 m, but not in the initial distance of 0–10 m. An-
thropometric parameters did not correlate signiﬁcantly
with any of the running phases, although vertical jump
performance correlated signiﬁcantly with all running
phases. No injuries or symptoms of discomfort were re-
ported during or after the applied plyometric training
A previous study (9) related to men classiﬁed running
performance in 3 phases: initial acceleration up to 10 m,
secondary acceleration from 10–36 m, and thereafter, a
phase of maximal or steady velocity. However, the dura-
tion of acceleration is dependent on numerous factors
such as gender and performance level. In women, the
phase of maximal velocity ranged between 25–35 m (28),
whereas the high-levels sprinters accelerated up to 60 m
(9). To our knowledge, there is no information about the
duration of the acceleration phase in an untrained pre-
pubertal population. The fact that in the present study a
signiﬁcant difference was observed between the duration
of 0–10 and 10–20 m, but not between the duration of 10–
20 and 20–30 m permitted us to speculate that the dis-
tance between 20–30 m may be roughly considered as the
phase where the children tend to achieve their maximum
velocity. Additionally, the distances between 0–10 and
10–20 m could be considered as initial and secondary (in-
The inﬂuence of the different training methods on
running performance has not been widely studied during
developmental ages and speciﬁcally during the prepuber-
tal period. Relevant studies to running programs have
shown that athletic boys have higher RV than do un-
trained population during prepubertal and pubertal stag-
es (22, 23). However, the training programs of these stud-
ies were general and not speciﬁc to RV. They included
strength, power, and endurance training without provid-
ing any speciﬁc information as to what extent they may
have selectively inﬂuenced sprint performance. Kotza-
manidis (17) reported that pure sprint training (short
running distances from 5–30 m, with full recovery inter-
vals) positively inﬂuenced 30-m RV. These results (17)
were in line with the ﬁndings of Delecluse et al. (9) con-
cerning the application of the same method in untrained
adults, but contrasted the Rimer and Sleivert (27) study
relating to a trained population. To our knowledge, there
are no other studies addressing the inﬂuence of plyomet-
ric training on RV in the prepubertal population. For this
reason the results of the present research will be dis-
cussed in relation to adult and pubertal population’s stud-
ies. In adults, relevant studies have pointed out that
jumping exercises that were nonspeciﬁc to running per-
formance (i.e., vertical-type jump exercise) did not cause
any effect on running speed (7, 13). On the contrary,
when the applied exercises were completely speciﬁc
(speed-bound) to running performance, the training pro-
gram had a positive effect on RV (27). The explanations
of the aforementioned results (27) were based on the as-
sumption that plyometric training reducing conduction
during support phase of the stride increases ﬁnally RV.
It is important to comment that in contrast to adult stud-
ies (7, 13, 27), Diallo and colleagues’ (10) and our ﬁndings
indicate that for a developmental population, RV also can
be enhanced by using jumping exercises that are nonspe-
ciﬁc to RV.
Generally speaking, for RV it has been reported that
the applied training programs demonstrate a selective ef-
fect on the different running phases (8). This selective
effect has been attributed to numerous factors, such as
the differences that were observed between the reported
running phases in dynamic and kinematic parameters
and muscle activation (14, 25). Diallo et al. (10) did not
mention details as to what extent their plyometric pro-
gram affected selectively the running phases. Based on
studies of trained adult populations, it was reported (27)
that the use of speed-bound exercises inﬂuenced all run-
ning phases including the initial acceleration (0–10 m).
Our ﬁndings are in line with this aforementioned study
(27) only for the intermediary acceleration (10–20 m) and
steady velocity phases (20–30 m). On the contrary, re-
garding the initial acceleration, an increasing tendency
was observed but this improvement was not signiﬁcant.
This discrepancy between the present results and those
of Rimmer and Sleivert (27) could be explained by the fact
that they have used speed-bound exercises that, in their
opinion, are identical to the kinematic and dynamic pa-
rameters of the stride length and conduction time during
initial acceleration (0–10 m). However, the same authors
(27) mentioned that this adaptation occurred only in the
intermediate distance of 30–40 m. Therefore, the question
of what type of adapted plyometric training may affect
RV needs further examination. In our study we have used
both speciﬁc and nonspeciﬁc jumping exercises to im-
prove RV, a factor that possibly explains the obtained re-
sults for the 0–10 m. Another factor that probably affect-
ed the obtained results for the 0–10-m distance was the
quality of the applied training program (intensity and vol-
ume) and the power deﬁcit of children compared with
adults (30). It is well known that the performance of the
initial acceleration (0–10 m) is affected mainly by concen-
tric action and power performance (29) whereas the phase
of maximal velocity is affected by muscle-tendon stiffness
as well (6, 24). It seems the applied protocol did not cause
a sufﬁcient power increase to enhance the initial accel-
eration. However, this issue needs further experimental
Another ﬁnding of the present study was that ply-
ometric training increased the vertical jump of the boys.
This issue has not been widely examined during prepu-
berty. Haywood et al. (16) reported that chronic training
caused a jumping enhancement in prepubertal gymnasts
and swimmers. Enhancement of the vertical jump after
plyometric training was reported for the initial (10) and
latest period (21) of puberty. The ﬁndings of our study
indicate that plyometric exercises cause an enhancement
in SJ in the prepubertal population regardless of the fact
that their neuromuscular system has not yet completely
matured (30) and their elastic tissue is more compliant
(19) than that of adults. A possible explanation for the
vertical jump enhancement in the current study could be
the rate of force development, power, and stiffness en-
hancement, as already reported in adults (2, 31, 33). How-
ever, this hypothesis needs further investigation for chil-
Concerning the anthropometrical parameters, previ-
ous studies in adults (20) and pubertal boys (3) have re-
ported that these do not affect running performance, be-
ing in agreement with the current results. The correla-
tions between SJ and all running distances indicate the
important role of lower limb power in all phases of RV,
as it was reported for adult (34, 35) and pubertal (20)
populations. Additionally, they underline that SJ can be
used as a predictor of running performance for preado-
lescents as well.
In conclusion, the plyometric training in prepubertal
boys has a positive effect on RV and vertical jumping per-
formance. However, this training affected predominantly
the phase of maximum velocity indicating speciﬁc adap-
tations, which require further research. Additionally, it
was shown that low-intensity plyometrics in combination
with a preceding general preparatory training period
could be applied in the training program of a prepubertal
population without an injury problem. However, further
research is necessary to identify the adaptations, which
could explain the obtained results.
The application of plyometric training in children is a con-
ﬂicting issue. It is considered that its application could
be dangerous for children’s muscle-tendon complex. How-
ever, this study showed that low-intensity plyometric ex-
ercises could be used safely during prepuberty. A basic
condition for this type of training is a preceding prepa-
ratory training program including exercise for coordina-
tion, ﬂexibility, and strength endurance. This program
could be considered as a protective mechanism against
possible injuries. Moreover, this type of plyometric exer-
cise could be used as a supplementary training program
for running speed and power enhancement during the
late prepubertal stage.
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Address correspondence to Dr. Christos Kotzamanidis,