International Journal of Sport Studies. Vol., 4 (12), 1455-1461, 2014
Available online at http: www.ijssjournal.com
ISSN 2251-7502 © 2014; Science Research Publications
Plyometric training programs for young soccer players: a systematic
review
Michailidis Yiannis*
Department of Physical Education and Sports Sciences, Democritus University, Komotini, Greece
*Corresponding Author, Email: [email protected]
Abstract
The purpose of this systematic review was to evaluate the
effectiveness of plyometric training programs on motor performance
of young soccer players. Research articles were selected if met the
next inclusion criteria a) included young persons under 18 years old,
b) included soccer players, c) described the outcomes of a plyometric
exercise intervention, d) included measures of strength, running speed
or jumping ability and e) used a randomized control trial or quasi
experimental design, f) published in peer-reviewed journals.
Nine studies used for the final review. The 9 studies were judged to
be of low quality (values of 3-6). Most of the studies found
statistically significant effects of improving motor performance
(speed, jumping ability, strength, agility, kicking performance) after a
plyometric training program. The current evidence suggests that a
twice a week program for 8-10 weeks beginning at 50-60 jumps the
first week and progress to 100-120 by the end. When soccer practice
is supplemented with a plyometric training protocol it leads to greater
performance gains.
Key words: plyometric training, power performance, children, soccer
Introduction
Soccer players have to master an extremely wide variety of running and jumping movements
because the game tends to be dominated by dynamic and even explosive movements like sprints and
sudden changes of direction (Bangsbo et al., 2006). These kinds of movements that characterized of
power are very important for a successful soccer player although represent only a small percentage of a
match’s total time (Reilly et al., 2000). These explosive actions are significant and for the performance
of young soccer players.
The last decade’s power training is common in weekly soccer practice. One major kind of power
training is the plyometric exercises. Despite its well established effectiveness in adults as a part of
physical conditioning training program the trainers are confused about the use of plyometrics in young
soccer players. Some years before plyometric training were deemed unsafe for youth until an update
from the National Strength and Conditioning Association determined that this recommendation was not
supported by current research (Faigenbaum et al., 2009).
Plyometric exercises are characterized by the use of the stretch-shortening cycle that develops
during the transition from a rapid eccentric muscle contraction to a rapid concentric muscle contraction
(Markovic and Mikulic, 2010; Markovic et al., 2007). These exercises can improve jumping ability
(Gheri et al., 1998; King and Cipriani, 2010; Fatouros et al., 2000) speed, acceleration (Kraemer et al.,
1455
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
2000; Rimmer and Sleivert, 2000) maximal and explosive strength (Fatouros et al., 2000; Herrero et
al., 2010; Saez-Saez de Villarreal et al., 2010) and agility (Thomas et al., 2009).
Currently a limited number of studies have examined the influence of plyometric exercise on young
soccer players. Evidence from studies with boys from other sports as basketball suggest that plyometric
training may be beneficial for maintenance or enhancement of the athletic performance when they are
combined with resistance training and sport specific training (Brown et al., 1986; Matavulj et al.,
2001).
The purpose of this systematic review was to examine the extent and quality of the current research
literature to evaluate the efficacy and safety of plyometric for improving motor performance in young
soccer players. Also this review will help for a deeper understanding about the characteristics of
plyometric training in young soccer players.
Materials and Methods
Computerized literature searches of articles until March 2014 were performed with the use of
MEDLINE, Scopus and SportDiscus databases. The following search terms were used in different
combinations to identify articles that performed plyometric exercise in young soccer players:
‘’soccer,’’ ‘’football,’’ ‘’children,’’ ‘’young,’’ ‘’plyometric exercise,’’ ‘’plyometric training,’’
‘’jumping training,’’ ‘’strength,’’ ‘’sport performance.’’
Inclusion Criteria and quality of the articles
Research articles were selected if they a) included young persons under 18 years old, b) included
soccer players, c) described the outcomes of a plyometric exercise intervention, d) included measures
of strength, running speed or jumping ability and e) used a randomized control trial or
quasiexperimental design, f) published in peer-reviewed journals. Articles that met the 6 criteria were
chosen for the final review.
Methodological quality of the included studies was evaluated by using the PEDro (Physiotherapy
Evidence Database) scale (PEDro scale). Although this scale has 11 items, only ten are scored, so the
score ranges from zero to ten. Each criterion except the first scored as 0 or 1. Table 1 describes the
results of the quality rating.
Table 1: Quality rating
Study
PEDro scale criteria
Eligibility criteria
specified
Random allocation
Sohnlein et
al.
Marques et
al.
Michailidis et
al.
Rubley et
al.
Buchheit et
al.
Meylan &
Malatesta
Thomas et
al.
Kotzamanidis
Diallo et
al.
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
0
1
1
0
0
0
1
0
1
Concealed allocation
0
0
0
0
0
0
0
0
0
Baseline similarity
0
1
1
1
1
1
1
1
1
Blinding of subjects
0
0
0
0
0
0
0
0
0
Blinding of coaches
0
0
0
0
0
0
0
0
0
Blinding of assessors
Measures of key
outcomes from more
than 85 % of subjects
Intention to treat
analysis
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
1
1
0
0
0
0
0
0
0
1
1
Between group
statistical comparisons
1
0
1
1
1
1
1
1
1
Point measures and
measures of variability
1
1
0
0
1
0
0
0
0
Total
3
5
5
4
5
4
4
5
6
1456
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
Data extraction
Data extraction performed by the author considering: 1) aspects of the study design and protocol; 2)
aspects of the study population, such as mean age, and gender; 3) aspects of the intervention such as
sample size, type of exercise, frequency and duration of the training program; 4) aspects of the
variables that measured and 5) reported results.
Also effect sizes were calculated for those studies that reported means and SD s using Cohen’s d.
Cohen’s description was used to classify effect sizes as small, medium or large (Cohen, 1998).
Table 2: Characteristics and results of the studies.
Study
Purpose
Design
Protocol
Sample
Indices
Measures
PTG:
baseline,
every 4
wks
CG:
baseline,
post
training
Results
Sohnlein et al.
2014
PT for improving
sprint, agility and
jumping
non
random
assigned
16 wks; 2 × wk;
24 sessions;
112 jumps/session
initial, 350 end; increase
15 jumps/wk
PTG n = 10
13.0 ± 0.9 yrs
CG n = 12
12.3 ± 0.8 yrs
males
speed, agility,
shuttle run, MB5,
long jump
Marques et al.
2013
Effect of jump &
sprint training
program on
strength & speed
abilities
random
aqssigned
6 wks; 2 × wk;
12 sessions;
136 jumps/session
initial, 185 end; increase
8 jumps/wk
PTG n = 26
CG n = 26
13.4 ± 1.4 yrs
males
Speed, CMJ,
kicking velocity
baseline,
post
training
PTG: speed time 0-30 m ↓-1.7 %,
kicking velocity ↑6.6 %, CMJ ↑7.7 %
P < 0.05
Michailidis et
al. 2013
Preadolescent
boys exhibit
plyometric
trainability or not
random
aqssigned
12 wks; 2 × wk;
24 sessions;
60 jumps/session initial,
120 end;
increase 5 jumps/wk
PTG n = 24
10.6 ± 0.5 yrs
CG n = 21
10.7 ± 0.7 yrs
males
Speed, CMJ, SJ,
DJ, MB5, LJ, leg
strength, wingate
test, agility,
kicking distance
baseline,
mid
training,
post
training
PTG: speed ↑3-5 %, vertical jump ↑1623 %, LJ ↑4.2 %, MB5 ↑23 %, leg
strength ↑28 %, agility ↑23 %,
anaerobic power −, kicking distance
↑22.5 % P < 0.05
CG: speed ↑1.2-1.8 %, P < 0.05
Rubley et al.
2011
PT effects on
vertical jump and
kicking distance
quasiexpe
rimental
convenien
ce sample
14 wks; 1 × wk;
14 sessions;
16 jumps/session initial,
60 end;
increase 3 jumps/wk
PTG n = 10
CG n = 6
13.4 ± 0.5 yrs
females
vertical jump 5
trials, 3 best
aver., kicking
distance
baseline,
mid
training (7
wks), post
training
PTG: post training jump height ↑
P < 0.014,
kicking distance ↑ P < 0.001
speed, shuttle
sprint test, CMJ,
hoping test
baseline,
post
training
ES: shuttle sprint test time ↓-0.08 %,
CMJ ↑14.8 %, hopping test ↑27.5 %, P
< 0.05
RS: shuttle sprint test time ↓-2.9 %,
CMJ ↑6.8 %, hopping test ↑13.5 %,
P < 0.05
PTG: speed time ↓-3.2 %, agility time
↓-6.1 %, MB5 ↑11.8 %, LJ ↑7.3 %, P <
0.05
CG: speed time ↓1.5 %, MB5 ↑4.95 %,
P < 0.05
Effects of ES vs
RSS on repeated
sprint ability
controled
study
10 wks; 1 × wk;
10 sessions
ES n = 8
RSS n = 7
14.5 ± 0.5 yrs
males
Meylan &
Malatesta
2009
PT influence on
explosive actions
quasiexpe
rimental
convenien
ce sample
8 wks; 2 × wk;
16 sessions;
50 jumps/session initial,
192 end;
increase 18 jumps/wk
PTG n = 14
13.3 ± 0.6 yrs
CG n = 11
13.1 ± 0.6 yrs
males
speed, SJ, CMJ,
CT, agility test,
MB5
baseline,
post
training
PTG: speed time ↓-2.1 %, agility time
↓-9.6 %, CMJ ↑7.9 % , CT ↑10.9 %
Thomas et al.
2009
2 PT techniques
on muscular
power and agility
random
aqssigned
6 wks; 2 × wk;
12 sessions;
80 jumps/session initial,
120 end;
increase 10 jumps/wk
n = 12
17.3 ± 0.4 yrs
males
speed, agility,
vertical jump
baseline,
post
training
CMJ, DJ, vertical jump ↑~4 %, agility
time ↓~-7 %, P < 0.05
Kotzamanidis
2006
PT on running
performance and
vertical jumping
quasiexpe
rimental
convenien
ce sample
10 wks; 2 × wk;
20 sessions;
60 jumps/session initial,
92 end;
increase 12 jumps/wk
PTG n = 15
11.1 ± 0.5 yrs
CG n = 15
10.9 ± 0.7 yrs
males
SJ, speed
baseline,
post
training
PTG: running velocity 0-30 m, 10-20
m, 20-30 m ↑, jump performance ↑,
P < 0.05
Buchheit et al.
2010
1457
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
Diallo et al.
2001
PT effects on
performance
random
aqssigned
10 wks; 3 × wk;
30 sessions;
8 wks reduce training;
200 jumps/session
initial, 300 end; increase
10 jumps/wk
PTG n = 10
12.3 ± 0.4 yrs
CG n = 10
12.4 ± 0.5 yrs
males
SJ, CMJ, DJ,
MB5, repeated
rebound jump for
15 seconds,
speed, % BF,
lean leg mass,
max cycling
power
baseline,
post
training,
post
reduce
training
PTG, CG: lean leg mass ↑ P < 0.01,
PTG: % body fat ↓ P < 0.05, sprint
cycling performance ↑ P < 0.01,
CMJ ↑ P < 0.01, SJ ↑ P < 0.05,
MB5 ↑ P < 0.01, RRJ15 ↑ P < 0.01,
speed 20m ↑ P < 0.05
PTG = plyometric training group; PT = plyometric training; CG = control group; ES = explosive strength; RSS = repeated shuttle sprint; wks: weeks; M5B = multiple 5
bounds; CMJ = counter movement jump; SJ = squat jump; DJ = drop jump; LJ = long jump; RRJ15 = repeated rebound jump for 15 seconds; CT = contact test; yrs = years
Results
After the literature review, were selected 9 studies which judged to be of low quality across to PEDro
scale. The mean rating of this scale for the studies was 4.56 out of 10 and ranged from 3 to 6 (Table 1).
Effectiveness of plyometric training for improving performance
All the studies (Buchheit et al., 2010; Diallo et al., 2001; Kotzamanidis, 2006; Meylan and Malatesta,
2009; Thomas et al., 2009; Rubley et al., 2011; Marques et al., 2013; Michailidis et al. 2013; Sohnlein
et al., 2014;) found statistically significant effects of improving motor performance after a plyometric
training program. Seven studies (Buchheit et al., 2010; Diallo et al., 2001; Kotzamanidis, 2006; Meylan
and Malatesta, 2009; Marques et al., 2013; Michailidis et al. 2013; Sohnlein et al., 2014) measured the
ability of speed and found statistically significant improvements (Table 2). Some researchers
mentioned the effect sizes and some others provided sufficient data to calculate effect size. Sohnlein et
al. (2014) and Meylan and Malatesta (2009) had large effect sizes (d = 1.4 and d = -1.28, respectively).
Kotzamanidis (2006) had a moderate effect size (d = -0.75), and Buchheit et al. (2010) and Thomas et
al. (2009) had small effect sizes (d = 0.21 and d = -0.37, respectively).
All the studies measured the ability to jump and found statistically significant improvements in
jumping ability. Five of these studies (Kotzamanidis, 2006; Meylan & Malatesta, 2009; Thomas et al.,
2009; Rubley et al., 2011; Sohnlein et al., 2014) had large effect sizes (d = 2.1, 1.1, 2.2, 2, 1.1, 1.41,
2.1, respectively) and one study (Buchheit et al., 2010) had a small effect size (d = -0.38).
One study (Michailidis et al., 2013) measured leg strength outcomes and demonstrated statistically
significant improvements. Outcomes for kicking performance were measured in 3 studies (Rubley et
al., 2011; Marques et al., 2013; Michailidis et al., 2013). All of them demonstrated a statistically
significant improvement. Only Rubley et al. (2011) provided sufficient data to calculate effect size
which was large (d = 2.62).
Four studies (Meylan & Malatesta, 2009; Thomas et al., 2009; Michailidis et al., 2013; Sohnlein et al.,
2014) measured agility outcomes and all the researchers mentioned statistically significant
improvements. Three of the studies had large effect sizes (Sohnlein et al., 2014, d = 1.3, Thomas et al.,
2009, d = 1.3, Meylan & Malatesta, 2009, d = -2.15).
Exercise dosage
When we compare a plyometric training program we have to check some characteristics like the
duration of the program, the frequency, the number of jumps, the kind of jumps, and the method for
increasing training volume. The duration of the plyometric training programs varied across studies
from 6 to 14 weeks. Independently from the duration all the researchers mentioned significant
improvements of motor performance (speed, agility, jumping ability).
The sessions per week varied across studies from once a week to 3 times a week. Buchheit et al. (2010)
and Rubley et al. (2011) exercised children once a week for 14 and 10 weeks respectively and they
found significant improvements. The most of the studies (Kotzamanidis, 2006; Meylan & Malatesta,
2009; Thomas et al., 2009; Marques et al., 2013; Michailidis et al., 2013; Sohnlein et al., 2014)
exercised children twice a week. Three times a week used only by Diallo et al. (2001).
Another one important characteristic of training is the kind of jumps. Hopping exercises and depth
jumps belongs to the group of plyometric exercises. If we want to compute the intensity of a training
program we have to know the kind of jumping exercises (height of jumps). In the most of the studies
did not include enough information’s about this aspect, so we did not discuss the kind of jumps.
The number of jumps is another one training characteristic. Rubley et al. (2011) had used a low number
of jumps per session (16 initial, 60 end) in comparison with all the other studies (from 50 initial to 350
1458
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
end). In a later study, Sohnlein et al. (2014) began at 112 jumps per session and increased 15
repetitions a week to approximately 350 jumps per session by the end of the intervention. This study
showed large effect sizes on running, jumping and agility such as the studies by Kotzamanidis (2006),
Meylan and Malatesta (2009) and Thomas et al. (2009). Small size effect showed by Buchheit et al.
(2010), and Rubley et al. (2011). These researchers did not include data for the number of jumps.
Discussion and Conclusion
This review showed that young soccer players may be benefited from a plyometric training program
that is integrated with their usual soccer practice routine by improving motor performance parameters.
In all studies the researchers observed significant improvements at the performance characteristics that
they study.
In two studies (Michailidis et al., 2013; Sohnlein et al., 2014) the participants in CG demonstrated
significant improvements in speed and in one study (Sohnlein et al., 2014) the improvement in MB5
was statistically meaningful. Buchheit et al. (2010) mentioned that the group of repeated shuttle sprint
training had improved at the tests of CMJ and hopping test. In this study the shuttle sprint group
performed a kind of exercise that enhances the leg power. Sprint with change of direction is a strong
stimulus for the improvement of this kind of power. The lack of changes in all the other motor
performance characteristics in participants of CG demonstrates the significance of plyometric training
incorporation in regular soccer practice to enhance lower leg power performance in young soccer
players.
In all studies the participants were children. Only in the study of Thomas et al. (2009) the average age
was 17.3 years. From the rest studies three performed to prepubertal children (< 12 years) and five to
pubertal children. Eight studies performed to males and one (Rubley et al., 2011) to young female
soccer players. Independently of the gender all the researchers mentioned significant improvements of
motor performance.
Vertical jump elevation mentioned from all the researchers. The adaptations in children after
plyometric training are likely to be more neural in nature because of the children’s limited potential to
increase their muscle strength and size because of their low testosterone levels. Also this kind of
training (plyometric) has been shown to be related mainly to neural adaptations (Baker, 1996).
Literature review showed that plyometric training improves the performance in all types of jumps
(CMJ, SJ, DJ, MB5).
One index that measured by the most of the researchers was the speed. Sprint performance
characterized by 3 phases (Delecluse et al., 1995): a) initial acceleration (0-10 m), b) secondary
acceleration (10-30 m) and c) maximal velocity phase (after 30 m). Nevertheless the duration of the
second or third phase may be dependent on gender and performance level (Delecluse et al., 1995). In
children maximal velocity develops at 20-30 m (Delecluse et al., 1995; Kotzamanidis, 2006). Literature
review showed that the effectiveness of plyometric training on young soccer players produced
contradictory results. Michailidis et al. (2013) mentioned that plyometric training elicited a marked
improvement of all sprinting phases. Meylan and Malatesta (2009) reported that sprint time improved
after training program. Thomas et al. (2009) reported a lack of change in sprint performance after
plyometric training. Also the discrepancy between the studies may be attributed to differences in the
participants’ conditioning level and the variation in quantity and quality of training. It has been shown
that trained boys are more responsive to various training stimuli than their untrained counterparts in
terms of speed improvement (Mero et al., 1991). The improvement of speed performance in CG
suggesting that soccer practice alone may contribute to speed development probably because of the
high frequency of short maximal sprints incorporated in this type of practice.
Leg strength measured only by Michailidis et al. (2013) and they found that a 12 week plyometric
training program resulted in a modest increase of leg strength. Probably this kind of exercises might
have induced an upregulation of motor unit recruitment and inhibition of protective antagonist muscle
action. As we mentioned above this improvement be attributed to neuromuscular adaptations.
In four studies (Meylan and Malatesta, 2009; Thomas et al., 2009; Michailidis et al., 2013; Sohnlein et
al., 2014) the researchers performed a kind of agility test and they mentioned significant improvements.
The characteristics of an agility test are the change of direction, with decelerations and accelerations.
These elements correlated with lower limp muscle power (Negreteand Brophy, 2000; Young et al.,
2002).
Kicking distance or velocity was also improved by plyometric training in three studies (Rubley et al.,
2011; Marques et al., 2013; Michailidis et al., 2013) This improvement may be attributed to the
increased strength and power of the leg muscles.
1459
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
When initiating an exercise intervention for children we have to care about safety. In the most of the
studies the plyometric training programs were part of the total soccer training, with short duration,
included a warm up and cool down protocol. Also the participants before execute the exercises, had to
learn the correct technique. If the instructors and children follow safety guidelines the plyometric
training is safe for them.
In conclusion after the literature review we can suggest that children demonstrate considerable
plyometric trainability as evidenced by the marked improvement of speed, jumping ability, strength,
and agility and kicking performance. It is needed more research to identify the physiological
mechanisms responsible for these performance gains.
From the results of the literature review we can say that plyometric training programs are effective for
improving motor performance in young soccer players between 10 and 17 years of age. Training
affects can be achieved with a twice a week program for 8 to 10 weeks. Exercise load should be
increased progressively weekly. For the volume of training we have to take care about the intensity
(height) and the number of the jumps. A number of 50-60 jumps the first week and progress to 100-120
by the end will be effective.
Conflict of interest
The authors declare no conflict of interest
References
Baker D, 1996. Improving vertical jump performance through general, special, and specific strength
training. J Strenght Cond Res. 10: 131–136.
Bangsbo J, Mohr M, Krustrup P, 2006. Physical and metabolic demands of training and match-play in
the elite soccer player. J Sports Sci. 24: 665–674.
Brown ME, Mayhew JL, Boleach LW, 1986. Effect of plyometric training on vertical jump
performance in high school basketball players. J Sports Med & Phys Fit. 26: 1–4.
Buchheit M, Mendez-Villanueva A, Delhomel G, Brughelli M, Ahmaidi S, 2010. Improving repeated
sprint ability in young elite soccer players: repeated shuttle sprints vs. explosive strength
training. J Strenght Cond Res. 24(10): 2715–2722.
Cohen J, 1998 The effect size index: d. In: Statistical Power Analyses for the Behavioral Sciences (2nd
ed.). Hillsdale, NJ: Lawrence Erlbaum Associates.
Delecluse C, Van Coppenolle H, Willems E, Van Leemputte M, Diels R, Goris M, 1995. Influence of
high-resistance and high-velocity training on sprint performance. Med & Sci Sports & Exer.
27: 1203–1209.
Diallo O, Dore E, Duche P, Van Praagh E, 2001. Effects of plyometric training followed by a reduced
training programme on physical performance in prepubescent soccer players. J Sports Med &
Phys Fit. 41: 342–348.
Faigenbaum A, Kraemer WJ, Blimkie CJR, Jeffreys I, Micheli LJ, Nitka M, Rowland TW, 2009.
Youth resistance training: Updated position statement paper from the national strength and
conditioning association. J Strenght Cond Res. 23: 60–79.
Fatouros IG, Jamurtas AZ, Leontsini D, Marinos S, Kostopoulos N, Buckenmeyer PJ, 2000. Evaluation
of plyometric exercise training, weight training, and their combination on vertical jumping
performance and leg strength. J Strenght Cond Res. 14: 470–476.
Gheri DJ, Ricard MD, Kleiner DM, Kirkendall DT, 1998. A comparison of plyometric training
techniques for improving vertical jump ability and energy production. J Strenght Cond Res.
12: 85–89.
Herrero AJ, Martin J, Martin T, Abadia O, Fernandez B, Garcia-Lopez D, 2010. Short-term effect of
plyometrics and strength training with and without superimposed electrical stimulation on
muscle strength and anaerobic performance: A randomized controlled trial. Part II. J Strenght
Cond Res. 24: 1616–1622.
King JA, Cipriani DJ, 2010. Comparing preseason frontal and sagittal plane plyometric programs on
vertical jump height in high-school basketball players. J Strenght Cond Res. 24: 2109–2114.
Kotzamanidis C, 2006. Effect of plyometric training on running performance and vertical jumping in
prepubertal boys. J Strenght Cond Res. 20: 441–445.
1460
Intl. j. Sport Std. Vol., 4 (12), 1455-1461, 2014
Kraemer WJ, Ratamess NA, Volek JS, Mazzetti SA, Gomez AL, 2000. The effect of the meridian shoe
on vertical jump and sprint performances following short-term combined plyometric/sprint
and resistance training. J Strenght Cond Res. 14: 228–238.
Markovic G, Jukic I, Milanovic D, Metikos D, 2007. Effects of sprint and plyometric training on
muscle function and athletic performance. J Strenght Cond Res. 21: 543–549.
Markovic G, Mikulic P, 2010. Neuro-Musculoskeletal and performance adaptations to lower-extremity
plyometric training. Sports Med. 40: 859–896.
Marques MC, Pereira A, Reis IG, van den Tillaar R, 2013. Does an in-season 6-week combined sprint
and jump training program improve strength-speed abilities and kicking performance in young
soccer players? J Hum Kin. 39: 157-166.
Matavulj D, Kukolj M, Ugarkovic D, Tihanyi J, Jaric, S, 2001. Effects of plyometric training on
jumping performance in junior basketball players. J Sports Med & Phys Fit. 41: 159–164.
Mero A, Jaakkola L, Komi PV, 1991. Relationships between muscle fiber characteristics and physical
performance capacity in trained athletic boys. J Sports Sci. 9: 161–171.
Meylan C, Malatesta D, 2009. Effects of in-season plyometric training within soccer practice on
explosive actions of young players. J Strenght Cond Res. 23: 2605–2613.
Michailidis Y, Fatouros IG, Primpa E, Michailidis C, Avloniti A, Chatzinikolaou A, Barbero-Alvarez
JC, Tsoukas D, Douroudos II, Draganidis D, Leontsini D, Margonis K, Berberidou F, Kambas
A, 2013. Plyometrics’ trainability in preadolescent soccer athletes. J Strenght Cond Res.
27(1): 38–49.
Negrete R, Brophy J, 2000. The relationship between isokinetic open and closed chain lower extremity
strength and functional performance. J Sport Rehab. 9: 46–61.
PEDro scale. Available at: www.pedro.org.au/. Accessed February 23, 2010.
Reilly T, Bangsbo J, Franks A, 2000. Anthropometric and physiological predispositions for elite
soccer. J Sports Sci. 18: 669–683.
Rimmer E, Sleivert G, 2000. Effects of a plyometrics intervention program on sprint performance. J
Strenght Cond Res. 14: 295–301.
Rubley MD, Haase AC, Holcomb WR, Girouard TJ, Tandy RD, 2011. The effect of plyometric
training on power and kicking distance in female adolescent soccer players. J Strenght Cond
Res. 25: 129-134.
Saez-Saez de Villarreal E, Requena B, Newton B, 2010. Does plyometric training improve strength
performance? A meta-analysis. J Sci & Med Sport. 13: 513–522.
Sohnlein Q, Mόller E, Stoggl T, In Press. The effect of 16 weeks plyometric training on explosive
actions in early to mid-puberty elite soccer players. J Strenght Cond Res.
Thomas K, Duncan F, French D, Hayes PR, 2009. The effect of two plyometric training techniques on
muscular power and agility in youth soccer players. J Strenght Cond Res. 23: 332–335.
Young WB, James R, Montgomery I, 2002. Is muscle power related to running speed with changes of
direction? J Sports Med & Phys Fit. 42: 282–288.
1461