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Journal of Sports Sciences
ISSN: 0264-0414 (Print) 1466-447X (Online) Journal homepage: http://www.tandfonline.com/loi/rjsp20
The effects of maturation on jumping ability and
sprint adaptations to plyometric training in youth
soccer players
Abbas Asadi, Rodrigo Ramirez-Campillo, Hamid Arazi & Eduardo Sáez de
Villarreal
To cite this article: Abbas Asadi, Rodrigo Ramirez-Campillo, Hamid Arazi & Eduardo
Sáez de Villarreal (2018): The effects of maturation on jumping ability and sprint
adaptations to plyometric training in youth soccer players, Journal of Sports Sciences, DOI:
10.1080/02640414.2018.1459151
To link to this article: https://doi.org/10.1080/02640414.2018.1459151
Published online: 03 Apr 2018.
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The effects of maturation on jumping ability and sprint adaptations to plyometric
training in youth soccer players
Abbas Asadi
a
, Rodrigo Ramirez-Campillo
b,c
, Hamid Arazi
d
and Eduardo Sáez de Villarreal
e
a
Department of Physical Education and Sport Sciences, Payame Noor University, Noor, I.R. of Iran;
b
Department of Physical Activity Sciences,
Universidad de Los Lagos, Osorno, Chile;
c
Research Nucleus in Health, Physical Activity and Sports, Universidad de Los Lagos, Osorno, Chile;
d
Department of Exercise Physiology, University of Guilan, Rasht, Iran;
e
Department of Sport and Informatics, Section of Physical Education and
Sport, Pablo de Olavide University, Sevilla, Spain
ABSTRACT
The aim of this study was to investigate the effects of maturation on power and sprint performance
adaptations following 6 weeks of plyometric training in youth soccer players during pre-season. Sixty
male soccer players were categorized into 3 maturity groups (Pre, Mid and Post peak height velocity
[PHV]) and then randomly assigned to plyometric group and control group. Vertical jump, standing long
jump, and 20-m sprint (with and without ball) tests were collected before- and after-intervention. After
the intervention, the Pre, Mid and Post-PHV groups showed significant (P ≤0.05) and small to moderate
effect size (ES) improvement in vertical jump (ES = 0.48; 0.57; 0.73), peak power output (E = 0.60; 0.64;
0.76), standing long jump (ES = 0.62; 0.65; 0.7), 20-m sprint (ES = −0.58; −0.66), and 20-m sprint with ball
(ES = −0.44; −0.8; −0.55) performances. The Post-PHV soccer players indicated greater gains than Pre-
PHV in vertical jump and sprint performance after training (P ≤0.05). Short-term plyometric training had
positive effects on sprinting and jumping-power which are important determinants of match-winning
actions in soccer. These results indicate that a sixty foot contact, twice per week program, seems
effective in improving power and sprint performance in youth soccer players.
ARTICLE HISTORY
Accepted 1 January 2018
KEYWORDS
Stretch-shortening cycle;
football; peak height velocity;
strength training;
acceleration
1. Introduction
Soccer is a sport with intermittent bouts of activity that
requires different physiological components. Numerous max-
imal- and high-intensity muscle actions are required during
soccer, including jumping, passing, kicking, tackling, turning,
sprinting and quick changing pace (Ramirez-Campillo et al.,
2014,2015b; Stolen, Chamari, Castagna, & Wisloff, 2005). In
fact, the most crucial moments of the soccer game such as
winning ball possession, scoring, assisting or preventing goals
depend on the ability of the players to perform high-speed
tasks and power production (Sohnlein, Muller, & Stoggl, 2014;
Thomas, French, & Philip, 2009; Vaczi, Tollar, & Meszler, 2013).
In addition, regarding previous findings it appears that sprint-
ing and jumping ability could be locomotive skills that form part
of the athletic motor skill spectrum (Meylan, Cronin, Oliver,
Hopkins, & Contreras, 2014; Ramirez-Campillo et al., 2015a).
Also, they are commonly used as indicators of neuromuscular
fitness in youth (Markovic & Mikulic, 2010;Sohnleinetal.,2014)
and as talent-identification markers to discriminate between
potential elite and non-elite youth soccer players (Arazi,
Coetzee, & Asadi, 2012; Meylan & Malatesta, 2009;Stolenetal.,
2005). Because of the advantage of having greater speed, accel-
eration, and power, a great deal of research has focused on the
development of sprint and jump performance using a myriad of
training methods, including sprint training, sprint drills, sprinting
against resistances, weight training, combined resistance and
sprint training, and plyometric training (Chaouachi et al., 2014;
Asadi, 2013;Meylanetal.,2014; Ramirez-Campillo et al., 2015a;
Saez de Villarreal, Kells, Kraemer, & Izquierdo, 2009;Saezde
Villarreal, Requena, & Cronin, 2012).
Plyometric training is a sport-specific, effective, time-saving,
and easy to implement training strategy in youth soccer facilities,
whichhasbeenshowntoinduceperformanceimprovements
such as jumping and sprinting (Komi, 2003; Markovic & Mikulic,
2010;SaezdeVillarreal,Suarez-Arrones, Requena, Haff, & Ferrete,
2015). Thus, plyometric training has been advocated as an appro-
priate approach to achieve soccer-related performance improve-
ments, which can be attributed mainly to neuromuscular
adaptations (Chaouachi et al., 2014; Meylan et al., 2014;Ramirez-
Campillo et al., 2015a). Adaptive responses to plyometric training
may differ depending on participant characteristics such as train-
ing level, gender and especially maturation (Saez de Villarreal
et al., 2012; Moran, Sandercock, et al., 2016;Moranetal.,2017).
In fact, previous studies reported that maturation plays a
critical role in performance adaptations due to training (Meylan
et al., 2014; Moran et al., 2016;Lloyd, Oliver, Hughes, & Williams,
2011). Based on these documents, the theory of windows of
trainability associated with natural accelerated development of
a specific athletic characteristic (i.e., sprint) has been articulated
(Meylan et al., 2014; Moran et al., 2017).
Previous meta-analysis regarding age-related jumping adap-
tations to plyometric training in youth athletes (Moran et al.,
2017) indicated greater adaptive responses between 10 and
12.9 years and 16 and 18 years compared to 13 and 15.9 years.
The authors addressed that jump performance adaptations to
CONTACT Eduardo Sáez de Villarreal esaesae@upo.es Faculty of Sport Sciences, Pablo de Olavide University, Ctra. de Utrera km 1, 41013 Sevilla, Spain
JOURNAL OF SPORTS SCIENCES, 2018
https://doi.org/10.1080/02640414.2018.1459151
© 2018 Informa UK Limited, trading as Taylor & Francis Group
plyometric training are “U”shape and athletes during Pre and
Post peak height velocity (PHV) showed more gains (Moran et al.,
2017). In contrast, those authors in another review study
reported that sprint gains following training are in relation to
age (i.e., liner shape) and participantsin Mid (ES = 1.15) and Post-
PHV (ES = 1.39) groups showed greater gains compared to Pre-
PHV (ES = −0.18) group (Moran et al., 2016). Although these
findings from review-meta analysis studies (Moran et al., 2016,
2017) showed that age and maturation may play a role in the
trainability of youth, an experimental study examining the effects
of plyometric training and maturation is still warranted and very
few studies have directly compared the effects of maturation on
sprint and power adaptations after plyometric training in soccer
athletes. However, a large number of studies examined the
effects of plyometric training on performance adaptations in
youth soccer players and found conflicting results (Chaouachi
et al., 2014; Meylan & Malatesta, 2009; Ramirez-Campillo et al.,
2015a,2015b;SaezdeVillarrealetal.,2015). Moreover, because
none of these studies have analyzed the independent effect of
the maturation of participants on adaptations induced by plyo-
metric training, the aim of this investigation was to compare the
effects of maturation on power and sprint performance adapta-
tions during 6 weeks of plyometric training in youth soccer
players.
2. Methods
2.1. Participants
Sixty healthy youth male soccer players from a semiprofes-
sional soccer academy with similar soccer training habits
volunteered to participate in this study and were categorized
into 3 maturity groups. A prior estimated sample size (n = 10
for each group) for β= 0.80 with α= 0.05 was calculated
based on tabled data from previous research (Markovic &
Mikulic, 2010)(Figure 1).
The participants included in this study were categorized into 3
maturation groups following a previously described equation by
Mirwald, Baxter-Jones, Bailey, and Beunen (2002). Briefly, to esti-
mate participant maturity status, anthropometric measurements
were taken and entered into an equation to predict maturity
offset, were maturity offset = −29.769 + 0.0003007·Leg Length
and Sitting Height interaction −0.01177·Age and Leg Length
interaction + 0.01639·Age and Sitting Height interaction +
0.445·Leg by Height ratio, where R = 0.96, R
2
= 0.915 and
SEE = 0.490. Based on peak height velocity (PHV) offset, the
participants ranged from −2.2 to +1.9 years were divided into
Pre-PHV, Mid-PHV, and Post-PHV groups (Table 1). Parental con-
sent was obtained as participants were <18 years of age. In order
to ensure no participants had any orthopedic or health related
conditions that could preclude them from participating in train-
ing all participants underwent a supervised screening underta-
ken by a physician. Exclusion criteria included participants with
potential medical problems or a history of ankle, knee, or back
pathologyinthe3monthsbeforethestudyorparticipantswith
orthopedic problems who compromised their participation or
performance in this study or any lower extremity reconstructive
surgery in the past 2 years or unresolved musculoskeletal dis-
orders. All participants had at least 2 years of soccer training.
None of the participants had any background in regular strength
and power training or competitive sports that involved any kind
of strength or power exercises during the treatment. The study
was conducted in accordance with the Declaration of Helsinki II
and the study was approvedby an institutional ethics committee
from the Payame Noor University (#1395). This study was per-
formed between June 2016 and August 2016.
2.2. Experimental design
This study is a short-term research design with three
assigned parallel training groups. Sixty youth soccer players
Figure 1. Study flow.
2A. ASADI ET AL.
were categorized into 3 maturity groups including three
training and control groups. All athletes performed soccer
specific training on three non-consecutive days (Monday,
Wednesday, Friday), while the training groups performed
plyometric training on the days in which soccer training
was not completed (Tuesday, Saturday) (Table 2). One week
prior to the initiation of the training intervention all athletes
were familiarized with the testing and training procedures.
On one day, the athletes were recruited to assessment of
height, weight, vertical and standing long jump, 20-m sprint
and 20-m sprint test with ball dribbling. These tests were
repeated after 6 weeks of training to compare maturation-
related adaptations (Figure 2).
All tests were performed one week pre and post 6 weeks
of plyometric training on one day in the afternoon. Before
testing, participants performed a general 10-minute warm-
up protocol consisting of sub-maximal running, active
stretching, and three submaximal vertical jumps. To deter-
mine reliability, two measurements were made in 10 parti-
cipants, 48 h apart.
Anthropometric Measures: Sitting and standing height were
measured to the nearest 0.1 cm with the use of a wall-
mounted stadiometer (Seca 222, Terre Haute, IN). Body mass
was measured to the nearest 0.1 kg using a medial scale
(Tanita, BC-418MA, Tokyo, Japan).
Jump Assessment: The countermovement vertical jump was
used to jump performance of the lower extremity muscles in
youth soccer players. Prior to the completion of performance test
all participants underwent a specific warm-up (i.e., 3–5sub-max-
imal jumps). During the jump, the participantswere instructed to
place their hands on their hips while performing a downward
movement (approximately 90° knee angle) followed by a max-
imal effort vertical jump. All the participants were instructed to
land in an upright position and to bend the knees after landing.
Following these approaches, participants completed three max-
imal countermovement vertical jumps each separated by a 30-s
rest period based upon previously established methods (Arazi
et al., 2012). All countermovement vertical jumps were per-
formed with a self-selected countermovement deep and using
an electronic contact platform (Ergo Jump Plus Bosco System,
Muscle LabV718, Langesund, Norway). The intraclass correlation
coefficient (ICC) for this test was 0.95.The highest vertical displa-
cement determined from the three jumps was then used to
estimate a peak power output with the use of the equation
developed by Sayers, Harackiewicz, Harman, Frykman, and
Rosenstein (1999): Peak Power [W] = [0.67] . [Jump Height (cm)]
Table 1. Participantsꞌcharacteristics (Mean [SD]).
Group Sample size Age (y) Height (cm) Body mass (kg) PHV offset (y)
Pre-PHV
EXP 10 11.5 ± 0.8 138.3 ± 6.0 31.0 ± 3.9 −1.8 ± 0.6
CON 10 11.7 ± 0.4 137.4 ± 5.0 33.1 ± 3.2 –1.9 ± 0.5
Mid-PHV
EXP 10 14.0 ± 0.7 154.5 ± 6.5 43.5 ± 6.3 0.3 ± 0.2
CON 10 14.2 ± 0.6 150.1 ± 7.2 41.2 ± 7.6 0.4 ± 0.3
Post-PHV
EXP 10 16.6 ± 0.6 171.5 ± 6.0 60.6 ± 6.7 1.3 ± 0.2
CON 10 16.2 ± 0.3 176.4 ± 5.0 62.4 ± 7.2 1.2 ± 0.4
EXP: Experimental, CON: Control, PHV: Peak height velocity
Table 2. Soccer and plyometric training sessions of youth soccer players during intervention.
Week days Intervention Time Duration (min)
Monday Soccer training: Technical drills, Tactical drills, Small-sided games 16.00–18.00 60–70
Tuesday Plyometric training: Depth jump from 20, 40 and 60 cm box 16.00–17.00 30–40
Wednesday Soccer training: Technical drills, Tactical drills, Simulated competitive games 16.00–18.00 60–70
Thursday Rest ––
Friday Soccer training: Technical drills, Small-sided games, Simulated competitive games 16.00–18.00 60–70
Saturday Plyometric training: Depth jump from 20, 40 and 60 cm box 16.00–17.00 30–40
Sunday Rest ––
Figure 2. Experimental design.
JOURNAL OF SPORTS SCIENCES 3
+45.3.[bodymass(kg)]–2.055. The accuracy of this formula has
been shown to be unaffected by sex differences and commonly
produced high intra-class correlations (ICC = 0.99) (Haff, Carlock,
& Hartman, 2005).
Standing Long Jump Test (SLJ). The SLJ was used to assess
maximal jump performance in the horizontal plain using arm-
swing. The test was performed using a 5-m fiberglass metric tape
laid on a wooden floor. Participants were instructed to jump
positioning (behind the starting line) their feet shoulders wide
apart and to perform a fast downward movement (approxi-
mately 120° knee angle) followed by a maximal effort horizontal
jump. Participants were instructed to bend their knees after
landing. Distance was measured from the starting line to the
point where the heels of the participants make contact with the
ground after landing using metric tape in cm. The best score was
obtained from the three trials for further analysis in this study
(Arazi et al., 2012; Asadi, 2013) and a 30-s rest was allowed to
participants for ensure recovery. The ICC for this test was 0.97.
Sprint Testing: A 20-meter sprint test was selected because
it is a common test used in the evaluation of soccer players
sprinting ability. The 20-m sprint test was conducted on a
grass surface with and without dribbling the ball (soccer-five,
ADIDAS, Herzogenaurach, Germany). After the completion of a
specific warm-up (i.e., 3–5 sub-maximal running in the 20-m
grass track) all participants performed three maximal 20-m
sprints, each separated by three-minute of rest. Participants
initiated the sprint from a standardized starting position that
was 0.5 m behind the start line. The sprint start was automa-
tically initiated as the participant passed the first timing gate
at the 0 m mark. Timing continued until the participants
passed through the final gate at 20-m. Times were recorded
to the nearest 0.01 s (JBL Systems, Oslo, Norway). The fastest
sprint time obtained from the three trials was selected for
analysis in this study (Ramirez-Campillo et al., 2015a,2015b).
The ICC for 20-m sprint and 20-m sprint with ball were 0.92
and 0.94, respectively.
2.3. Training programme
All soccer players performed soccer practice three days/
week for 60–70 min during pre-season. All participants in
the present study were required to complete all the pre-
scribed training sessions, with close supervision by a trained
researcher in order to ensure fulfillment of prescribed train-
ing parameters, with emphasis on technique and adequate
recovery to minimize the risk of injury. Plyometric drills
included 2 sets of 10 repetitions of drop jumps from 20,
40, and 60 cm (i.e., 60 contacts) performed on grass soccer
field (Ramirez-Campillo et al., 2014). Although the training
volume during the 6-week period did not increase, partici-
pants performed with maximal effort (maximal jump height
while minimizing contact time), ensuring an adequate train-
ing stimulus, as demonstrated in youths (Asadi, 2013)and
soccer players (Thomas et al., 2009). The rest period
between repetitions and sets was of 7 (Ramirez-Campillo
et al., 2014)and120sThomasetal.,2009), respectively,
as previous research had demonstrated that this is an ade-
quate rest interval for this type of training.
2.4. Data analysis
All values are presented as mean ± standard deviation (SD). Pre-
and post-values for the dependent variables were analyzed to
determine if the distributions were normal using the Shapiro-
Wilk Normality test. Differences in all performance variables
were analyzed using 2 × 2 × 3 (time [pre and post] × groups
[experimental and control] × maturity [Pre, Mid and Post-PHV])
repeated measures ANOVA. When a significant F value was
achieved across time or ages, Bonferroni post hoc procedures
were performed to locate the pairwise. Regarding Pre-test dif-
ferences among maturity groups, ANCOVAs were used to test
for differences among groups (Pre, Mid and Post-PHV) for the
dependent variable values. Statistical significance was set at
α≤0.05. Effect sizes (ES) were calculated using Cohenʼsd.The
magnitude of the ES statistics was considered trivial <0.20;
small, 0.20–0.50; moderate, 0.5–0.80; large, 0.8–1.30; and very
large >1.30 (Seitz, Reyes, Tran, Saez de Villarreal, & Haff, 2014).
The ES is reported in conjunction with the 95% confidence
interval (CI) for all analyzed measures. These methods were
preferred to traditional null hypothesis testing which can be
ineffective in gauging practical importance. The scale for inter-
preting the probabilities was as follows: possible = 25–75%;
likely = 75–95%; very likely = 95–99.5%; most likely>99.5%
(Hopkins, Marshall, & Batterham, 2009). Effects were considered
unclear if the confidence interval overlapped thresholds for
substantial positive and negative values. Otherwise, the effect
was clear and reported as the magnitude of the observed value
with a qualitative probability (Hopkins et al., 2009;Meylanetal.,
2014). Analyses were conducted within all groups to examine
the effectiveness of the plyometric training program and
between training and control groups to examine effectiveness
of the plyometric training program at different maturity levels
compared to the control condition.
3. Results
The soccer players in the control groups did not show any
significant changes in performance variables after 6 weeks and
experimental groups indicated significant differences com-
pared to control groups in all performance tests following
the 6-week training period (P ≤0.05).
The training groups demonstrated small to moderate signifi-
cant increases in the vertical jump test (Pre-PHV, P = 0.01; Mid-
PHV, P = 0.001; Post-PHV, P = 0.001). However, the Post-PHV
group (ES = 0.73, CI = −0.47 to 1.93) indicated greater changes
(p = 0.034) than Pre-PHV group (ES = 0.48, CI = −0.29 to 1.25) in
vertical jump gains after plyometric training (likely vs. possibly
training effects). Additionally, all experimental groups demon-
strated small to moderate significant increases in peak power
output achieved during the vertical jump and similarly, small to
moderate significant improvements in SLJ were achieved (Pre-
PHV, P = 0.001, 0.004; Mid-PHV, P = 0.001, 0.006; Post-PHV,
P = 0.001, 0.001 respectively) (Table 3,andFigure 3).
In 20-m sprint dribbling all experimental groups demon-
strated significant enhancements (Pre-PHV, P = 0.04, small; Mid-
PHV, P = 0.03, moderate; Post-PHV, P = 0.01, moderate). In the 20-
m sprint the Mid- (P = 0.04) and Post-PHV (P = 0.004) groups
achieved moderate significant improvements. However, the Pre-
4A. ASADI ET AL.
PHV group (P = 0.05) demonstrated only a trivial improvement
(ES = −0.12) (Table 3 and Figure 3). Likewise, the Post-PHV group
(ES = −0.66, CI = 0.51 to −1.82) indicated greater changes
(p = 0.021) than Pre-PHV group (ES = −0.12, CI = 1.02 to −1.25)
in 20-m sprint gains after plyometric training indicating possibly
vs. likely training effects for the Post-PHV group.
4. Discussion
In this study vertical jump, peak power and standing long jump
significantly increased in all experimental groups after plyometric
training. Although previous researchers showed that plyometric
training may play a critical role in the performance development
of youth soccer players (Ramirez-Campillo et al., 2015b;Thomas
et al., 2009; Vaczi et al., 2013), an experimental study examining
the effects of maturation for performance enhancements is neces-
sary. We found that plyometric training induced meaningful
changes in power performance and the adaptive responses were
greater for older youths (i.e., Post-PHV group) in vertical jump
performance compared to Pre-PHV group (Figure 3). Previous
studies addressed that improvement in power performance after
plyometric training could be due to various neuromuscular adap-
tations, such as increased neural drive to the agonist muscles,
changes in the muscle-tendon mechanical-stiffness characteristics,
improvements in intermuscular coordination, changes in muscle
size and/or architecture (Arazi et al., 2012;Markovic&Mikulic,
2010). With comparing maturity, the older youths (Mid-PHV and
Post-PHV) showed a meaningful tendency toward greater power
changes (up to likely improvement) in responses to plyometric
training compared to Pre-PHV group (possibly improvement only)
(Table 3). Although, there were no statistically significant differ-
ences among training groups other than a greater VJ improve-
ment in Post-PHV group compared to Pre-PHV group, the
meaningfully greater adaptations in older youths may play a role
during soccer game-related events. In agreement with our find-
ings,Lloyd,Radnor,andDeSteCrox(2016) reported that adaptive
responses in jumping ability after plyometric training are greater
Table 3. Changes in performance variables (95% confidence interval [CI]) after soccer plus plyometric training (EXP) or soccer-only training (CON) in players with
different maturity.
Group PRE POST ES
EXP vs. CON
ES (95% CI)
Training effect
description Training benefits (%)
Vertical jump (cm)
Pre-PHV EXP 33 ± 1.6 38 ± 1.2* 0.48 (−0.29 to 1.25) 0.49 (−0.24 to 1.36) Small ↑†14.7
CON 33.2 ± 1.4 34.1 ± 1.1 0.02 (−0.03 to 0.07)
Mid-PHV EXP 33.3 ± 2.5 39.1 ± 2.5* 0.57 (−0.69 to 1.83) 0.51 (−0.61 to 1.88) Moderate ↑†23.6
CON 34 ± 2.4 35.2 ± 2.7 0.04 (−0.02 to 0.1)
Post-PHV EXP 40.6 ± 4.5 51.6 ± 2.6* 0.73 (−0.47 to 1.93) 0.69 (−0.42 to 1.91) Moderate ↑‡28.6
CON 40.1 ± 3.9 42.7 ± 2.7 0.08 (−0.01 to 0.9)
Peak power output (w)
Pre-PHV EXP 456.7 ± 160.7 581.9 ± 220.8* 0.6 (−0.55 to 1.76) 0.51 (−0.5 to 1.79) Moderate ↑†32.2
CON 463.4 ± 155.6 472.1 ± 176.2 0.01 (−0.05 to 0.16)
Mid-PHV EXP 498.6 ± 215.6 689.6 ± 327.2* 0.64 (−0.52 to 1.80) 0.59 (−0.33 to 1.46) Moderate ↑†32.8
CON 502.1 ± 194.2 528.4 ± 209.4 0.2 (0.04 to 0.08)
Post-PHV EXP 1452.4 ± 560.5 1892.3 ± 560.9* 0.76 (−0.41 to 1.93) 0.47 (−0.42 to 1.83) Moderate ↑‡43.2
CON 1324.8 ± 470.4 1414.8 ± 436.7 0.3 (0.05 to 1.7)
Standing long jump (cm)
Pre-PHV EXP 146 ± 16.8 157.3 ± 16.7* 0.62 (−0.54 to 1.78) 0.76 (−0.18 to 1.63) Moderate ↑†9
CON 142.2 ± 15.4 145.8 ± 13.3 0.1 (−0.04 to 0.6)
Mid-PHV EXP 174.8 ± 26.6 191 ± 18.6* 0.65 (−0.51 to 1.81) 0.94 (−0.31 to 2.05) Moderate ↑‡10.2
CON 172.6 ± 25.4 171.3 ± 22.9 0.05 (−0.8 to 0.93)
Post-PHV EXP 199 ± 13.8 210 ± 15.1* 0.7 (−0.46 to 1.87) 0.87 (−0.38 to 1.98) Moderate ↑†4.7
CON 196.1 ± 12.4 197.3 ± 14.2 0.09 (−0.79 to 0.96)
20-m sprint (s)
Pre-PHV EXP 4.48 ± 0.85 4.3 ± 0.75* −0.12 (1.02 to −1.25) −0.50 (−1.61 to 0.69) Trivial ↓†5.7
CON 4.72 ± 0.77 4.7 ± 0.8 0.01 (0.04 to 0.6)
Mid-PHV EXP 3.82 ± 0.48 3.53 ± 0.45* −0.58 (0.8 to −1.73) −0.46 (−1.57 to 0.72) Moderate ↓†8.1
CON 3.76 ± 0.37 3.71 ± 0.33 0.14 (0.74 to −1.01)
Post-PHV EXP 3.83 ± 0.52 2.8 ± 0.4* −0.66 (0.51 to −1.82) −0.54 (−1.64 to 0.65) Moderate ↓‡11.8
CON 3.09 ± 0.68 3.07 ± 0.59 −0.03 (0.85 to −0.91)
20-m sprint with ball (s)
Pre-PHV EXP 8.27 ± 1.1 7.75 ± 1.1* −0.44 (0.71 to −1.58) −0.37 (−1.48 to 0.80) Small ↓†5.7
CON 8.17 ± 1.4 8.14 ± 0.99 0.2 (0.85 to −0.9)
Mid-PHV EXP 6.53 ± 0.83 5.88 ± 0.67* −0.8 (0.37 to −1.97) −0.93 (−2.04 to 0.33) Moderate ↓‡9.3
CON 6.62 ± 0.91 6.60 ± 0.87 0.02 (0.86 to −0.9)
Post-PHV EXP 5.76 ± 0.68 5.33 ± 0.43* −0.55 (0.6 to −1.7) −0.63 (−1.74 to 0.57) Moderate ↓†7
CON 5.80 ± 0.77 5.74 ± 0.81 −0.08 (0.8 to −0.95)
Values are presented as mean and standard deviation; * = Significantly different from baseline (p ≤0.05) and compared to the respective maturity control at POST
(p ≤0.05). PHV: Peak height velocity. ↑, improvement in performance; ↓, decrement in sprint time; †Possibly and ‡Likely effects of training.
Figure 3. Training effects (% of change) in performance variables in youth soccer
players.
JOURNAL OF SPORTS SCIENCES 5
for the Post-PHV group compared to Pre-PHV group. Therefore,
our results confirm that plyometric training may improve vertical
jumping ability performance in older youths compared with
younger youths.
The jump performance improvement after plyometric train-
ing might be explained by enhanced motor neuron excitability
and or neuromuscular adaptations (Mirzaei, Norasteh, & Asadi,
2013). On the other hand, Vissing et al. (2008) reported that
plyometric training could improve jumping ability and power
performance via better utilization of the stretch-shortening
cycle properties and neural drive to agonist muscles, greater
plasticity after plyometric training in muscle size, and
enhancements in muscle cross-sectional area and possible
transitions in fast-twitch muscle fibers resulting in greater
jumping ability gains in older youths. Moreover, hormone-
related hypertrophy of type II muscle fibers as well as the
growth spurt-related increases in muscle coordination and
motor unit activation greatly influences power performance
(Lloyd et al., 2011; Meylan et al., 2014; Rogol, Roemmich, &
Clark, 2002), and it seems that these adaptations could
increase muscle ability to product greater force during jump-
ing resulting greater training adaptations in vertical jump
when compared with younger youths; however, in this study
we did not directly measure these elements and could be
guess and speculation.
The plyometric training also improves 20-m sprint (Mid-
PHV, ES = −0.58; Post-PHV, ES = −0.66), and 20-m sprint with
ball (Pre-PHV, ES = −0.44; Mid-PHV, ES = −0.8; Post-PHV,
ES = −0.55). These findings are in line with previous studies
(Ramirez-Campillo et al., 2015a,2015b; Sohnlein et al., 2014;
Vaczi et al., 2013). However, the rates of changes are not
similar between studies. Ramirez-Campillo et al. (2015b)
reported that 6 weeks of plyometric training induced mean-
ingful changes in 20-m sprint (ES = −0.5) in 14-y old soccer
players. Whereas, this research team in another study
(Ramirez-Campillo et al., 2015a) with 13-y soccer players
found that 7 weeks of plyometric training had trivial effects
(ES = −0.35) on 20-m sprint performance lower than our
findings. The reason of discrepancy in the rate of training
effects between these findings and those reported by previous
studies in youth soccer players (Meylan & Malatesta, 2009;
Ramirez-Campillo et al., 2015a; Vaczi et al., 2013) might be
due to different individual adaptive responses to plyometric
training (Chaouachi et al., 2014; Saez de Villarreal et al., 2009).
In relation to maturation-effects on sprint performance
after plyometric training, the magnitudes of changes in 20-m
sprint were greater in Post-PHV group compared to others (ES;
−0.66 vs. −0.58 vs. −0.12); however, with comparing maturity
groups the Post-PHV group indicated greater gains than Pre-
PHV group after training (likely vs. possibly training effects).
On the other hand, older youths showed small to moderate
changes whereas Pre-PHV group indicated trivial changes.
With comparing time gains between experimental groups, it
could be meaningful differences when these ability transfers
to soccer-related events (i.e., Post = −0.33 s, Mid = −0.29 s, and
Pre = −0.14 s). It is well known that sprint running perfor-
mance is the product of stride rate and stride length with
numerous components influencing this apparently simple for-
mula. Because both elements are clearly influenced by the
anthropometric characteristics, one of the main possible
explanations for the decrement in the sprint performance
observed in the Post-PHV group could be the anthropometric
change. During maturation, the natural development of sprint
performance occurs due to greater muscular size, increased
limb length, changes to musculotendinous tissue, enhanced
neural and motor development and better movement quality
and coordination (Oliver & Rumpf, 2014). In accordance to
maturation-related sprint development, Meyers, Oliver,
Hughes, Cronin, and Lloyd (2015) and Moran et al. (2016),
reported that an increase in sprint performance appears at
Mid and Post-PHV. The potential mediators of sprinting velo-
city development around peak height velocity could be due to
increase in stride length, accentuated by improved stabiliza-
tion of stride frequency and ground contact times (Moran
et al., 2016). Positive transfer of power and strength gains to
sprint performance has been reported by previous researchers
(Lloyd et al., 2016; Markovic & Mikulic, 2010; Seitz et al., 2014),
thereafter sprint adaptations to plyometric training in older
youth of soccer players.
5. Conclusions
The present data demonstrated that low-volume high-inten-
sity plyometric training, in the amount of 60 foot contacts
per session, on a twice weekly basis, can help to improve
pre-season short distance sprint and jump performance in
youth soccer players. To acutely improve jumping ability and
sprint performance, older children seem to benefit more
than younger children from plyometric training. Although
speculative, these specific training responses seem to be
maturity related, reflecting that the adaptive processes
experienced during 6 weeks of plyometric training could
be influenced by maturity. Regarding the magnitude of
training effects, older youths (i.e., Mid and Post-PHV groups)
indicated greater gains in performance adaptations; how-
ever, meaningful differences were occurred between Post-
PHV group and Pre-PHV group which indicated greater
meaningful effects from 6 weeks plyometric training in ver-
tical jump and 20-m sprint performance. The performance
improvements shown in this study are of great interest for
soccer coaches and are directly applicable to soccer players
in different maturity status. We suggest that plyometric
training might be effective in eliciting gains in jumping
and sprinting abilities in boys, whereas those who are
older may achieve greater meaningful more benefits from
the training in vertical jump and short distance sprint.
Acknowledgments
The authors are grateful to the participants of this study for having
performed maximal efforts until volitional fatigue. There is no financial
support for this project. No funds were received for this study from
National Institutes of Health, Welcome Trust, University, or others.
Disclosure statement
No potential conflict of interest was reported by the authors.
6A. ASADI ET AL.
References
Arazi, H., Coetzee, B., & Asadi, A. (2012). Comparative effect of land and
aquatic based plyometric training on the jumping ability and agility of
young basketball players. South African Journal of Research in Sport,
Physical Education and Recreation,34,1–14.
Asadi, A. (2013). Effects of in-season short term plyometric training on
jumping and agility performance of basketball players. Sport Science for
Health,9, 133–137.
Chaouachi,A.,Othman,B.A.,Hammami,R.,Drinkwater,E.J.,&Behm,D.G.
(2014). The combination of plyometric and balance training improves sprint
and shuttle run performances more often than plyometric-only training
with children. Journal of Strength and Conditioning Research,28,401–412.
Haff, G. G., Carlock, J. M., & Hartman, M. J. (2005). Force-time curve
characteristics of dynamic and isometric muscle actions of elite
women olympic weightlifters. Journal of Strength and Conditioning
Research,19, 741–748.
Hopkins, W. G., Marshall, S., & Batterham, A. (2009). Progressive statistics
for studies in sports medicine and exercise science. Medicine and
Science in Sports and Exercise,41(1), 3–13.
Komi, P. V. (2003). Stretch shortening cycle. In P. V. Komi (Ed.), Strength and
power in sport. Oxford: Blackwell Science.
Lloyd, R. S., Oliver, J. L., Hughes, M. G., & Williams, C. A. (2011). The
influence of chronological age on periods of accelerated adaptation
of stretch-shortening cycle performance in pre and postpubescent
boys. Journal of Strength and Conditioning Research,25, 1889–1897.
Lloyd, R. S., Radnor, J. M., & De Ste Crox, M. B. A. (2016). Changes in sprint
and jump performance after traditional, plyometric and combined
resistance training in male youth pre and post-peak height velocity.
Journal of Strength and Conditioning Research,30, 1239–1247.
Markovic, G., & Mikulic, P. (2010). Neuro-musculoskeletal and performance
adaptations to lower-extremity plyometric training. Sports Medicine,40,
859–895.
Meyers, R. W., Oliver, J. L., Hughes, M. G., Cronin, J. B., & Lloyd, R. S. (2015).
Maximal sprint speed in boys of increasing maturity. Pediatric Exercise
Science,27,8
5–94.
Meylan, C., & Malatesta, D. (2009). Effects of in-season plyometric training
within soccer practice on explosive actions of young players. Journal of
Strength and Conditioning Research,23, 2605–2613.
Meylan, C. M., Cronin, J. B., Oliver, J. L., Hopkins, W. G., & Contreras, B.
(2014). The effect of maturation on adaptations to strength training
and detraining in 11-15-year-olds. Scandinavian Journal of Medicine and
Science in Sports,24, e156–e164.
Mirwald, R. L., Baxter-Jones, A. D., Bailey, D. A., & Beunen, G. P. (2002). An
assessment of maturity from anthropometric measurements. Medicine
and Science in Sports and Exercise,34(4), 689–694.
Mirzaei, B., Norasteh, A. A., & Asadi, A. (2013). Neuromuscular adaptation
to plyometric training: Depth jump versus countermovement jump on
sand. Sport Sciences for Health,9(3), 145–149.
Moran, J., Sandercock, G. R. H., & Ramirez-Campillo, R. (2016). Maturation-
related effect of low-dose plyometric training on performance in youth
hockey players. Pediatric Exercise Science,29, 194-202.
Moran, J., Sandercock, G. R. H., Ramirez-Campillo, R., Meylan, C., Collison, J.,
& Parry, D. A. (2017). Age-related variation in male youth athletes
countermovement jump following plyometric training: A meta-analysis
of controlled trials. Journal of Strength and Conditioning Research,31,
552–565.
Moran, J., Sandercock, G. R. H., Rumpf, D., & Parry, D. A. (2016). Variation in
responses to sprint training in male youth athletes: A meta-analysis.
International Journal of Sports Medicine,38(1), 1-11.
Oliver, J. L., & Rumpf, M. C. (2014). Speed development in youths. In R.
Lloyd & J. Oliver (Eds.), Strength and conditioning for young athletes:
Science and application (pp. 80–93). London/New York: Routledge.
Ramirez-Campillo, R., Burgos, C., Henriquez-Olguin, C., Andrade, D. C.,
Martinez, C., Alvarez, C., . . . Izquierdo, M. (2015a). Effect of unilateral,
bilateral and combined plyometric training on explosive and endur-
ance performance of young soccer players. Journal of Strength and
Conditioning Research,29, 1317–1328.
Ramirez-Campillo, R., Meylan, C. A., Alvarez, C., Henriquez-Olguin, C.,
Martinez, C., Canas-Jamett, R., . . . Izquierdo, M. (2014). Effects of in-
season low-volume high-intensity plyometric training on explosive
actions and endurance of young soccer players. Journal of Strength
and Conditioning Research,28, 1335–1342.
Ramirez-Campillo, R., Meylan, C. M. P., Alvarez-Lepín, C., Henriquez-Olguin,
C., Martinez, C., Andrade, D. C., . . . Izquierdo, M. (2015b). The effects of
interday rest on adaptation to 6-weeks of plyometric training in young
soccer players. Journal of Strength and Conditioning Reserach,29, 972–
979.
Rogol, A. D., Roemmich, J. N., & Clark, P. A. (2002). Growth at puberty.
Journal of Adolescent Health,31, 192–200.
Saez de Villarreal, E., Kells, E., Kraemer, W. J., & Izquierdo, M. (2009).
Determining variables of plyometric training for improving vertical
jump height performance: A meta- analysis. Journal of Strength and
Conditioning Research,23, 495–506.
Saez de Villarreal, E., Requena, B., & Cronin, J. B. (2012). The effects of
plyometric training on sprint performance. A meta-analysis. Journal of
Strength and Conditioning Research,26, 575–584.
Saez de Villarreal, E., Suarez-Arrones, L., Requena, B., Haff, G. G., & Ferrete,
C. (2015). Effects of plyometric and sprint training on physical and
technical skill performance in adolescent soccer players. Journal of
Strength and Conditioning Research,29, 1894–1903.
Sayers, S. P., Harackiewicz, D. V., Harman, E. A., Frykman, P. N., &
Rosenstein, M. T. (1999). Cross-validation of three jump power equa-
tions. Medicine and Science in Sports and Exercise,31, 572–577.
Seitz, L. B., Reyes, A., Tran, T. T., Saez de Villarreal, E., & Haff, G. G. (2014).
Increases in lower-body strength transfer positively to sprint perfor-
mance: A systematic review with meta-analysis. Sports Medicine,44,
1693–1702.
Sohnlein, Q., Muller, E., & Stoggl, T. L. (2014). The effect of 16-week
plyometric training on explosive actions in early to mid-puberty elite
soccer players. Journal of Strength and Conditioning Research,28, 2105–
2114.
Stolen, T., Chamari, K., Castagna, C., & Wisloff, U. (2005). Physiology of
soccer: An update. Sports Medicine,35, 501–536.
Thomas, K., French, D., & Philip, P. R. (2009). The effect of two plyometric
training techniques on muscular power and agility in youth soccer
players. Journal of Strength and Conditioning Research,23, 332–335.
Vaczi, M., Tollar, J., & Meszler, B. (2013). Short term high intensity plyo-
metric training program improves strength, power, and agility in male
soccer players. Journal of Human Kinetics,36,17–26.
Vissing, K., Brink, M., Lønbro, S., Sørensen, H., Overgaard, K., Danborg, K., . . .
Aagaard, P. (2008). Muscle adaptations to plyometric vs. resistance
training in untrained young men. Journal of Strength and Conditioning
Research,22(6), 1799–1810.
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