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The changing characteristics of talented soccer players--a decade of work in Groningen


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Abstract Talent development programmes for professional soccer clubs aim to guide players towards professional level performance. We identify whether the intermittent endurance capacity of these players may have changed over time. Since the 2000/2001 competition season, the intermittent endurance capacity of players in the talent development programmes of two professional soccer clubs was measured annually. A total of 492 players participated, divided across seven age categories (under 13 (U13), U14, U15, U16, U17, U18, U19) and resulting in 953 measurements. Analyses of variance showed an improvement in intermittent endurance capacity from the 2000/2001 season to 2009/2010 of around 50% in all age groups (P < 0.05). A possible explanation is the increased quantity and quality of training over the years. When identifying, developing and selecting young players, scouts, trainers and coaches have to be aware that the current level of soccer and its underlying performance characteristics - such as intermittent endurance capacity - are improving over time. This factor may have consequences for current young players aiming to make it to the top 10 years from now.
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Journal of Sports Sciences
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The changing characteristics of talented soccer players
– a decade of work in Groningen
Marije T. Elferink-Gemser a b , Barbara C.H. Huijgen a , Manuel Coelho-E-Silva c , Koen
A.P.M. Lemmink a d & Chris Visscher a
a Centre for Human Movement Sciences, UMCG, University of Groningen, The Netherlands
b Institute for Studies in Sports and Exercise, HAN University of Applied Sciences, Nijmegen,
The Netherlands
c Faculty of Sport Science and Physical Education, University of Coimbra, Portugal
d School of Sports Studies, Hanze University of Applied Sciences, Groningen, The
Version of record first published: 01 Oct 2012.
To cite this article: Marije T. Elferink-Gemser , Barbara C.H. Huijgen , Manuel Coelho-E-Silva , Koen A.P.M. Lemmink & Chris
Visscher (2012): The changing characteristics of talented soccer players – a decade of work in Groningen, Journal of Sports
Sciences, 30:15, 1581-1591
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The changing characteristics of talented soccer players – a decade of
work in Groningen
Centre for Human Movement Sciences, UMCG, University of Groningen, The Netherlands,
Institute for Studies in Sports
and Exercise, HAN University of Applied Sciences, Nijmegen, The Netherlands,
Faculty of Sport Science and Physical
Education, University of Coimbra, Portugal, and
School of Sports Studies, Hanze University of Applied Sciences, Groningen,
The Netherlands
(Accepted 28 August 2012)
Talent development programmes for professional soccer clubs aim to guide players towards professional level performance.
We identify whether the intermittent endurance capacity of these players may have changed over time. Since the 2000/2001
competition season, the intermittent endurance capacity of players in the talent development programmes of two
professional soccer clubs was measured annually. A total of 492 players participated, divided across seven age categories
(under 13 (U13), U14, U15, U16, U17, U18, U19) and resulting in 953 measurements. Analyses of variance showed an
improvement in intermittent endurance capacity from the 2000/2001 season to 2009/2010 of around 50% in all age groups
(P50.05). A possible explanation is the increased quantity and quality of training over the years. When identifying,
developing and selecting young players, scouts, trainers and coaches have to be aware that the current level of soccer and its
underlying performance characteristics – such as intermittent endurance capacity – are improving over time. This factor may
have consequences for current young players aiming to make it to the top 10 years from now.
Keywords: Intermittent endurance capacity, performance, talent identification, talent development, training
Soccer is the most popular sport in the Netherlands,
with over a million active participants (Royal Dutch
Soccer Association [KNVB], 2008). At many of the
3,417 soccer clubs, children can start playing soccer
from the age of five years. There are about half a
million Dutch youth players under 19 years of age
(n¼569,086). To ensure that the high level of
Dutch soccer performance is maintained, currently
ranked second place by the International Federation
of Association Football (FIFA) (FIFA, 2011),
professional clubs have extensive talent development
programmes. The current procedure to identify
talented players is for young players from the age of
11 years, and sometimes younger, to be observed by
soccer scouts during regional competitions. Those
players who attract the attention of the scouts are
invited to visit the club. At the club, talent training
days are organised in which players are given the
opportunity to convince a team of scouts, expert
trainers, coaches and staff that they should be
selected to join their talent development programme.
Today players can start on a development pro-
gramme in most Dutch professional clubs when they
are around the age of 12 years; however, this has not
always been the case. Until the 2004/2005 season,
most talent development programmes did not start
players any younger than around the age of 14 years.
Soccer has recently grown into a multi-million euro
labour market where the stakes to perform well are
high (Hoffmann, Ging, & Ramasamy, 2002; Lucifora
& Simmons, 2003; Magee & Sugden, 2002). One of
the consequences is that at the professional level,
performance boundaries are pushed constantly to
improve performance, which seems to be the main
reason for this shift towards starting candidate players
on talent development programmes at ever younger
ages. It remains unclear, however, whether earlier
talent identification selection and development (i.e.,
before maturational milestones such as peak height
velocity) is a good solution (Coelho et al., 2010b).
Correspondence: M.T. Elferink-Gemser, Centre for Human Movement Sciences, UMCG, University of Groningen, The Netherlands.
Journal of Sports Sciences, November 2012; 30(15): 1581–1591
ISSN 0264-0414 print/ISSN 1466-447X online Ó2012 Taylor & Francis
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The goal of talent development programmes is to
guide players towards professional status in adult-
hood. To better achieve this aim, insight into the
characteristics of those players who are on the road to
the top is required (Elferink-Gemser, Visscher,
Lemmink, & Mulder, 2004; Williams & Reilly,
2000). One of the key characteristics that can
distinguish between successful and less successful
soccer players is their intermittent endurance capacity
(Reilly, Bangsbo, & Franks, 2000; Visscher, Elferink-
Gemser, & Lemmink, 2006). During a game, high-
intensity activities such as jumping, kicking, tackling,
turning and sprinting are performed repeatedly,
alternating with recovery periods of low-intensity
exercise (Mohr, Krustrup, & Bangsbo, 2003; Spen-
cer, Bishop, Dawson, & Goodman, 2005). Decisive
moments in soccer matches are often preceded by
short, high-intensity sprints in the range of 10–30 m
(Impellizzeri et al., 2008; Rampinini et al., 2007;
Reilly et al. 2000). A high level of intermittent
endurance capacity, which is covered by both the
anaerobic and aerobic energy systems (Lemmink &
Visscher, 2006), is therefore required to meet the
demands of the game (Hoff, 2005; Reilly, 1997).
In talented soccer players, intermittent endurance
capacity improves with age and can be predicted by
their age, their hours of soccer training and their
additional training hours (Roescher, Elferink-Gem-
ser, Huijgen, & Visscher, 2010). Several researchers
have shown that training is a major contributor to the
development of soccer expertise (Helsen, Hodges,
Van Winckel, & Starkes, 2000; Hoff, 2005). In field
hockey, a sport closely related to soccer in terms of
the physiological performance characteristics re-
quired, a combination of age, gender, performance
level and additional training hours, and anthropo-
metrics and motivation can be used to predict
intermittent endurance capacity (Elferink-Gemser,
Visscher, Van Duijn, & Lemmink, 2006). The role of
anthropometric factors, such as height, lean body
mass and body fat percentage, in the increase in
anaerobic and aerobic capacity has also been
illustrated in earlier studies (Gabett, 2002; Malina,
Bouchard, & Bar-Or, 2004).
A recent study on sport selection classified under-
14 soccer players in Portugal as local players and
regional elite players (Coelho e Silva et al., 2010a).
Regional elite players were advanced in their maturity
status, and were heavier, taller, and performed better
in explosive lower limb strength and in repeated
sprints. An additional study from the same group
performed a 2-year follow-up analysis and compared
the growth, maturity status, functional capacities and
sport specific skills of adolescent players who discon-
tinued competitive soccer, and those who continued
and moved to a higher level (Figueiredo, Goncalves,
Coelho e Silva, & Malina, 2009). At baseline,
differences between groups were significant in most
functional capacities. The Ghent Youth Soccer
Project is another example of a multidisciplinary
study of youth soccer players that assessed the
relationships between physical and performance
characteristics and competitive level, controlling for
variation related to maturity (Vaeyens et al., 2006).
The results revealed that non-elite players were
outperformed by elite players in aerobic endurance,
anaerobic power, flexibility, speed, strength and
technical skill (Philippaerts et al., 2006).
Players can only become experts if they deliber-
ately train to improve their performance – in other
words, if they continuously commit effort to suffi-
cient hours of training and remain motivated
(Ericsson, 1998, 2003). Although the importance
of intermittent endurance capacity for soccer players
has been acknowledged, it is unknown whether the
performance levels of current talented players differ
from those of 10 years ago. This is a relevant
question because the game of soccer is constantly
evolving and, as a consequence, the performance
characteristics of successful professional soccer
players have also been changing. An example is the
changing shape of ‘successful’ professional soccer
players with respect to the significant increase in
height and body mass from 1973/1974 to 2003/2004
(Nevill, Holder, & Watts, 2009). Therefore, the goal
of the current study was to investigate whether there
have been changes in the level of the intermittent
endurance capacity and related characteristics (i.e.,
anthropometrics and training hours) in talent devel-
opment programmes over the last 10 years. Results
may yield insight into these changes, which may in
turn help us to understand the dynamic nature of
soccer and provide scouts, trainers and coaches with
information for use in identifying and developing
talented players.
A total of 492 talented soccer players from two
Dutch professional clubs participated in the study.
The players were selected by scouts, trainers, and
coaches and competed at the highest level, meaning
that they belong to the top 0.5% of soccer players in
their age group (KNVB, 2008). They were well
trained and followed a programme of intensive
practice at their respective soccer clubs. In addition,
they trained alone outside the clubs.
Players were tested from 2000/2001 through to the
2009/2010 competitive soccer season. Each year, the
entire youth academy was tested and a comparison
was made between players of a similar age across
different seasons. At the end of every season, the club
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made a decision whether or not a player was allowed
to stay in the youth academy. As a consequence,
some players have been tested only once whereas
others have been tested repeatedly in consecutive
seasons resulting in a total of 953 measurements,
divided across the age groups and seasons. Players
were analysed by age group, starting with under 13
(U13) up to under 19 (U19) leading to a total of
seven age groups. For each age group, scores in the
different seasons were compared to each other. From
the 2000/2001 season to the 2009/2010 season,
measurements were taken annually, with the excep-
tion of 2003/2004, resulting in nine measurement
instances for all the age groups except U13.
Measurements for U13 started in the 2004/2005
season, resulting in measurements for six seasons
compared to nine seasons for the other age groups.
For each age group, Table I gives information about
the number of players tested in the different seasons.
Because the purpose of this study was to investigate
whether players from the same age category perform
differently over the years, we adopted a between
participants design.
All the players were informed of the study proce-
dures before they gave their verbal consent to
participate. The clubs and trainers gave permission
for this study, and procedures were in accordance
with the ethical standards of the Medical Faculty of
the University of Groningen, which conform to the
World Medical Association Helsinki Declaration.
The players completed the interval shuttle run test
(ISRT) on a natural or artificial grass soccer field at
the same location each time. The measurements
were taken at the end of the competitive season,
which generally varied from March to May. Ambient
temperature, humidity and wind conditions were
documented. Measurement sessions were conducted
during regular team playing hours, resulting in
testing which covered nearly all players in the youth
academy. However, players could have missed a part
of the measurement due to, for example, injury or
absence. For each measurement, this was the case for
less than 20% of the players. Therefore, it can be
assumed that the largest part of the missing data is
random, and that it can be expected that the current
data provide a good illustration of performance in
intermittent endurance capacity in talented young
soccer players.
Height, weight and body fat percentage were
measured using standard procedures (Elferink-
Gemser et al., 2004). Body fat percentage was
estimated by means of leg-to-leg bioelectrical im-
pedance (BIA) analysis (Valhalla BIA, Valhalla, Inc.,
San Diego, CA) (Nunez et al., 1997). Bioelectrical
impedance analysis is often used to estimate fat free
mass and fat components (Lukaski, 1990). The
method used in this study proved to be reliable for
measuring per cent body fat, and results correlated
highly with per cent body fat as measured with
underwater weighing and dual X-ray absorptiometry
(Nunez et al., 1997). Lean body mass was calculated
from body weight and percentage body fat.
Training characteristics
Date of birth and training characteristics, cumulated
years of soccer experience, hours of soccer practice
per week and hours of additional practice per week
were documented. In a questionnaire, players were
asked how many years they had played competitive
soccer as a measure of cumulated years of soccer
experience. Players filled in the number of soccer
training sessions they attended per week, the dura-
tion of these training sessions in that competitive
season and how many soccer matches they played
per week. In the Netherlands, the competitive soccer
season lasts approximately 43 weeks, starting in
September and ending in June. In addition, players
were asked how many hours per week they trained in
other sports, or by themselves, throughout the year.
Time spent in physical education at school, which
was on average 2.5 hours per week, was excluded.
Interval shuttle run test
Intermittent endurance capacity was measured using
the interval shuttle run test (ISRT) (Lemmink,
Verheijen, & Visscher, 2004a; Lemmink, Visscher,
Lambert, & Lamberts, 2004b). During the ISRT,
players are required to run back and forth on a 20 m
course with pylons set 3 m in front of the turning
lines (Figure 1). The frequency of the sound signals
on a pre-recorded compact disc increases in such a
way that running speed is increased by 1 km h
every 90 seconds from a starting point of 10 km h
and by 0.5 km h
every 90 seconds from 13 km
. Every 90-second period was divided into two
45-second periods in which players run for 30 sec-
onds and walk for 15 seconds (work to rest ratio
2:1). Players were instructed to complete as many
runs as possible. The test stopped when the
participants could not keep up the pace (i.e., were
more than 3 m away from the 20 m lines on two
consecutive audio signals) or felt unable to complete
the run. The number of fully completed 20 m runs
was recorded as the test score. The reliability and
validity of the ISRT for intermittent sport players has
been confirmed (Lemmink et al., 2004a, 2004 b).
A decade of Groningen soccer studies 1583
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Statistical analyses
For every age group in every season, mean scores and
standard deviations were calculated for the ISRT.
Furthermore, mean scores and standard deviations
for other possible relevant characteristics – such as
anthropometrics and training (soccer and additional)
– were calculated by age group and season. For each
age group, mean differences between competitive
seasons and effects sizes (d) were calculated. Cohen
(1988) suggested that effect sizes around 0.20 are
small, around 0.50 are moderate and around 0.80 are
large. Separate one-way analyses of variance (ANO-
VAs) were conducted for each age grouping to
examine possible differences in the scores within an
age group over time (2000/2001 through to 2009/
2010) followed by Bonferonni post-hoc tests. The
ISRT scores over the seasons are illustrated in Figure
3, separately for each age group. Trend lines indicate
the change over time for each age group. The
difference in runs from the 2000/2001 season until
the 2009/2010 season and the percentage change over
these seasons was calculated by means of trend lines.
An alpha of 0.05 was adopted for all significance tests.
The characteristics of the players per season in each
age group are summarised in Table I. No significant
changes over the years were found for height and
weight (P40.05), except for U14 (P50.05).
Body fat percentages decreased for all age groups
(P50.05), except for U14 (P40.05). With the
exception of U14 and U15, no differences were
identified for lean body mass (P40.05). No
differences were identified for cumulative soccer
years (P40.05) or hours of additional practice per
Figure 1. The course for the interval shuttle run test (ISRT).
Figure 2. Intermittent endurance capacity of talented soccer players U13, U14, U15, U16, U17, U18, and U19 between the 2000/2001,
2005/2006 and 2009/2010 season.
1584 M. T. Elferink-Gemser et al.
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week (P40.05). This was the case for all age
groups. In contrast, the hours of soccer practice per
week increased over the years for all age groups
(P50.05), except for U14 (P40.05).
The findings from the ANOVAs that examined
differences in ISRT scores for each age group from
2000/2001 to 2009/2010 are presented in Table II.
In Table III, mean differences in number of runs on
Figure 3. Intermittent endurance capacity of talented soccer players U13, U14, U15, U16, U17, U18, and U19 from the 2000/2001 season
until the 2009/2010 season.
A decade of Groningen soccer studies 1585
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Table I. Intermittent endurance capacity, anthropometrics, and training characteristics of talented soccer players U13, U14, U15, U16, U17, U18, and U19 from the 2000/2001 season until the 2009/
2010 season.
Age group Season NISRT (runs) Height (m) Weight (kg) Body fat %
Lean body
mass (kg)
Cum. soccer
Soccer practice/
week (h)
Additional practice/
week (h)
U13 2004/2005 20 81.0 +17.4 1.52 +0.071.5 40.7 +7.8 10.7 +2.6 36.2 +6.1 6.3 +1.3 5.9 +0.4 2.7 +3.2
2005/2006 54 79.7 +20.7 1.55 +0.10 43.1 +9.3 6.9 +2.0 40.1 +8.2 6.1 +1.2 6.0 +0.6 2.4 +2.6
2006/2007 13 87.2 +21.1 1.51 +0.08 39.5 +4.8 6.9 +1.8 36.7 +4.4 - - -
2007/2008 19 100.4 +18.2 1.55 +0.11 40.7 +4.6 10.7 +1.2 36.3 +4.8 6.1 +1.9 7.0 +0.0 -
2008/2009 39 99.5 +20.3 1.54 +0.08 40.9 +6.0 7.7 +2.7 37.6 +5.2 6.2 +1.3 6.2 +0.9 1.5 +0.0
2009/2010 26 95.2 +15.3 1.51 +0.06 40.4 +4.0 11.1 +2.1 37.2 +5.3 6.8 +1.2 6.0 +0.5 -
Total 171 88.8 +21.4 1.53 +0.08 41.3 +7.0 8.2 +2.7 38.0 +6.5 6.2 +1.3 6.2 +0.7 2.5 +2.8
U14 2000/2001 13 58.8 +15.5 1.61 +0.08 47.6 +6.6 9.1 +2.6 43.4 +6.8 7.2 +1.5 6.0 +1.3 3.8 +1.7
2001/2002 9 86.6 +18.3 1.67 +0.07 57.2 +8.1 9.7 +1.4 51.6 +7.6 7.4 +1.2 6.5 +0.8 3.9 +1.9
2002/2003 4 92.8 +19.0 1.71 +0.08 61.0 +9.8 6.9 +1.1 56.8 +9.7 6.3 +2.1 7.5 +0.0 3.7 +3.8
2004/2005 14 92.1 +12.5 1.60 +0.07 47.3 +6.5 9.1 +2.4 43.0 +5.7 7.2 +1.1 5.8 +0.7 3.8 +3.7
2005/2006 21 106.5 +10.3 1.67 +0.09 54.3 +9.6 7.2 +2.7 50.7 +8.2 7.6 +1.4 6.1 +0.3 2.9 +2.9
2006/2007 12 98.2 +14.6 1.60 +0.05 44.9 +5.4 7.3 +2.0 41.6 +4.7 6.7 +1.3 6.0 +1.2 1.1 +0.6
2007/2008 15 101.5 +11.7 1.62 +0.07 48.5 +6.7 8.1 +2.3 44.5 +6.3 6.9 +1.4 6.2 +0.6 1.8 +1.5
2008/2009 20 111.1 +18.4 1.59 +0.07 46.3 +6.0 7.4 +2.5 43.1 +6.0 7.4 +1.5 6.5 +1.1 2.9 +3.2
2009/2010 4 90.5 +16.2 1.57 +0.10 42.8 +4.3 6.5 +2.3 39.9 +3.1 7.5 +1.3 6.2 +0.4 -
Total 112 95.7 +21.0 1.62 +0.08 49.1 +8.1 8.0 +2.5 45.5 +7.6 7.2 +1.4 6.2 +0.9 2.9 +3.0
U15 2000/2001 27 72.3 +16.9 1.69 +0.08 55.2 +9.8 10.1 +3.4 49.4 +7.6 7.9 +1.9 6.0 +0.8 3.8 +3.0
2001/2002 11 81.8 +18.1 1.66 +0.07 56.2 +7.6 10.1 +2.6 50.5 +6.3 7.8 +1.5 6.6 +1.1 4.5 +3.6
2002/2003 18 86.4 +19.1 1.69 +0.07 57.0 +8.9 7.4 +2.2 52.8 +8.2 8.1 +1.5 7.0 +0.8 2.8 +3.1
2004/2005 23 99.4 +19.3 1.66 +0.10 54.9 +9.1 9.9 +3.0 49.4 +7.8 7.5 +2.1 6.8 +1.2 2.9 +3.1
2005/2006 22 98.5 +20.3 1.72 +0.07 62.5 +8.2 7.3 +1.5 57.9 +7.2 8.0 +1.7 6.2 +0.5 2.8 +3.5
2006/2007 16 107.7 +17.3 1.70 +0.08 57.8 +10.3 7.1 +2.9 53.6 +8.7 8.2 +1.7 6.0 +0.5 2.1 +2.2
2007/2008 21 112.5 +12.4 1.71 +0.07 58.9 +9.3 8.7 +2.8 53.8 +8.7 7.8 +1.6 6.4 +0.8 1.7 +1.2
2008/2009 17 111.5 +15.7 1.71 +0.07 60.4 +5.7 9.1 +2.4 54.9 +5.2 8.0 +1.9 6.8 +0.8 2.6 +1.9
2009/2010 6 110.3 +21.7 1.72 +0.08 63.5 +7.3 7.6 +1.7 57.1 +6.7 8.5 +1.0 6.9 +1.2 -
Total 161 96.3 +22.4 1.69 +0.08 57.9 +8.9 8.8 +2.9 52.6 +7.9 7.9 +1.7 6.5 +0.9 2.9 +3.0
U16 2000/2001 17 79.4 +28.0 1.73 +0.08 62.2 +7.4 10.9 +3.1 55.4 +6.3 8.5 +1.7 6.4 +1.8 3.4 +2.5
2001/2002 18 86.5 +11.7 1.73 +0.08 62.3 +8.2 10.8 +4.5 55.5 +6.5 8.3 +2.0 7.1 +0.7 3.2 +2.6
2002/2003 15 80.2 +19.9 1.75 +0.05 63.7 +6.0 8.7 +3.9 58.0 +4.9 9.2 +1.2 7.4 +1.2 3.6 +2.6
2004/2005 18 99.1 +12.1 1.77 +0.06 63.9 +7.5 10.1 +2.9 57.3 +5.7 7.8 +1.8 7.6 +0.8 2.4 +2.2
2005/2006 17 108.5 +22.2 1.76 +0.07 67.7 +5.8 7.8 +2.3 62.3 +4.1 8.6 +2.1 8.3 +0.8 1.7 +2.0
2006/2007 22 99.5 +25.6 1.75 +0.06 64.4 +6.8 8.1 +2.0 59.1 +5.8 8.2 +1.7 7.3 +0.5 1.8 +1.7
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Table I. (Continued).
Age group Season NISRT (runs) Height (m) Weight (kg) Body fat %
Lean body
mass (kg)
Cum. soccer
Soccer practice/
week (h)
Additional practice/
week (h)
2007/2008 16 131.9 +17.2 1.75 +0.07 64.4 +7.1 9.1 +3.4 58.4 +6.2 8.7 +1.3 8.3 +1.0 1.6 +1.1
2008/2009 15 115.1 +16.7 1.76 +0.06 64.8 +8.2 8.2 +3.4 59.3 +6.8 9.1 +1.7 7.4 +1.2 1.5 +2.1
2009/2010 9 103.7 +7.1 1.71 +0.09 63.2 +9.0 8.7 +2.9 57.6 +8.9 8.9 +1.6 7.4 +1.2 -
Total 147 100.0 +24.9 1.75 +0.07 64.1 +7.3 9.2 +3.3 58.1 +6.2 9.1 +1.2 7.5 +1.2 2.5 +2.3
U17 2000/2001 21 85.8 +17.5 1.78 +0.05 66.6 +6.0 9.9 +2.6 59.9 +5.2 9.8 +1.3 6.5 +1.0 2.2 +1.8
2001/2002 12 91.8 +14.3 1.76 +0.07 70.2 +5.4 11.0 +3.0 62.4 +3.6 9.8 +1.7 7.5 +1.8 4.2 +4.0
2002/2003 18 87.1 +22.4 1.78 +0.07 68.6 +10.9 9.7 +4.3 61.6 +8.0 10.1 +1.6 7.1 +0.9 3.8 +2.6
2004/2005 19 109.9 +14.8 1.76 +0.07 65.9 +7.6 9.8 +2.9 59.4 +6.8 10.0 +1.6 8.1 +1.2 3.3 +4.8
2005/2006 15 96.4 +21.3 1.78 +0.08 68.2 +8.8 8.1 +2.0 62.7 +8.2 9.9 +1.7 8.7 +1.2 2.3 +3.0
2006/2007 16 104.2 +23.8 1.77 +0.08 68.3 +5.6 7.7 +2.0 63.0 +5.1 10.4 +1.4 9.5 +1.6 1.8 +2.9
2007/2008 17 127.6 +16.8 1.79 +0.05 73. +8.8 11.0 +2.5 65.1 +8.3 9.5 +2.0 9.4 +1.5 1.0 +1.3
2008/2009 13 124.3 +14.8 1.77 +0.07 69.7 +7.7 10.4 +2.5 62.5 +7.0 9.4 +0.9 9.4 +1.6 -
2009/2010 7 118.0 +9.9 1.79 +0.06 68.6 +7.4 8.7 +3.6 62.4 +5.0 10.4 +1.5 7.7 +0.6 -
Total 138 103.5 +23.4 1.77 +0.07 68.7 +7.9 9.6 +3.0 62.0 +6.7 9.9 +1.5 8.1 +1.7 2.5 +2.3
U18 2000/2001 27 91.1 +18.5 1.77 +0.08 69.7 +8.4 7.0 +2.3 64.7 +7.3 10.0 +2.7 7.2 +1.7 1.8 +1.6
2001/2002 13 87.6 +16.9 1.80 +0.06 70.8 +7.7 7.0 +3.0 65.8 +7.0 10.8 +1.2 7.6 +1.3 2.0 +2.5
2002/2003 11 90.3 +23.8 1.78 +0.07 70.7 +4.9 7.5 +1.5 65.4 +4.3 9.9 +1.8 7.0 +1.0 3.5 +2.9
2004/2005 5 100.2 +22.9 1.76 +0.05 67.1 +7.1 6.5 +1.8 62.7 +6.2 11.5 +0.7 7.5 +0.0 2.2 +2.6
2005/2006 19 115.1 +19.3 1.81 +0.08 74.0 +6.2 7.9 +2.2 68.1 +5.9 11.5 +0.9 9.3 +2.3 2.6 +2.4
2006/2007 9 118.9 +8.4 1.83 +0.08 74.7 +7.7 7.3 +2.5 69.2 +6.3 11.9 +0.8 8.8 +0.6 3.2 +2.6
2007/2008 12 121.4 +13.4 1.79 +0.09 73.1 +8.0 11.0 +3.9 64.9 +6.0 9.9 +3.1 9.8 +0.8 1.4 +1.7
2008/2009 24 138.4 +20.9 1.79 +0.06 72.3 +5.8 9.1 +3.2 65.7 +5.6 10.8 +1.8 9.0 +0.9 -
2009/2010 16 117.6 +16.9 1.79 +0.07 72.0 +6.7 10.5 +4.1 69.3 +5.0 10.8 +1.9 8.7 +0.9 -
Total 137 110.4 +25.5 1.79 +0.07 71.7 +7.1 8.1 +2.9 66.0 +6.2 10.6 +2.0 8.3 +1.7 2.5 +2.3
U19 2000/2001 10 94.2 +26.2 1.78 +0.05 74.9 +7.5 8.5 +2.2 68.4 +5.7 12. +1.2 8.2 +2.2 0.0 +1.5
2001/2002 15 75.3 +20.6 1.77 +0.06 72.1 +6.7 7.8 +2.5 66.5 +6.0 11.5 +1.9 7.5 +1.6 1.5 +1.8
2002/2003 9 98.1 +10.7 1.80 +0.07 72.7 +7.0 8.8 +1.7 66.3 +6.4 12.7 +0.9 6.5 +0.9 4.5 +6.8
2004/2005 8 106.5 +17.1 1.79 +0.06 69.5 +7.6 5.0 +2.4 66.0 +7.1 10.8 +2.3 8.1 +0.8 1.6 +0.7
2005/2006 11 115.7 +25.8 1.77 +0.05 68.0 +4.6 9.5 +2.0 61.5 +3.4 11.7 +2.1 9.5 +2.5 3.2 +4.4
2006/2007 8 123.4 +11.5 1.84 +0.07 77.6 +7.0 6.9 +1.9 72.1 +5.9 12.5 +0.5 9.4 +0.7 0.9 +0.6
2007/2008 11 119.2 +12.8 1.81 +0.08 74.5 +8.6 11.2 +2.2 66.1 +6.6 11.1 +2.4 9.8 +0.8 2.0 +1.2
2008/2009 8 127.8 +25.2 1.77 +0.10 72.6 +10.6 11.7 +3.9 64.0 +8.1 10.8 +3.2 10.0 +10.9 -
2009/2010 7 109.7 +23.0 1.83 +0.05 76.8 +7.6 8.6 +2.7 69.4 +7.0 11.6 +0.9 9.0 +0.0 -
Total 87 105.4 +25.8 1.79 +0.07 73.4 +7.7 8.6 +3.1 66.0 +6.2 11.7 +1.9 8.7 +1.9 2.5 +2.3
A decade of Groningen soccer studies 1587
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the ISRT are shown as well as their effect sizes. Post-
hoc tests illustrate which competitive seasons differ
significantly from each other for talented soccer
players U13 up to U19.
Figures 2 and 3 illustrate the increase in the
intermittent endurance capacity of talented soccer
players U13, U14, U15, U16, U17, U18 and U19
from 2000/2001 to 2009/2010. An overall improve-
ment of more than 50% was found for all age groups.
We examined whether there were changes in the
intermittent endurance capacity of players in talent
development programmes at professional soccer
clubs over the last decade. Annual measurements
were taken for almost 500 players belonging to the
talent development programme of either one of two
professional soccer clubs, aged U13, U14, U15,
U16, U17, U18 and U19, starting from the 2000/
2001 competitive season. We analysed our data with
analyses of variance. The limitation of this approach
is that it lacks information on the repeated measure
effect, i.e., some players have been measured only
once whereas others have been measured more
frequently. Nevertheless, because age groups were
compared with each other and each player was part
of a particular age group during one season only, no
repeated measures were present within the analyses
presented. The results showed that the intermittent
endurance capacity of current players is considerably
higher than that of the players at the same
competitive level 10 years ago across all age
categories. The percentage improvements were
moderate to large and over 50% on average. This
means that the performance of players on the ISRT a
decade ago was only two thirds of current perfor-
mance on the same test for intermittent endurance
A possible explanation for the better performances
on the ISRT may be the increase in training hours.
However, we have to be careful in interpreting these
results since the number of soccer-specific as well as
additional training hours was based on an estimation
of the average hours of training per week and not, for
example, on daily training logs. The results showed
that over the years, extra training sessions were
introduced in the talent development programmes,
whereas no such trend has been observed for
additional training hours. Currently, most players
in the younger age categories say they spend around
6 hours per week on soccer training, 2 hours on
additional training as well as playing one game per
week on the weekend. In the older age categories,
most players spend around 10 hours per week on
soccer training, with additional training and games
similar to the younger players. It seems, however,
unlikely that the extra hours of training can explain
the huge improvement in intermittent endurance
capacity. According to the multilevel model for
intermittent endurance capacity, every additional
hour of soccer training only accounts for an
improvement of 3.5 runs on the ISRT (Roescher
et al., 2010), whereas we found a more than tenfold
It may be that the quality of training plays a much
larger role (Ericsson, 2003). In comparison to 10
years ago, trainers in talent development pro-
grammes are more often highly qualified. The level
of a coach’s knowledge and skills in various areas
affects the performance of an athlete (Abraham,
Collins, & Martindale, 2006). Along with higher
quality training, players could get more from their
training if they feel responsible for the progress they
make. Unfortunately, we have no measures for these
variables over the entire study period making it
difficult to draw such conclusions. Other researchers
have shown that successful athletes seem to get more
from their practice sessions when performing simi-
larly large numbers of hours of practice and, as a
consequence, are better able to improve their
performance (Cleary & Zimmerman, 2001; Elfer-
ink-Gemser, Visscher, Lemmink, & Mulder, 2007;
Ertmer & Newby, 1996; Jonker, Elferink-Gemser,
Toering, Lyons, & Visscher, 2010). Elite youth
soccer players are known to score higher on
reflection and effort than non-elite counterparts
(Toering, Elferink-Gemser, Jordet, & Visscher,
2009). This means that they may be more aware of
their strong and weak points, and more willing to
exert effort in training and during games and, as a
consequence, improve themselves to a greater extent.
The results of the present study clearly illustrate
the evolving nature of soccer and the need for scouts,
trainers and coaches to constantly anticipate this
evolution when selecting and training elite players. In
modern elite soccer, the total distances covered are
much greater than 30 years ago (Bradley et al., 2009;
Reilly & Thomas, 1976). Compared to former days,
Table II. ANOVA’s comparing the intermittent endurance
capacity from the 2000/2001 season until the 2009/2010 season
of talented soccer players U13, U14, U15, U16, U17, U18, and
Age group F-value Degrees of freedom P-value
Between Within
U13 7.36 5 165 50.001
U14 15.33 8 103 50.001
U15 13.08 8 152 50.001
U16 12.15 8 138 50.001
U17 11.74 8 129 50.001
U18 16.01 8 128 50.001
U19 6.72 8 66 50.001
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Table III. Mean differences in number of runs on the ISRT (D), effect sizes (d) and post-hoc tests comparing the intermittent endurance capacity from the 2000/2001 season until the 2009/2010 season
of talented soccer players U13, U14, U15, U16, U17, U18, and U19.
Season U13 U14 U15 U16 U17 U18 U19
2000/2001 2001/2002 - 727.8* 1.64 79.6 0.54 77.1 0.33 76.0 0.38 3.5 70.20 19.9 70.80
2002/2003 - 734.0* 1.96 714.2 0.78 70.8 0.03 71.3 0.06 0.8 70.04 73.5 0.19
2004/2005 - 733.3* 2.37 727.2* 1.49 719.7 0.91 724.2* 1.49 79.1 0.44 76.6 0.56
2005/2006 - 747.8* 3.62 726.2* 1.40 29.2* 1.15 710.6 0.54 724.0* 1.27 720.6 0.83
2006/2007 - 739.4* 2.62 735.4* 2.07 720.1 0.75 718.4 0.88 727.8* 1.94 728.2 1.44
2007/2008 - 742.7* 3.11 740.3* 2.71 752.5* 2.26 741.8* 2.44 730.3* 1.88 724.0 1.21
2008/2009 - 752.3* 3.07 739.3* 2.40 735.8* 1.55 738.5* 2.38 747.3* 2.40 725.7 1.31
2009/2010 - 731.7* 2.00 738.1* 1.95 724.3 1.19 32.2* 2.26 726.5* 1.50 719.4 0.63
2001/2002 2002/2003 - 76.2 0.33 74.6 0.25 6.3 70.39 4.6 0.25 72.7 0.13 723.4 1.40
2004/2005 - 75.5 0.35 717.6 0.94 712.6 1.06 718.2 1.24 712.6 0.63 726.4 1.65
2005/2006 - 720.0* 1.34 716.6 0.87 722.0* 1.24 74.7 0.25 727.5* 1.52 740.5* 1.73
2006/2007 - 711.6 0.70 725.9* 1.46 713.0 0.65 712.4 0.63 731.3* 2.35 748.1* 2.88
2007/2008 - 714.9 0.97 730.7* 1.98 745.4* 3.09 735.8* 2.29 733.8* 2.22 743.9* 2.56
2008/2009 - 724.5* 1.34 729.7* 1.75 726.6* 1.98 732.6* 2.23 750.8* 2.67 745.6* 2.28
2009/2010 - 73.9 0.23 728.5 1.43 717.2 1.78 726.3 2.13 730.0* 1.78 739.2* 1.58
2002/2003 2004/2005 - 0.7 70.04 713.0 0.68 718.9 1.15 722.8* 1.20 79.9 0.42 78.4 0.59
2005/2006 - 713.8 0.90 712.0 0.61 728.3* 1.34 79.3 0.43 724.8* 1.14 717.1 0.89
2006/2007 - 75.4 0.32 721.2* 1.17 719.3 0.84 717.1 0.74 728.6* 1.60 724.7 2.28
2007/2008 - 78.7 0.55 726.1* 1.62 751.7* 2.78 740.5* 2.05 731.1* 1.61 720.5 1.79
2008/2009 - 718.3 0.98 725.1* 1.44 734.9* 1.90 737.2* 1.96 748.1* 2.15 722.2 1.53
2009/2010 - 2.3 70.13 23.9 1.17 723.5 1.57 730.9* 1.78 727.4* 1.32 715.8 0.65
2004/2005 2005/2006 1.3 0.07 714.5 1.26 1.0 70.05 79.5 0.53 13.5 0.74 714.9 0.70 714.0 0.42
2006/2007 76.2 0.32 76.1 0.45 78.3 0.45 70.4 0.02 5.8 0.29 718.7 1.08 721.7 1.16
2007/2008 719.4* 1.09 79.4 0.78 713.1 0.81 732.8* 2.21 717.6 1.12 721.2 1.13 717.5 0.84
2008/2009 718.5* 0.98 719.0* 1.21 712.1 0.69 716.1 1.10 714.4 0.97 738.2* 1.74 719.1 0.99
2009/2010 714.2 0.87 1.6 70.11 710.9 0.53 74.6 0.29 78.1 0.64 717.4 0.86 712.8 0.16
2005/2006 2006/2007 77.5 0.36 8.4 70.66 79.2 0.49 9.1 70.38 77.8 0.35 73.8 0.26 77.6 0.39
2007/2008 720.7* 1.06 5.1 70.45 714.1 0.83 723.3* 1.18 731.2* 1.63 76.3 0.38 73.5 0.17
2008/2009 719.8* 0.97 74.5 0.31 713.1 0.72 76.6 0.34 727.9* 1.52 723.3* 1.16 75.1 0.47
2009/2010 715.5* 0.85 16.0 71.78 711.9 0.56 4.9 70.29 721.6 1.30 72.5 0.14 1.2 0.25
2006/2007 2007/2008 713.2 0.67 73.3 0.25 74.8 0.32 732.4* 1.49 723.4* 1.14 72.5 0.22 4.2 70.35
2008/2009 712.3 0.59 712.9 0.78 73.8 0.23 715.7 0.72 720.1 1.01 719.5 1.22 2.5 70.22
2009/2010 78.1 0.43 7.7 70.50 72.6 0.13 74.2 0.22 713.8 0.76 1.2 70.10 8.9 70.75
2007/2008 2008/2009 0.9 70.05 79.6 0.62 1.0 0.07 16.7 0.99 3.3 70.21 717.0 0.97 78.6 0.43
2009/2010 5.1 70.31 11.0 0.78 2.2 0.12 28.2* 2.14 9.6 70.70 3.8 70.25 9.5 70.51
2008/2009 2009/2010 4.2 70.24 20.6 1.19 1.2 0.06 11.5 0.89 6.3 70.30 20.7* 71.09 18.1 70.75
A decade of Groningen soccer studies 1589
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the current amount of high-intensity running, which
is similar in the English League to the Italian Serie A
and the Spanish Primera Division (Di Salvo et al.,
2007; Mohr et al., 2003) is very high (Bradley et al.,
2009). A quantitative comparative analysis of English
League matches played in the 1991/1992 and 1997/
1998 seasons further supports evidence for increased
intensity during modern elite soccer. With changing
game requirements, players aiming to make it to the
top need well-developed interval endurance capacity
since in highly trained young soccer players, fitness
levels are an important determinant of match
running performance (Buchheit, Mendez-Villanue-
va, Simpson, & Bourdon, 2010).
In conclusion, it is advised to consider how soccer
will evolve in future when measuring and interpret-
ing the interval endurance capacity of players on a
regular basis. As a consequence, when working with
reference values to interpret the players’ level of
performance in certain tests, it is very important to
update these reference values on a regular basis. In
other words, when identifying, developing and
selecting players, scouts, trainers and coaches have
to be aware that the current level of soccer and its
underlying performance characteristics – such as
intermittent endurance capacity – have increased
over the years and may well continue to improve in
future. This factor likely has consequences for
training young players aiming to excel 10 years
from now.
We thank all players, trainers, and staff of the soccer
clubs FC Groningen and Sc Heerenveen for their
continued cooperation. In addition, we thank the
sports science students of the Centre for Human
Movement Sciences in Groningen for their help in
gathering the data.
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... Soccer is one of the sports where the RAE is observed at every level, from youth players up to the senior level, from recreational to national, international, and the absolute elite level-the FIFA World Cup. This comes as no surprise, given that soccer is the world's largest sport and has an increasingly high degree of competition and increasingly early selection [51]. Furthermore, soccer is a sport in which players benefit from being physically precocious [52]. ...
... In soccer, as in sports in general, the competition is growing increasingly fierce, and more and more players invest more and more time, especially as salaries and transfer values are increasing almost exponentially [64][65][66]. Furthermore, Elferink-Gemser et al. [51] also reported a trend of increasing physical demand in soccer. Thus, the RAE could be expected to become stronger over time. ...
... This indicates that the selection procedures are probably even more focused on present performance than on future prospects. Thus, the more physically developed boys will be picked over the slower developers, favoring the relatively earlier born [51]. ...
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The relative age effect (RAE) is a statistical bias observed across sport contexts and consists of a systematic skewness in birth date distribution within an annual-age cohort. In soccer, January 1 st is the common cut-off date when categorizing players in competitions according to their chronological age, which potentially disadvantages those within the cohort who were born later in the year. Thus, relatively older soccer players in their cohort can be favored in talent identification, selection, and development. The aim of the current study was to investigate the variations in RAE in male and female international youth world-cup tournaments (U17 and U20) in the period from 1997–2019 and in international senior world-cup-tournaments from 2006–2019. A total of 20,401 soccer players participating in 47 different tournaments were analyzed. The birthdate distributions were categorized into four quartiles (January-March, Q1; April-June, Q2; July-September, Q3; October-December, Q4) and compared to a uniform distribution using Chi-square analysis with Cramer’s V ( Vc ) as a measure of effect size. Based on the existing data concerning RAE in elite junior and senior soccer, it was hypothesized that: (I) the RAE is present in youth soccer world cup tournaments but is stronger in male players than in female players; (II) the younger the soccer players, the stronger the RAE; and (III) the RAE in world cup soccer tournaments has strengthened over time. All these hypotheses were supported by the data; novel findings included that the effect has now entered women’s soccer, and in men’s soccer it persists into senior world cup tournaments. Thus, a strong RAE bias occurs in selection among elite soccer players competing in international world cup tournaments.
... For example, elite athletes complete between 800-1200 training hours per year in typical endurance sports such as cross-country skiing [19][20][21][22], rowing [23,24], triathlon [25], and swimming [1]. In more technically demanding sports such as soccer [26], handball [27], and athletics [28,29], elite athletes complete between 500-700 annual training hours. ...
... The significant difference in weekly training volume between the five sport types, indicated that student athletes playing soccer or other team and ball sports trained fewer hours per week than student athletes in endurance sports, weight-bearing sports, and other sports ( Table 2). Previous research indicates that elite athletes in typical endurance sports train between 800-1200 hours per year [1,19,21,22,24,25], while elite athletes in more technically demanding sports train approximately 500-700 hours per year [26][27][28][29]. As such, the findings from the present study correspond with already existing reference values for training volume. ...
... An unexpected finding is that student athletes in weight-bearing sports have a similar weekly training volume to endurance and other sports student athletes. Based on the literature [26][27][28][29], one would expect student athletes in weight-bearing sports to train fewer hours per week, with greater similarity to those playing soccer and other team and ball sports. A possible explanation for this finding is that gymnastics was included in the weight-bearing category and is a sport requiring high training volume for high-standard performance [48]. ...
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This cross-sectional study examined self-reported weekly training volume and perceived training distress in Norwegian student athletes according to gender, type of sport, school program, and school year. The Norwegian version of the Multicomponent Training Distress Scale (MTDS-N) was completed by 608 student athletes (M age = 17.29 ± .94). Univariate and multivariate techniques were used in data analyses. Results revealed significant differences in weekly training volume between sport types. No significant differences in weekly training volume were found for gender, school year, or school program. However, a multivariate effect was found for gender, with females perceiving higher levels of training distress than males. A multivariate interaction effect between school year and training volume was also observed. We recommend that practitioners use a conceptual framework to periodize training and monitor training distress in student athletes, particularly in females, to preserve physiological and psychological well-being and ensure a progressive training overload leading to positive performance development.
... The purpose of a soccer academy is to develop players to represent the first team, thereby reducing the financial strain of having to buy players and/or potentially profiting from their sale (1). To develop more high-quality home-grown players, the English Premier League (EPL), the Football Association (FA) and representatives from the Football League, developed a strategic plan known as the 'Elite Player Performance Plan' (EPPP) (2). ...
Purpose: To audit the current provision of performance nutrition services provided to male adolescent players within academies from the English soccer leagues. Methods: Practitioners from all eighty-nine academies (status categorised as one-four according to the Elite Player Performance Plan, EPPP) completed an online survey to audit: a) job role/professional accreditation status of persons delivering nutrition support, b) activities inherent to service provision, c) topics of education, d) on-site food, fluid and supplement provision and e) nutritional related data collected for objective monitoring. Results: More full-time accredited nutritionists are employed within category one (14/26) versus category two (0/18), three (1/41) and four (0/4). Respondents from category one clubs report more hours of monthly service delivery (62 ± 57 h) than category two (12 ± 9 h), three (14 ± 26 h) and four (12 ± 14 h), inclusive of one-to-one player support and stakeholder education programmes. Category one practitioners reported a greater prevalence of on-site food, fluid and supplement provision on training and match days. Across all categories, players from the professional development phase receive more frequent support than players from the youth development phase, despite the latter corresponding to the most rapid phase of growth and maturation. Conclusion: We report distinct differences in the extent of service provision provided between categories. Additionally, players from all categories receive nutrition support from non-specialist staff. Data demonstrate that performance nutrition appears an under-resourced component of academy sport science and medicine programmes in England, despite being an integral component of player development.
... 8,19 It may also reflect the increase in youth football development intensification over the last decade and its association with a greater injury odds ratio and greater mechanical stress on the growth plate of the lower limbs. 26,27 Lastly, the unique specificity of our cohort of youth elite footballers from a Middle Eastern country raises the potential impact of ethnicity on injury pattern. 28 The hip-pelvis was the most common body region affected by the physeal injuries accounting for 45% of all time-loss physeal injuries. ...
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Introduction Physeal injuries have been overlooked in epidemiological research in youth sports. Our prospective study investigated the incidence, severity, and burden of physeal injuries in a youth elite football academy. Methods 551 youth male football players from Under-9 to Under-19 were included and observed over four consecutive seasons. Injuries involving the physis were diagnosed and recorded according to type, location, and diagnosis. Injury incidence (II), severity (days lost), and injury burden (IB) were calculated per squad per season (25 players/squad). Results There were 307 physeal injuries: 262 apophyseal- (85%), 26 physeal- (9%), 2 epiphyseal- (1%) and 17 other physeal-injuries (5%) with 80% (n=245) causing time-loss. The overall mean incidence of time-loss physeal injuries was 6 injuries/squad-season leading to a total of 157 days lost/squad-season. The U-16s had the highest burden with 444 days lost per squad-season [Median: 20 (95%CI:12-30) days; II: 10 (95%CI:7.3.1-13.4)]. Apophyseal injuries of the hip-pelvis resulted in the greatest burden [Median: 13 (95%CI: 10-17); II: 2.5 (95%CI: 2.1-3.0)]. Peak apophyseal injury incidence per body parts occurred in U-11 for foot-ankle (II: 2.4; 95% CI: 1.0-4.9), U-14 for knee (II: 4.5; 95% CI: 2.7-7.1), and in U-17 for hip-pelvis (II: 6.4; 95% CI: 4.2-9.3). Conclusion Physeal injuries accounted for a quarter of all-time loss with the largest injury burden in U-16. Most physeal injuries involved the lower limb and affected the apophysis. Physeal and apophyseal injuries incidence, burden and pattern vary substantially depending on age. Hip-pelvic apophyseal injuries accounted for the largest injury burden.
... If a player participated in the assessment in both seasons, only the data from the first assessment was taken. However, the two seasons and the corresponding birth cohorts in the sample (2001-2004 and 2002-2005, respectively) may confound the analysis of performances' differences between selection levels (Elferink-Gemser et al., 2012). To control for this assumption, two-way ANOVAs for each performance factor were conducted testing whether there was an interaction effect between future success and the respective birth cohorts tested at the first and second season. ...
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Recent studies have provided empirical evidence on the prognostic relevance of objective performance diagnostics in the soccer talent identification and development process. However, little is known about the prognostic validity of coaches' subjective evaluations of performance. This study evaluated objective and subjective assessments within a nationwide talent development program and addressed motor, perceptual skill, and personality-related performance factors. Male players (N = 13,869; M age = 12.59 ± 1.07 years) from the age groups U12 to U15 of the German soccer talent development program participated in this study. Participants completed an objective motor diagnostic (sprint, agility, dribbling, ball control, juggling) and were subjectively rated by their coaches (kicking skills, endurance, individual tactical skills, psychosocial skills). All nine predictors were assessed with sufficient psychometric properties (α ≥ 0.72; except dribbling and ball control: α ≥ 0.53). Players' success three seasons later was operationalized by achieving professional youth academy level or not (success rate, 9%). Independent-samples t-tests analyzed univariate mean group comparisons between future selected and non-selected players. Logistic regression models examined the multivariate prognostic validity of all assessments by predicting success with subjective (model 1), objective (model 2), and both groups of predictors (model 3). Confirming the univariate prognostic validity, future selected outperformed non-selected players regarding all predictors (each p < 0.001, except for agility in U15: p < 0.01). Tactical skills, kicking skills, and sprint were of highest predictive value (d ≥ 0.61 in each age group). Multivariate results provided empirical evidence for the subjective (7% ≤ Nagelkerke's R2 ≤ 11%; each p < 0.001) and objective (8% ≤ Nagelkerke's R2 ≤ 13%; each p < 0.001) assessments' prognostic validity. However, model 3 revealed the best statistical explanatory power in each age group (0.15 ≤ Nagelkerke's R2 ≤ 0.20; p < 0.001). In this combined assessment model, sprint, tactical skills, and dribbling were found to be the most predictive variables. In conclusion, this study reinforces the call for multidimensional diagnostics integrating objective and subjective assessments. Future research is needed to address the demands for longitudinal analyses of subjective ratings, the integration of biological maturation, and empirical evidence for female soccer.
... Football academies in England are specialist-training programmes established and funded by professional football clubs with the primary objective of developing players towards senior professional status [14,25]. As a result of the complex and dynamic nature of the talent development process in youth football, over 90% of players who join an academy fail to make it as a professional [36]. ...
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The world’s greatest professional football players are able to execute effective tactical decisions as well as fulfil various physical demands. However, the degree to which both are associated with greater potential in a football academy is unknown. Therefore, the aim of this study was to investigate decision-making skill and physical performance as contributing factors to coach potential rankings in an English football academy. Ninety-eight outfield academy players (Foundation Development Phase [FDP] under-9 to under-11 n = 40; Youth Development Phase [YDP] under-12 to under-16 n = 58) participated in the study. They engaged in 45 film-based simulations at two occlusion phases (e.g., the visual display is cut-off at a precise time during an action), firstly “during” and secondly “post” execution, to examine decision-making skill. Participants also completed four fitness tests to examine physical performance. A classification of “higher-potentials” (top third) and “lower-potentials” (bottom third) were applied through coach rankings. Independent t -tests compared the decision-making and physical performance tests. Higher-potentials made significantly more accurate decisions within the “post” phase within the FDP ( P < 0.05) and the “during” phase within the YDP ( P < 0.05). Additionally, higher-potentials were significantly faster for the 0–30 m sprint in both the FDP and YDP ( P < 0.05), with higher-potentials within the YDP also significantly faster in the 0–10 m sprint ( P < 0.05) and jumped significantly higher in the countermovement jump ( P < 0.05). These findings indicated that greater football potential may be associated with superior perceptual-cognitive expertise and quicker sprint ability in both academy age phases, with a greater discriminatory function within the older cohort.
... Many professional soccer clubs worldwide have formalized talent development programs (often referred to as academies) that aim to produce players who can progress to represent their first team or that can be sold for financial gain (1). The development of academy soccer players is multi-faceted, where a significant emphasis is placed upon technical, tactical, physical and psychological development (2). ...
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Purpose: To inform the energy requirements of highly trained adolescent soccer players, total energy expenditure (TEE) was quantified in academy soccer players from the English Premier League (EPL). Methods: Twenty-four male adolescent soccer players from an EPL academy (n=8 U12/13; n=8 U15; n=8 U18) were assessed for baseline maturity (maturity offset), body composition (DXA) and resting metabolic rate (RMR; indirect calorimetry). Subsequently, TEE, energy intake (EI) and physical loading patterns were assessed over a 14-day in-season period using doubly labelled water, the remote food photographic method and global positioning system technology, respectively. Results: Under-18 players presented with greater RMR (2236±93 kcal⋅day) and TEE (3586±487 kcal⋅day; range: 2542-5172 kcal⋅day) than both U15 (2023±162 and 3029±262 kcal⋅day, respectively; TEE range: 2738-3726 kcal⋅day) and U12/13 players (1892±211 and 2859±265 kcal⋅day, respectively; TEE range: 2275-3903 kcal⋅day) (all P<0.01), though no difference in TEE was apparent between the U12/13 and U15 age-groups. Fat-free mass was significantly different between all comparisons in a hierarchal manner (U18: 57.2±6.1 kg > U15: 42.9±5.8 kg > U12/13: 31.1±3.5 kg; all P<0.01). Within age-groups, no differences were apparent between EI and TEE (U12/13: -29±277 kcal⋅day, P=0.78; U15: -134±327 kcal⋅day, P=0.28; U18: -243±724 kcal⋅day, P=0.37), whilst U18 players (3180±279 kcal⋅day) reported higher EI than both U15 (2821±338 kcal⋅day; P=0.05) and U12/13 players (2659±187 kcal⋅day; P<0.01). Conclusion: The TEE of male academy soccer players progressively increase as players progress through the academy age-groups. In some individuals (evident in all age-groups), TEE was greater than that previously observed in adult EPL soccer players.
... Over the past few years, physical requirements have changed for youth soccer players (Elferink-Gemser et al., 2012). The performance required of the players is increasing steadily, especially in terms of physical performance to keep up with national and international competition (Finn and McKenna, 2010;Gonaus et al., 2019). ...
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Strength training in youth soccer has both a preventive and a sports-specific component. Whole-body electromyostimulation (WB-EMS) could represent an interesting time-saving add-on to classical strength exercises in performance-oriented soccer. The objective of this study was to find out whether a 10-week superimposed WB-EMS training might have a more positive impact on strength parameters in male youth elite soccer players than regular athletic strength exercises alone. A total of 30 male youth soccer players from a youth academy aged 15 to 17 years participated in the study. Before and after the intervention, the isometric extension and flexion forces of trunk and knee, and the hip abduction and adduction forces were tested. Twelve players (control group) absolved a conventional 20-minute strength training once a week for a period of ten weeks. Eighteen players absolved the same exercises but with superimposed WB-EMS. Blood creatine kinase concentration was measured for training control. ANO-VAs, Friedman tests and post hoc t-tests were calculated (p = 0.05) to examine the strength development during the training period between the groups. While we could not find significant strength increases in the leg, hip and trunk muscles in the control group (<4%), the strength of the WB-EMS group improved significantly in 4 of the 6 muscle groups tested. In this group, the strength of knee flexors increased significantly by 20.68 ± 21.55%, knee extensors by 31.43 ± 37.02%, hip adductors by 21.70 ± 12.86% and trunk flexors by 33.72 ± 27.43%. The rates of strength increase are partly in line with other studies, partly clearly higher, which might be explained by the athletically active target group. A 10-week superimposed WB-EMS training improves the strength of certain leg, hip and trunk muscles in male adolescent elite soccer players to a greater extent than a pure athletic strength training of the same duration.
As players in high performance youth soccer (HYPS) environments undergo large changes in growth and maturation throughout the course of their development, they require specific nutritional intakes if they are to meet these demands. The purpose of this review was to synthesise current nutritional research conducted within HYPS players. A systematic approach, following PRISMA guidelines, was employed to capture all articles related to nutrition within HPYS using the databases MEDLINE and SPORTDiscus. Study quality and risk of bias were assessed using a Downs and Black instrument. Observational and intervention studies which investigated an element of nutritional status, knowledge, or intervention in academy aged players (U9 to U23s) within HPYS settings were included. Fifty-three articles qualified assessing: current nutritional intake and energy balance (n = 21); ergogenic aids/supplements (n = 13); hydration status (n = 6); the influence of Ramadan fasting (n = 4); Vitamin D status (n = 4); female HPYS players (n = 3); nutrition knowledge (n = 2). Outcomes demonstrate a large proportion of HPYS players exhibit insufficient energy and carbohydrate intake, and a lack sufficient periodisation of nutrition to account for varying training/match loads. Large variability in energy intake and expenditure exists between and within chronological age groups, indicating the potential impact on growth and maturation. Female HPYS data is lacking but indicates similar trends to male counterparts. HYPS players do not currently meet their energy requirements however the impact of growth and maturation is not fully understood. Furthermore, within this demographic future research is required into the barriers and enablers of players achieving adequate energy intake.
HRM activities include resourcing and development, compensation and incentives, and involvement and job design. In modern football, players influence the value of a team. In this regard, the benefits of club collaboration with talent identification and talent development programmes are the expansion of football, savings in player values, monetization, and transferring value to the teams. This study examined the role of German clubs in the country’s talent identification programme using a qualitative meta-synthesis approach that followed Sandelowski and Barroso’s method. From the 70 documents selected, 923 open codes and 186 concepts were obtained. The results demonstrated that legal developments and their implications in the centralized and global management of German football leagues have been significant in optimally managing clubs and establishing appropriate cooperation with other football institutions, including the German Football Association (DFB) and the German Football League (DFL) with DFB regional bases, performance centres, amateur clubs, and regional/state associations.
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Basketball experts, non-experts, and novices were studied for differences in their self-regulatory forethought and self-reflection processes regarding their free-throw shooting. Forty-three adolescent boys participated individually in the study, which involved a practice session in a gymnasium. The subjects were queried regarding their forethought goals, strategy choice, self-efficacy as well as their self-reflection attributions and feelings of satisfaction as they practiced their shooting. Among the significant results, experts set more specific goals, selected more technique-oriented strategies, made more strategy attributions, and displayed higher levels of self-efficacy than non-experts and novices. Forethought phase processes intercorrelated significantly as did self-reflection phase processes. In addition, self-reflection attributions were predictive of forethought strategy selection during further efforts to learn. The results were discussed in terms of a social cognitive model of self-regulation.
Top football matches are characterized by increased work and increased movement velocity. Football players spend a substantial amount of time to improve physical capacities such as aerobic endurance and strength and the strength derivatives speed and power. The average oxygen uptake for international level football teams is reported to range from 55 to 68 ml·kg-1·min-1 and the half-squat maximal strength from 120 to 180 kg. The hearts' stroke volume has recently been shown to be the element in the oxygen chain that mainly limits aerobic endurance for athletes. This finding has given rise to more intensive training interventions to secure high stroke volumes, that in turn have proved positive in changing both maximal oxygen uptake and football performance in terms of distance covered, involvements with the ball and number of sprints in a game. The training employed has consisted of 4x4 min interval training at 90 to 95% of maximal heart rate uphill running interspersed with 3 min jogging at 70% of maximal heart rate to facilitate removal of lactate. Research has revealed that a football-specific training routine with the ball is as effective as plain running. Strength training to produce neural adaptations has proven effective in changing not only strength in terms of "one repetition maximum", but also sprinting velocity and jumping height in elite football players without any change in body mass. The same training has also improved running economy and thus aerobic endurance performance. The effective training regimen used for a European Champions League team was 4 times 4 repetitions of half-squats with emphasis on maximal mobilisation of force in the concentric action.
A methodology to assess work rate in competitive professional football was designed and validated. The technique required monitoring by observation the intensity and extent of discrete activities during match play and was found to have a measurement error of less than one percent. Performance was observed over 51 games. A complete match typically involved approximately nine hundred separate movement activities per player. The overall distance covered per game was observed to be a function of positional role, the greatest distance covered in outfield players being in mid fielders, the least in centre backs.
The second edition of "Growth, Maturation, and Physical Activity" has been expanded with almost 300 new pages of material, making it the most comprehensive text on the biological growth, maturation, physical performance, and physical activity of children and adolescents. The new edition retains all the best features of the original text, including the helpful outlines at the beginning of each chapter that allow students to review major concepts. This edition features updates on basic content, expanded and modified chapters, and the latest research findings to meet the needs of upper undergraduate and graduate students as well as researchers and professionals working with children and young adults. The second edition also includes these new features: -10 lab activities that encourage students to investigate subject matter outside of class and save teachers time-A complete reference list at the end of each chapter -Chapter-ending summaries to make the review process easy for students-New chapters that contain updates on thermoregulation, methods for the assessment of physical activity, undernutrition, obesity, children with clinical conditions, and trends in growth and performance-Discussions that span current problems in public health, such as the quantification of physical activity and energy expenditure, persistent undernutrition in developing countries, and the obesity epidemic in developed countriesThe authors are three of the world's foremost authorities on children's growth and development. In 29 chapters, they address introductory concepts and prenatal growth, postnatal growth, functional development, biological maturation, influencing factors in growth, maturation and development, and specific applications to public health and sport. In addition, secular trends in growth, maturation, and performance over the past 150 years are considered. You'll be able to recognize risk factors that may affect young athletes; you'll also be able to make informed decisions about appropriate physical activities, program delivery, and performance expectations. "Growth, Maturation, and Physical Activity, Second Edition, " covers many additional topics, including new techniques for the assessment of body composition, the latest advances in the study of skeletal muscle, the human genome, the hormonal regulation of growth and maturation, clarification of dietary reference intakes, and the study of risk factors for several adult diseases. This is the only text to focus on the biological growth and maturation process of children and adolescents as it relates to physical activity and performance. With over 300 new pages of material, this text expertly builds on the successful first edition.
Recent research in many different domains of expertise has shown that the large differences in performance between experts and novices are frequently reproducible under standardized conditions and can often be captured with representative tasks in the laboratory. Furthermore, these differences in performance are predominantly mediated by complex skills acquired over a decade, as a result of high daily levels of activities which are specially designed'to improve performance (deliberate practice). The effects of extended deliberate practice are remarkably far‐reaching and include physiological adaptations and qualitative changes in performance mediated by acquired cognitive skills. Most importantly, expert performers have acquired mental representations that allow them to plan and reason about potential courses of action and these representations also allow experts to monitor their performance, thus providing critical feedback for continued complex learning. The study of elite performance also reveals how acquired representation and skills provide the necessary tools for the ultimate eminent achievement, namely the generation of creative innovations to the domain. This paper is a revised and updated version of my keynote address at the international conference on Creativity & culture: Talent development in the arts and sciences sponsored by European Council on High Ability, Vienna, Austria, 19-22 October (22 October).
Conventional single frequency bioimpedance analysis (BIA) systems require technician placement of arm and leg gel electrodes, a suitable location for recumbent measurements, and a separate measurement of body weight. The aim of this study was to evaluate a new single frequency 50 kHz leg-to-leg bioimpedance analysis (BIA) system combined with a digital scale that employs stainless steel pressure-contact foot pad electrodes for standing impedance and body weight measurements. Healthy adults were evaluated for 1) electrode validity and 2) potential for body component estimation. Pressure-contact foot-pad electrode measured impedance was highly correlated with (N= 9, r = 0.99, P < 0.001) impedance measured using conventional gel electrodes applied to the plantar surface of both lower extremities; mean(±SD) impedance was systematically higher by about 15 ohms for pressure contact electrodes (526 ± 56 ohms vs 511 ± 59 ohms; P< 0.001). Second, the relationship between stature-adjusted leg-to-leg impedance (H2/Z) measured by the new system and two body composition components (total body water by 3H2O dilution (N = 144); and fat-free body mass, by underwater weighing and dual x-ray absorptiometry (N = 231)) was modeled using multiple regression analysis. Correlation coefficients for H2/Z alone versus body composition components were lower for leg-to-leg BIA than for arm-to-leg BIA: correlation coefficients and SEEs became similar for the leg-to-leg and arm-to-leg BIA systems with addition of three covariates (age, gender, and waist/hip circumference ratio) to regression models. The leg-to-leg pressure contact electrode BIA system has overall performance characteristics for impedance measurement and body composition analysis similar to conventional arm-to-leg gel electrode BIA and offers the advantage of increased speed and ease of measurement.
This article investigates wage determination among professional soccer players appearing in the Italian league. Given the popularity of "top" soccer players, the relationship between individual productivity and pay can lead to "superstar" effects. In that context, the marginal revenue product of a soccer player is related to the extra price that a spectator is willing to pay to see him play (live or on television) times the number of spectators who are attracted. The authors use rare data on individual earnings and other personal characteristics of a set of soccer players in the 1995-1996 Italian league season to estimate human capital earnings equations and test for superstar effects in wage determination via convexity of earnings in performance. Earnings are found to be highly convex in two performance measures after controlling for a set of personal characteristics and team fixed effects.