Physical performance of youth football (soccer) players playing in European and National Leagues’ matches

Authors: Emmanouil Smpokos, Antonios Tsikakis, Ricardo Peres, Vangelis Lappas, Pedro Caravela,  Paulo Oliveira, Manolis Linardakis  and the ‘Olympiacos FC Academy Research Group’

Corresponding Author:
Emmanouil Smpokos
E-mail: [email protected] or [email protected] (Dr. E. Sbokos)
Phone number: 0030 6945233315
Fax number: 0030 2155308859

Emmanouil
Smpokos, PhD/MSc, is the senior physiologist at the Research and Development
Department, Olympiacos Academy Football Club, Piraeus, Greece and fitness coach
of the U-19; Antonios Tsikakis is the fitness coach at the Department in U-17 ;
Ricardo Peres is the Technical Director and the Head coach of the U-19 of
Olympiacos FC Academy ; Vangelis Lappas is the head of Goalkeepers’ Department
and the Goalkeeper coach of the U-19 team of Olympiacos FC Academy; Pedro
Caravela is the Head of the Scouting Department and assistant coach of U-19
team of Olympiacos FC Academy; Paulo Oliveira is assistant coach of Olympiacos
FC Academy ; Manolis Linardakis, PhD/MSc, is Biostatistician at Department of
Social Medicine, Faculty of Medicine, University of Crete, Heraklion, Greece.  

Physical performance of youth football
(soccer) players playing in European and National Leagues’ matches

ABSTRACT

The current study assessed the
physical performance of youth Greek football (soccer) players between the Union
of European Football Associations (UEFA) Youth and National Leagues’ matches.
This effort was based on 271 measurements of nine physical/motor activities
recruited from 25 players with a mean age of 18.4 (±1.2 years) during August
2017 and January 2018 from official-matches of UEFA Youth (n=6) and National
Leagues (n=16). Measurements were recruited using Global-Positioning-System
Technology-(GPS) and differences were assessed through analysis of covariance.
56.0% of the players were 18.0+ years old, 52.0% were midfielders, and 56.5% of
players’ participations were recorded in full time (90.0+ minutes). Between the
two competitions of UEFA Youth and National Leagues’ matches, it has been found
that there is significant difference only in mean number of decelerations (71.4
vs. 61.7, respectively, p=0.010). High mean levels of total distance-(TD), very
high-intensity-speed-running-distance-(VHS),
maximal-sprinting-speed-distance-(MS), high-speed-running-(HSR),
distance/time-(D/T), sprints, number of accelerations and
maximum-velocity-(Vmax) were noticed as well as in UEFA Youth Leagues’ matches
but did not differed significantly in relation to counterparts (p>0.05). The
researchers observed that youth football players displayed similar efforts in
all matches maintaining a high level of physical performance, without
separating the matches according to the competition, due to the educational
behavior adopted within the football academy of the club.

Keywords: GPS, youth, motor skills, football, match analysis

INTRODUCTION

Modern association football (soccer) is characterized by highly dynamic and acyclical game movements, interspersed with frequent bouts of high-speed movements and a number of high variability of actions, players’ motor, and mental preparation as well as technical-tactical skills monitoring all these actions using time-motion analysis (TMA) (1,2,26). The number of studies on match running performance has exponentially increased over the current decade in youth football (soccer) populations, providing information that could aid the development of physical conditioning programs (26). Most of theprofessional football academies are seeking to optimize the early detection and physical development of their young football players according to age and playing position (27). The match-running performance of elite male youth football players has been extensively described that the elite youth footballers cover 9-12 Km during an official match, of which 1.5-3.3 Km is high-intensity running (HIR) (24). In a study conducted in youth population (aged 17 years) of elite football players it was found that they have covered 5-7 km during an official match, of which approximately 15% (0.4-1.5 km) with high-intensity activities and the ability to perform in intermittent fitness tests was related to the total distance (TD) covered, as well as with the distance covered in high intensity activities (6,7).

Nevertheless while some information is
available about the physical and physiological demands of highly trained young
footballers during match play (3-5,30), little is known about whether those
physical capacities change during official matches in domestic and European
competitions. Although many studies have reported significant correlation
between field or laboratory test results and running performance during
football matches suggesting that individual physical capacities can account for
match-related performance (6,15,20), none to current knowledge, has compared
performance between deferent official competitions. In this case and among
other factors, an important point is the youth athletes’ motivation of
participation that could be affecting their performance (23,31).

With this in mind, the aim of the present
study was to assess the measurements of physical performance of youth Greek
football (soccer) players playing in UEFA (Union of European Football
Associations) Youth and National Leagues’ matches.

Material and Methods

Subjects

The study is based on data collected from 16 Greek
Youth National League team’s matches and six UEFA Youth leagues’ matches during
the football season 2017/2018. Data were collected for half of an annual season
spanning 24 weeks, from August 27th, 2017 to January 14th,
2018.

Twenty-five youth football players (13
midfielders; 5 defenders; 4 forwards, and 3 wingbacks with the mean age of 18.4
years (±1.2 years) competing in the first division of the U-19 Greek football
league were analyzed in the present study. Their total measurements were 271
retrieving from 22 matches. Their weight was measured on calibrated digital
scales (Seca 861; Seca, Hamburg, Germany) to the nearest 0.1 kg and height was
measured to the nearest 0.5 cm with a wall mounted stadiometer (Seca 225;
Seca), without shoes. Body mass index (BMI) was calculated as weight divided by
height, squared (kg·m-2). The player’s field position, kicking leg,
matches’ outcome, matches and measurements and minutes playing per match were
also recorded. The study was approved by the institutional ethics board and
written informed consent was obtained for each participant or their parents at
the beginning of the season, who agreed to participate in the research (29).

Physical/motor activity measurements

Each match was monitored using a computerized
semi-automatic video match analysis image recognition system (data were
supplied by Viper pod 2, STATSport, Belfast, UK). The data systematically
analyzed using proprietary software to provide an interactive coaching and
analysis tool that provided a comprehensive data on each individual (17). Match data collection for this study was
carried out at the football club’s official stadium and both home and away
stadiums, respectively (28).

Each player’s physical activity, during each
match, was monitored using portable global positioning system (GPS) units
(Viper pod 2, STATSports, Viper Belfast, UK). This device provides position
velocity and distance data at 10Hz. Each player wore a special adjustable
neoprene harness which enables this device to be fitted to the upper part of
his back (i.e. between the left and right scapula). All devices were activated
30 minutes before data collection to allow acquisition of satellite signals,
and synchronize the GPS clock with the satellite’s atomic clock (21). GPS data were downloaded after every
match and analyzed using the respective software package (Viper PSA software,
STATSport, Belfast, UK). In order to avoid inter-unit error, players wore the
same GPS device for each game (3,18). The
players’ external load that were selected for analysis included total distance
covered (TD; km), relative total distance: distance/time (meters/minutes)
(D/T), maximum sprint velocity reached (Vmax) (m/s), and high speed categories
were used: Very High Speed running (VHS; from 19.8 to 25.2km/h) and Maximal
Speed-Sprint (MS;>25.2km/h) or High Speed Running (zone 5 + zone 6)
(HSR;>19.8km/h, in meters) (10,18). A
sprint was defined as a running exercise lasting at least 1 sec at the speed of
at least 25.2km/h (>7 m/s). Acceleration activity was measured on the basis
of the change in GPS speed data and was defined as a change in speed for a
minimum period of 0.5 s with a maximum acceleration in the period at least 0.5
m·s-2. The acceleration was considered finished when the player
stopped accelerating. The classification of accelerations by zone is based on
the maximum acceleration reached in the acceleration period. The same approach
was used with regard to deceleration. The load and intensity measures were
identified as total number of accelerations or decelerations (>2 m·s-2)
and accelerations/min or decelerations/min, respectively. In addition, the
“dynamic stress load” was calculated as the total of the weighted impacts.
Impacts were weighted using convex-shaped function (approximately a cubic
function), an approach similar to the one used in the speed intensity
calculation, with the key concept being that an impact of 4g is more than twice
as hard on the body as an impact of 2g. The weighted impacts were totaled and
finally scaled to give more workable values expressed in arbitrary units (AU).
The load and intensity measures were identified as Dynamic Stress Load (DSL) (2). Both speed intensity and dynamic stress
load were calculated automatically using a custom algorithm included in the
proprietary software provided by the manufacturers (Viper Version 1.2,
STATSports, Belfast, UK). High Metabolic Load Distance (HML; distance covered
>25.5 W·kg-1) was used as measure of movement intensity (12). The HML distance measure combines the
energy cost of all constant velocity running above 5.5m·s-1 and
acceleration and deceleration activity over 2 m·s-2 during
intermittent running (9,25). Players who
did not get into HSR zones because of covering short, sharp distances were
given credit in their HML score since
the intensity of the work could be greater (28).

Statistical Analysis

Data were analyzed
using the SPSS software (IBM SPSS Statistics for Windows, Version 25.0. Armonk,
NY: IBM Corp). Distributions of descriptive characteristics of the 25 youth
football players were estimated. Multivariate analysis of covariance (mancova)
was performed to assess the differences of physical/motor activity measurements
between the two groups (measurements came from UEFA Youth League and National
Youth League). Effect size (η2) and heterogeneity of comparisons
were also estimated (based on Levene’s test). Age, body mass index, players’
position, kicking leg, minutes playing per match, and matches’ outcome were
used as covariates. Finally, the percentage differences of physical/motor
activity measurements were graphically illustrated.  

RESULTS

A comprehensive overview of
the studied samples and their characteristics is given in Table 1. Fifty-six
percent of the youth footballers (n=14) had mean age of 18.0+ years, body
weight 71.2kg, height 1.77cm, and BMI 22.6kgŸm-2.
The majority of the players were midfielders (52%) followed by defenders (20%),
forwards (16%), and wingbacks (12%). Furthermore, with regard to the match
outcome the team had succeeded 59.1% wins or 27.3% defeats while 16 youth
footballers had theirdominant
kicking leg as the right one and six had their dominant as the left leg.
One-hundred and fifty three or 56.5% of players’ participations were recorded
in full time (90.0+ minutes) of the 22 matches.

Table 1. Characteristics of 25 youth Greek football players and matches of the
current study. 

    N %
Age, years 18.0+ 14 56.0
  mean±stand. dev. [min, max] 18.4±1.2 [16.8, 21.8]
Weight, kg mean±stand. dev. 71.2±5.5
Height, m mean±stand. dev. 1.77±0.06
Body Mass Index, kgŸm-2 mean±stand. dev. 22.6±1.1
Players’ position defenders 5 20.0
  wingbacks 3 12.0
  midfielders 13 52.0
  forwards 4 16.0
Kicking leg right 16 64.0
  left 6 24.0
  both 3 12.0
Matches’ outcome win 13 59.1
  draw 3 13.6
  defeat 6 27.3
Matches and
measurements
UEFA youth league 6 (72)
  National league 16 (199)
Minutes playing per match 90.0+ 153 56.5
  mean±stand. dev. 72.1±27.6

Body measurements were
obtained at the beginning of the season 2017/2018.

The 271 measurements
of physical/motor activities were obtained during the 27th August
2017 and 14th January 2018 retrieving from 22 matches.

Analytical differences in
physical/motor activities of the 25 youth players between the two competitions
of UEFA Youth and National Youth leagues’ matches are presented in Table 2.Between the nine physical/motor
activities measurements, it has been found significant difference only in mean
number of decelerations (71.4 vs. 61.7, respectively or difference -9.7;
p=0.010). High mean levels of TD, VHS, MS, HSR, D/T, sprints, number of accelerations
and Vmax were noticed in UEFA Youth Leagues’ matches but did not differed
significantly in relation to counterparts (p>0.05).

Table 2. Differences in physical/motor activities of youth Greek football
players in the season 2017/18 which playing in European and National leagues’
matches.

  Players participation in      
UEFA Youth
League,n=6
National Youth
League, n=16
     
measurements 72 199    
         
  marginal means (stand. errors) Difference p-value η2
Total Distance, TD, meters 9,391 (366) 8,806 (206) -585 0.187 0.007
Very high-intensity speed running distance, VHS, meters (sprinting or speed 19.8-25.2 km/h) 408.1 (22.1) 379.0 (12.9) -29.1 0.282 0.005
Maximal sprinting speed running distance, MS, meters (sprinting or speed >25.2 km/h) 95.2 (8.5) 82.7 (4.9) -12.4 0.230 0.006
High Speed Running, HSR, meters (running speed >19.8 km/h) 505.0 (28.6) 464.3 (16.1) -40.7 0.239 0.005
Distance/Time, D/T, meters/minutes 99.5 (1.4) 97.9 (0.8) -1.7 0.315 0.004
Sprints, number 35.3 (1.8) 32.5 (1.0) -2.8 0.193 0.006
Accelerations >2m/s2,n 54.1 (2.5) 52.4 (1.4) -1.7 0.577 0.001
Decelerations >2m/s2,n 71.4 (3.1) 61.7 (1.7) -9.7 0.010 0.025
Maximum velocity (Vmax),m/s 8.33 (0.08) 8.24 (0.04) -0.09 0.346 0.004

Analysis of covariance (Levene’s test was used for testing
heterogeneity). Age, body mass index, players’ position, kicking leg, minutes
playing per match and matches’ outcome were used as covariates. 

Figure 1presents the percentage differences in nine physical/motor
activities of youth footballers of National in relation to European leagues’
matches. The higher percentage difference is showed for decelerations (-13.9%)
as it was only founded significantly (p=0.010).

Figure 1. Percentage differences inphysical/motor activities of youth Greek football players of
National in relation to European leagues’ matches.

Figure 1

TD; total distance; VHS, Very High Speed running; MS, Maximal
Speed-Sprint;  HSR, High Speed Running;
D/T, total distance:time

Discussion

In the current study
and for the first time, the researchers investigated the physical/motor
activities of youth Greek football players playing in UEFA Youth and National
Leagues’ matches using GPS monitors. The main finding was that between the two
competitions there was no significant difference in nine physical/motor activities
with exception to the number of decelerations.

Based on the results
of the present study it can be concluded that in terms of physical/motor
activities of youth football players who compete in any competition (Domestic
or European league matches) had displayed similar performance in all matches.
This could be explained by a great number of factors affecting football
players’ performance. Studies have shown that apart from the primary
contribution of players’ motor skills their match performance is also greatly
affected by the lack of soccer motivation, the technical-tactical skills, game
strategy, efficiency of decision-making processes, personality traits, or
probably due to the educational behavior adopted within the academy in that
footballers arenot to separate the
matches according to importance of thecompetition
(8,11,16,31). However, there is still a gap in the literature to be able to
draw conclusions about the comparison of motor activities of youth footballers
in two different competitions. Searching the literature, there has not been a
study found that investigated the differences between motor skill activities in
youth footballers between different competitions. The majority of studies
employed field testing procedures, such as linear speed (13,14,22) as a means
to determine age-specific or individualized speed thresholds (26). In a study
performed on a professional Greek footballers (soccer) teamit demonstrated the changes in all types of tested motor skills in
official matches in Domestic National and European championships (28). The
seasonal variations of the study that were investigated during the three
periods of the season 2016/17 (1st period was the pre-season to the
1/3 of the Greek Super League, the 2nd period was the 2/3 of the
Championship, and the 3rd was the last part 3/3 of the Championship)
separated by approximately 14 matches in each period as in our study (16
National Youth League matches). In terms of endurance skills the youth team
displayed almost the same TD in UEFA Youth League match play compared with the
professional footballers (1st period of the season) (9391m vs
9806m).

Another study carried
out between two German Bundesliga teams analyzed the effects of endurance and
speed skills on their teams’ final standing in the league table (19). The study
showed that the players from the second team (despite being ranked lower in the
league table than the first team) attained better scores in all types of tested
motor skills than the players from the first team (19).

One of the limitations of the study was the data of the present study
focusing in physical performance only considered for the first half of the
entire season because they lost the qualification for the knockout stage in the
third round of the competition. Therefore, studies dealing with an entire full
season or more consecutive seasons are needed to better comprehend the in match
related physical parameters. This study is also reflective of one team only
(albeit one of the top league teams) and hence may not represent the customary
official match demands of other domestic league teams that may be influenced by
different coaching philosophies (28). Moreover, most of the youth footballers,
in contrary with the professional players, are attending schools, and they were
not recorded (through daily activity questionnaire), which could limit the
participation of the players in theteam’s official and training
obligations.

CONCLUSIONS

Based on the obtained results, high mean levels of all
types of nine physical/motor activities were noticed between the two
competitions (UEFA Youth & National Leagues’ matches) although no
significant differences were
observed with the exception in number of decelerations. We observed that youth
football players displayed similar efforts in all matches maintaining a high
level of physical performance, without separating the matches according to the
competition importance a process of educational philosophy adopted within the
Academy of the Club. However, motivating distinction, personal or collective,
enhances competition among athletes and teams participating in similar
competitions. While academies constantly invest in the search and development
new talented athletes, with improved skills and better performance in their
physical condition.     

APPLICATIONS
IN SPORT

Young footballers
seem to put equal efforts in the participating competitions without
distinguishing their significance and this may be explained due to a variety of
factors influencing their performance, including their personal abilities, the
technical-tactical skills, game strategy, efficiency of decision-making
processes, personality traits, or probably due to the educational behavior
adopted within the football (soccer) academy.

Technical staff of the Academies should be educators,
teachers, and parents simultaneously. Training of young athletes, cannot
include only improvement of physical condition or soccer techniques learning.  Primarily, technical staff should focus on
developing the personality of the young in total, reporting and consolidating
basic principles and values, such as emulation, good cooperation, and behavior
towards fellow athletes and trainers, synergy, and respect. Especially in
sports since ancient times the dogma of “a
healthy mind in a healthy body
” is emphasized (in Latin “mens sana in corpore sano” or in Ancient
Greek “νοῦς ὑγιής ἐν σώματι ὑγιεῖ” – https://www.encyclopedia.com)
and hence the technical staff, taking advantage of the constantly good physical
condition, can mold and develop the mental virtues of the youth, the correct
non-competitive and competitive thinking and behavior. Critical thinking needs
to constantly accompany young athletes, to take care of their body and that of
their peers and opponents, to behave with caution and respect in every game or
training, avoiding conflict or reactions that put in danger their physical and
mental health. Technical staff
must empower young athletes and their abilities, avoiding potential injuries
that could constitute impediments to their physical and athletic development.

ACKNOWLEDGMENTS

The authors would like to extend their
gratitude to all players who participated in this study. The ‘Olympiacos FC Academy
Research Group’ include: Nikolaos Kolokythas, Athanasios Rossidis, Anastasios
Lazarou, Dimitrios Kalogerakos, Emmanouil Askounis, Nikolaos Katsikostas, Ariel
Ibagaza, Aristeidis Kyriazis, Dimitrios Mavrogennidis, Nikolaos Topoliatis,
Iakovos Chatziraptis.

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