International Journal of Performance Analysis in Sport
2014, 14, 493-503.
45-344.
Changes in physical performance variables in an
English Championship League team across the
competitive season: the effect of possession
Ryland Morgans1, David Adams2, Richard Mullen2, and Morgan D Williams2
1
Liverpool Football Club, Anfield, Liverpool, England, UK. L4 0TH.
2
University of South Wales, Division of Sport, Health and Exercise, Upper Glyntaff,
Pontypridd, Wales, UK. CF37 4AT.
Abstract
This study examined changes in physical match performance of six
players from an English Championship League team across the
competitive season and examined the effect of team possession. Sprint and
high intensity distances and frequency of efforts were all greatest in earlyseason, and were significantly reduced in both mid-and-late-season
phases (all p < 0.0001). None of these variables were, however, related to
team possession (p range = 0.2759 to 0.7411). Total distance covered on
the other hand was sustained and did not significantly change over the
season phases (p = 0.9219), but it was negatively associated with
possession (p = 0.0080). This association suggests that physical demands
were lower when this team was in possession of the ball. In summary,
evidence of residual fatigue at mid-and-late-season was obtained from
sprint and high intensity variables. Given possession was associated with a
reduced total distance covered during matches, it may be speculated that
better quality teams are able to maintain possession for longer periods of
matches and thus require less recovery time due to reduced physical
match demands.
Keywords: Soccer, time-motion analysis, sprinting, high intensity running,
possession
1. Introduction
The physical demands on soccer players during matches are often assessed using total
distance covered and the extent to which that distance is covered at given intensities.
Professional players can cover 10-13km in total distance with 8-10% being at high
intensity (Mohr et al., 2003; Di Salvo et al., 2009; Di Mascio and Bradley, 2012).
Professional players also generally cover greater distances at high intensity than their
lower standard counterparts (Bangsbo et al., 1991; Mohr et al., 2003; Andersson et al.,
2008; Mohr et al., 2008). Some regard these high intensity distances as a key indicator
of physical fitness (Mohr et al., 2003). Yet, players’ current fitness status alone cannot
explain the observed total distance and the distances covered at various intensities
493
during matches and other factors have a significant impact (Bangsbo, 1994). For
example, Bradley et al. (2009) found that high intensity distances in the English Premier
League (EPL) were partly explained by technical differences (pass frequency and
accuracy) and tactical (possession or direct style) strategies. In terms of total distance,
Rienzi et al. (2000) reported that when a single match was analysed, South American
professional players covered 1000m less than EPL players, which they attributed to the
tactical restrictions associated with a different style of play. These and other studies
suggest that physical and technical actions during match play interact in a dynamic
nature (McGarry and Franks, 2003; Reed and O’Donoghue, 2005; Dellal et al., 2011).
Exploring the impact of other variables upon total and high intensity distance, as
indicators of physical performance would appear to be important for future
investigation. Gaining and maintaining ball possession is one variable that might have
an impact upon physical match performance variables. Ball possession, described as the
ability to pass the ball accurately with minimum touches, and retain the ball when under
pressure from the opposition (Lago and Martin, 2007; Redwood-Brown, 2008), has
been regarded as a critical factor during matches and allows a team to control the
structure and tempo of the match (Shafizadeh et al., 2012). The ability to accurately and
successfully pass the ball over a range of distances and in different directions has also
been shown to separate elite players from less able counterparts (Lago and Martin,
2007; Redwood-Brown, 2008). Previous research on possession has mainly focused on
its determinants (Lago and Martin, 2007), and few studies have reported the effect of
possession on physical match performance variables (Bradley et al., 2013a; Morgans et
al, In Press).
A possession-based style of play may reduce physical demands imposed on players and
help preserve performance across the season (Morgans et al, In Press). Bradley et al.
(2013a) suggest that when in possession of the ball, a team’s physical demands are
lower compared to when they are defending and having to react to opposition
movements. If true, the amount of ball possession may determine physical match
performance measures. Thus, when teams maintain high possession, they may reduce
exposure to high physical demands, which may permit a more sustained physical
performance across the season (Morgans et al, In Press). The importance of sustaining
match performance across the season to meet the technical, tactical and physical
demands of competitive match play has previously been identified as vital for success in
domestic league competitions (Collet, 2012). In particular, the demands of the English
Championship League (ECL) are high, requiring players to regularly compete with at
times, only two days to recover before the next match (Morgans et al, In Press). A likely
consequence of such demands and in-adequate recovery is residual fatigue (Cormack et
al., 2008), which can result in physical and technical match performance decrements.
Moreover, as the season advances the accumulating effect of residual fatigue may
further impact match performance in late-season, ultimately impairing match outcome
and possibly reducing the chances of promotion to the EPL.
To date, despite the impact that physical performance might have on overall team
performance during competition, limited research (Morgans et al, In Press) has
examined within season changes in physical match performance variables in relation to
ball possession. Therefore, the aims of this study were, firstly, to examine the total
494
distance, sprint and high intensity distances covered and frequency of efforts of a
professional soccer team across an ECL competitive season; and, secondly, to examine
the effect of possession on physical match performance.
2. Methods
2.1. Participants
Six male participants (mean age = 23.5 ±2.1 years; stature = 1.80 ±0.10 m), representing
the core-playing group from an ECL soccer club were monitored across a season. All
participants were outfield players (central defenders n = 2, wide defender n = 1, central
midfielders n = 3) who made a median of 37 match appearances (min = 27, max = 45),
inclusive of domestic cup competitions (maximum number of matches = 49). The
average: matches played; time on pitch; time between matches; and matches per day
ratio by competition phase are shown in Table 1 for the group. The forward players’
data were excluded due to in-sufficient match appearances made over the season to
meet the inclusion criteria. Out of the 49 competitive matches played, 23 were home
matches, 23 were away fixtures and the remaining three matches were domestic cup
competitions. Only data obtained from home ECL matches were included in the study.
This removed the impact of confounding variables such as: different strategies adopted
by teams when playing away from home; pitch dimensions; venue; accommodation and
travel that have been purported to affect physical demands of matches (Andersson et al.,
2007; Lago, 2009; Bradley et al., 2011; Lago-Peñas and Ballesteros, 2011). In total, 95
rows of data formed the dataset used in the analysis with the participants playing a mean
of 18 (min = 9, max = 21) home matches. The competition phase was divided into three
phases (early = August to November; mid = December to February; and late = March to
May). The opponents were determined by the Football League fixture schedule and the
quality of opposition (based on league position) was evenly distributed across the
season (See Table 2). During the early, mid and late phase of the season the points per
match record was 1, 0.9 and 2.2 respectively. The University Human Research Ethics
Committee and the professional soccer club from which the participants volunteered
approved the study.
Table 1. Number of all League and domestic cup matches played, time on pitch, time
(hours) between matches and matches per day ratio by competition phase.
Number of matches played
Time on pitch (sum)
Time on pitch
Time between matches (hours)
Match:day ratio
Early
Mean ±SD
Mid
Mean ±SD
Late
Mean ±SD
18 ± 5
16 ± 1
9±2
1601 ± 484
1404 ± 175
724 ± 158
89 ± 9
90 ± 6
83 ± 15
171 ± 79
139 ± 7
161 ± 28
7±3
6 ± 0.4
6±1
495
Table 2. Distribution of home match opponents’ league position by competition phase.
Phase
Early
Mid
Late
Match Number
1
3
5
7
10
12
13
16
18
20
22
23
25
28
29
31
34
36
37
40
42
44
46
League Position
(LP)
4
13
5
24
15
9
7
2
22
20
3
16
14
21
12
11
18
6
8
1
10
17
23
LP
Median
LP
Range
11
2 to 24
14
3 to 21
9
1to 23
2.2 Match analysis procedures
Using a multi-camera computerised tracking system all outfield players’ movements
were captured during each match by eight colour cameras positioned at stadium roof
height (Randers et al., 2010) with a sampling frequency of 25Hz. Several authors have
previously documented the installation process (e.g., Carling et al., 2008; Randers et al.,
2010). Captured data were analysed using match-analysis software (Prozone® Stadium
Manager, ProZone® Sports Ltd, Leeds, UK) to produce a single dataset on each
player’s activity during a match. The system has been independently validated to verify
the capture process and accuracy of data (Carling et al., 2008).
Match data for each player during each match were recorded and analysed via the same
computerised semi-automatic match analysis system (ProZone®, Stadium Manager
Leeds, UK). The set of physical match performance and ball possession variables
included: total distance covered; sprint distance (total distance covered >7 m/s); high
intensity distance (total distance covered >5.5-6.9 m/s plus sprint distance); frequency
of sprint efforts (total number of sprint efforts >7 m/s); and frequency of high intensity
efforts (total number of high intensity efforts >5.5-6.9 m/s); possession (time the home
team had the ball divided by the time the ball was in play); and time on pitch were
reported. The speeds for each category have been previously reported (Di Salvo et al.,
2009) and all ProZone® match-analysis has been shown to provide valid and reliable
496
measures during competitive match play (e.g., Di Salvo et al., 2006; Carling et al.,
2008).
2.3 Statistical analyses
All statistical analyses were performed using JMP version 10.02 discovery software
(SAS Institute, JMP Statistical Discovery, NC, USA). To assess differences in
possession across the phase of season; one-way analysis of variance was used. To
examine differences across the season a repeated measures design mixed model using
Restricted Maximum Likelihood (REML) method for fitting (fixed factors =
competition phase [early, mid and late], and possession; random factor = participant)
was used. Possession was included as a fixed factor to control for its purported affect on
physical performance. When F statistics for the competition phase were significant, ttests with Bonferroni correction (p < 0.0167) were used. All least square means
differences were reported alongside 95% confidence intervals (95% CI). When
appropriate, effect size (ES) was also calculated as the mean difference between paired
groups divided by the common standard deviation.
3. Results
3.1. Match Performance
The descriptive statistics for physical match performance and ball possession across the
three competition phases are shown in Table 3. Total distance was the only physical
performance variable not to change across the season. All sprint and high intensity
physical match performance variables significantly changed across the season. Post-hoc
analysis revealed that the same pattern across the season occurred for sprint and high
intensity variables (See Table 4). The highest sprint and high intensity distance and
frequency of efforts were all found in early-season, followed by a significant decrease at
mid-season that remained until late-season.
Team possession did not significantly change across the season, although a trend toward
significance was observed (p = 0.0804). Yet, on inspection of the ES for the phase of
season comparisons of team possession, a level of instability across the season was
revealed (early versus mid d = 0.4; early versus late d = 0.8 and mid versus late d = 1.1).
Furthermore, when compared to the other physical performance variables, total distance
was the only variable with a significant effect (p = 0.0080) for ball possession. From the
parameter estimate, when ball possession increased by 1%, total distance covered
reduced by 29 m (95% CI 8 to 50 m).
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Table 3: Physical match performance and possession descriptive statistics (mean ± standard deviation) by competition phase.
N
Possession
(%)
Total
Distance (m)
Sprint
Distance
(m)
Sprint
Frequency
High Intensity
Distance
(m)
High Intensity
Frequency
Early
42
50±6
10513±1196
268±118
37±14
916±299
117±35
Mid
31
48±4
10722±942
183±112
25±13
751±283
93±28
Late
22
53±3
10556±1044
192±93
26±11
811±280
98±29
Total
95
Fixed Effect Phase
(p-value)
Fixed Effect
Possession (p-value)
50±5
10591±1076
223±117
30±14
838±296
105±33
0.0804
0.9219
<0.0001
<0.0001
<0.0001
<0.0001
-
0.0080
0.7411
0.2759
0.2819
0.6070
Competition
phase
Table 4: Post-hoc competition phase comparisons (least squares mean and 95% CI) for possession and physical match performance.
Early v Mid
P
Early v Late
P
Mid v Late
P
-2(-6 to 3)
0.4464
4(-1 to 8)
0.1235
5(0 to 10)
0.0304
Total Distance (m)
43(-171 to 258)
0.6897
20(-223 to 263)
0.8706
-23(-296 to 250)
0.8659
Sprint Distance (m)
-82(-120 to -43)
<0.0001
-87(-131 to -44)
<0.0001
6(-43 to 54)
0.8267
Possession
Sprint Frequency
High Intensity Distance (m)
High Intensity Frequency
-12(-17 to -8)
<0.0001
-11(-16 to -6)
0.0059
1(-4 to 7)
0.6311
-191(-276 to -107)
<0.0001
-135(-231 to -40)
<0.0001
56(-51 to 163)
0.3027
-30(-38 to -21)
<0.0001
-22(-32 to -13)
<0.0001
7(-4 to 18)
0.1933
498
4. Discussion
The aims of this study were to analyse the physical match performance of a professional
soccer team during an ECL season and to examine the effect of possession on physical
match performance. When team possession was controlled for, the core playing group’s
sprint and high intensity distances and frequency of efforts were all significantly less at
both mid- and late-season than those reported during early-season. Over the season,
total distance covered was sustained, but a greater reliance during mid-and-late-season
was placed on moderate and low running speeds (< 5.5m/s). The reduced sprinting and
high intensity running observed at both mid- and late-season may signify residual
fatigue as the season progressed (Cormack et al., 2008). Team possession was also
negatively related to total distance and this relationship may have implications for the
ways in which coaches manage players and adapt tactics in order to manipulate match
demands.
4.1. High Intensity and Sprinting
Having the capacity to produce sprint and high intensity actions is vital in soccer and
other team sports. In possession, players need to move quickly into space to evade
defenders and receive the ball. Sustaining this capacity over the season is therefore
important for soccer players to consistently perform their role at a high level.
Observations of reduced high intensity running and some technical skills during the
season have been well documented (e.g., Bangsbo, 1994; Rampinini et al., 2007;
Bradley et al., 2009). Yet, not all studies have reported the same pattern of reductions at
the same time points across the season. One study, Rampinini et al. (2007) found that
physical performance variables including total, high intensity and very high intensity
running distances were greater at the end of the season compared to early-season values.
The authors suggested that the different level of opposition encountered during different
phases of the season in conjunction with the impact of the competition’s mid-season
break might explain their observations. From our study, the reduced sprint and high
intensity distances and efforts observed following the early-season might be an
indication that players were in a state of residual fatigue. Cormack et al. (2008) have
suggested that during the season players who compete in a state of incomplete recovery
will be exposed to accumulated decrements in physical capacity attributed to reduced
neuromuscular drive. Based on the high frequency of matches (See Figure 1), the
opportunity to promote full recovery before subsequent matches was highly unlikely.
To gain a more clear understanding, the effect of team possession on player’s
physiological status (readiness to play) and time-series monitoring of markers of fatigue
is therefore warranted, rather than relying on physical match performance data of
players alone.
An alternate explanation of the decrements in sprint and high intensity activity may be
that players became de-conditioned as a result of limited training time leading to
insufficient stimulus to maintain physical fitness (Bangsbo, 1994). Although it may also
be argued that regular match-play itself when performed repeatedly within short time
intervals (seven days) may warrant the maintenance of physical fitness. It has been
suggested however, that conditioning and training programmes have improved since
that study (Di Salvo and Pigozzi, 1998) and it is unlikely that total distance decrements
would be observed as a result of de-conditioning.
499
4.2 Total Distance and Team Possession
Few studies have investigated the relationship between ball possession and physical
match performance variables and the findings from these studies are mixed. For
example, Bradley et al. (2013a) studied a large pool of players from a number of teams
and reported that ball possession did not influence the overall physical match
performance but did affect the frequency of high intensity efforts. In contrast to Bradley
and co-workers, Morgans et al. (In Press) only studied home matches over a season of a
single ECL team. Such a study design eliminates factors that can affect physical and
technical match performance such as pitch dimensions and different styles of play
associated with using datasets obtained from multiple teams. Morgans et al. (In Press)
found that when in possession, the total distance covered per min by an ECL team was
less when compared to the distance covered per minute when out of possession. Similar
to the present study, no significant differences were found for sprint and high intensity
variables. In that study however, team possession (median = 62%, IQR = 60 to 67%)
across the season was greater than the present study (mean and standard deviation =
50±5%). Despite the differences in team possession between the studies, both reported a
negative association between possession and total distance covered. A number of
factors contribute to team possession (Collet, 2012; Bradley et al., 2013a,b) including
successful short passing (Redwood-Brown, 2008), longer sequences of passing (Carling
et al., 2005), and the ability to utilise defenders to build-up play and maintain
possession (Adams et al., 2013). Possession is also considered an indicator of successful
teams (Jones et al., 2004; Lago-Peñas and Dellal, 2010; Shafizadeh et al., 2012), but not
of individual match outcomes. Therefore, from a physical performance perspective, a
possession style of play may support the long-term success of a team by reducing the
physical demands that players are exposed to.
The team studied previously by Morgans et al. (In Press) and the team in the present
study finished the season in top four and bottom four-league table position, respectively.
The successful team, on average, maintained team possession 62% of the time during
matches and sustained both high intensity and sprint activities across the season. Even
with such contrasting final league position at the end of the ECL season, both teams
covered less distance when in possession of the ball. In broad terms, the task of
defending requires a player to position themselves between the ball and the goal. The
additional distances covered at moderate intensity as a result of defending can be
explained by the need for defenders to change position in anticipation or reaction to
either the ball or attacker movements. Otherwise, if an attacking player becomes unmarked in an important area of the field, the opportunity to shoot and score increases.
One possible explanation for why similar findings were not observed in the Bradley et
al. (2013a) study, may be due to the pooling of data resulting in the loss of information,
since factors such as ball possession in the offensive phase (Lago-Peñas and Dellal,
2010), score and status of the match (Rampinini et al., 2007), match location (Lago and
Martin, 2007; Lago, 2009; Lago-Peñas and Dellal, 2010) may all impact on physical
match performance variables in elite soccer. Taking a smaller more in-depth case-study
design of a small group of players studied over time, similar to Morgans et al. (In Press)
and the present study, may have revealed information that otherwise is lost due to the
pooling of data. Such descriptive reports however, should not be generalized beyond the
context of the sample of players studied.
500
For the coach, developing a possession-based strategy that seems to physically spare
players across a season should be considered to avoid possible decrements in physical
match performance as the season progresses. Small-sided games and coaching drills that
vary in pitch size and the number of touches and integrate high intensity actions with
the ball have been documented as ideal practices to develop fitness qualities suited to a
possession style of play (Dellal et al., 2012; Bradley et al., 2013a) and combined with
accurate monitoring may better inform coaching decisions.
5. Conclusions
In conclusion, this study showed that total distance did not significantly change,
suggesting that overall match intensity was sustained across the season. Yet, possible
effects of residual fatigue were documented by a significant reduction in sprint and high
intensity distances and efforts made during matches at both mid-and-late-season. With
small squads of players and little time to recover between matches, coaches may be
unable to rest players in an attempt to avoid exposing them to competing in a fatigued
state. Given that ball possession has been associated with reduced total distance during
matches in this study and has previously been linked with successful teams (Jones et al.,
2004; Lago-Penas and Dellal, 2010; Collet, 2013), it may be speculated that better
quality teams are able to maintain ball possession for longer periods of matches and
thus require less recovery time due to reduced physical match demands. Moreover,
based on the relationship between team possession and distance covered, when a team
dominate possession, these players may recover quicker than expected following
matches since distances covered will be expected to be less. Therefore, ECL teams with
lower technical and tactical ability should pay more attention to tailoring training loads
during the latter stages of the season, since greater physical stress will be placed upon
players during competition. On the other hand, post-match recovery training may need
to be extended or modified when possession during the previous match is low.
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Performance Analysis in Sport, 12, 14-23.
Corresponding author
Ryland Morgans
Liverpool Football Club, Anfield, Liverpool, England, UK. L4 0TH.
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