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Adherence to an Injury Preventative Warm
Up Program Elicits Performance
Enhancements in Male Collegiate Footballers
Following a 5 Week Warm Up Intervention
Student Name:
Jordan Tyrer
Programme of Study:
BSc Sport and Exercise Science
Supervisor:
Dr. Neil Messenger
CENTRE FOR SPORT & EXERCISE SCIENCES
Faculty of Biological Sciences
UNIVERSITY OF LEEDS
Abstract
The International Federation of Football Associations’ (FIFA) injury preventative warm up
program, the “FIFA 11+” can elicit physical performance improvements in footballers.
However, factors such as the time-consuming nature of such programs mean they are often
unused in sub-elite football. The purpose of this study was to establish whether an adapted
and shorter version of the “FIFA 11+” could still elicit performance improvements in adult
footballers. 5 week warm up programs were administered to 14 male collegiate footballers
(age; 20.57 ± 1.40 yrs, height; 179.58 ± 5.92 cm, weight; 76.97 ± 8.22 kg) with participants
performing either an injury preventative warm up program (n = 7), or a dynamic warm up
program (n = 7) as a control. Paired-sample t-tests (P < .05) showed significant
improvements in jump height for the countermovement jump (CMJ) (p = .033) and
countermovement jump with arms (CMJWA) (p = .037), as well as a non-significant
improvement (p = .077) in single leg stance score for the injury preventative group. The
dynamic warm up group observed no significant improvements in any performance test.
These results suggest that a shorter version of the “FIFA 11+” can still elicit performance
enhancements in male adult footballers.
Keywords: warm up, performance enhancement, countermovement jump, balance,
injury prevention
Introduction
Like with most sports, playing football carries a risk of injury at both amateur and
professional level1. Historically, dynamic stretching as part of a warm up strategy prior to
sport participation has been strongly advocated and widely used2. Typically, a dynamic warm
up would contain active stretches and exercises that mimic the movements associated with
the sport in question in order to raise body and muscles temperature
3. However, there is
evidence to suggest that the use of these warm up protocols alone do little to reduce the risk
of serious lower limb injuries4-7
, such as anterior cruciate ligament injuries. More recently,
specific injury prevention programs have been designed and developed in order to target and
reduce the injury risks associated with football. Because football is such a widely played,
spectated and well financed sport, footballs governing body, the International Federation of
Football Associations (FIFA) have investigated ways in which best to reduce the associated
injury risks of football. With help from the FIFA Medical and Research Centre, a series of
injury preventative warm up programs were designed with the aim of significantly reducing
the injury risks associated with football world-wide8. Initially “The 11” protocol was
proposed, which was then later updated to the “FIFA 11+” program. The “FIFA 11+”
contains exercises that are considered to be pivotal in reducing the injury risk in football. It
focusses on core stabilisation, eccentric training of thigh muscles, proprioceptive training,
dynamic stabilisation and plyometric exercises. The main focus of the program is the
promotion of proper neuromuscular control during all of the exercises in order to fully
facilitate the physical and neural adaptations that the warm up program is designed to elicit9.
Following the introduction of specific injury preventative programs such as the “FIFA 11+”,
there is a growing amount of evidence that shows the warm up protocol can significantly
reduce the risk of injury8,10-13
, thus showing how important an effective injury preventative
warm up program can be in reducing the risk of injury to footballers.
Because of their impact on reducing injury, professional football clubs will often
spend up to 45 minutes completing warm up programs14
. In an elite environment where the
coaching staff have a near continuous interaction with the players throughout a week, as well
as access to specific support staff such as physiotherapists, sports scientists and strength and
conditioning coaches, these lengthy warm up procedures are easily achievable. When we also
consider the huge financial practices of elite football, it is perhaps understandable as to why
such a length of time is dedicated to preventing injury in squads that can potentially be worth
millions of pounds.
In non-elite settings however, meta-analysis have found that injury preventative warm
ups are rarely, if at all adhered to by coaching staff13
. Often, a short dynamic warm up
procedure is used by coaches as a means of warming up their players as opposed to a more
specific injury preventative program, perhaps due to a lack of knowledge regarding the
benefits of an injury preventative warm up13
. As well as this, in sub-elite and amateur football
where coaching staff may only work with their players for a few hours a week, coaches will
rarely afford long durations of time to performing a warm up. In practice the “FIFA 11+”
takes 20-25 minutes to perform entirely15,16
which in reality, coaches may consider too long a
duration to afford to a warm-up process within their limited interaction time. As a result,
injury preventative warm up programs may be neglected, thus potentially exposing players to
a higher risk of injury.
It has been suggested that in order to improve the uptake of injury preventative warm
ups by coaches, it may be important to focus on player performance improvements as a
secondary effect of a specific injury preventative warm up17
. A number of studies have
investigated the effects that injury preventative warm ups have on jumping and balancing
performances, both of which are important attributes in footballers18
. Investigations into the
performance benefits associated with injury preventative warm ups is a relatively recent area
of research where the results are not entirely conclusive. The majority of studies show how
significant performance improvements are observed following injury preventative warm up
interventions16,18-21
whilst other studies have demonstrated contrasting results 22,23
.
It could be said that if a warm up program could reduce the risk of injury, elicit
significant performance improvements and last for a shorter duration of time than previous
injury preventative warm ups such as the “FIFA 11+”, then perhaps coaches may be more
receptive to the use of injury preventative programs.
As a result, the purposes of this study are to investigate whether such a program can
elicit significant balance and jumping improvements in male collegiate footballers. A 5 week
intervention period of an injury preventative warm up, adapted from the “FIFA 11+” but that
takes less time to complete, was administered to collegiate footballers from the University of
Leeds Men’s Football Club. It was hypothesised that the injury preventative warm
intervention would elicit significant performance improvements in the jumping and balancing
ability of the participants who received the warm up program. It is also hypothesised that a
control group who were administered a traditional dynamic warm up program will observe no
significant improvements in physical performance tests.
Methods
Participants for the study were volunteers from the University of Leeds Men’s
Football Club. The study included 14 injury free club members (age; 20.57 ± 1.40 yrs, height;
179.58 ± 5.92 cm, weight; 76.97 ± 8.22 kg). Ethical approval was obtained from the
university’s ethical committee for the protection of the participants throughout the testing and
training procedures. All participants were provided with information regarding the
procedures and consequences of participating in the study before the study began. The
participants subsequently gave informed consent and completed health screening
questionnaires prior to participation in the study.
For both the benchmark and final testing days, all participants were provided with the
same model of cushioned running shoe (Saucony ProGrid 12) in their corresponding size.
The participants then completed a warm up containing a combination of injury preventative
and dynamic exercises (table 1) before testing procedures began, in order to minimise the risk
of injury14
during the balance and jump tests.
Table 1: Contents and procedures of the warm up administered to all participants prior to the
benchmark and final testing protocols.
Order Exercise Repetitions Exercise Description
1 Squat 6
Participants should perform a squat
movement to the best of their ability,
keeping their heels on the floor and a
neutral head position.
2 Calf raise 10
Participants should extend at the ankle
joint, whilst standing unaided, keeping
balance and performing the movement as
competently as possible.
3 Single leg ½
squat 4 each leg
Keeping their hands on their hips, and the
non-supporting leg in front of the body,
participants are to perform 4 single leg ½
squats until their flexed knee is at a 90⁰
angle before returning to a standing
position and repeating the process.
4 Double leg hop 6
Whilst standing with feet shoulder width
apart, participants should perform 6 quick
consecutive jumps.
5 Single leg hop
and holds 3 each leg
Participants are to hop on one leg 3 times
before attempting to cushion the landing in
a stationary position before returning to a
standing position and repeating the process.
Once the warm up was completed the participants performed the single leg stance test in
accordance with the test’s defined protocol24
. Each participant performed four balance tests in
total starting with a leg of their choice, followed by the opposite leg. After a 30 second rest
between each trial the participants then repeated the procedure, and their performance was
timed via a stop-watch. The timer was started when the participant moved onto one leg with
his hands on his hips and was stopped when the participant lost balance or re-adjusted his
posture, as defined by the testing protocol24
.
Following the balance tests, the participants completed jumping trials consisting of
3counter-movement jumps (CMJ) followed by 3 counter-movement jumps with arms
(CMJWA). The CMJ protocol required participants to keep their hands on their hips
throughout the jump as a means of assessing isolated leg power, where-as the CMJWA
protocol required participants to jump with their hands and arms unrestricted, thus allowing
for the use of their upper extremities in assisting the jump. As such, it was expected that the
participants would achieve greater jump heights in the CMJWA test as opposed to the CMJ,
as it is more of a test of a person’s whole body power rather than just leg power alone, as
seen with the CMJ. Both tests were used as opposed to just one so that a more extensive
measure of the performance effects of the different warm up protocols could be examined.
All jumps were performed from two adjacent force platforms, in conjunction with a 13
camera Qualisys OQUS system to record three dimensional kinematic data, which was used
to evaluate whether the landing of each jump had occurred upon the force plate. As such, a
single retro-reflective marker was attached using double sided adhesive tape to the same part
of the heel on each of the right shoes that were given to the participants. Prior to the
completion of the jumps each participant performed a 3 second static trial in order to obtain
each participant’s weight. This required each participant to stand still upon the force platform
thus giving each participant’s stationary ground reaction force. This value could then be
divided by acceleration due to gravity (-9.81 m∙s) thus giving the weight of each participant.
The participants were then assigned to either the injury preventative warm up group
or the dynamic warm up control group. The injury preventative group were members of the
University’s 1st and 2
nd team squads whilst the members of the control group consisted of the
University’s 3rd
and 4th
team squads. Both groups trained separately and on different days to
one another, there for the delivery and monitoring of both warm up protocols could be
accounted for. Both groups were evenly represented by each playing position (goalkeeper; n
= 1, defender; n = 3, midfielder; n = 2, attacker; n = 1).
Benchmark testing occurred at the beginning of the playing season, with both warm
up interventions taking place immediately afterwards, as the playing season got underway.
Final testing occurred midway through the playing season. Both groups were administered a
5 week warm up intervention that they completed 3 times a week, prior to their training
sessions and matches. The injury preventative warm up included a 4 minute pre-warm up
activation period that consisted of exercises aimed to increase the number of recruited motor-
units as well as the rate of which those motor-units were recruited within the major muscle
groups associated with football25
(table 2), followed by a 10-12 minute injury preventative
warm up consisting of 16 exercises (table 3). In comparison the control group were
administered a 10-12 minute football specific dynamic warm up (table 4). Both warm up
procedures required the same equipment (8 cones) and were performed using the same layout
(figure 1).
Figure 1: Layout of both the injury preventative and dynamic warm up areas.
● = cone
15 m
30 cm
ST
AR
T
FIN
ISH
Table 2: Contents and procedures of the pre-injury preventative warm up activation exercises
prescribed to the injury preventative group.
Order Exercise Repetitions/Duration Exercise Description
1 Squat 8
Participants should perform a squat
movement to the best of their ability,
keeping their heels on the floor and a
neutral head position.
2 Squat into
calf raise 6
Participants should perform a squat
movement however when returning to
standing position participants are to fully
extend ankles, knees and hips and arrive
into a calf raise position, holding it for three
seconds before repeating the whole process.
3
Single-leg
static balance
with eyes
closed
30 seconds each leg
Participants are to close their eyes and
attempt to balance in a stationary position
on one leg for 30 seconds before swapping
legs
4 Single leg ½
squats 4 each leg
Keeping their hands on their hips, and the
non-supporting leg in front of the body,
participants are to perform 4 single leg ½
squats until their flexed knee is at a 90⁰
angle before returning to a standing
position and repeating the process.
5
Single leg
hop and
holds
4 each leg
Participants are to hop on one leg 3 times
before attempting to cushion the landing in
a stationary position before returning to a
standing position and repeating the process.
6
Single leg
partner
balance
30 seconds each leg
In partners, participants are to face one
another and hold their partners forearms
whilst attempting to balance on one leg
while their partner applies light,
unpredictable pressure in different
directions.
Table 3: Contents and procedures of the injury preventative warm up administered to the
injury preventative group.
Order Exercise Exercise Description
1 Jogging For 3 lengths of the warm up area, participants should jog at
comfortable pace.
2 Skipping For 2 lengths of the warm up area, participants should skip as high as
they can whilst maintain forward momentum.
3 Dynamic lunges
with torso twist
For 1 length of the warm up area, participants should perform
consecutive lunges for either leg, twisting their torso across their front
knee and alternating legs each time.
4 Dynamic sumo
squats
For 1 lengths of the warm up area, participants should adopt an extra
wide squat stance and perform a squat with the same movement
principles as a standard squat.
5
Bent leg kick
across with torso
twist
For 1 length of the warm up area, participants should kick across the
midline of their body, whilst rotating their torso in the opposite
direction to the kick. Alternating legs each time.
6 Straight leg kicks
For 1 length of the warm up area, participants should kick as high as
they can with a straight leg in a controlled manner, alternating legs
each time.
7 Door kick downs
For 1 length of the warm up area, participants should perform a
controlled kicking motion that mimics the movement of attempting to
kick through a door.
8 Tic-Tocs
For 1 length of the warm up area, participants should swinging each
leg laterally and as high as possible, keeping both legs straight whilst
maintaining forward momentum and alternating legs each time.
9 Bounds For 1 length of the warm up area, participants should run with a
purposely over-extended stride length at a quick pace.
10 Single leg bounds
For 2 lengths of the warm up area, participants should perform a single
leg jumping action. Participants should then repeat the process for the
opposite leg.
11
Broad jump into
60% of a maximal
sprint
For 1 length of the warm up area, participants should perform a single
maximal broad jump, followed by a sprint of 60% of their maximal
speed.
12 Broad jumps For 1 length of the warm up area, participants should perform
consecutive maximal broad jumps for the length of the warm up area.
13
Run into maximal
vertical jump and
land
For 2 lengths of the warm up area, participants should perform a
maximal vertical jump following a short run up, land and jog through
to the end of the warm up area. Participants should then repeat the
process jumping off of the opposite leg.
14
Footwork patterns
into 75% of
maximal sprint
For 3 lengths of the warm up area, participants should perform a
precise ‘in and out’ whole body movement through the starting cones
before performing a 75% of their maximal sprint speed though to the
end of the warm up area.
15 Sprint variations
For 5 lengths of the warm up area, participants should complete 5
sprints of incrementally increasing speed that includes a sudden stop at
the end of the warm up area.
Table 4: Contents and procedures of the football specific dynamic warm up administered to
the dynamic warm up group.
Order Exercise Exercise Description
1 Jogging For 3 lengths of the warm up area, participants should jog at a
comfortable pace.
2 Skipping For 2 lengths of the warm up area, participants should skip as high
as they can whilst maintain forward momentum.
3 Sidesteps
For 2 lengths of the warm up area, participants should face
perpendicularly to the direction of warm up area whilst quickly
performing a quick lateral sidestep movement for the length of the
warm up area. Participants should then repeat the process facing in
the other direction.
4 Lunges For 2 length of the warm up area, participants should perform
quick lunges for either leg.
5 Straight leg
kicks
For 2 lengths of the warm up area, participants should kick as high
as they can with a straight leg, alternating legs each time.
6 Hamstring
sweeps
For 2 lengths of the warm up area, participants should best
perform a ‘hamstring sweep’ by keeping one leg bent with the
other straight and out in front of them. Whilst keeping their heel
on the floor and raising their toes, a stretch through the calf and
hamstring should be felt, participants should simultaneously bend
at the hips bringing their torso towards the ground and sweep the
floor with their hands in one smooth motion. Participants should
then repeat the process for the opposite leg whilst maintaining
forward momentum.
7 Open/Close
the gate
For 2 lengths of the warm up area, whilst balancing on one leg
participants should flex their non-supportive leg at the hip bringing
their knee towards their torso, then laterally move the leg away
from the midline of their body in a smooth and controlled
movement, alternating legs each time. For the second length
participants should repeat the process but in the opposite order so
that the leg starts laterally and moves back toward the midline of
the body.
8 Sprints
For 5 lengths of the warm up area, participants should perform 5
sprints of incrementally increasing speed that includes a sudden
stop at the end of the warm up area.
Upon completion of the 5 week period, all participants were recalled to perform the
same testing procedures as before, with all tests being completed in the same order.
Following the conclusion of the warm up intervention and final testing procedures,
Visual3D software was used in order to obtain flight time for each of the participant’s jumps,
measured from the instant of take-off to the instant of landing (figure 2). Using the flight time
of each jump, jump height was calculated using the same process as shown by previous
studies26,27
that also calculated jump height from force platform data. This method of
determining jump height shows high levels of reliability and validity28
and is shown below:
𝐽𝑢𝑚𝑝 𝐻𝑒𝑖𝑔ℎ𝑡 = 𝑣𝑡𝑜
2
2∙𝑔 Eq 1
where vto is the vertical take-off velocity, and g is acceleration due to gravity (-9.81 m∙s-1
).
In order to calculate vto, flight time for each participant’s jumps was used in the following
equation:
𝑣𝑡𝑜 = 𝑔∙𝑡𝑓𝑙𝑖𝑔ℎ𝑡
2 Eq 2
where t flight is flight time, and g is acceleration due to gravity (-9.81 m∙s-1
).
0
500
1000
1500
2000
2500
0 0.625 1.25 1.875 2.5 3.125 3.75 4.375 5 5.625
Gro
un
d r
ea
ctio
n f
orc
e (N
)
Time (s)
t flight
Figure 2: method of obtaining flight time (tflight) from a participant’s CMJ
performance.
Once jump heights had been calculated for each participant’s CMJ and CMJWA trials
paired-samples t-tests were performed using SPSS Statistics in order to determine significant
changes between pre and post intervention scores for both groups in all of the balance and
jump trials, with a significance value of P < .05 indicating a significant change.
Results
Significant changes (P < .05) were found in performance scores following both the
injury preventative and dynamic warm up protocols (table 5).
Table 5: Descriptive statistics of the performance measure outcomes following paired-
samples t-test analysis (P < .05)
Performance
measure Warm-up
Group mean
change (post
intervention
– pre
intervention)
Standard
deviation
t-
value
p-
value
CMJ Dynamic .20 cm ± 3.81 cm .140 .893
CMJ Injury
preventative 2.85 cm* ± 2.73 cm 2.77 .033*
CMJWA Dynamic - 2.10 cm* ± 1.77 cm 3.74 .020*
CMJWA Injury
preventative 3.10 cm* ± 3.06 cm 2.69 .037*
Single leg
stance test Dynamic - 2.19 s ± 9.60 s .604 .568
Single leg
stance test
Injury
preventative 13.37 s ± 16.60 s 2.13 .077
*significant difference between pre and post intervention score
A significant improvement (t [6] = 2.77, p = .033) in CMJ height was found for the
intervention group, with all members of the group observing an improvement in jump height
following the 5 week intervention (figure 3). In comparison, the control group observed a
non-significant improvement (t [6] = .140, p = .893) for CMJ height (figure 4), following the
5 week dynamic warm up protocol.
Figure 3: Pre and post CMJ heights for the injury preventative group
Figure 4: Pre and post CMJ heights for the dynamic warm up group
A significant improvement in jump height for the CMJWA (t [6] = 2.69, p = .037)
was also found for the intervention group, with 6 of the group’s participants showing an
improved jump height (figure 5) following the injury preventative warm up. The control
group in comparison actually observed a significant reduction (t [6] = 3.74, p = .020) in jump
0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6 7
Ju
mp
Hei
gh
t (c
m)
Participant
Pre-intervention Post-intervention
0
5
10
15
20
25
30
35
40
1 2 3 4 5 6 7
Ju
mp
Hei
gh
t (c
m)
Participant
Pre-intervention Post-intervention
height for the CMJWA (figure 6) following the dynamic warm up protocol. As expected,
individual CMJWA scores for both groups were greater than their corresponding CMJ scores.
Figure 5: Pre and post CMJWA heights for the injury preventative group
Figure 6: Pre and post CMJWA heights for the dynamic warm up group
A non-significant improvement of (t[6] = 2.13, p = .077) was found for the
intervention group’s balance scores, with every member of the group observing an
improvement (Figure 7) following the injury preventative warm up intervention. In
0
5
10
15
20
25
30
35
40
45
50
1 2 3 4 5 6 7
Ju
mp
Hei
gh
t (c
m)
Participant
Pre-intervention Post-intervention
0
5
10
15
20
25
30
35
40
45
1 2 3 4 5 6 7
Ju
mp
Hei
gh
t (c
m)
Participant
Pre-intervention Post-intervention
comparison, the control group saw a non-significant reduction (t [6] = .604, p = .568) in
balance score, with just 2 members of the group showing an improved score (Figure 8)
following the 5 week dynamic warm up program.
Figure 7: Pre and post balance scores for the injury preventative group
Figure 8: Pre and post balance scores for the dynamic warm up group
0
10
20
30
40
50
60
70
80
90
100
110
120
1 2 3 4 5 6 7
Tim
e in
ba
lan
ce (
s)
Participant
Pre-intervention Post-intervention
0
10
20
30
40
50
60
70
80
90
1 2 3 4 5 6 7
Tim
e in
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s)
Participant
Pre-intervention Post-intervention
Discussion
The purpose of this study was to test whether a shorter version of the “FIFA 11+”
warm up protocol could elicit jump and balance score improvements in 14 male collegiate
footballers. A 5 week injury preventative warm up program elicited significant improvements
in both CMJ (p = .033) and CMJWA (p = .037) scores, where-as a dynamic warm up
prompted no significant change in CMJ (p = .893) score and actually saw a significant
reduction in CMJWA (p = .020) performance. The injury preventative group also saw an
improvement in balance score, however the improvements were found not to be significant (p
= .077), whilst the control group also saw no significant change in balance scores (p = .568).
When trying to understand the mechanisms that may have caused the improvements
in jump heights for the intervention group, it should be considered that any improvements in
leg power would likely be associated with an improved ability to jump18
. The explosive
single and double leg bounding and jumping exercises that were included in the injury
preventative warm up are likely contributors to the improvements in jump height scores as
such exercises improve the strength, neuromuscular recruitment and co-ordination of the
muscle groups associated with jumping29
. When we also consider that the injury preventative
group performed these exercises 3 times a week for a total of 5 weeks we can perhaps begin
to understand why improvements in jump performance were observed. In comparison the
control group did not perform these type of exercise and subsequently saw no improvements
in CMJ and actually saw a significant reduction in CMJWA score.
The reasons for the reduction in CMJWA scores for the dynamic group are less
obvious. As part of the dynamic warm up, the group didn’t perform the same exercises
associated with improved jumping performance as seen in injury preventative group. This
could explain why no jumping improvements were observed, although as to why each of the
participants CMJWA scores significantly reduced is more puzzling. Perhaps the timing of the
intervention may have played a part. Seeing as how the benchmark testing occurred before
the playing season was fully underway and the final testing occurred midway through the
season accumulated fatigue from the participant’s matches and training session may have
meant fatigue, which can significantly affect vertical jump performance30
, caused a reduction
in final testing jump performances. If we also consider that lower extremity fatigue can cause
biomechanical alterations during jumping and landing and increase the risk of injury31
, as
well as cause participants to produce significantly reduced amounts of force when jumping
and landing whilst fatigued32
we can perhaps understand why reduced jump scores were seen
for the control group. One reason as to why the injury preventative group did not display the
signs of fatigue could be down to the constituents of the warm up program potentially
protecting the participants against the effects of accumulated fatigue. The injury preventative
group were consistently performing exercises that have been shown to reduce the risk of
injury8,10-13
, the mechanisms of which could be due to those exercises eliciting strength and
neuromuscular control improvements29
in the lower extremities. Neuromuscular control is
defined as the unconscious response to a change in joint stability33
, which has been shown to
improve significantly following injury preventative warm ups15,16,20,21
. As a result, these
changes may have allowed for a greater tolerance towards fatigue, thus potentially explaining
why the injury preventative group’s results seemed less affected than the control groups.
Several limitations to the study should be noted. It could be said that the group
assignment of the participants is one such limitation. The intervention group’s participants
were 1st and 2
nd team squad players only, whilst the control group were made up of 3
rd and 4
th
team players. This was done due to the training schedules of all of the playing squads and so
that both warm up interventions could be delivered to both the control and injury preventative
groups. However, seeing as higher level footballers often display greater physiological
capabilities34
such as strength and power levels35
, aerobic endurance36
and fatigue tolerance34
to name but a few, it would make sense that higher level squad players would produce greater
results in physical performance tests like jump and balance tests. The results of this study
would advocate this theory, however due to the nature of the paired sample t-test, it is the
degree of change from pre to post scores for each group, independently from one another that
is measured for. This would suggests that the main variable responsible for the significant
improvements in testing scores was the type of warm up intervention and the difference in
physical capabilities of each group’s participants was less of a factor.
The study’s small sample size could also be considered a limitation to this study.
Small sample sizes can affect the reliability of a study’s results37
and may also stand as a
possible explanation as to why despite a relatively large post intervention improvement in the
injury preventative groups averaged balance scores the changes were found not to be
significant. When considering the balance performances of both of the groups, we can see
that the results of both groups performances contain large standard deviations from the mean
score (table 5). Because of the large within-subject differences and a small sample size, the
ability to determine whether changes in balance score were predominantly due to the type of
warm up becomes difficult. As a result, it could be said that a larger sample size may have
allowed for results that more reliably reflect the effects of different warm up interventions on
balancing ability.
Interestingly, similar research that examined the performance effects of the full “FIFA
11+” protocol20
included a much larger sample size (intervention; n = 42, control; n = 39). It
was shown that the injury preventative program did lead to significant improvements in
balance performances (p = .005) in time-to-stabilisation test. This potentially highlights the
effects that a larger sample size has on balance scores, although it should be noted that the
full “FIFA 11+” protocol was used as well as a longer intervention period and so direct
comparisons between the studies are difficult.
The single leg stance test was used as the balance test for this study. It was chosen as
it requires no additional equipment and the test’s simplicity allowed for a relatively efficient
means of testing, which was necessary as all 14 participants were tested on the same days in
the same laboratory. However, the test relies on a subjective assessment of when the
participant has lost balance and although the testing protocol defines when a loss of balance
occurs24
it is still reliant on human judgement which in turn can be erroneous and lack
consistency. On top of this, football is a highly dynamic sport, so the use of the single leg
stance test may not truly represent the balance requirements of the sport. Previous
research15,20,21
has demonstrated significant improvements in balance performance following
similar warm up interventions when a more dynamic means of balance assessment such as
the time-to-stabilisation test20,21
or the star excursion balance test15,16
was used. This could
perhaps explain why no significant improvements in balance performance were observed
following the injury preventative warm up intervention as the testing protocol may not have
best represented the participants’ balancing capabilities.
When looking at jump performances specifically, CMJ performance significantly
improved in collegiate footballers following a warm up intervention containing similar
exercises to those used in the injury preventative warm up in this sudy19
. As well as this,
following an intervention of FIFA’s “The 11” program, the predecessor to the “FIFA 11+”,
significant improvements in CMJ performance were observed18
, albeit in young children (age
10.4 ± 1.4 yrs). On top of this, similar studies to this one have shown that both balance ability
and jump performance were significantly improved following warm up interventions21
,
further adding to the evidence that injury preventative warm ups can elicit performance
improvements in footballers. Having said this, contrasting studies have shown no significant
improvements in performance tests following injury preventative warm ups17,20,22,23
. As a
result, the performance impacts of an injury preventative warm up in footballers remains
inconclusive.
In conclusion, this study has shown that jump performances are significantly
improved following an injury preventative neuromuscular warm up intervention, where- as a
dynamic warm up intervention does not elicit such improvements as was hypothesised.
Although balancing ability was shown to be improved following the injury preventative
intervention it was found to be in a non-significant manner, contrasting to previous research.
The results of this study would suggest that a shorter and adapted version of the “FIFA 11+”
program is enough to elicit jump performance improvements in collegiate footballers. Injury
preventative warm ups significantly reduce the risk of injury in adult footballers8,10-13
however there is a growing amount of evidence, this study included, that would suggest
injury preventative warm ups can also elicit significant performance improvements as well.
This perhaps shows the importance of injury preventative warm ups for not only the well-
being but also the performance of athletes.
Acknowledgements
The author is highly thankful to the University of Leeds Men’s Football Club for the
use of their players as the participants for this study as well as the University of Leeds Sports
Science Department for the use of its facilities.
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