Hamstring strains are among the most common injury in sport and are most often observed in sports that involve sprinting, turning, and jumping (8,38,63). The prevalence of hamstring strains has been measured between 11 and 16% in studies of soccer, Australian rules football, and cricket (92). This can result in an average of 6 players per squad suffering a hamstring injury (defined as “preventing player participation in a match”) each season in professional soccer and Australian rules football

1. Hamstring Strain
Prevention in Elite
Soccer Players
Anthony N. Turner, MSc, CSCS*D,1
Jon Cree, MSc, CSCS,1
Paul Comfort, MSc, CSCS*D,2
Leigh Jones, BSc,3
Shyam Chavda, MSc, CSCS,1
Chris Bishop, MSc,1
and Andy Reynolds, MSc4
1
London Sport Institute, Middlesex University, London, United Kingdom; 2
College of Health and Social Care,
University of Salford, Manchester, United Kingdom; 3
Sport and Exercise Science Department, Huntingdonshire
Regional College, Huntingdon, Cambridgshire, United Kingdom; 4
Medical Services, Harlequins RFC, London,
United Kingdom
A B S T R A C T
HAMSTRING STRAINS ARE A
COMMON SOFT TISSUE INJURY IN
ELITE SOCCER. THE INJURY AND
REINJURY RATES FOR THIS ARE
HIGH, AND EFFICACIOUS PRE-
VENTION STRATEGIES ARE YET TO
BE STANDARDIZED. AFTER THE
RESEARCH HEREIN, TRAINING
MODALITIES EMPHASIZING
HAMSTRING ECCENTRIC
STRENGTH TRAINING PRO-
GRESSING FROM LOW-VELOCITY
TO HIGH-VELOCITY ACTIVITIES
AND THE PREVENTION OF
FATIGUE (I.E., CONDITIONING
DRILLS) ARE RECOMMENDED.
INTRODUCTION
T
he growth of soccer as a recrea-
tional and competitive sport
has been evidenced through lit-
erature, and it is estimated that around
200 million people participate, includ-
ing both sexes and across all age
groups (30,66,70). Scandinavian studies
documented a high risk of injury within
sport, accounting for 10–17% of all
acute injuries seen in an emergency
room (26,58,96). It has also been repor-
ted that the risk of injury to profes-
sional soccer players is around 1,000
times higher than for industrial
occupations regarded as high risk
(31,38,40,91).
Hamstring strains are among the most
common injury in sport and are most
often observed in sports that involve
sprinting, turning, and jumping
(8,38,63). The prevalence of hamstring
strains has been measured between 11
and 16% in studies of soccer, Australian
rules football, and cricket (92). This can
result in an average of 6 players per squad
suffering a hamstring injury (defined as
“preventing player participation in
a match”) each season in professional
soccer and Australian rules football (92).
The aim of this review therefore is to
explore the pathophysiology and mech-
anism of hamstring strain injury and
review current injury prevention strate-
gies. Recommendations for hamstring
injury prevention will then be consid-
ered together with implications for
training.
DEFINING THE PROBLEM
The documentation for the occurrence
of hamstring injuries is available primar-
ily in soccer (38,71,86,92), rugby (12),
and Australian rules football (65), where
a high prevalence has been reported (11–
16% of total injuries). Work by the Foot-
ball Association, who undertook an epi-
demiological study of injuries sustained
in English professional soccer over 2
competitive seasons (1997–99), docu-
mented that 12% of all injuries were
hamstring strains (40,92). This is further
supported by Dvorak and Junge (30) and
Hawkins et al. (39) who found that more
posterior upper leg injuries occurred in
elite soccer players than lower leg, with
the majority of them being acute trau-
matic strains. In addition, Rolls and
George (71) conducted a prospective
analysis of all academy-aged players
from an English Premier League club
during one season and found that of
the 93 players assessed 20 suffered ham-
string injuries that season (21.5%).
Arnason et al. (5) hypothesized a signifi-
cant relationship between the total num-
ber of injury days per team and team
performance. Throughout the duration
of the 1999 Icelandic Football League
season, 17 teams, spread over the 2 upper
divisions, recorded approximately 10
injury days per player. They then sug-
gested that injuries to key players would
detract from team success. Furthermore,
though players can be substituted for
part or a whole match, or replaced by
acquiring a new player from other clubs,
the limited resources of most teams to be
able to buy quality replacements, and in
the age of transfer windows when even
wealthy clubs are unable to do so, inju-
ries may also be seen as a financial issue.
Despite its prevalence, the treatment of
hamstring strains continues to be
K E Y W O R D S :
soccer; hamstring; injury; Nordics; eccen-
tric loading; prevention
VOLUME 36 | NUMBER 5 | OCTOBER 2014 Copyright Ó National Strength and Conditioning Association10

2. a frustration to medical personnel, not
only because of high incidences but
also because of the high reoccurrence
rates that exist with this injury. Brooks
et al. (12) recorded a 23% reoccurrence
rate of hamstring strains and noted that
these reoccurring injuries were signifi-
cantly more severe than new injuries.
This is corroborated by Hawkins and
Fuller (38), Petersen and Holmich (67),
and Verrall et al. (84) with the latter
research team suggesting that athletes
who have previously suffered a poste-
rior thigh injury have a 4.9 times
increased risk of a hamstring strain
than those without. This higher risk
of recurrence of injury may be attrib-
utable to incomplete rehabilitation
practices that commonly neglect the
eccentric and high-velocity require-
ments of the hamstring muscles during
sporting activities (19).
The literature demonstrates that ham-
string strains within professional soccer
are an ongoing quandary for players,
coaches, and medical staff. It has been
argued that the solution lies with pre-
vention strategies rather than from
treatment alone (8,39,83). Significantly,
Woods et al. (92) revealed that some of
the 91 English professional soccer clubs
sustained very few hamstring strains
over a period of 2 seasons, whereas
other clubs reported very high rates.
They suggest that these differences
could be because of a variety of variables
in injury diagnosis, training techniques,
and medical management; however, it
does at least suggest that the occurrence
of these injuries can be reduced.
Despite the aforementioned prevalence,
there is a surprising lack of research for
the prevention of hamstring strains,
perhaps because of the limited under-
standing of the pathophysiology and
risk factors that predispose athletes to
this injury (92). There is currently no
consensus for the most effective preven-
tion regime; however, there are several
modalities in place that are generally
regarded as appropriate and safe. These
modalities are based on the predictive-
causative factors of hamstring strains,
namely, inadequate hamstring strength
(8,11,35), strength imbalance between
hamstrings and quadriceps (22,33,95),
poor hamstring flexibility or reduced
range of motion (8,24,67), early fatigue
(35,92), and improper warm-up proto-
cols (67,79). These factors, and more
recent research on the beneficial effects
of increasing eccentric hamstring
strength (57,61), may hold the key to
reducing the risk of hamstring strains.
PATHOPHYSIOLOGY AND
MECHANISM OF INJURY
To reduce the risk of hamstring
strains, it is important to establish
the etiology and mechanics of the
injury mechanism. If patterns can be
determined in the events leading up
to an injury, then this information
may be applied to facilitate prevention
and rehabilitation (8).
PATHOPHYSIOLOGY
The hamstring group consists of 3
individual muscles: biceps femoris,
semitendinosus, and semimembrano-
sus. The hamstrings work primarily
to flex the knee and extend the hip.
It is commonly hypothesized that
one reason for the susceptibility of
hamstring strain injury is because of
its biarticular formation, whereby it
crosses over 2 joints and is therefore
subject to stretch at more than one
point (28,40,65,92).
Also creating knee flexion, the ham-
strings co-contract to minimize both
anterior and lateral tibial translation
(2,31,50) aiding knee stability (1). In
addition, the biceps femoris muscle
secondarily acts as a lateral rotator of
the semiflexed knee and extended hip.
Specific to soccer, it has been suggested
that the hamstrings’ main roles are to
control the running action and stabilize
the knee during turns or tackles (90).
Given the rotational demands of soccer
(multiple changes of direction), this
may explain the specific predisposition
of this muscle to injury as corroborated
by the research of Hawkins et al. (40)
and Woods et al. (92) who annotated
player’s injuries over 2 seasons from 91
professional soccer clubs. Hamstring
strains accounted for 12% of total in-
juries (40,92), of which 53% involved
the biceps femoris (92). This is further
supported by Connell et al. (20), who
assessed hamstring injuries in 60 male
professional football players. The biceps
femoris was recorded to be the most
commonly injured muscle, further con-
firming the findings of earlier reports by
De Smet and Best (27) and Brandser
et al. (10). More specifically, it is re-
ported that it is the long head of biceps
femoris that is most commonly injured
during sprinting activities (20,53,77).
The biceps femoris has 2 heads, a long
head that has an origin of the medial
facet of the ischial tuberosity and a short
head that has an origin of the lateral
linea aspera, lateral supracondylar line,
and the intramuscular septum. Both
heads run down to form one common
tendon at the head of fibula, the lateral
condyle of the tibia, and the fascia of
the leg. The 2 heads have 2 different
nerve innervations, the long being sup-
plied by the tibial branch of the sciatic
nerve and the short head being sup-
plied by the peroneal branch. This dual
innervation has been postulated to
cause asynchrony of the nerve stimula-
tion to the muscle and therefore could
predispose the biceps femoris to imbal-
ances and subsequent tears (52,78).
MUSCLE STRAIN
CHARACTERISTICS
Muscle strain injury is characterized by
a disruption of the muscle-tendon unit,
usually occurring at the proximal muscu-
lotendinous junction (20,27,76). Strains
usually occur when the muscle is either
elongated passively or activated during
stretch (55). When the muscle is activated
eccentrically, a greater magnitude of force
can be generated (1.5–2 times greater) in
comparison with either an isometric or
a concentric contraction (55). Lack of
preconditioning or larger than usual force
can lead to injury to the muscle, myoten-
dinous unit, or the tendon itself (55).
Clinically, sport physicians will classify
injuries into a 3-point grading system.
Grade 1 being a mild injury where
a few fibers are torn, grade 2 a moder-
ate injury where several fibers are torn,
and grade 3 is a complete tear (13).
Magnetic resonance imaging or com-
puterized tomography scan is often
Strength and Conditioning Journal | www.nsca-scj.com 11

3. used to determine the position and size
of the injury because the size of the tear
has been linked to the number of days
lost to the injury (87). The position of
tear does change the level of pain felt
by the athlete but does not seem to
determine the length of injury (84).
MECHANISM OF INJURY
Schache et al. (76) were able to record
biomechanical measurements using
kinematic and ground reaction force
data for pre- and post-hamstring injury
suffered while sprinting. They demon-
strated that the injured leg showed
greater knee extension and hamstring
muscle-tendon length during the ter-
minal swing than the uninjured leg
and before injury. This was in addition
to an increased peak vertical ground
reaction force and loading rate and
an increased peak hip extensor torque
and peak hip power generation during
initial stance. They concluded that the
injury most likely occurred before the
foot strike during the terminal swing
phase of the sprinting movement as
a result of an eccentric muscle action
where the bicep femoris was length-
ened across both the hip and knee
(76). This supports previous literature
that hypothesized the temporal occur-
rence of the majority of hamstring
injuries. For example, most studies sug-
gest that hamstring strains occur most
commonly during rapid sprint acceler-
ation and during the later part of the
swing phase (terminal swing) when
the hamstrings are working to deceler-
ate the limb and control extension of
the knee (8,24,34,67,92). Here, the ham-
strings must change from functioning
eccentrically to decelerate knee exten-
sion and hip flexion and to functioning
concentrically as an active extensor of
the hip joint. It is stipulated that during
this rapid changeover from eccentric to
concentric function, the hamstring is
most vulnerable to injury (85). These
findings correspond to that of Thelen
et al. (80) who provided a direct mea-
surement for hamstring muscle kine-
matics. The study showed that peak
hamstring muscle lengths, specifically
the biceps femoris muscle, occurred in
the late swing phase before foot contact
and that biceps femoris excitation
increased markedly between 70 and
80% of the gait cycle and continued
through the end of the swing phase.
RISK FACTORS
Understanding the individual risk fac-
tors for hamstring strains is an impor-
tant feature in preventing injury and is
the basis from which preventative
measures can be developed. Risk fac-
tors tend to be subcategorized into 2
main sections, nonmodifiable and mod-
ifiable. Nonmodifiable factors are issues
that cannot be changed, whereas the
modifiable factors can be.
NONMODIFIABLE FACTORS
The most common nonmodifiable fac-
tors in the literature are previous
injury, age, and black or aboriginal eth-
nic origin (8,34,84,92).
Previous injury. It has been postulated
that athletes who have previously suf-
fered a posterior thigh injury have a 4.9
times increased risk of reinjury than
those who have not (85). It was hypoth-
esized by Verrall et al. (85) that the
buildup of scar tissue around the mus-
culature reduces its functional capacity,
thus increasing the risk of injury. This
correlates to Bhar and Holme (8) who
state that a previous injury can lead to
a reduced range of motion or reduced
strength, thereby indirectly affecting
injury risk. This is evidence of the cumu-
lative injury cycle of Herring (43), in
which inappropriately treated injuries
can lead to recurring injuries. Essen-
tially, the injury leads to scar tissue for-
mation, which can cause a loss of range
of motion at one or more body seg-
ments which in turn leaves the athlete
susceptible to reinjury.
Alternatively, the athlete may be vulner-
able to injury if they have not injured
their hamstrings previously but have suf-
fered an injury either proximally or dis-
tally to the hamstring—for example, from
gluteal or calf musculature. The athlete
will develop movement patterns to com-
pensate for loss of range of motion at the
injury site by moving excessively at adja-
cent segments. This concept is referred
to as relative flexibility (a process by
which the body finds the path of least
resistance to motion), which links move-
ment dysfunction to pathology (73).
Essentially, during a multijoint functional
movement, the stiff joint or muscle will
prevent motion so the required move-
ment is achieved by another joint mov-
ing through an excessive range of
motion. This, in turn, leads to muscle
imbalances that increase the risk of fur-
ther injury (16).
Age and exposure. Verrall et al. (85)
demonstrated hamstring strains to be
more common in older athletes. This
supports evidence from Arnason et al.
(4) who undertook a comparative epi-
demiological study of injuries in youth
and senior football club players. They
concluded that the occurrence of inju-
ries was higher at a senior club level.
Both studies fail to offer an explana-
tion; however, a study by Gabbe et al.
(34) proposed that the increased risk
was attributed to a loss in skeletal mus-
cle mass. They suggest that as the
body ages, there is a reduction in the
cross-sectional area of skeletal muscle
and an increase in nonmuscular con-
nective tissue; this may further explain
the increased risk of reinjury. As the
force that a muscle can generate is pro-
portional to the cross-sectional area,
a reduction in muscle strength is there-
fore seen. These changes combined
with age-related degeneration of mus-
cle fibers may increase the risk of ham-
string injury. However, for the
population concerned, that is, elite
athletes, this is not likely to be a causa-
tive factor as the level of atrophy
and degeneration reported by these
studies concern more senior athletes
(.40 years).
Rolls and George (71) studied elite soc-
cer players from 9 to 19 years and
found that the older subjects suffered
more hamstring injuries. They contrib-
uted this to the fact that those subjects
were in full-time training, whereas the
younger subjects had their exposure
limited. The authors conceded that
although this was a plausible theory,
they lacked the quantitative data to
compare training exposure with injury
prevalence. However, Dvorak and Junge
Hamstring Strain Prevention in Elite Soccer Players
VOLUME 36 | NUMBER 5 | OCTOBER 201412

4. (30) conducted a literature review of
injury rates in soccer players and found
an incidence rate ranging from 0.5 to 45
injuries per 1,000-hour exposure.
Regardless of the actual rate, however,
this may be evidence that the increased
exposure of soccer players contributes to
their increased rate of injury. It may be
hypothesized that this creates more time
to develop the muscle imbalances dis-
cussed later in this text.
Ethnicity. The studies from Woods
et al. (92) and Verrall et al. (85) both
show that players with a black or
aboriginal ethnic origin are more at
risk of sustaining a hamstring strain
than Caucasian players. Verrall et al.
(85) suggest that because aboriginal
players are considered to be the fast-
est and most skillful players, they are
more likely to have a greater propor-
tion of type II (fast twitch) muscle
fibers that in turn may predispose
them to injury. This specific predispo-
sition is not fully understood; how-
ever, it has been postulated that
type II muscle fibers are more suscep-
tible to injury because of the faster
contraction times or stretch being
placed upon a muscle when it is con-
tracting (9).
Conversely, Woods et al. (92) suggest
that the increased risk of injury could
relate to the anterior tilt of the pelvis
usually seen in black or aboriginal eth-
nicities. Therefore, because of the biar-
ticular formation of the hamstring
group attaching onto the ischial tuber-
osity, an anterior tilt of the pelvis would
cause the hamstring complex to be
placed at a greater stretch, thus increas-
ing the risk of injury. Similarly, Russek
(72) demonstrated that individuals
from Asian and African backgrounds
exhibit joint hypermobility more so
than Caucasian populations. In addi-
tion, evidence has been submitted that
hypermobile individuals have compro-
mised proprioceptive acuity, especially
at the knee (36). This combination of
joint hypermobility, decreased propri-
oception, and increased anterior pelvic
tilt may lead to greater stretch of the
hamstring muscular-tendon unit and
thus a strain.
MODIFIABLE FACTORS
Although a number of risk factors have
been proposed for hamstring strains,
such as poor posture, neuromeningeal
tightness, decreased muscular control,
and poor technique (8), there are only
limited data for these variables. There-
fore, in this discussion, we will focus on
the most prominent and researched fac-
tors: low hamstring strength, fatigue,
and quadriceps flexibility.
Quadriceps flexibility. The study by
Gabbe et al. (34) was the only study
found which discussed the possibility
of quadriceps flexibility as a risk factor
for hamstring injury. Despite this, how-
ever, the arguments put forward by the
authors were significant enough to
include in this article. They suggest
that the relationship is because of an
alteration in the mechanics of running
and sprinting. At the pre-swing posi-
tion, the rectus femoris muscle is
lengthened and acts eccentrically to
arrest extension of the hip and flexion
of the knee (64). In this stretched posi-
tion, its tendon absorbs energy to be
released during the active flexion of
the hip and knee, when the leg is accel-
erated forward. Before initial foot con-
tact, the hamstrings must contract
eccentrically to decelerate this forward
momentum. If the rectus femoris mus-
cle is tight, however, there may be a rise
in the passive elastic recoil of the ten-
don, further increasing the acceleration
of the leg. This increases the load on
the hamstrings, thereby increasing the
risk of injury. It should be noted, how-
ever, that this is speculative, and the
relationship between the increased
tightness of the rectus femoris and
the resultant increase in force produc-
tion needs to be researched further to
support such a claim.
Fatigue. Woods et al. (92) reported that
most strains occurred at the end of
matches and training sessions. This is
corroborated by Price et al. (69), who
documented that 36% of injuries sus-
tained in competition occurred during
the last third of each half. Moreover,
evidence from Pinniger et al. (68) sug-
gests that when soccer players become
fatigued during maximal sprinting,
early activation of the biceps femoris
and semitendinosus muscles occurs
during the swing phase of the cycle.
This is in agreement with Verrall
et al. (85) who states that this recruit-
ment pattern may be because of local
muscle fatigue and may be causative to
hamstring strains. In agreement, the
recent study of Wright et al. (94) dem-
onstrated that as fatigue increases so
too does biceps femoris activity during
knee extension (concentric quadriceps)
movements in recreational soccer
players.
These studies highlight a possible
positive relationship between fatigue
and hamstring strains. Despite this
plausible link, however, there is yet
to be a study that examines these var-
iables within elite athletes. However,
in vitro animal studies by Mair et al.
(60) may provide further support to
such a hypothesis. The extensor dig-
itorum longus muscles from 48 rabbits
were fatigued to different levels of
severity, then stretched to failure,
and compared with their nonfatigued
contralateral controls. The results
demonstrated that fatigued muscles
are able to absorb less energy before
reaching the degree of stretch that
causes injury, suggesting that fatigue
is an important factor in the pathogen-
esis of acute muscle strains. However,
it should also be noted that muscles
were injured at the same length,
regardless of fatigue.
Strength. It seems logical to suggest
that the body must be appropriately
conditioned to combat the physical
demands of sport and that prevention
strategies should, in part, be based on
an analysis of variables, such as an ath-
lete’s ability to produce and absorb
force. In addition, the fact that low
hamstring strength, particularly in
comparison with quadriceps strength,
has been proposed as a potential risk
factor (8,21,33,95) may further corrob-
orate this.
Quadriceps to hamstring strength has
invariably been determined by com-
paring the concentric strength of each
Strength and Conditioning Journal | www.nsca-scj.com 13

5. muscle group isokinetically (7,14,95).
Fowler and Reilly (33) analyzed injured
professional soccer players and found
that the hamstring to quadriceps con-
centric strength ratio (H:Q) of the
injured leg (0.5) was approximately
0.13 lower than that of the uninjured
leg (0.63). This was in agreement with
several other studies which reported
that a concentric H:Q of ,0.6 was an
indicator of an increased risk of ham-
string injury (32). This verifies the prin-
ciple that an H:Q lower than 0.6 may
incline a soccer player toward injury
(90). Not surprisingly, the literature
suggests that players at higher compet-
itive and skill levels have higher con-
centric H:Q ratios (90), in the vicinity
of 0.72–0.83 in professional, semipro-
fessional, and college levels (17).
Though widely analyzed and reported, it
has been argued that H:Q concentric
strength is not a functional assessment
and thus not related to the mechanisms
of injury (19). A more functional assess-
ment of strength is to express the H:Q in
terms of hamstring eccentric strength to
quadriceps concentric strength because
of the primary role of the hamstrings
to brake knee extension and tibial trans-
lation, as outlined previously in this arti-
cle. With this in mind, the eccentric
torque produced by the hamstrings
(Hecc) would need to match the con-
centric torque of the quadriceps (Hconc)
to prevent possible injury, that is, a Hecc:
Qconc of 1:1. This has been supported by
previous research (14,21,95). Additionally,
when sprinters with previous hamstring
injuries were compared with those with-
out previous injuries, the injured runners’
hamstrings were weaker at all speeds
eccentrically and at low speeds concen-
trically and were also less flexible (48).
As previously stated, most hamstring
strains occur during rapid acceleration.
It is conjectured that if the forces nec-
essary to resist knee extension and
begin hip extension are too high, the
tolerance levels of the muscle-tendon
system could be surpassed which
would ultimately lead to a musculoskel-
etal lesion (21,95). It is perhaps this
movement for which the hamstrings
are not functionally conditioned.
Several articles have therefore sug-
gested that because this movement oc-
curs during eccentric muscle actions,
eccentric strength training could hold
the answer in the prevention of these
injuries (3,25,49,61,92). This is also
supported by LaStayo et al. (55) who
note that muscle and tendon appear
very capable of adapting to such high
forces, as long as the muscle experien-
ces the stimulus progressively and
repeatedly. This adaptation of tendon
and skeletal muscle occurs through
an increased reorganization and syn-
thesis of collagen structures (51). Kjaer
(51) showed that heavy resistance
exercise, specifically eccentric exercise,
improved symptoms within patients
and that an increase in collagen struc-
tures would be present with this inten-
sity and type of modality. This study,
along with that of LaStayo et al. (55),
correlates with several other authors
(92,93) who have emphasized high-
velocity eccentric exercise (with inher-
ent high forces) during the late stage
of rehabilitation, which should be
used in conjunction with exercises
for both directly above and below
the hamstrings—for example, gluteals
and calf complex.
In this regard, training studies have pri-
marily focused on the Nordic ham-
string curl (Figure) (75). A 10-week
preseason hamstring strength training
program incorporating eccentric over-
load demonstrated significant im-
provements in hamstring injury rate,
isokinetic strength, and maximal sprint
speed in elite male soccer players dur-
ing the following 10-month season
(6,61). Mjølsnes et al. (61) examined
the effects of a similar 10-week training
program, comparing the traditional
hamstring curl (concentric training)
and the Nordic hamstring exercise
(eccentric training) on well-trained
soccer players. The results showed that
the Nordic hamstring group showed
an 11% improvement in eccentric ham-
string torque and isometric hamstring
strength, whereas the hamstring curl
group observed no change. However,
with respect to injury strain rates, no
comparison was made. It is also
significant to point out that the Nordic
hamstring curl is very difficult to per-
form without a specific strength base.
Consequently, and until the athlete is
able to perform the exercise, they are
advised to perform the concentric por-
tion of leg curls (i.e., leg flexion) bilat-
erally, followed by the eccentric
portion unilaterally, thereby increasing
the relative load (18).
Furthermore, the effects of a standard-
ized warm-up protocol incorporating
either the Nordic exercise or a propri-
oceptive neuromuscular facilitation
(PNF) flexibility routine on hamstring
injury rates during a 2-year period in
elite Scandinavian soccer teams were
conducted (5). The study was over 4
consecutive seasons (1999–2002), with
the first 2 seasons being used as a base-
line from which comparisons could be
made. The concluding 2 seasons incor-
porated the intervention program
whereby only the Nordic exercise
group had significantly fewer ham-
string injuries and on average fewer
injuries than they had for the previous
3 years. The flexibility group showed
no improvements.
It is essential with any training program
that it works toward the specificity of
movement in terms of velocity. Sale
(74) claims that knee angular velocity
during a sprint gait cycle is as high as
600–7008/s. However and despite these
high velocities, electromyographic activ-
ity of the hamstrings is high during the
swing phases (48). With this in mind,
Table 1 provides recommendations on
frequency, volume, and periodization of
the Nordic hamstring curl. The program
should take place over at least a 10-week
period in the preseason. Initially, loading
is increased by attempting to control the
eccentric contraction for longer and over
a fuller range of motion. A dramatic
increase in repetitions is not required
because of the resultant increased forces
exerted, as the athlete is able to control
the exercise through a greater range
of knee extension, thereby creating
overload.
As previously mentioned, hamstring
strains are also reported to occur at
Hamstring Strain Prevention in Elite Soccer Players
VOLUME 36 | NUMBER 5 | OCTOBER 201414

6. the proximal insertion of the ham-
string. During the Nordic hamstring
exercise, however, the proximal/hip
attachment of the muscle stays in a rel-
atively constant position, whereas the
distal/knee insertion moves through
a range of up to 908 (75). The stiff-
leg/Romanian deadlift, where the knee
angle is kept relatively constant while
the hamstrings contract at the hip
attachment, may therefore provide an
appropriate addition for hamstring
strength because this exercise targets
the proximal insertion. One criticism
of the stiff-leg/Romanian deadlift
would be that it does not address the
eccentric role of the hamstrings in
decreasing anterior tibial translation
and increasing knee stability (18).
The tibial translation problem could
be addressed by including both eccen-
tric movements of the stiff-leg/
Romanian deadlift and Nordic curl in
a program (18).
After these strength-based exercises,
and in the opinions of the authors, the
athletes may benefit from a progression
to higher velocity eccentric exercises,
for example, weightlifting (emphasizing
the catch phase) and plyometrics
(emphasizing the landing phase; dis-
cussed later in this text). Moreover,
Olympic-style lifts should, by consen-
sus, be taught with a top-down
approach (29). This will also help to
initially emphasize the posterior chain
musculature and minimize the anterior
quadriceps activity (29). Once a compe-
tent movement with a hang start posi-
tion has been achieved, a fuller range of
motion will need to be taught (e.g., start-
ing from the floor and finishing in a deep
squat position) and conducted to facili-
tate a higher maximal load (29). More-
over, plyometric training, within this
context, should principally address
landing mechanics via the use of drop
lands. The intensity can be increased by
gradually dropping from greater heights
and progressing to unilateral landings.
For a review of plyometric training,
see Turner and Jeffreys (81).
Although there have been no direct
epidemiological studies examining the
effects of plyometric training (or
Olympic-style lifting) on hamstring
muscle strain, Hewett et al. (44) identi-
fied an increase in hamstring torque
under plyometric training protocols.
Indirectly, this may suggest that plyo-
metric exercises could potentially
reduce the risk of injury and provide
eccentric strength adaptations similar
to that of the Nordic hamstring exercise.
Furthermore, as these exercises apply
both high velocities and forces through-
out the stretch-shortening cycle (45,82),
Figure. The Nordic hamstring curl (assisted [A] and unassisted [B]).
Table 1
Recommended frequency, volume, and periodization of Nordic hamstring
curl training during the 10-week preseason period and into the
competitive season
Week Sessions per week Sets Repetitions
1–2 2 2 3
3–4 2 3 3
5–6 3 4 3
7–8 2 2 5
9–10 2 3 5
11 onward 2 4 5
Strength and Conditioning Journal | www.nsca-scj.com 15

7. they inherently duplicate the muscle
activation pattern during the reported
mechanism of injury. As many studies
have also shown improvements in per-
formance parameters, such as speed,
strength, vertical jump height, and
decreases in lower extremity injuries,
as a consequence of a plyometric pro-
gram, its integration should be wel-
comed within most clubs (15,41,82).
Muscle imbalance. Because of the pre-
vious injury or postural predisposition,
the activation patterns of muscles in
specific movements change. This
change can cause extra load or pro-
longed load to a muscle and therefore
be a cause of injury (47).
In relation to hamstring injuries, hip
flexion and the activation of gluteal
muscles have been well discussed
(56,57,62). Lewis and Sahrmann (57)
showed that the muscle pattern can
be changed via verbal cues and the
hamstring muscles are activated
throughout hip extension. With this
said, an athlete who has been previously
injured or has learned to alter their run-
ning style might overload the hamstring
and therefore cause injury. Particular
attention should be focused on exercises
that allow the gluteals and the ham-
string complex to function as one.
Weimann and Tidow (88) among other
sprint coaches discuss the need for syn-
ergy between the gluteal muscles and
the adductor magnus. Adductor mag-
nus has 2 branches, one that acts to
adduct and flex the femur and one that
helps to extend the femur. Previous
electromyogram studies have not
looked at the activation or imbalances
of the adductor magnus solely because
of the technical difficulty of inserting
the electrode because of its deep posi-
tion in the posterior part of the leg.
However, it is theorized that if the glu-
teal and adductor magnus are not acti-
vating correctly, there is altered
rotation and pull on the femur, which
can cause increased stress to the pelvis
and subsequent load to the hamstrings.
In addition, the adductor magnus has
a secondary function of extending the
femur, which means that a weak
adductor magnus will also put addi-
tional load on the hamstring complex.
A second form of imbalance that has
very little review is the different activa-
tion patterns of medial (semitendinosus
and semimembranosus) and lateral
(biceps femoris) hamstring muscles.
Hubley-Kozey et al. (46) reported that
the medial to lateral hamstring ratio
was increased with patients with previ-
ously diagnosed knee arthritis. It could
be postulated that a similar change oc-
curs with other knee injuries or previous
hamstring injuries. This additional acti-
vation of the medial hamstrings could be
a causative factor in the medial ham-
strings being the most commonly injured
muscle.
Lynn and Costigan (59) showed that
the position of the ankle changes the
activation of the hamstring complex.
They found that external rotation in
open chain exercises increases the acti-
vation of biceps femoris and medial
rotation increases the activation of
the medial hamstring muscles leading
the author of this article to suggest that
by selecting or adapting routine exer-
cises with medial rotation of the ankle
we could strengthen and lessen the
effect of muscle imbalances between
the different hamstring muscles.
Hamstring flexibility. Flexibility proto-
cols are consistently included into an
athlete’s training schedule to improve
performance and more importantly
reduce the risk of injury (24). Dadebo
et al. (24) noted that 40% of the total
training time was dedicated to flexibility
training in English Premiership soccer
clubs. Despite this, however, the role of
stretching in enhancing flexibility and
reducing injury remains contentious.
Witvrouw et al. (89) examined 146 male
professional soccer players before the
1999/2000 Belgian soccer season. They
found that players who sustained a ham-
string strain had significantly less ham-
string flexibility before their injury
compared with the uninjured players.
They concluded that players with
increased hamstring muscle tightness
have a significantly higher risk of a sub-
sequent musculoskeletal lesion. In
addition, Cross and Worrell (23) exam-
ined the effects of static stretching on the
incidence of lower extremity musculo-
tendinous strains in 195 division III col-
lege soccer players in the 1994 and 1995
seasons. All variables were consistent
between the 2 seasons except for the
incorporation of a lower extremity–
stretching program in the 1995 season.
The results indicate that the number of
lower extremity musculotendinous
strains was reduced significantly
(48.8%) in 1995 compared with 1994
(43 versus 21 injuries). However, no data
were presented demonstrating whether
the players improved their flexibility. It is
therefore likely that a multitude of factors
may have contributed to the reduction in
the injury rate (63).
Rolls and George (71) conducted a pro-
spective analysis of 93 players between
the ages of 9 and 19 years at an English
Premier League club during one season
(2001–02), investigating the relation-
ship between injury and length of the
hamstrings. They measured hamstring
length using a variety of common as-
sessments, including modified sit and
reach, straight leg raise, active knee
extension, passive knee extension, and
seated knee extension. They found no
significant correlations between injured
and noninjured legs or between injured
and noninjured subjects. Similarly,
Hennessey and Watson (42) noted that
the differences in hamstring flexibility
were not evident between the injured
and the noninjured groups in 34 top-
level athletes from rugby, hurling, and
Gaelic football, and thus, it was sug-
gested that hamstring flexibility was
not a risk factor for hamstring injuries.
This is also supported by Larsen et al.
(54), who showed a static stretching
regime to be ineffective at improving
hamstring flexibility with healthy vol-
unteers. As previously highlighted,
these reports also corroborate with
Arnason et al. (3), who found a 2-year
stretching intervention to be ineffective
at reducing injury in elite soccer
players.
A possible explanation for the discrep-
ancies in results is the methodological
dissimilarities. All studies stretched
Hamstring Strain Prevention in Elite Soccer Players
VOLUME 36 | NUMBER 5 | OCTOBER 201416

8. and/or assessed the hamstring muscle
group in a different way. The study by
Hartig and Henderson (37) was
a paired exercise, where stretching
was performed standing. Cross and
Worrell (23) focused on individualized
static stretching, where the subject had
to grasp their ankles, and the study by
Arnason et al. (3) was based on a part-
ner PNF stretching exercise. It is there-
fore interesting to note that the
justification for stretching to prevent
hamstring strains appears largely
unfounded. In studies that do support
a beneficial effect, this relationship
should be viewed with caution as cor-
relations do not mean cause and effect,
especially in injuries that have a multi-
factorial etiology.
CONCLUSIONS AND PRACTICAL
APPLICATIONS
The injury and reinjury rates of ham-
string strains within professional soc-
cer have proven to be a frustration to
medical personnel. Consequently, pre-
vention strategies should be consid-
ered key and may be achieved
through adequate exercises focusing
on eccentric strength at both high
and low velocities and conditioning
drills focusing on the reduction of
fatigue. Appropriate low-velocity
strength training may include the Nor-
dic hamstring exercise, but it is sug-
gested that the stiff-leg/Romanian
deadlift should also be incorporated
to target the proximal insertion. Spe-
cific knowledge of muscle imbalances
around the posterior chain is
important for particular athletes. Sim-
ple modifications to an athlete’s pro-
gram, in respect to foot rotation or
gluteal/abductor magnus activation,
can lead to an improvement of function
around the pelvic girdle.
High-velocity strength training should
focus on plyometric exercises with ini-
tial emphasis on landing and the safe
dispersal of high forces. These drills
may then be progressed to depth jump
drills whereby reactive strength is
incorporated after the acceptance of
high eccentric loads. It is also recom-
mended that Olympic-style lifting be
included, progressing from the hang
start position to the full movement to
facilitate greater absolute load and
thereby emphasizing the catch posi-
tion where high eccentric loading is
experienced and progressively accom-
modated (Table 2).
Conflicts of Interest and Source of Funding:
The authors report no conflicts of interest
and no source of funding.
Anthony N.
Turner is
a strength and
conditioning
coach and is the
Programme
Leader for the
MSc in Strength
and Conditioning
at the London Sport Institute, Middlesex
University, England.
Jon Cree is
a strength and
conditioning
coach and the
Programme
Leader for the
BSc Strength and
Conditioning at
the London Sport
Institute, Middlesex University, England.
Paul Comfort is
the Program
Leader for the
MSc Strength
and Conditioning
at the University
of Salford.
Leigh Jones is
the curriculum
coordinator for
sport and exercise
sciences at Hun-
tingdonshire
Regional College
and the manag-
ing director of Future Fitness Training
Academy.
Shyam Chavda
is an academy
strength and con-
ditioning coach
for British Fenc-
ing and QPR
Football Club and
the Sport techni-
cian and weightlifting coach at the Lon-
don Sport Institute, Middlesex University.
Chris Bishop is
the lead strength
and conditioning
coach for Opti-
mum Elite Fit-
ness and
a lecturer on the
BSc Sport &
Exercise Science Program at the London
Sport Institute, Middlesex University.
Table 2
Suggested hamstring strain prevention exercises based on the evidence
presented herein
1. Nordic hamstring curls (see Figure and Table 1)
2. Stiff-leg/Romanian deadlift
3. Bilateral drop landing
4. Bilateral depth jumps
5. Hang power clean/hang power snatch
6. Squat clean/squat snatch (emphasizing a deep catch)
7. Single leg, multiplanar variations of exercises
Strength and Conditioning Journal | www.nsca-scj.com 17

9. Andy Reynolds
is Head of Medi-
cal Sciences at
Halequins RFC,
and the 1XV
Physiotherapist.
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Hamstring Strain Prevention in Elite Soccer Players
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