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van der HorstN, etal. Br J Sports Med 2017;51:1583–1591. doi:10.1136/bjsports-2016-097206
ABSTRACT
There are three major questions about return to play
(RTP) after hamstring injuries: How should RTP be
defined? Which medical criteria should support the
RTP decision? And who should make the RTP decision?
The study aimed to provide a clear RTP definition and
medical criteria for RTP and to clarify RTP consultation
and responsibilities after hamstring injury. The study
used the Delphi procedure. The results of a systematic
review were used as a starting point for the Delphi
procedure. Fifty-eight experts in the field of hamstring
injury management selected by 28 FIFA Medical
Centres of Excellence worldwide participated. Each
Delphi round consisted of a questionnaire, an analysis
and an anonymised feedback report. After four Delphi
rounds, with more than 83% response for each round,
consensus was achieved that RTP should be defined as
’the moment a player has received criteria-based medical
clearance and is mentally ready for full availability
for match selection and/or full training’. The experts
reached consensus on the following criteria to support
the RTP decision: medical staff clearance, absence of
pain on palpation, absence of pain during strength and
flexibility testing, absence of pain during/after functional
testing, similar hamstring flexibility, performance on
field testing, and psychological readiness. It was also
agreed that RTP decisions should be based on shared
decision-making, primarily via consultation with the
athlete, sports physician, physiotherapist, fitness trainer
and team coach. The consensus regarding aspects of RTP
should provide clarity and facilitate the assessment of
when RTP is appropriate after hamstring injury, so as to
avoid or reduce the risk of injury recurrence because of a
premature RTP.
INTRODUCTION
Hamstring injuries are the most prevalent muscle
injury in football, and 12%–33% of athletes with
a hamstring injury experience a recurrence within
a year after the initial injury.1–5 The burden of
hamstring injury is high: for the professional player
an average of 18 days and 3 matches missed per
season,5 and for the professional football club an
average of 15 matches and 90 days missed per
season.5 The inability to play because of injury,
but also because of unnecessary prolonged absence
from play during rehabilitation, affects the indi-
vidual player and team performance. Lower injury
burden and higher match availability are signifi-
cantly associated with a higher final league ranking,
points per league match and success in the Union of
European Football Association Champions league
or Europa League.6
Reducing the risk of injury recurrence is a key
priority after the initial hamstring injury. Recurrent
injuries require more extensive rehabilitation than
the primary injury, and previous injury is an undis-
puted risk factor for future injury.3 7–10 Particularly
alarming is the observation that recurrence rates
have not improved over the last 30 years.11–13 High
recurrence rates might be due to inadequate rehabil-
itation and/or premature return to play (RTP).14 15
Of all recurrences, more than half occur within
the first month after RTP.10 16 This has prompted
interest in RTP after hamstring injury.17–21
Unfortunately, different concepts of RTP make
it difficult to analyse and compare various studies
of RTP after hamstring injury.22 23 It is recognised
that diversity in definitions and methodologies
contributes to significant differences in the results
and conclusions obtained from sports injury
research.24–27 Furthermore, in accordance with the
Strategic Assessment of Risk and Risk Tolerance
framework (figure 1), it is commonly agreed that
any RTP decision should be based on an assess-
ment of the risk and the acceptable risk tolerance
threshold.28 29 So far, no studies have specified
how risk should be assessed when clinicians are
faced with the RTP decision after hamstring injury,
although this moment is vital if injury recurrence
is to be prevented. A recent systematic review of
the literature showed that there is great diversity
in how RTP after hamstring injury is defined and
which criteria are used to assess RTP readiness.22
Also, because multiple stakeholders have their own
reasons why RTP should be accelerated or delayed,
it is imperative to provide clarity on who is to
be consulted and who is responsible for the RTP
decision.
The aim of this Delphi procedure was to deter-
mine, based on expert consensus, a clear defini-
tion of and medical criteria for RTP and to clarify
responsibilities for RTP after hamstring injury.
MATERIALS AND METHODS
Study design and setting
This Delphi study was part of the Hamstring Injury
Prevention Strategies project, which includes several
studies focusing on the prevention of hamstring
(re-)injuries. The present Delphi procedure is one of
these studies and aimed to achieve consensus on the
terminology, definition and medical criteria for RTP,
and who should be involved and responsible for the
Return to play after hamstring injuries in football
(soccer): a worldwide Delphi procedure regarding
definition, medical criteria anddecision-making
Nick van der Horst,1 FJG Backx,1 Edwin A Goedhart,2 Bionka MA Huisstede,1 on behalf
of HIPS-Delphi Group
Consensus statement
To cite: van der HorstN,
BackxFJG, GoedhartEA,
etal. Br J Sports Med
2017;51:1583–1591.
1Department of Rehabilitation,
Nursing Science & Sports,
Rudolf Magnus Institute of
Neurosciences, University
Medical Center Utrecht, Utrecht,
The Netherlands
2FIFA Medical Center
Royal Netherlands Football
Association, Zeist, The
Netherlands
Correspondence to
Dr Nick van der Horst,
Department of Rehabilitation,
Nursing Science & Sports,
University Medical Center
Utrecht, Rudolf Magnus
Institute of Neurosciences, P.O.
Box 85500, Utrecht 3508 GA,
The Netherlands;
n. vanderhorst- 3@ umcutrecht. nl
Accepted 10 March 2017
Published Online First
30March2017
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Consensus statement
RTP decision after hamstring injury. The study was carried out
by the Department of Rehabilitation, Physical Therapy Science,
and Sport at the University Medical Centre of Utrecht, the Neth-
erlands. Before the start of this project, a systematic review of
the definition of, and criteria for, RTP after hamstring injury was
performed.22 The results of the systematic review were used as a
starting point for the Delphi procedure.
Delphi procedure
We used a series of sequential questionnaires or ‘rounds’, inter-
spersed by feedback, to achieve consensus of opinion among
a panel of experts.30 31 This scientific method was originally
developed in the 1950s and has been effectively used in sports
medicine research.32–35 Each Delphi round comprised a ques-
tionnaire, an analysis and a feedback report.
Steering committee
The steering committee that facilitated and guided this
Delphi study consisted of a full professor in sports medicine,
a senior researcher with experience in Delphi procedures, a
team doctor of a national football team and a PhD student.
All members have a clinical (sports medicine, (sports) physical
therapy) and scientific background. The steering committee
was responsible for preparing and analysing the questionnaires
and for reporting the results in anonymised feedback reports.
Expert panel
The FIFA Medical Centres of Excellence (FMCoEs) have a
demonstrable record of leadership in football medicine and
have been accredited through a strict selection process by
FIFA. These centres provide a network of knowledge and
experience in research and clinical management of hamstring
injuries. All FMCoEs (n=40) were invited to select up to
three experts in hamstring injury management to participate
in our Delphi study, adhering to the inclusion criteria as listed
in Box 1. These criteria are commonly used when selecting
experts who participate in a Delphi study.33 36–38 After selec-
tion, the steering committee contacted all experts via email
to provide information about the aim, methods and privacy
statements for the Delphi study.
Procedure
Online surveys were used and adhered to principles of respon-
dent anonymity and feedback between rounds.30 For all Delphi
Figure 1 The Strategic Assessment of Risk and Risk Tolerance (StARRT) framework for RTP decisions.28 RTP, return to play.
Box 1 Experts’ inclusion criteria for participation to the
Delphi study
►The selected FIFA Medical Centre of Excellence considers
this expert to be a key person in the field of hamstring injury
management
►The expert is a researcher OR medical / health professional
with experience in hamstring injury rehabilitation in a sport
setting
►The expert has sufficient knowledge of English language
►The expert has an evidence-based attitude
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Box 2 Items* included to start discussion on definition
and criteria for RTP after hamstring 182 injury
Items for discussion on definition of RTP after hamstring
injury
►Availability for match selection and/or full training
►Clearance by medical staff
►A completed game
►Full activity
►A 100% recovery score on fitness and skill testing
►Absence of symptoms on injured leg
►Completion of a rehabilitation program
►Reaching pre-injury level
Items for discussion on criteria for RTP after hamstring
injury
►Medical staff clearance
►Absence of pain
►Similar hamstring strength
►Similar hamstring flexibility
►Functional performance
*All items were derived from a systematic review.on definition and
criteria for RTP after hamstring injury.22
Consensus statement
rounds, experts received an invitation via email with a link
to an online questionnaire. Experts were given 6 weeks to
complete the questionnaire, with reminders emailed at 3 and
5 weeks. A structured web-based questionnaire was developed
consisting of three parts: part I for general questions about
RTP consultation and responsibilities, part II for the definition
of RTP and part III for criteria to support the RTP decision
after hamstring injury. During the whole procedure, we used
structured questions, such as ‘Do you feel this item should be a
part of the RTP definition?’ or ‘Do you feel this item should be
a criterion to support the RTP decision after hamstring injury?’
Answer options were ‘yes’, ‘no’ or ‘no opinion’. Experts were
encouraged to provide justification for their answers. Topics
that did not reach consensus were included in the next Delphi
round. For some questions, the steering committee added a
‘note from the steering committee’, based on expert opinion
or the literature.
Cut-off point for consensus
A cut-off score of ≥70% agreement was proposed for consensus
because this cut-off is often used in Delphi procedures.36 37 39
RTP terminology
The expert panel was asked to reach consensus regarding which
term for RTP in sports should be adopted (eg, return to sport,
RTP, return to competition, etc).
Definition of RTP after a hamstring injury
Results from the systematic review22 that we conducted to
inform the Delphi process (Box 2) were used as the starting
point for the Delphi process for the definition of RTP. Experts
were asked which terms should or should not be included in
the RTP definition. Experts were also invited to open-ended
question regarding the definition of RTP after hamstring
injury.
Medical criteria to support the RTP decision after a hamstring
injury
Similar to the definition of RTP, a systematic review of the medical
criteria used to support the RTP decision after hamstring injury
was used as a starting point for this part of the Delphi process.22
Experts were asked which criteria should or should not be used
to support the final RTP decision and to provide any additional
criteria they thought relevant.
RTP responsibilities
The relevant stakeholders in RTP decision-making were initially
identified from the published literature.40 41 Experts were addi-
tionally asked to name other stakeholders involved in RTP
consultation and decision-making.
Data analysis
Data from all Delphi rounds were extracted from the online
survey database to SPSS V.22.0, and anonymously reported
in feedback reports. For questions with a ‘yes/no/no opinion’
answer format, the percentage of answers in each category was
calculated. Qualitative data (ie, expert answers and justifica-
tions) were analysed by content analysis and discussed by the
steering committee. This information and the main arguments
of the experts were summarised and included in a ‘note from the
steering committee’ and added to each question. If consensus was
not reached on a topic, these notes were included in a follow-up
question on a related subject, used to rephrase the original ques-
tion or to compose new questions on this topic.
RESULTS
After four consecutive Delphi rounds, performed between July
2015 and July 2016, full consensus was achieved on three main
content areas. The final consensus is presented in the RTP model
for hamstring injuries in football (figure 2).
Expert panel
Fifty-eight experts were recruited from 28 FMCoEs worldwide
(participating experts are included in the acknowledgements
section). Eleven FMCoEs did not respond to the invitation and
one FMCoE could not participate due to migration. The partici-
pating experts had a range of experiences in clinical practice and
research, including full professor, medical director, lecturer, sports
physician, orthopaedic surgeon, physical therapist, performance
coach, athletic trainer and/or clinical researcher. Most members
had written multiple high-quality international publications, and
had an average of 15.8 (SD ±8.2; range: 3–35) years of practical
experience in the field of hamstring injury management in football.
The response rates in this Delphi procedure were 93% (round 1),
90% (rounds 2 and 3) and 84% (round 4).
Cut-off point for consensus
In Delphi round 1, the expert panel agreed that a cut-off score of
≥70% would be used to define consensus.
RTP terminology
In Delphi round 1, most experts chose either ‘return to play’
or ‘return to competition’ as the term to define RTP. In Delphi
round 2, consensus was reached to adopt return to play—
including its acronym RTP—as the term for return to play in
sports, with the justification being that it is simple, well-known
and adopted worldwide at many levels, including conferences
and publications. It was agreed that ‘return to competition’
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Figure 2 The RTP model for hamstring injuries in football for RTP decision-making, RTP definition and RTP criteria after hamstring injury. GPS, global
positioning system; RTP, return to play.
Consensus statement
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Table 1 Expert advice on performance on field testing to assess
eligibility for RTP after hamstring injury
Clinical test %* Clinical test %*
Position-specific GPS-targeted
match-specific rehabilitation
82 20 m sprint 57
Repeated sprint ability test 76 Nordic hamstring exercise 55
Single leg bridge 71 Triple hop test 53
Deceleration drills 71 Muscular endurance 45
Acceleration drills 68 YoYo/shuttle run test 43
T-test 63 Speed testing 39
40 m sprint 61 Functional movement screen 35
H-test 58 Single hop test 33
*Percentage of experts stating this test could be suggested for functional
performance assessment. Consensus (eg, ≥70%) was only achieved for the tests
presented in bold letters.
GPS, global positioning system; RTP, return to play.
Consensus statement
should be included in the definition of the generic term ‘return
to play’.
Definition of RTP after a hamstring injury
In the first Delphi round, consensus was reached to include ‘avail-
ability for match selection and/or full training’ and ‘clearance by
medical staff ’ as part of the RTP definition after a hamstring
injury. There was also consensus that ‘a completed game’ should
not be included in the RTP definition because RTP clearance
should be given before a player resumes play and availability to
play a match might be based on non-medical (eg, tactical, team-
based) factors or decisions. The expert panel suggested consid-
ering inclusion of ‘a player’s positive mental attitude (athlete’s
readiness)’ in the definition of RTP after hamstring injury.
In Delphi rounds 2 and 3, there was consensus that ‘full
activity’, ‘a 100% recovery score on fitness and skill testing’,
‘absence of symptoms on injured leg’, ‘completion of a reha-
bilitation programme’ and ‘reaching preinjury level’ should not
be included in the definition of RTP after hamstring injury. The
rationale was that these items are not specific enough and/or
should be considered as criteria for RTP, but not for RTP defini-
tion. In Delphi round 3, consensus was achieved on including ‘a
player’s positive mental attitude (athlete readiness)’ in the defini-
tion of RTP, because mental readiness was considered important
to eliminate anxiety and because a positive mental attitude is
perceived to diminish the risk of reinjury and to improve
performance.
The expert panel reached consensus that RTP should be
defined as ‘the moment a player has received criteria-based
medical clearance and is mentally ready for full availability for
match selection and/or full training’.
Medical criteria to support the RTP decision after a hamstring
injury
After discussion and specification of criteria through all rounds
of this Delphi consensus procedure, the following criteria were
included: medical staff clearance, similar hamstring flexibility
(compared with preinjury data and/or uninjured side, depending
on which data are available or are most reliable for the indi-
vidual player according to the medical staff), performance on
field testing, psychological readiness, and absence of pain on
palpation, strength testing, flexibility testing and/or functional
testing. Additionally, the expert panel stated that specification of
criteria was required. The experts agreed that ‘similar hamstring
flexibility’ could involve a 0%–10% difference between injured
and uninjured leg or compared with preinjury data. The expert
panel reached consensus that hamstring flexibility should be
assessed by means of both the active and the passive straight leg
raise test. The rationale was that the passive straight leg raise
test is considered as the gold standard for hamstring flexibility
measurements in daily practice, and it is important to measure
both the active and passive components.42
With regard to ‘performance on field testing’, the expert panel
mentioned a number of field tests used in clinical practice to
support the RTP decision after hamstring injury (see table 1). In
Delphi round 3, the experts were asked whether they had prac-
tical experience with other field tests of functional performance
and whether they would recommend using these tests to support
the RTP decision after hamstring injury (see table 1). Consensus
was reached that the repeated sprint ability test,43 deceleration
drills, single leg bridge and position-specific global positioning
system (GPS)-targeted match-specific rehabilitation were rele-
vant functional performance tests to support the RTP decision
after hamstring injury. In addition to the consensus achieved on
the inclusion of these tests, the experts frequently commented
that performance on field-testing should involve explosive
movements to mimic football performance.
No consensus was reached for the inclusion or exclusion of
‘similar eccentric hamstring strength’ as a criterion to support the
RTP decision after hamstring injury. The expert panel remained
divided, with two irreconcilable opinions: one group of experts
stated that similar eccentric strength assessment is important as
a criterion for RTP as the eccentric phase is also the contraction
mode in which injury occurs, and strength asymmetries should
be eliminated because they can increase the risk of injury. The
other group of experts stated that strength measurements are not
functional, asymmetries are normal, and that too many factors
influence the measurement of strength, so that reliable measure-
ments are not possible. In Delphi round 4, consensus was
reached to add ‘similar eccentric hamstring strength’ (compared
with preinjury data and/or uninjured side, depending on which
data are available or are most reliable for the individual player
according to the medical staff) as a potential criterion to support
the RTP decision provided that both sides of the argument would
be described in the consensus.
The experts agreed that ‘neuromuscular function’ should
not be included as a criterion for RTP after hamstring injury.
Although the experts stated that neuromuscular function is
always important, specifying the concept and assessment of
neuromuscular function would go beyond the scope of this
Delphi procedure and was therefore not indicated as a criterion.
The exclusion of MRI assessment as a potential criterion for
RTP decision-making after hamstring injury was supported by
recent studies.20 44 Baseline MRI parameters are not predictive of
hamstring reinjury, and MRI is not of additional predictive value
compared with baseline patient history and clinical examination
alone.20 45 Completion of a number of full training sessions was
also excluded as a criterion as ‘availability for full training and
match selection’ was already included in the definition of RTP
after hamstring injury.
RTP responsibilities
In Delphi round 2, consensus was reached that the sports physi-
cian, physiotherapist, fitness trainer and athlete are the primary
stakeholders to be involved in RTP decision-making. There was
discussion about the role of the team coach, who not being medi-
cally qualified might allow an early RTP to improve team perfor-
mance, despite potential medical risks. However, in Delphi
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Consensus statement
round 3, the expert panel reached consensus on the inclusion of
the team coach for RTP consultation because of his/her ability to
assess the sport-specific performance level, his/her role in team
selection and his/her function in the multidisciplinary team staff.
The sports physician (who often acts as the head of the medical
staff) was chosen to be ultimately responsible for the RTP deci-
sion, based on the input provided by the multidisciplinary team
and the athlete.
DISCUSSION
This Delphi study involving 58 experts from 28 FIFA Medical
Centres of Excellence worldwide reached consensus on a clear
definition and medical criteria for RTP after hamstring injury
and who should be consulted about RTP and take ultimate
responsibility for the RTP decision (see figure 2).
Definition and medical criteria for RTP
The absence of clear and uniform definitions and medical criteria
for RTP has been a methodological issue in studies of different
musculoskeletal domains, such as RTP after anterior cruciate
ligament injury, ankle injury and concussion.46–49 A clear defini-
tion of RTP is needed for consistency when investigating issues
related to RTP, including reinjury risk factors, RTP prognostic
factors and intervention programmes.22 24–27 Differences in the
definition and criteria for RTP after hamstring injury make it
difficult to compare study results and lead to uncertainty about
which findings should be implemented in clinical practice.22 The
2016 consensus statement on return to sport defined RTP as a
continuum comprising three key elements—return to partici-
pation, return to preinjury sport and return to performance.50
This approach complements criteria-based rehabilitation,
and considers the entire rehabilitation and recovery process,
including the phase beyond return to sport where the athlete
returns to his/her desired performance level.50 However, it is
important to differentiate between the return to sport process
and the final RTP decision, where RTP is viewed as an endpoint
(or primary outcome). This Delphi study explicitly focused on
the final RTP decision (when is the player fully available for
match selection and full training) and involved consensus among
experts in the field of prevention and treatment of hamstring
injuries in football. Although not yet studied and validated in
clinical practice, this Delphi study may help clinicians faced with
the problem of when an athlete should RTP after a hamstring
injury. Furthermore, both the definition and criteria can be
used in research, potentially leading to greater uniformity and
promoting comparability of research.
Medical criteria for RTP after hamstring injury
Absence of pain and psychological readiness
Absence of pain on palpation of the hamstrings, during strength
and flexibility testing, and during or after functional perfor-
mance was considered important as pain may indicate incom-
plete tissue healing. Athletes with localised discomfort on
palpation just after RTP following hamstring injury were four
times (AOR: 3.95; 95% CI: 1.38 to 11.37) more likely to sustain
a reinjury than athletes without discomfort on palpation.20
However, pain perception is influenced by tissue damage and
by cognitive factors such as fear of reinjury or fear of pain.51 52
The fear of pain or reinjury generates avoidance behaviour.52 53
In addition, athletes mention fear of reinjury as the main reason
for not returning to sport.54
The relationship between fear of reinjury and unsuccessful
RTP led to the suggestion that psychological readiness be
included in RTP guidelines.55–57 We included psychological
readiness in both the definition and criteria for RTP after
hamstring injury. The expert panel agreed that the psycho-
logical readiness of the player should be considered before
RTP clearance. Studies focusing on other musculoskeletal
injuries previously emphasised the importance of psycholog-
ical readiness assessment as a part of the RTP decision.55–57
For example, the Knee Self-Efficacy Scale is recommended for
the RTP evaluation of patients rehabilitating from an anterior
cruciate ligament injury.58 However, there are no valid tools to
quantify psychological readiness after hamstring injury reha-
bilitation. The potential relationship between psychological
factors and RTP after hamstring injuries remains an important
topic for future research.
Similar hamstring strength and hamstring flexibility
An isometric knee flexion force deficit just after RTP is asso-
ciated with an increased risk of hamstring injury.20 Our expert
panel did not reach consensus regarding whether ‘similar eccen-
tric hamstring strength’ should be a criterion to support the
RTP decision. Although there was consenus that other contrac-
tion modes should not be included as a criterion to support the
RTP decision. Hamstring peak torque, quadriceps peak torque
and conventional concentric hamstring:quadriceps ratios (as
measured with different test speeds and muscle contractions)
are not associated with an increased risk of hamstring reinjury.8
There is also no relationship between concentric hamstring
to opposite hamstring (H:Hopp) ratio and hamstring reinjury.
However, eccentric strength asymmetries are predictive of
hamstring muscle injuries in football players.59 Furthermore,
67% of all football players clinically recovered from hamstring
injuries had at least one hamstring isokinetic testing deficit of
more than 10%.21 Thus elimination of isokinetic strength asym-
metries is not a requirement for RTP, although it is not known
whether isokinetic strength deficits are associated with the risk
of hamstring reinjury.21
From a biomechanical perspective, strength is preferably
measured in a (sub)maximally stretched position, for which a
fair amount of hamstring extensibility is required.60–63 There is
ongoing debate regarding the relationship between hamstring
flexibility and risk of hamstring injury.7 8 Many studies have
not found hamstring flexibility to be a risk factor for hamstring
injury.8 64 However, the H-test (an active hamstring flexibility
test) showed promising results as a complement to clinical exam-
ination.65 Experts in our Delphi study stated that this test seems
promising as it involves an active flexibility component as well
as assessment of insecurity in the athlete. However, there was
no consensus on the inclusion of this test to support the RTP
decision because experts stated there was insufficient evidence to
support the use of the test and because the test lacks functionality.
Performance on field testing
Performance on field testing was considered vital by the
expert panel when assessing RTP readiness, as it mimics the
actual sports requirements. Furthermore, many criteria-based
hamstring injury rehabilitation protocols have suggested
including performance-based criteria, such as a normal week
of training sessions,66 sport-specific scenarios21 and functional
phase training.17 As most hamstring injuries occur in the
latter stages of a match or training, fatigue and its associated
decline in functional performance need to be considered in
addition to field testing.5 67 68 Therefore, one could argue that
both qualitative and quantitative assessments of functional
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Consensus statement
performance should be performed in a fatigued state.14 Future
research should focus on the development of a sport-specific
test battery for RTP after hamstring injury, in which functional
aspects, fatigue, hamstring flexibility, absence of pain and
potentially hamstring strength are assessed in the light of the
RTP decision.
Hamstring RTP decision-making
Owing to the complexity of RTP decision-making, as well as
potential competing interests and different views of various
stakeholders, it is commonly agreed that RTP decisions should
be based on multidisciplinary consultation.23 41 69 Although the
sports physician may be best qualified to synthesise medical
information, step 3 of the Creighton model29 describes some
important RTP decision modifiers (eg, financial interests,
timing in season, internal pressure, etc). Generally, the sports
physician is only responsible for the medical part of the RTP
decision and does not have the final say over these decision
modifiers (such as financial, legal or team-tactical issues).
Hence, the sports physician may have responsibility for the
decision without authority to make it.69 Ultimately, the best
interests of the athlete are decisive, and this covers more
than just the medical risk assessment.28 29 41 Therefore, in our
opinion, different stakeholders with different views should be
involved in the final RTP decision, bearing in mind the best
interests of the athlete.
Strengths and weaknesses of this study
Delphi studies have the advantage of using the knowledge and
expertise of participating experts to reach consensus.30 70 71 This
Delphi study involved a multidisciplinary sample of clinical and
academic experts with extensive experience in hamstring injury
research and rehabilitation. Although there is no scientifically
proven minimally acceptable response rate, a response rate
of 60% has been used as the threshold of acceptability.72 This
Delphi consensus study had an excellent response rate of >83%
for each Delphi round.
The results of Delphi studies should be viewed in the light of
the expert panel’s opinion at any given point in time,70 because
opinions may change in the light of new evidence and paradigm
shifts.73 Therefore, both the definition and criteria for RTP after
hamstring injury should be re-evaluated in the future, based on
new research findings.
When drafting this consensus, no limitations regarding
(medical) staff and tools were considered. This makes the
consensus more suitable for a professional setting compared
with an amateur setting due to differences regarding team
staff and (access to) tools such as GPS tracking systems. Teams
with limited access to a comprehensive team staff are advised
to still consider and acknowledge the multifaceted nature of
the RTP decision, as discussed in this manuscript. This Delphi
consensus procedure additionally advised simpler functional
tests if GPS tracking systems and/or speed measurement equip-
ment is unavailable (eg, repeated sprint ability test, decelera-
tion drills, etc), although GPS tracking systems are considered
an important tool for functional assessment by the majority of
our expert panel due to their ability to mimic sport-specific
function.
This study provided medical criteria to assess the health status
of the athlete. This is only the first step in the three-step RTP
assessment after hamstring injury (see figure 1).28 29 In addi-
tion to the health status evaluation, the assessment of tissue
stresses (from type of sport, level of play, etc) and RTP decision
modifiers (timing and season, pressure from the athlete or
external, financial issues, etc) should form a solid basis for RTP
decision-making.28 29
Clinical relevance
Although experts’ opinions are considered a low level of
evidence, we consider this study to be an important first step
in standardising and improving the final RTP decision after
hamstring injury. In addition, the criteria to support the RTP
decision were generated by clinical and academic authorities in
the field of hamstring injury management. These criteria will
help both clinicians and (clinical) researchers to assess the risk of
RTP after hamstring injury.
Future research
There is a need for high-quality prospective research to vali-
date RTP criteria. Considering the multidimensional nature
of hamstring injuries, RTP criteria should not be validated as
univariate factors, but interaction between criteria as well as
the varying weighting of criteria due to time and circumstances
needs to be considered.74 75
CONCLUSION
A panel of 58 international experts reached consensus
regarding RTP terminology, definition, medical criteria,
responsibilities and consultation for RTP after hamstring inju-
ries in football. The results are reported in the RTP model for
hamstring injuries in football. The RTP decision should always
be a multidisciplinary decision. For RTP readiness assessment
of the player after a hamstring injury, emphasis is placed on
pain relief, flexibility assessment, psychological readiness and
functional performance. MRI findings should not be used for
RTP readiness assessment.
Acknowledgements The authors would like to thank FIFA and the FIFA Medical
Centres of Excellence network for their support and cooperation in expert selection
and recruitment.
Collaborators The collaborators of HIPS-Delphi group include: CSA Ahmad (USA);
TEA Andersen (Norway); JP Araujo (Portugal); FE Arroyo (Mexico); CM Askling
(Sweden); PD Batty (UK); BB Bayraktar (Turkey); CB Beckmann (Germany); M Bizzini
(Sweden); M Cohen (Brazil); SPC Connelly (UK); D Constantinou (South Africa);
AS Edwards (UK); J Espregueira-Mendes (Portugal); DJ Exeter (New Zealand); ML
Fulcher (New Zealand); aus der Fünten (Germany); WE Garrett (USA); M Grygorowicz
(Poland); TB Haag (Germany), R Hejna (Poland); JM Houghton (UK); AI Isik
(Turkey); S Kemp (UK); C Kruiswijk (Netherlands); GG Lewin (UK); T Lewis (UK); M
Lichaba (South Africa); N Loureiro (Portugal); RL Loursac (France); NAM Maffiuletti
(Sweden); AM Marles (France); J Mendiguchia (Spain); NM Miyauchi (Japan); HM
Moksnes (Norway); CS Motaung (South Africa); EN Noel (France); GJ O’Driscoll
(UK); TO Okuwaki (Japan); K Peers (Belgium); T Piontek (Poland); R Pruna (Spain);
Ranson CA (UK); YS Saita (Japan); MB Santos (Brazil); CS Schneider (Germany); KS
Schwarzenbrunner (Austria); HJ Silvers (USA); A Stålman (Sweden); EV van den Steen
(Belgium); S Sundelin (Sweden); JL Tol (Qatar); NJ Veldman (Netherlands); R Weiler
(UK); R Whiteley (Qatar); E Witvrouw (Qatar); A Yekdah (Algeria); JE Zachazewski
(USA).
Contributors Four authors have made substantial contributions to this manuscript:
NH, EAG, BMAH and FJGB. They have all participated in the concept and design,
analysis and interpretation of data, and drafting and revising the manuscript. All
authors have read the manuscript and agreed to submission for publication. The
HIPS-Delphi Group, the name of our expert panel, contributed to the full contents
of the consensus. We would therefore like to acknowledge the ’HIPS-Delphi Group’
with authorship as well.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
© Article author(s) (or their employer(s) unless otherwise stated in the text of the
article) 2017. All rights reserved. No commercial use is permitted unless otherwise
expressly granted.
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1590 van der HorstN, etal. Br J Sports Med 2017;51:1583–1591. doi:10.1136/bjsports-2016-097206
Consensus statement
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criteria and decision-making
procedure regarding definition, medical
football (soccer): a worldwide Delphi
Return to play after hamstring injuries in
Huisstede
Nick van der Horst, FJG Backx, Edwin A Goedhart and Bionka MA
doi: 10.1136/bjsports-2016-097206
30, 2017 2017 51: 1583-1591 originally published online MarchBr J Sports Med
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