Background Hamstring muscle injury (HMI) is the most common injury in professional football and has a high re-injury rate. Despite this, there are no validated criteria to support return to play (RTP) decisions.
Aim To use the Delphi method to reach expert consensus on RTP criteria after HMI in professional football.
Methods All professional football clubs in England (n=92) were invited to participate in a 3-round Delphi study. Round 1 requested a list of criteria used for RTP decisions after HMI. Responses were independently collated by 2 researchers under univocal definitions of RTP criteria. In round 2 participants rated their agreement for each RTP criterion on a 1–5 Likert Scale. In round 3 participants re-rated the criteria that had reached consensus in round 2. Descriptive statistics and Kendall's coefficient of concordance enabled interpretation of consensus.
Results Participation rate was limited at 21.7% (n=20), while retention rate was high throughout the 3 rounds (90.0%, 85.0%, 90.0%). Round 1 identified 108 entries with varying definitions that were collated into a list of 14 RTP criteria. Rounds 2 and 3 identified 13 and 12 criteria reaching consensus, respectively. Five domains of RTP assessment were identified: functional performance, strength, flexibility, pain and player's confidence. The highest-rated criteria were in the functional performance domain, with particular importance given to sprint ability.
Conclusion This study defined a list of consensually agreed RTP criteria for HMI in professional football. Further work is now required to determine the validity of the identified criteria.
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Contributors MZ and AR developed the study protocol. All authors approved the study protocol. IB was responsible for initial contact with football clubs. MZ created the online surveys, performed data analysis and prepared the first draft of the manuscript. AR provided feedback and revised manuscript. MZ made necessary changes and all authors approved the final version of the manuscript prior to submission.
Competing interests None declared.
Ethics approval The University of Birmingham Ethics Committee (UK) approved the study protocol.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement A complete report of the whole Delphi process is available in the online supplementary material. Additional unpublished data are available on request from the corresponding author. The unpublished data contain all the responses given in round 1 of the Delphi process and all the ratings collected for each criterion in rounds 2 and 3.
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