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159 HaOS or CHaOS? The prognostic value of the hamstring outcome score (HaOS) to predict the risk of hamstring injury
  1. Sander van de Hoef1,
  2. Michel S Brink2,
  3. Nick van der Horst3,
  4. Maarten van Smeden4,
  5. Frank Backx1
  1. 1Utrecht University, University Medical Center, Division Brain, Department Rehabilitation, Physical Therapy Science and Sports, Utrecht, Netherlands
  2. 2University of Groningen, University Medical Center Groningen, Center for Human Movement Sciences, Groningen, Netherlands
  3. 3FIFA Medical Center, Royal Netherlands Football Association, Zeist, Netherlands
  4. 4Leiden University Medical Center, Department of Clinical Epidemiology, Leiden, Netherlands


Background Hamstring injury incidence remains high among male soccer players. One of the reasons is low adherence for effective hamstring injury prevention programs. Insight in injury risk can contribute to better adherence for injury prevention measures. The hamstring outcome score (HaOS) might provide an insight in injury risk.

Objective To determine the relation between the HaOS and both previous and new hamstring injuries in male amateur soccer players, and to determine the prognostic value of the HaOS to predict the risk of hamstring injuries.

Design Data was collected during a large cluster-RCT investigating a hamstring injury prevention program.

Setting This study was executed during one competition (2016–2017) in 32 first class amateur soccer teams.

Participants 400 adult male amateur soccer players started the study.

Assessment of risk factors The participants filled in a baseline-questionnaire consisting of injury history and the HaOS. During one full competition hamstring injuries were registered prospectively.

Main outcome measurements Previous hamstring injuries, new hamstring injuries and the HaOS (total score and subdomains) were considered in this study.

Results In 356 players, a significant relation was found between the HaOS (total score and all HaOS subdomain scores) and previous and new hamstring injury (F=17,4; p<0.0001 and T=3.59, p=0.001, respectively). This indicated that more hamstring injuries during the previous season was related to lower scores on the HaOS and lower HaOS scores correspond with more new hamstring injuries. With a cut-off score of 80% on the HaOS, logistic regression models showed a probability of 11%, 18% and 28% on a new hamstring injury in players with 0,1 or 2 previous injuries, respectively.

Conclusion The HaOS is significantly associated with both previous and new hamstring injury and might be a useful tool to provide insight in players’ hamstring injury risk when used in combination with injury history.

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