Background/aim To investigate the role of eccentric knee flexor strength, between-limb imbalance and biceps femoris long head (BFlh) fascicle length on the risk of future hamstring strain injury (HSI).
Methods Elite soccer players (n=152) from eight different teams participated. Eccentric knee flexor strength during the Nordic hamstring exercise and BFlh fascicle length were assessed at the beginning of preseason. The occurrences of HSIs following this were recorded by the team medical staff. Relative risk (RR) was determined for univariate data, and logistic regression was employed for multivariate data.
Results Twenty seven new HSIs were reported. Eccentric knee flexor strength below 337 N (RR=4.4; 95% CI 1.1 to 17.5) and possessing BFlh fascicles shorter than 10.56 cm (RR=4.1; 95% CI 1.9 to 8.7) significantly increased the risk of a HSI. Multivariate logistic regression revealed significant effects when combinations of age, history of HSI, eccentric knee flexor strength and BFlh fascicle length were explored. From these analyses the likelihood of a future HSI in older athletes or those with a HSI history was reduced if high levels of eccentric knee flexor strength and longer BFlh fascicles were present.
Conclusions The presence of short BFlh fascicles and low levels of eccentric knee flexor strength in elite soccer players increases the risk of future HSI. The greater risk of a future HSI in older players or those with a previous HSI is reduced when they have longer BFlh fascicles and high levels of eccentric strength.
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Twitter Follow Ryan Timmins at @ryan_timmins, Matthew Bourne at @mbourne5 and David Opar at @davidopar, Anthony Shield at @das_shield, Morgan Williams at @drmorgs, Christian Lorenzen at @athleticexcel
Contributors RGT was the principle investigator and was involved with study design, recruitment, analysis and manuscript write up. MNB was involved with recruitment, analysis and the manuscript preparation. AJS, MDW, CL and DAO were involved with the study design, analysis and manuscript preparation. All authors had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.
Funding This study was partially funded by a Faculty of Health Sciences Research Grant from the Australian Catholic University.
Competing interests A Faculty of Health Research Grant from the Australian Catholic University partially funded the research; AJS and DAO are listed as co-inventors on a patent filed for a field test of eccentric hamstring strength (PCT/AU2012/001041.2012) as well as being shareholders in a company responsible for commercialising the device; RGT, MNB, MDW and CL have no relationships with companies that might have an interest in the submitted work in the previous 3 years; their spouses, partners, or children have no financial relationships that may be relevant to the submitted work; and RGT, MNB, AJS, MDW, CL and DAO have no financial interests that may be relevant to the submitted work beyond what is already declared
Ethics approval This study was approved by the Human Research Ethics Committee of the Australian Catholic University (approval number: 2014 26V) and informed consent was provided to all participants.
Provenance and peer review Not commissioned; externally peer reviewed.
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