Background Hamstring injuries remain prevalent across a number of professional sports. In football, the incidence has even increased by 4% per year at the Champions League level over the last decade. The role of muscle strength or strength ratios and their association with risk of hamstring injury remain restricted by small sample sizes and inconclusive results.
Purpose The purpose of this study is to identify risk factors for hamstring injury in professional football players in an adequately powered, prospective cohort study. Using both established (isokinetic) and novel (eccentric hamstring test device) measures of muscle strength, we aimed to investigate the relationship between these strength characteristics over the entire range of motion with risk of hamstring injury.
Methods All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included isokinetic strength, Nordic hamstring exercise strength and dynamic hamstring: quadriceps ratios.
Results Of the 413 players included (68.2% of all league players), 66 suffered a hamstring injury over the two seasons. Only isokinetic quadriceps concentric at 300°/s (adjusted for bodyweight) was associated with risk of hamstring injury when considered categorically. Age, body mass and playing position were also associated with risk of hamstring injury. None of the other 23 strength variables examined were found to be associated with hamstring injury.
Conclusion The clinical value of isolated strength testing is limited, and its use in musculoskeletal screening to predict future hamstring injury is unfounded.
- risk factor
- injury prevention
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Contributors ND: principal investigator, data collection and analyses, writing, editing and outline of the manuscript. EW: first principal supervisor of PhD programme, concept and outline as well as writing and editing of the manuscript. RB: second main supervisor, concept and outline as well as writing and editing of the manuscript. AFB: statistical analyses and data analyses, writing of the manuscript. RW: investigator and coauthor, particularly with the data collection and writing of the manuscript. AB: organisation and planning of study, data collection and writing of manuscript. AM: study design and ethical approval, data collection and organisation, and writing of the manuscript. AF: statistical analyses.
Competing interests None declared.
Patient consent Obtained.
Ethics approval Institutional Review Board, Anti-Doping Lab, Qatar.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Patient-level data and/or full data set and/or and/or statistical code are available from the corresponding author.