The hamstrings-to-quadriceps (H:Q) strength ratio is not an independent risk factor for either hamstrings or anterior cruciate ligament injury.
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The association of H:Q ratio with injury does not differ between conventional and functional ratio types.
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Methodological limitations and variations in the assessment protocols found in the literature often create erroneous conclusions regarding the value of H:Q strength ratio as an injury prediction tool.
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Monitoring strength imbalances along with other modifiable factors during the entire competitive season may provide a better understanding of the association between the H:Q ratio and injury.
Abstract
Background
For the past 30 years, the hamstring (H)-to-quadriceps (Q) (H:Q) torque ratio has been considered an important index of muscle strength imbalance around the knee joint. The purpose of this systematic review was to examine the value of H:Q torque ratio as an independent risk factor for hamstring and anterior cruciate ligament (ACL) injuries.
Methods
Database searches were performed to identify all relevant articles in PubMed, MEDLINE, Cochrane Library, and Scopus. Prospective studies evaluating the conventional (concentric H:Q), functional (eccentric H: concentric Q), and mixed (eccentric H at 30°/s: concentric Q at 240°/s) H:Q ratios as risk factors for occurrence of hamstring muscle strain or ACL injury were considered. Risk of bias was assessed using the Quality In Prognosis Studies tool.
Results
Eighteen included studies reported 585 hamstrings injuries in 2945 participants, and 5 studies documented 128 ACL injuries in 2772 participants. Best evidence synthesis analysis indicated that there is very limited evidence that H:Q strength ratio is an independent risk factor for hamstring and ACL injury, and this was not different between various ratio types. Methodological limitations and limited evidence for ACL injuries and some ratio types might have influenced these results.
Conclusion
The H:Q ratio has limited value for the prediction of ACL and hamstring injuries. Monitoring strength imbalances along with other modifiable factors during the entire competitive season may provide a better understanding of the association between H:Q ratio and injury.
Graphical Abstract
Keywords
ACL
Isokinetic
Prospective
Strains
Strength imbalance
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Peer review under responsibility of Shanghai University of Sport.