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The Relationship of Hamstrings and Quadriceps Strength to Anterior Cruciate Ligament Injury in Female Athletes

Myer, Gregory D MS, CSCS; Ford, Kevin R MS; Barber Foss, Kim D MS, ATC; Liu, Chunyan MS; Nick, Todd G PhD; Hewett, Timothy E PhD

Clinical Journal of Sport Medicine: January 2009 - Volume 19 - Issue 1 - p 3-8
doi: 10.1097/JSM.0b013e318190bddb
Original Research

Objective: To determine the association of quadriceps and hamstrings strength to anterior cruciate ligament (ACL) injury risk in female athletes. The primary hypothesis was that there would be decreased knee flexor and increased knee extensor strength in female athletes who went on to ACL injured status (FACL) compared to uninjured female (FC) and male (MC) control subjects.

Study Design: Matched case control.

Setting: Institutional Biomechanics Laboratory.

Participants: Prospectively measured FACL (n = 22) female athletes who subsequently suffered confirmed noncontact ACL ruptures (16 during soccer and 6 during basketball play) were matched (1:4 ratio) to female controls (FC; n = 88) using limb (dominant or nondominant), pubertal status, sport, and nearest height and mass. In addition, male controls (MC) were matched (1:1 ratio) to FACL to serve as a secondary comparative control.

Assessment of Risk Factors: Isokinetic (concentric) knee extension/flexion strength (300 degrees/s).

Results: FACL subjects had decreased hamstrings strength compared to MC (15%; 95% CI, 1 to 27%; P = 0.04). FC were not different from MC in hamstrings strength. Conversely, FACL subjects did not differ compared to the MC in quadriceps strength, and the FC demonstrated decreased quadriceps strength relative to MC (10%; 95% CI, 3 to 18%; P = 0.01).

Conclusions: The results of this investigation indicate that female athletes who suffered ACL injury subsequent to strength testing had a combination of decreased hamstrings strength but not quadriceps strength compared to males. In direct contrast, female athletes who did not go on to ACL injury had decreased quadriceps strength and similar hamstrings strength compared to matched male athletes.

From *Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; †Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, Ohio; ‡Rocky Mountain University of Health Professions, Provo, Utah; §Department of Kinesiology and Health Promotion, University of Kentucky, Lexington, Kentucky; ¶Center for Epidemiology and Biostatistics, Cincinnati, Ohio; and **Departments of Pediatrics, Orthopaedic Surgery, College of Medicine and the Departments of Biomedical Engineering and Rehabilitation Sciences, University of Cincinnati, Cincinnati, Ohio.

Submitted for publication June 18, 2008; accepted October 2, 2008.

This work was supported by National Institutes of Health Grant R01-AR049735 and R01-AR055563.

The authors state that they have no financial interest in the products mentioned within this article.

Reprints: Gregory D. Myer, MS, CSCS, Cincinnati Children's Hospital, 3333 Burnet Avenue, MLC 10001, Cincinnati, OH 45229 (e-mail:

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