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Document Title: Ahmad-AJSM-Mar06.shtml
Article Title: Effect of Gender and Maturity on Quadriceps-to-Hamstring Strength Ratio and Anterior Cruciate Ligament Laxity
Authors: Christopher S. Ahmad, MD, A. Martin Clark, MD, Niels Heilmann, J. Scott Schoeb, MD, Thomas R. Gardner, PE and William N. Levine, MD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: March 2006
Volume 34, pages 370-374
Keywords: ACL injury prevention, knee injury prevention, hamstring strength, musculature, gender, musculoskeletal maturity, menarche, onset of ovulation.
(Reference-denoting numbers appear in the same font and point size as the document text. As with all Knee Library documents, this article is provided in full-text form, complete with all figures and tables.)
Comments: In this study, Ahmad et al. found that after menarche (where menarche is defined as the first ovulation, hence the first period), females demonstrate a greater quadriceps-strength increase than hamstring-strength increase. This disproportionate hamstring strength seems to be a major factor in the 2-8 times higher ACL risk of females. For this reason, a cornerstone of all female-athlete knee-injury-prevention programs, such as Cincinnati Sportsmetrics and Girls-Can-Jump, is hamstring strengthening. (Another excellent article dealing with female athletes is BarberWestin-AJSM-Mar06.shtml.)
ABSTRACT
Background: Exercise programs have been introduced to reduce the ACL injury risk in female athletes. The most effective age at which to start these programs is not known.
Hypothesis: Age and gender affect ligament laxity and quadriceps-to-hamstring strength ratio.
Study Design: Cross-sectional study; Level of evidence, 3.
Methods: Fifty-three female and 70 male recreational soccer players, 10 to 18 years of age, were studied with physical examination, KT-1000 arthrometry, and manual maximum quadriceps and hamstring strength using a handheld dynamometer. The subjects were separated into 4 groups to examine maturity-related intergender differences: group G1, premenarchal girls (n = 24); group B1, boys 13 years and younger (n = 38); group G2, girls 2 or more years after menarche (n = 29); and group B2, boys 14 years and older (n = 32).
Results: Both knees of 123 soccer players were evaluated. The mean ages for groups G1, B1, G2, and B2 were 11.50 ± 1.69, 10.63 ± 1.85, 15.5 ± 1.43, and 15.59 ± 1.24 years, respectively, and the mean laxity measurements were 8.84 ± 2.12, 8.51 ± 1.61, 8.85 ± 1.86, and 7.33 ± 1.27 mm, respectively. Laxity was significantly less for the mature boys (P = .0015) than for the immature boys, mature girls, and immature girls. With increasing maturity, significant increases in both quadriceps and hamstring muscle strength were observed for both boys and girls (P < .05). Boys demonstrated a greater percentage increase in hamstring strength with maturity (179%) compared with girls (27%) (P < .05). Mature girls (2.06) had significantly greater quadriceps-to-hamstring ratio when compared with immature girls (1.74), immature boys (1.58), and mature boys (1.48) (P < .05).
Conclusion: Female athletes after menarche increase their quadriceps strength greater than their hamstring strength, putting them at risk for anterior cruciate ligament injury. Anterior cruciate ligament–prevention programs based on improving dynamic control of the knee by emphasizing hamstring strengthening should be instituted for girls after menarche.
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