© 2010 The Journal of Bone and Joint Surgery, Inc.

Differences Between Sexes in Lower Extremity Alignment and Muscle Activation During Soccer Kick

Robert H. Brophy, MD., Sherry Backus, DPT., Andrew P. Kraszewski, MS., Barbara C. Steele, MD., Yan Ma, PhD., Daniel Osei, MD., Riley J. Williams, MD.


Investigation performed at the Motion Analysis Laboratory, Hospital for Special Surgery, New York, NY

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.

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Background Injury risk in soccer varies by sex. Female soccer players face a greater risk of anterior cruciate ligament injury and patellofemoral problems, while male players are more likely to experience sports hernia symptoms. The purpose of this study was to test the hypothesis that females have different lower-extremity alignment and muscle activation patterns than males during the soccer kick.

Methods Thirteen male and twelve female college soccer players underwent three-dimensional motion analysis and electromyography of seven muscles (iliacus, gluteus maximus, gluteus medius, vastus lateralis, vastus medialis, hamstrings, and gastrocnemius) in both the kicking and the supporting lower extremity and two additional muscles (hip adductors and tibialis anterior) in the kicking limb only. Five instep and five side-foot kicks were recorded for each player. Muscle activation was recorded as a percentage of maximum voluntary isometric contraction.

Results The male soccer players had significantly higher mean muscle activation than their female counterparts with respect to the iliacus in the kicking limb (123% compared with 34% of maximal voluntary isometric contraction; p = 0.0007) and the gluteus medius (124% compared with 55%; p = 0.005) and vastus medialis muscles (139% compared with 69%; p = 0.002) in the supporting limb. The supporting limb reached significantly greater mean hip adduction during the stance phase of the kick in the females compared with that in the males (15° and 10°, respectively; p = 0.006).

Conclusions Differences between the sexes in lower extremity alignment and muscle activation occur during the soccer instep and side-foot kicks. Decreased activation of the hip abductors and greater hip adduction in the supporting limb during the soccer kick in female athletes may be associated with their increased risk for anterior cruciate ligament injury.

Clinical Relevance Programs targeting these differences in muscle activation and lower extremity alignment during the kick should be evaluated for use in injury prevention in soccer athletes. Future research is warranted to investigate how differences between the sexes at the hip may relate to differences in the risk of lower extremity injury among athletes in soccer and other sports.

For further information: http://www.ejbjs.org/cgi/content/abstract/92/11/2050