Document Title: Hewett-AJSM-Nov96.shtml
Article Title: Plyometric Training in Female Athletes -- Decreased Impact Forces and Increased Hamstring Torques
Authors: Timothy E. Hewett, PhD, Amanda L. Stroupe, Thomas A. Narice, ATC, and Frank R. Noyes, MD
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: November 1996
Volume 24, Number 6, pages 765-773
Keywords: female ACL, female athlete knee-injury prevention, plyometrics (ballistic-jump training).

(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: This study shows that a ballistic-jumping-training program improved jump performance (10% increase in jump height) as well as jump biomechanics (e.g. improved side-to-side uniformity, lowered peak forces on the knee upon landing, and improved technique). Hewett et al. provide a thought-provoking and insightful discussion of jump kinematics and dynamics, and the review the research into the disparity in ACL-injury incidence in males versus females. They point out that the mechanical mechanisms that male athletes employ in order to compensate for high landing forces are different from those used by their female counterparts. (Remember that kinetic energy increases with the square of speed. So, if we double the speed of a given incident in which an athlete loses control, then the resulting injury would be expected to be four times as severe. ) Note: The term "adduction" denotes movement towards the centre-line of the body. The term "abduction" denotes movement away from the centre-line of the body.

ABSTRACT

The purpose of this study was to test the effect of a jump-training program on landing mechanics and lower extremity strength in female athletes involved in jumping sports. These parameters were compared before and after training with those of male athletes. The program was designed to decrease landing forces by teaching neuromuscular control of the lower limb during landing and to increase vertical jump height. After training, peak landing forces from a volleyball block jump decreased 22%, and knee adduction and abduction moments (medially and laterally directed torques) decreased approximately 50%. Multiple regression analysis revealed that these moments were significant predictors of peak landing forces. Female athletes demonstrated lower landing forces than male athletes and lower adduction and abduction moments after training. External knee extension moments (hamstring muscle-dominant) of male athletes were threefold higher than those of female athletes. Hamstring-to-quadriceps muscle peak torque ratios increased 26% on the nondominant side and 13% on the dominant side, correcting side-to-side imbalances. Hamstring muscle power increased 44% with training on the dominant side and 21% on the nondominant. Peak torque ratios of male athletes were significantly greater than those of untrained female athletes, but similar to those of trained females. Mean vertical jump height increased approximately 10%. This training may have a significant effect on knee stabilization and prevention of serious knee injury among female athletes.

To access the full text of this article, please click here.
There is no charge for viewing articles. However, a password is required.
If you do not already have a password, please e-mail Michael Frind at frind@execulink.com for one.
Prior to requesting a password, please make certain you have read the Site Terms of Use pertaining to this site.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Copyright American Journal of Sports Medicine, American Orthopaedic Society for Sports Medicine, November/December 1996. For details regarding copyright as it applies to this page, please visit the page entitled Site Terms of Use and Aspects of Copyright on this site.

This website was created for the benefit of the world's largest knee-injury community, Bob's ACL WWWBoard (also known as the Kneeboard), accessible to everyone at http://factotem.org.

Documents posted on this site serve merely as a virtual library, and are intended solely for purposes of making access to high-quality peer-reviewed medical-journal articles convenient for all users of the Kneeboard. Knee-injury patients are hereby encouraged to discuss this material with their respective medical teams.

Site Terms of Use and Aspects of Copyright

Printing Hints and Tips