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Document Title: Chappell-AJSM-Feb07.shtml
Article Title: Kinematics and Electromyography of Landing Preparation in Vertical Stop-Jump -- Risks for Noncontact Anterior Cruciate Ligament Injury
Authors: Jonathan D. Chappell, MD, R. Alexander Creighton, MD, Carol Giuliani, PhD, Bing Yu, PhD, and William E. Garrett, MD, PhD.
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: February 2007
Volume 35, pages 235-241
Keywords: biomechanics, kinematics, kinetics, anterior cruciate ligament (ACL) injury risk factors, jump landing, female athlete ACL injury incidence and prevention.
(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, done using state-of-the-art technology (3D infrared camera, floor-mounted force plate system, EMG sensors) confirms what has long been suspected: the jump-landing movement parameters are determined prior to the actual landing itself. In other words, these parameters are "firmware settings". The authors compared males and females in jumping landing, and noted that the females have less knee and hip flexion at jump landing, decreased hamstring activation (i.e. more stress on the ACL), and increased quadriceps activation (again more ACL stress). Fortunately, this disconcerting state of affairs can be rectified through a targeted, diligently pursued knee-injury-prevention training program. Other good articles on these topics are Noyes-AJSM-Feb05.shtml, Ahmad-AJSM-Mar06.shtml, BarberWestin-AJSM-Mar06.shtml, Mandelbaum-AJSM-Jul05.shtml, and Chappell-AJSM-Mar02.shtml.
ABSTRACT
Background: Biomechanical analysis of stop-jump tasks has demonstrated gender differences during landing and a potential increase in risk of noncontact anterior cruciate ligament injury for female athletes. Analysis of landing preparation could advance our understanding of neuromuscular control in movement patterns and be applied to the development of prevention strategies for noncontact anterior cruciate ligament injury.
Hypothesis: There are differences in the lower extremity joint angles and electromyography of male and female recreational athletes during the landing preparation of a stop-jump task.
Study Design: Controlled laboratory study.
Methods: Three-dimensional videographic and electromyographic data were collected for 36 recreational athletes (17 men and 19 women) performing vertical stop-jump tasks. Knee and hip angular motion patterns were determined during the flight phase before landing.
Results: Knee and hip motion patterns and quadriceps and hamstring activation patterns exhibited significant gender differences. Female subjects generally exhibited decreased knee flexion (P = .001), hip flexion (P = .001), hip abduction (P = .001), and hip external rotation (P = .03); increased knee internal rotation (P = .001); and increased quadriceps activation (P = .001) compared with male subjects. Female subjects also exhibited increased hamstring activation before landing but a trend of decreased hamstring activation after landing compared with male subjects (P = .001).
Conclusion: Lower extremity motion patterns during landing of the stop-jump task are preprogrammed before landing. Female subjects prepared for landing with decreased hip and knee flexion at landing, increased quadriceps activation, and decreased hamstring activation, which may result in increased anterior cruciate ligament loading during the landing of the stop-jump task and the risk for noncontact ACL injury.
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