Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
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©Journal of Sports Science and Medicine (2009) 08, 663 - 671

Research article
Muscle Strength and Qualitative Jump-Landing Differences in Male and Female Military Cadets: The Jump-ACL Study
Anthony I. Beutler1, , Sarah J. de la Motte1, Stephen W. Marshall2, Darin A. Padua2, Barry P. Boden3
Author Information
1 Uniformed Services University of the Health Sciences, Bethesda, MD
2 The University of North Carolina at Chapel Hill, Chapel Hill, NC
3 The Orthopaedic Center, Rockville, MD, USA

Anthony I. Beutler
✉ Uniformed Services University of the Health Sciences, Bethesda, MD, USA
Email: abeutler@usuhs.mil
Publish Date
Received: 28-05-2009
Accepted: 20-10-2009
Published (online): 01-12-2009
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ABSTRACT

Recent studies have focused on gender differences in movement patterns as risk factors for ACL injury. Understanding intrinsic and extrinsic factors which contribute to movement patterns is critical to ACL injury prevention efforts. Isometric lower- extremity muscular strength, anthropometrics, and jump-landing technique were analyzed for 2,753 cadets (1,046 female, 1,707 male) from the U.S. Air Force, Military and Naval Academies. Jump- landings were evaluated using the Landing Error Scoring System (LESS), a valid qualitative movement screening tool. We hypothesized that distinct anthropometric factors (Q-angle, navicular drop, bodyweight) and muscle strength would predict poor jump-landing technique in males versus females, and that female cadets would have higher scores (more errors) on a qualitative movement screen (LESS) than males. Mean LESS scores were significantly higher in female (5.34 ± 1.51) versus male (4.65 ± 1.69) cadets (p < 0.001). Qualitative movement scores were analyzed using factor analyses, yielding five factors, or “patterns”, contributing to poor landing technique. Females were significantly more likely to have poor technique due to landing with less hip and knee flexion at initial contact (p < 0.001), more knee valgus with wider landing stance (p < 0. 001), and less flexion displacement over the entire landing (p < 0.001). Males were more likely to have poor technique due to landing toe-out (p < 0.001), with heels first, and with an asymmetric foot landing (p < 0.001). Many of the identified factor patterns have been previously proposed to contribute to ACL injury risk. However, univariate and multivariate analyses of muscular strength and anthropometric factors did not strongly predict LESS scores for either gender, suggesting that changing an athlete’s alignment, BMI, or muscle strength may not directly improve his or her movement patterns.

Key words: Jump-landing, ACL injury risk, motor patterns, qualitative movement screen


           Key Points
  • Important differences in male and female landing technique can be captured using a qualitative movement screen: the Landing Error Scoring System (LESS).
  • Female cadets were more likely to land with shallow sagittal flexion, wide stance width, and more pronounced knee flexion.
  • Male cadets were more likely to exhibit a heel-strike or asymmetric foot-strike and to land with toe out.
  • Lower extremity muscle strength, Q-angle, and navicular drop do not significantly predict landing movement pattern in male or female cadets.
 
 
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