Influence of Relative Hip and Knee Extensor Muscle Strength on Landing Biomechanics

STEARNS, KRISTEN M.1; KEIM, ROBERT G.2; POWERS, CHRISTOPHER M.1

Medicine & Science in Sports & Exercise: May 2013 - Volume 45 - Issue 5 - p 935–941
doi: 10.1249/MSS.0b013e31827c0b94
Applied Sciences

Purpose: This study aimed to determine whether the tendency of women to exhibit higher knee extensor moments relative to hip extensor moments during the deceleration phase of landing can be explained by the relative strength of the knee and hip extensors.

Methods: Forty recreationally active individuals participated in this study (20 men and 20 women). The maximum isometric strength of the knee extensors and hip extensors was assessed using a load cell and custom testing setup. Lower extremity kinematics and kinetics were collected during a double-leg drop-jump task.

Results: When compared with men, women demonstrated a significantly higher knee–hip extensor moment ratio during the deceleration phase of landing (1.42 ± 0.6 vs 1.12 ± 0.3, P < 0.001). In addition, the knee–hip extensor isometric strength ratio was significantly higher in women compared with men (1.01 ± 0.2 vs 0.89 ± 0.2, P < 0.001). The Pearson partial correlation (controlling for sex) revealed a significant positive association between the knee–hip extensor isometric strength ratio and the knee–hip extensor moment ratio (r = 0.41, P = 0.005).

Conclusion: The tendency of women to exhibit higher knee extensor moments relative to hip extensor moments may be explained, in part, by the relative strength of the hip and knee extensors.

1Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA; and 2Rossier School of Education, University of Southern California, Los Angeles, CA

Address for correspondence: Kristen M. Stearns, Ph.D., P.T., Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 E. Alcazar St., CHP-155, Los Angeles, CA 90089-9006; E-mail: kristen.stearns@gmail.com.

Submitted for publication June 2012.

Accepted for publication October 2012.

©2013The American College of Sports Medicine