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Contributions of lower extremity joints to energy dissipation during landings

ZHANG, SONG-NING; BATES, BARRY T.; DUFEK, JANET S.

Medicine & Science in Sports & Exercise: April 2000 - Volume 32 - Issue 4 - p 812-819
Applied Sciences: Biodynamics

ZHANG, S-N., B. T. BATES, and J. S. DUFEK. Contributions of lower extremity joints to energy dissipation during landings. Med. Sci. Sports Exerc., Vol. 32, No. 4, pp. 812–819, 2000.

Purpose: The purpose of the study was to investigate changes in lower extremity joint energy absorption for different landing heights and landing techniques.

Methods: Nine healthy, active male subjects volunteered to perform step-off landings from three different heights (0.32 m, 2.5 m-s; 0.62 m, 3.5 m-s; and 1.03 m, 4.5 m-s) using three different landing techniques (soft, SFL; normal, NML; and stiff landing, STL). Each subject initially performed five NML trials at 0.62 m to serve as a baseline condition and subsequently executed five trials in each of the nine test conditions (3 heights × 3 techniques).

Results: The results demonstrated general increases in peak ground reaction forces, peak joint moments, and powers with increases in landing height and stiffness. The mean eccentric work was 0.52, 0.74, and 0.87 J·kg−1 by the ankle muscles, and 0.94, 1.31, and 2.15 J·kg−1 by the hip extensors, at 0.32, 0.62, and 1.03 m, respectively. The average eccentric work performed by the knee extensors was 1.21, 1.63, and 2.26 J·kg−1 for the same three heights.

Conclusions: The knee joint extensors were consistent contributors to energy dissipation. The ankle plantarflexors contributed more in the STL landings, whereas the hip extensors were greater contributors during the SFL landings. Also a shift from ankle to hip strategy was observed as landing height increased.

Exercise Science Unit, Biomechanics/Sports Medicine Laboratory, The University of Tennessee, Knoxville, Knoxville, TN 37996; and University of Oregon, Eugene, OR

Submitted for publication February 1998.

Accepted for publication September 1998.

Address for correspondence: Song-Ning Zhang, Department of Exercise Science and Sport Management, Biomechanics/Sports Medicine Laboratory, The University of Tennessee, Knoxville, 1914 Andy Holt Ave., Knoxville, TN 37996; E-mail: szhang@utk.edu.

© 2000 Lippincott Williams & Wilkins, Inc.