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Fatigue Effects on Knee Joint Stability During Two Jump Tasks in Women

Ortiz, Alexis1,2; Olson, Sharon L3; Etnyre, Bruce4; Trudelle-Jackson, Elaine E5; Bartlett, William3; Venegas-Rios, Heidi L6

Journal of Strength & Conditioning Research: April 2010 - Volume 24 - Issue 4 - pp 1019-1027
doi: 10.1519/JSC.0b013e3181c7c5d4
Original Research

Ortiz, A, Olson, SL, Etnyre, B, Trudelle-Jackson, EE, Bartlett, W, and Venegas-Rios, HL. Fatigue effects on knee joint stability during two jump tasks in women. J Strength Cond Res 24(4): 1019-1027, 2010-Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 ± 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury-predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes.

1Physical Therapy Program, School of Health Professions, University of Puerto Rico-Medical Sciences Center, San Juan, Puerto Rico; 2Department of Physical Education & Recreation, University of Puerto Rico-Rio Piedras Campus, San Juan, Puerto Rico; 3School of Physical Therapy, Texas Woman's University, Houston, Texas; 4Department of Kinesiology, Rice University, Houston, Texas; 5School of Physical Therapy, Texas Woman's University, Dallas, Texas; and 6Department of Biostatistics & Epidemiology, University of Puerto Rico-Medical Sciences Campus, San Juan, Puerto Rico

This study was conducted in the Musculoskeletal Laboratory at the Physical Therapy Program from Texas Woman's University-Houston Campus.

Address correspondence to Dr. Alexis Ortiz,

© 2010 National Strength and Conditioning Association