Effect of Fatigue on Knee Biomechanics in Stop-Jump Tasks


Non-contact ACL injuries frequently occur during athletic maneuvers involving landing, cutting, and pivoting. Fatigue may contribute by altering lower extremity biomechanics. This study analyzed the impact of fatigue on knee kinetics and kinematics during stop-jump tasks.


20 recreational athletes performed stop-jump tasks before and after a fatiguing exercise routine. 3D motion analysis and force plates quantified knee joint angles and forces.


After fatigue, anterior tibial shear forces increased 21% and knee flexion angles decreased 14% during landings. Fatigued females showed a 96% increase in valgus moment compared to a 43% decrease in varus moment for males. Jump height decreased, indicating a successful fatigue protocol.


Increased anterior tibial shear forces suggest greater ACL strain with fatigue, especially in females. Decreased knee flexion also increases anterior tibial translation and ACL load. The valgus moment increase in females further augments ACL stresses.

Fatigue appears to alter neuromuscular control and landing strategies in a manner that could heighten injury risk. Females demonstrated riskier biomechanics both at baseline and after fatigue. ACL injury prevention programs should emphasize proper landing technique even under fatigued conditions.


Fatigue degrades landing biomechanics during stop-jump maneuvers, increasing anterior tibial forces and knee moments that load the ACL. Females experience greater ACL stresses that could heighten injury susceptibility. Avoiding fatigue and training controlled landings may help reduce injury risk.


1. Chappell JD, Herman DC, Knight BS, Kirkendall DT, Garrett WE, Yu B. Effect of fatigue on knee kinetics and kinematics in stop-jump tasks. Am J Sports Med. 2005;33(7):1022-1029.

2. Benjaminse A, Habu A, Sell TC, et al. Fatigue alters lower extremity kinematics during a single-leg stop-jump task. Knee Surg Sports Traumatol Arthrosc. 2008;16(4):400-407.

3. McLean SG, Fellin RE, Suedekum N, Calabrese G, Passerallo A, Joy S. Impact of fatigue on gender-based high-risk landing strategies. Med Sci Sports Exerc. 2007;39(3):502-514.

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