Effect of Fatigue and Gender on Lower Limb Neuromuscular Function

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Approximately two-thirds of anterior cruciate ligament (ACL) tears are sustained under noncontact circumstances. Some investigators believe that fatigue may result in deleterious alterations in lower limb biomechanics that increase the risk of noncontact ACL injury. One important question is whether muscular fatigue uniformly alters lower limb biomechanics during cutting, pivoting, decelerating, or landing. A second question is whether fatigued female athletes have significant differences in knee and hip kinetics and kinematics and muscle activation patterns that may increase their risk of ACL injury. The issues are whether changes are required in ACL injury prevention training programs to account for fatigue-related lower limb biomechanical changes. We conducted a formal systematic review that involved 37 studies (485 female and 321 male athletes). The results indicated that published fatigue protocols did not uniformly produce alterations in lower limb biomechanical factors. There were few fatigue × gender interactions, and the question of whether the fatigued state places female athletes at greater risk of injury remains to be answered. There were no consistent data that demonstrated that the type of fatigue protocol (peripheral vs. general), athletic task selected (single-legged vs. double-legged), or task model (planned vs. reactive) strongly influenced changes in knee and hip kinematics and kinetics. Therefore, justification does not appear warranted for major changes in ACL injury prevention training programs to account for potential fatigue effects. The large variation in findings indicates the need for continued research in this area and refinement of fatigue protocols, athletic tasks selected for analysis, and methods of analysis.