Background: Neuromuscular fatigue has been suggested as an extrinsic factor in the mechanism of noncontact anterior cruciate ligament injury in both genders.
Purpose: To determine and describe the lower extremity kinematic and kinetic differences caused by neuromuscular fatigue during drop landings and compare changes between age- and skill-matched male and female athletes.
Methods: Inverse dynamic solutions estimated lower extremity flexion-extension and varus-valgus kinematics and kinetics for 14 female and 16 male athletes performing a single-legged 50-cm drop landing. Subjects performed landings prefatigue and postfatigue with fatigue induced via a parallel squat exercise (60% of 1 repetition maximum) until failure. A mixed-model, repeated-measures analysis of variance (fatigue * gender) was performed on select kinematic and kinetic variables.
Results: Neuromuscular fatigue caused men and women to land with more hip flexion (main effect fatigue, P = .012; main effect gender, P = .001). Men exhibited greater peak knee flexion angles postfatigue; women did not alter knee flexion (fatigue * gender, P = .028). Men exhibited larger peak knee varus angles irrespective of fatigue (main effect gender, P = .039; main effect fatigue, P = .127; fatigue * gender, P = .153); women demonstrated larger peak valgus angles overall (main effects gender, P = .009). There were no changes with fatigue (main effect fatigue, P = .127) or a different response due to fatigue with gender (fatigue * gender, P = .091). Women exhibited greater knee anterior shear force postfatigue (fatigue * gender, P = .010). Men and women exhibited lower knee extension moments (main effect fatigue, P = .000; main effect gender, P = .927; fatigue * gender, P = .309) and abduction moments (main effect fatigue, P = .014; main effect gender, P = .670; fatigue * gender, P = .191).
Conclusion: Neuromuscular fatigue caused significant alterations in women that may be indicative of the noncontact anterior cruciate ligament injury mechanisms.
Clinical relevance: Current noncontact anterior cruciate ligament prevention programs should incorporate a fatigue component to help minimize the deleterious effects of neuromuscular fatigue on landing mechanics.