Energetic Analysis of Landing: a Novel Approach to Understanding Anterior Cruciate Ligament Injuries

Background: Greater sagittal plane energy absorption (EA) in the 100 ms immediatelyfollowing ground contact during landing likely results in greater anterior cruciate ligament(ACL) loading and is the result of the combined EA of the hip, knee, and ankle. Further,greater total EA has been associated with landing biomechanics that are purported toincrease ACL injury risk. However, it is currently unknown what modifiable biomechanicalfactors are predictive of lower extremity EA and should be addressed in ACL injuryprevention programs.Purpose: To identify modifiable biomechanical predictors of hip, knee, and ankle EA.Study Design: Descriptive laboratory study.Methods: Seventy-seven volunteers (40 males, 37 females; Age = 20.1 ± 2.2 years; Height= 1.74 ± 0.10 m; Mass = 70.3 ± 16.1 kg) had peak strength and muscle activation measuredduring maximal voluntary isometric hip extension, knee extension, knee flexion, and ankleplantarflexion contractions. Subjects then performed double-leg jump landings during whichlower extremity biomechanics were assessed (kinematics and kinetics, and electromyography). Multiple, stepwise regression analyses were used to predict hip, knee,and ankle EA during the 100 ms following ground contact from the measured biomechanicalfactors.Results: Greater peak hip flexion, lesser hip flexion at ground contact, and greater peak hipextension strength significantly predicted greater hip EA (R = 0.545, R = 0.297, Adjusted R = 0.266, P < 0.001). No biomechanical factors were identified that significantly predictedknee EA (P > 0.05). Greater ankle extension (plantarflexion) at ground contact, peak ankle