Combined Effects of Drop Height and Fatigue on Landing Mechanics in Active Females

Drop height and fatigue have been shown in isolation to affect landing mechanics and increase the risk of sustaining an anterior cruciate ligament injury. The purpose of this study was to identify the combined effects of drop height and fatigue on landing mechanics in recreationally active females. To assess this, 11 healthy, young adult females performed a series of drop jumps from randomized heights before and following a lower extremity fatiguing protocol. Findings for kinematic results demonstrated that hip flexion decreased at initial contact (P = .003) and maximum hip (P = .005) and knee flexion (P = .001) angles increased with increases in drop height. Kinetic results demonstrated that vertical ground reaction forces and joint moments and powers increased as height increased. Ground reaction forces and maximum knee valgus increased from pre- to postfatigue with interactive effects observed in frontal plane hip angle at impact and peak ankle moment. These results confirm the effects of drop height and fatigue and highlighted interactions between these factors. The differential effect of fatigue as a function of drop heights helps to illustrate potentially risky situations that should be addressed in training and injury prevention programs.