ABSTRACTMoran, KA, Clarke, M, Reilley, F, Wallace, ES, Brabazon, D, andMarshall, B. Does Endurance Fatigue Increase the risk of injurywhen performing drop jumps? J Strength Cond Res 23(5):1448–1455, 2009—Although from an athletic performanceperspective it may be beneficial to undertake drop jump trainingwhen fatigued (principle of ‘‘specificity’’ of training), such endurancefatigue may expose the body to a greater risk of injury if itcauses an increase in peak impact accelerations. This studyaimed to determine if endurance fatigue resulted in an increasein tibial peak impact acceleration and an associated change inknee kinematics when completing plyometric drop jumps.Fifteen females performed drop jumps from 3 heights (15, 30,and 45 cm) when fatigued and nonfatigued. Treadmill runningwas used to induce endurance fatigue. The following variableswere assessed: tibial peak impact acceleration, knee angle atinitial ground contact, maximum angle of flexion, range of flexion,and peak knee angular velocity. Fatigue resulted in significantlygreater (p , 0.05) tibial peak impact acceleration and kneeflexion peak angular velocity in drop jumps from 15 and 30 cm,but not from 45 cm. Fatigue had no effect on any of the kneeangles assessed. The neuromuscular system was affectednegatively by endurance fatigue at 15 and 30 cm, indicatingthat coaches should be aware of a potential increased risk ofinjury in performing drop jumps when fatigued. Because fromthe greater drop height of 45 cm the neuromuscular system hada reduced capacity to attenuate the impact accelerations perse, whether nonfatigued or fatigued, this would suggest thatthis height may have been too great for the athletes examined.KEY WORDS injury, plyometric, impact, landing