Hip-abductor fatigue, frontal-plane landing angle, and excursion during a drop jump

Context: The influence of hip-muscle function on knee-joint kinematics during landing has been inadequately investigated. Objective: To determine the effect of bilateral hip-abductor fatigue on frontal-plane tibiofemoral landing characteristics and vertical ground-reaction force (vGRF) during the landing phase of a drop jump. Design: Experimental, pretest-posttest. Setting: Research laboratory. Participants: 20 recreationally active college-age students. Intervention: Isometric bilateral hip-abductor-fatigue protocol. Main Outcome Measures: Frontal-plane tibiofemoral landing angle, excursion, and vGRF during landing from a drop jump under prefatigue, postfatigue, and recovery conditions. Results: After the fatigue protocol, participants landed in a greater valgus orientation than in the prefatigued state. No differences in frontal-plane excursion or vGRF were noted. Conclusions: Isolated bilateral hip-abductor fatigue alters frontal-plane lower extremity orientation during a double-leg landing. Because an increase in valgus orientation has been observed at or near the time of noncontact anterior cruciate ligament injuries, we recommend improving hip-abductor muscle performance to lessen the risk of such injuries.