The purpose of the present study was to examine and to clarify the effects of hip abductor fatigue on the trunk, pelvis and lower leg biomechanics during single-leg landing (SLL) in male recreational level athletes, and the conclusion was that they could be likely to have the increased risk of ipsilateral knee ligament injury after isolated hip abductor fatigue during SLL.
Weakness of the hip abductors is responsible for the increases in range of motion of knee abduction and knee adductor moments. However, little attention has been paid to the relationship between hip abductor fatigue and the whole-body biomechanics including the trunk, pelvis, and lower leg. The purpose of the present study was to examine and to clarify the effects of hip abductor fatigue on the trunk, pelvis and lower leg biomechanics during single-leg landing (SLL) in male recreational level athletes.
Twenty male recreational level athletes (mean age = 20.0±1.5 yrs) participated. An informed consent form approved by Institutional Review Board of our university was obtained in each subject. The subjects performed single-leg landing, which was jumping from a 30-cm high box to a distance of 25% of their height away from the box, down to force plates. For the isolated hip abductor fatigue protocol, subjects performed an abduction movement using a weight of 10 kg wrapped around the distal part of the lower leg in a lateral position until they could not raise up the lower leg. Thereafter, it was replaced with a weight of 5 kg and continued until they were unable to raise up the lower leg again. The dominant leg (20 right) was chosen for the fatigue protocol. After performing SLL several times, two trials were recorded for each subject before fatigue and after protocol. SLL in each subject was captured using a motion analysis system. Motion analysis system was consisted of 8 cameras (120 frames/s; Pro-reflex, Qualisys, Sweden), two force plates (frequency 600 Hz; AM6110, Bertec, Columbus, OH, USA), and 46 retro-reflective markers. The motion of markers was recorded by Qualisys Track Manager Software (version 2.7). To calculate trunk, pelvis, and lower leg biomechanics, Visual 3D (C-motion Company, Rockville, MD, USA) was utilized. Three-dimensional kinematics and kinetics were evaluated at knee and hip joints during landing phase. Knee internal rotation was defined as tibial rotation with respect to the femur. Simultaneously, three-dimensional kinematics of trunk and pelvis were assessed in the same way. As a statistical analysis, the data were compared between before and after fatigue protocol in each group using two-tailed Paired t-test. The statistical significance level was set at P=0.05.
Knee abduction and internal rotation angles were significantly larger after fatigue than before fatigue, and external knee flexion moment was significantly smaller after fatigue. In terms of trunk and pelvic movement, left inclination of pelvis and right inclination of trunk were significantly larger after fatigue. Knee flexion angle, external knee flexion moment, hip flexion angle, and hip adduction angle were significantly smaller after fatigue.
According to a previous report, simulated hip abductor weakness caused small alterations of frontal plane knee mechanics during a jumping task. In the present study, hip abductor fatigue led to changes of lower leg biomechanics as well as trunk and pelvis. Namely, weakness of the hip abductor muscle might cause Trendelenburg like movement of the pelvis and compensatory movement of the trunk.
Male recreational level athletes are likely to have the increased risk of ipsilateral knee ligament injury after isolated hip abductor fatigue during SLL.