The purpose of the present study was to investigate the biomechanical relationship between static lunge and single-leg landing with three different toe directions, and we concluded that the knee kinematics during static lunge could predict knee ligament injury risk during single-leg landing in male recreational level athletes.
According to previous studies, foot position during static lunge and jumping tasks is related to malalignment of the knee joint. Generally, closed kinetic chain exercise such as static lunge is useful for rehabilitation to avoid overloading of anterior cruciate ligament (ACL). Although static lunge is never related to ACL injury, it is possible that athletes may have ACL injury with malalignment of knee joint during jumping tasks. The purpose was to investigate and clarify the biomechanical relationship between static lunge and single-leg landing with three different toe directions.
A total of 23 male recreational level athletes (mean age = 20.0 ± 1.1 yrs) participated. A written informed consent form approved by Institutional Review Board of our university was obtained in each subject. The subjects performed static lunge and single-leg landing. The subjects performed weight-bearing static lunge tests (SL) on measured limb under three different toe directions, including 0 degrees (Toe Neutral: TN), 20 degrees (Toe-In: TI), and -20 degrees (Toe-out: TO). To perform the Static Lunge, the measured foot was placed in front and the unmeasured foot was placed behind the measured foot. Subject was asked to tilt the trunk by 30 degrees and the knee flexion on measured side was set at 60 degrees. Single-leg landing tasks (SLL) were jumping from a 30-cm high box to a distance of 25% of their height away from the box, down to force plates. Similarly, SLL was done under three different toe directions, including TN, TI, and TO. The dominant leg (23 right) was chosen for the measurement. After performing SL and SLL several times, two trials were recorded for each subject 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 (14mm in diameter). The motion of markers was recorded by Qualisys Track Manager Software (version 2.7). Three-dimensional knee kinematics and kinetics at the timing of the knee flexion of 60 degrees were calculated using Visual 3D (C-motion Company, Rockville, MD, USA). Knee internal rotation was defined as tibial rotation with respect to the femur. As a statistical analysis, Pearson's correlation coefficient was used to evaluate the relationship between SL and SLL.
Knee abduction angle showed significant correlation between SL and SLL in three different directions (TI: r=0.631, TN: r=0.678, TO: r=0.572). In terms of knee internal rotation, strong correlation was found in three different directions (TI: r=0.846, TN: r=0.791, TO: r=0.749). In addition, external knee abduction moment presented significant correlation in three different directions 8 TI: r=0.574, TN: r=0.499, TO: r=0.469).
Significant correlation between SL and SLL was found in knee abduction angle, knee internal rotation, and external knee abduction moment under all three different directions. Therefore, SL was useful to know the biomechanics of SLL for each subject.
The knee kinematics during static lunge can predict knee ligament injury risk during single-leg landing in male recreational level athletes.