Motion characteristics of the medial and lateral longitudinal arch during landing.

This study determined sagittal plane motion of the medial longitudinal arch (MLA) and lateral longitudinal arch (LLA) as well as the kinematics of the arch during landing. IRB-approved informed consent was obtained from 10 healthy male subjects (23.4 +/- 3.4 years old) who performed single leg landings from a height of 10 cm with their knee extended. The subjects were then asked to stop and balance after each landing. Each trial was recorded using cineangiography. Images were obtained at a rate of 60 Hz using a radiation exposure equivalent to 200 mA (1 ms) with an intensity of 50 kV. Simultaneous ground reaction forces were measured using a force plate. The data were analyzed using a template method. Sagittal motion was defined as the change in the angle and the translational motion of the arch. A paired t test was performed to determine the differences in the measured values between the MLA and the LLA. The magnitude of the arch angle increased with time for 80-100 ms in all subjects. The magnitude of the arch angle for the LLA was significantly larger than that for the MLA. Regarding translational motion, the motion of the MLA was larger than that of the LLA. It was clear that each longitudinal arch had a different deformation pattern in absorbing the impact on landing. The MLA had a small angular change and a moderate degree of translational motion. Conversely, the motion of the LLA was mainly an angular change with a small translational motion.