Evaluating the Shock Induced to the Legs during the 90 Degree Military Marching Using Acceleration Curves

The objective of this study was to evaluate the shock induced to the legs during the 90 degree military marching using acceleration curves. Subjects of this study were 13 Imam Hossein University Students performing 90 degree military marches at self-selected speeds recorded by a high speed camera at 300 fps from the sagittal plane. Two passive markers were placed on the hip and ankle of the participants. Horizontal component of hip velocity and accompanying ankle acceleration curves while marching were deduced and the magnitudes of peak acceleration at the moment of impact with the ground were recorded. Cyclic acceleration curves for consecutive movements were identified in all the subjects. Average propulsion velocity of 0.60±0.14m/s and average horizontal, vertical and resultant peak accelerations were 8.67± 1.58, 5.93± 1.60g, and 10± 1.72 g. Unlike walking and running, the magnitude of horizontal acceleration at the instant of impact was larger than that of the vertical, in 90 degree marching. Although the forward velocity was remarkably slow, the accelerations obtained in this study were higher than those encountered with running at a velocity of 4 m/s. Directions and magnitudes of the acceleration indicate the irrational ground reaction force which can be highly prone to injury. The inclusion of special energy absorption parts in the armed forces boots, marching exercises using visual feedback on acceleration profiles, or adoption of alternative marching techniques could all contribute to reduce or eliminate injury problems.