تاثیر طول گام بر مولفه های عمودی و خلفی نیروی عکس العمل زمین و نرخ بارگذاری در حین انجام حرکت »بدو-رو«: مولفه ای برای خطر شکستگی استرسی در اندام تحتانی نظامیان

Background: stress fracture occur following bone exposure to cyclic sub-threshold loadings before repairing previous micro-fractures. the aims of this study were: 1) to assess and compare the ground reaction force and loading rate responses of the fixed-cadence marching at the fourth step and single-leg landing; and 2) the effect of over striding in the fourth step of fixed-cadence marching on the ground reaction forces and loading rates.materials and methods: a total of ten male students of police (naja) university were enrolled. five experiments including two single leg landing, two fixed-cadences marching, and regular running experiments were applied. the experiments data were collected with 200 hertz using a force plate device.results: the results showed a high correlation between the fixed-cadence marching at the fourth step and single leg landing with both studied step lengths for the peak vertical and posterior components of ground reaction force and loading rate (r = 0.863, r = 0.781, r = 0.847, and r = 0.798 for step length of 25 centimeter, and r=0.865, r=0.74, r=0.831, and r=0.716 for step length of 50 centimeter; p < 0.05). by increasing the step length, all variables increased significantly (p < 0.05). the increase in the amount and rate of ground reaction forces can increase the risk of stress fracture on the lower extremities of soldiers and officers.conclusion: as a mechanism to prevent over striding and consequently stress fractures in the fixed-cadence marching, it is suggested that recruits with the same height can be arranged to a group during marching, so that their step length maintain around their preferred one.