Abstract: BACKGROUND: While stress fractures impact both military and non-military persons, there are several unique aspects to the problem in the military context. One of the primary differences is in the physical activities and demands on the recreational and competitive runners versus military personnel. In addition to typical exposures to running for fitness and recreation, military personnel must routinely engage in physical activities such as running and marching while carrying additional loads. The load that soldiers are expected to carry has increased substantially, from WWI and WWII to the current conflicts in Afghanistan and Iraq. While, the effects of load carriage on the biomechanical aspects of gait have been examined by several researchers, there is still much that is unknown in terms of how these additional loads influence the risk of overuse injuries such as tibial stress fractures.
PURPOSE: The purpose of this research is to determine the effects of load carriage and fatigue on mechanical variables associated with increased risk of tibial stress fractures. It is hypothesized that an increase in load carried will result in changes in gait mechanics leading to increased stresses, strains, and strain rates in the tibia. It is also hypothesized that fatigue will result in changes in gait mechanics and muscular activity leading to increased stresses, strains, and strain rates in the tibia.
SPECIFIC AIMS: The specific aims of this research are to determine the effect of increased load carriage and fatigue on gait mechanics during a walking protocol and to determine the effect of increased load carriage and fatigue on the resulting stress/strain profile in tibia.
STUDY DESIGN: In order to determine the effects of load carriage and fatigue on mechanical variables associated with increased risk of tibial stress fractures, traditional kinematic and kinetic analyses derived from motion capture and force plate data will be combined with subject-specific finite element models of the tibia utilizing customized musculoskeletal modeling software.
SIGNIFICANCE: The immediate significance of this research to the Armed Forces is the ability to quantify the effects of load carriage and fatigue, in situations similar to those encountered by military personnel, on the mechanical loading of the tibia. It is this mechanical loading and the stresses and strains it causes in the bone that ultimately leads to injury. The results of this study can then be used to evaluate the relative changes in bone loading parameters and thus the potential risk of tibial stress fracture due to these conditions. Equipment/Software used:
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