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Introduction: Mal-alignment and dysfunction of the foot have been shown to result in an increased rate of injury and unique injury patterns. Aberrant foot function has been shown to contribute to repetitive stress and acute injuries. High-arched athletes have been shown to experience a greater rate of bony injury to the lateral aspect of the lower extremity while low-arched athletes experience greater rates of soft-tissue injury to the medial aspect of the lower extremity. Though foot type has been linked to these injury patterns, the mechanism by which these injury patterns occur remains unknown. Multi-segment foot models have been developed and allow for direct examination of motion within the foot. Therefore, the purpose of the current studies is to directly examine motion within the foot during vertical loading and dynamic loading tasks. Methods: Ten high- and 10 low-arched female athletes performed five trials in each of the following randomized conditions: walking, running, downward stepping, landing and a sit-to-stand exercise. Three-dimensional kinematics and ground reaction forces were collected simultaneously using a 7-camera motion capture system and force platform, respectively. Results: The HA athletes were less everted than the LA athletes in the ankle and mid-forefoot joints in all activities. The HA and LA athletes exhibited similar excursion values in all joints. Additionally, the HA athletes had a greater arch index and greater arch deformity during in the sit-to-stand task. Discussion and Conclusions: The HA athletes are less everted in all movements than the LA athletes; however excursion values were similar between the two groups. These data suggest the reason for different injury patterns within these two groups is not due to greater frontal plane ranges of motion. Furthermore, the sit-to-stand exercise showed that the HA athletes have a greater arch index but have greater deformation in response to a vertical load. The LA athletes exhibited less arch deformity but this deformity appears to be limited by the floor. The current study suggests the mechanism leading to different injury patterns in the HA and LA athletes is vertical compression of the arch.

In my thesis, a novel distance field transform Method is proposed basing on an iterative method adaptively performed on an evolving active band. Our method utilizes a narrow band to store active grid points being computed. Unlike the conventional fast marching method, we do not maintain a priority queue, and instead, perform iterative computing inside the band. This new algorithm alleviates the programming complexity and the data-structure (e.g. a heap) maintenance overhead, and leads to a parallel amenable computational process. During the active band propagating from a starting boundary layer, each grid point stays in the band for a lifespan time, which is determined by analyzing the particular geometric property of the grid structure. In this way, we find the Face-Centered Cubic (FCC) grid is a good 3D structure for distance transform. We further develop a multiple-segment method for the band propagation, achieving the computational complexity of O(m · N) with a segment-related constant m.