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CHARACTERIZING PRIMARY STABLIZERS OF THE FOOT AND ANKLE THROUGH FOOT ORTHOTIC APPLICATION DURING DYNAMIC TASK

A Griffith

Abstract

Aaron Griffith. Mississippi State University, Starkville, MS.

BACKGROUND: Foot orthoses are devices made to insert into the shoes to provide cushion and off-loading of foot structures. They are either prefabricated or custom-made. The general difference between custom foot orthotics (CFO) and non-custom foot orthotics (NCFO) is that CFO’s are designed specifically for the contour of a patient’s foot and to treat specific pathologies in the foot and ankle primarily based on mechanical dysfunction or postural deformity. NCFO’s are worn to provide stability and postural support for the foot and its surrounding muscles. The first goal of the project was to examine the etiology of distal lower extremity injury associated with foot orthotic modality in field and court sports by comparing changes in lower extremity neuromuscular stability. The second goal was to examine the interaction between athletic footwear, NCFO and playing surfaces with the most prevalent distal lower extremity pathologies directly associated with foot orthotic modalities. METHODS: The Tibialis Anterior (TA) and Medial Gastrocnemius (MG) were the two muscle groups of interest along with kinetic and kinematic variables of the lower extremity across four conditions. Two separate experiments were conducted during this study to test 2 hypotheses. Both hypotheses are supported by the preferred movement pathway theory, which indicates that foot orthotics do not significantly change skeletal alignment of the body but rather alter input signals through mechanoreceptors in the skin and muscle originating from the plantar region of the foot. This causes change in “muscle tuning” of the lower extremity, thereby producing a change in muscle activity with the goal of dampening soft tissue vibrations within the lower extremity. RESULTS: Normal distribution Electromyography (EMG) parameters was checked with a Shapiro-Wilk test and analyzed by way of two-way ANOVA and Paired T-TEST. A measurable difference was seen amongst the TA on different surfaces. Muscle tension amongst the TA considerably reduced on turf surfaces as opposed to the court platform while simultaneously peak forces increased within both platforms. Correlating to muscle effort managing the most common distal lower extremity injury across all platforms with orthotics. In the MG there was a higher instance of muscle tension in the turf conditions in relation the peak forces generated, however on court the peak forces remained higher, and the mean effort showed no difference in reduction need to efficiently change direction. CONCLUSIONS: The energy of work needed to complete the movements within the study varied amongst all groups and showed measurable trends in conditions involved or uninvolved with orthotics regardless of the surface that the tasks were completed upon. A range of 15% to 90% of overall effort was required throughout the duration of this study.

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