Doctoral Dissertations

Date of Award

8-2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Kinesiology

Major Professor

Songning Zhang

Committee Members

Joshua T. Weinhandl, John Sorochan , Jeff Reinbolt

Abstract

Annually, over 4 million high school and college athletes participate in competitive sports played on turf surfaces. Since the introduction of synthetic turf in the 1970s, it has become a common alternative to natural grass playing surfaces. However, athletes playing on synthetic turf has been found to have an increased incidence of lower extremity injury compared to natural grass.

Mechanical surface testing has found that synthetic turf exhibits significantly higher rotational and translational tractions compared to natural grass. The cleat-turf interface is often examined using a force platform, an instrument commonly used in a biomechanical laboratory. Mobile surface testing instruments have been developed to examine traction characteristics and have rarely examined measurement agreement with the measurements taken by the force platform. The one system that attempted to establish this relationship was found to overestimate horizontal forces and underestimate vertical forces significantly, and no system has examined free moment agreement. Aim one of this study was to compare agreement levels between a force platform, and a customized novel mobile surface testing instrument (fLEX). Additionally, within the laboratory setting, there has been no clear method for mounting synthetic turf to a force platform in order to acquire force platform data during human subject testing. Therefore, the aim two was to examine agreement between the force platform and fLEX to identify the best synthetic turf mounting method for high (cleatform) and low (court shoe) traction interfaces during static and dynamic movements. The method for producing a high level of agreement may be suitable for future human testing in the laboratory setting.

For Aim one, fLEX rotational and translational measurements were not found to be significantly different from measurements obtained by the force platform. Torque measurements by fLEX were found to have a mean system bias of less than 1% of free moment measurement by the force platform. Translational measurements were found to have high vertical and shear force agreement with the force platform yielding a relative bias of less than 1 and 3.8 %, respectively.

For Aim two, it was found an independent piece of synthetic turf with the backing glued to an aluminum mounting plate and bolted into a force platform (mounting method two) yielded agreement levels most similar to aim 1. fLEX torque and vertical force system biases were less than 4%, and shear bias was less than 11%. Only low static traction and high dynamic traction shear force measurements were found to be statistically different between systems. Mounting method two used double-sided tape on the backing of an independent piece of synthetic turf in lieu of glue. This condition was found to have a similar measurement agreement to aim one during low traction conditions. However, during high traction trials, the bonding of tapes failed, and synthetic turf detached from the mounting plate. Mounting condition three used the same adhesive method as the mounting method two, but the turf was not independent of the surrounding turf and yielded the lowest level of agreement. The poor agreement of mounting method three could have been linked to the surrounding wood surface interacting with the mounting plate. This interaction may have resulted in applied forces not being experienced by the force platform.

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