Efficacy/Resiliency of Chest Protectors to Reduce the Risk of Injury due to Baseball Impacts in Children
Principal Investigator: Gopal Jayaraman, Ph.D.
Institution: Michigan Technological University, Houghton, MI.
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Biomechanical efficacy of chest protectors against baseball injury. Gopal Jayaraman, Ph.D. Thomas R. Grimm, Ph.D. Robert L. Whipple, M.S. Trevor Hegg, M.S. Joseph A. Lehtola, M.S. Dale R. Burkhouse, M.S., A.T.C. “Injuries in Baseball Course”, American Sports MEdicine Institute, Birmingham, Alabama. January 22-25, 1998|
Abstract: The purpose of this study is to evaluate the biomechanical efficacy of chest protectors in reducing the risk of chest injury due to baseball impacts in children. The criteria used to predict the biomechanical efficacy of the chest protectors is the probability of severe chest injury due to blunt frontal impacts. The probability of severe injury is determined by the time history of the chest compression and compression rate which is termed the viscous compression response. In the first phase of the project, the biomechanical response of the chest in terms of the maximum viscous compression is determined experimentally with and without chest protectors using a fifth percentile female hybrid III crash dummy which approximates a 10 year old boy. It is shown from the experimental results that the probability of severe chest injury without protection is 25% for an impacting ball speed of 56 mph and 99+% for an impacting ball speed of 67 mph. The probability of severe injury with a chest protector is determined as 5% at a ball speed of 56 mph and 70% at a ball speed of 67 mph. These probabilities indicate the inadequacy of chest protectors to effectively reduce the probability of severe chest injury for ball speeds greater than 67 mph. The second phase of the project is to develop a finite element model of a fifth percentile female Hybrid III chest model to evaluate the effectiveness of the chest protectors. This would serve as a useful and meaningful tool in predicting the injury risk to the chest due to baseball impacts under varying conditions and provide critical parameters for optimum design of the chest protector. The finite element models of the baseball, the chest of the Hybrid III crash dummy and the three types of chest protectors are validated both statistically and dynamically using the experimental results from phase I of this project. Based on the criterion that a viscous compression response above 39.37 in/s implies a high risk of injury, the analysis of the finite element model predicts the viscous compression response of 6 in/s for a ball speed of 27 mph, a viscous compression response of 40 in/s for a ball speed of 60 mph and a viscous compression response of 80 in/s for a ball speed of 90 mph. The study concludes that the protection of the chest protector is found to be inadequate for ball speeds above 60 mph as documented by the experimental results from Phase I, as well as the finite element modeling of Phase II. This finite element model will be employed in the future to advance an optimum design for baseball chest protectors.
Contact response characteristics of baseball chest protectors. Jayaraman, G. Conference on Commotio Cordis, ASTM. Denver, CO., May 17, 1995.