The influence of baseball modulus and mass on head and chest impacts: a theoretical study

Abstract

Although not common, injuries that result in death do occur in youth baseball. Specifically, in the 5- to 14-year old age group a total of 68 deaths between 1973 and 1995 have been directly attributed to impacts from baseballs to the head and chest. The purpose of this work was to determine the effect of lowering ball modulus and ball mass on the likelihood of reducing impact injury. A theoretical model, based upon the assumption of ideal elastic behavior, was used to calculate the impact response of the head. At a constant ball velocity, lowering both modulus and mass had the greatest influence in decreasing peak head acceleration, Gadd Severity Index, and Head Injury Criterion. Independently lowering the modulus or the mass decreased the impact variables and the estimates of injury, but the decreases varied with the specific impact variable and injury criterion. To study the impact response of the ball and chest, an existing viscoelastic lumped-element model of the chest was used. Lowering ball modulus and mass had various effects, e.g., lowering ball modulus did not affect peak sternal displacement, but it did decrease peak sternal velocity. These theoretical models aid in illustrating that impact response depends upon ball modulus and mass, the physical properties of the target, and the specific impact variable studied. This theoretical model suggests that a softer and lighter than traditional baseball would be the most likely ball model to minimize impact injuries because this ball consistently reduced all impact response variables studied. Since impact injury criteria for youths are presently not validated, the degree to which impact injuries may be reduced remains uncertain.

Helmets and Mouth Guards: The Role of Personal Equipment in Preventing Sport-Related Concussions

“…Theoretical biomechanical studies have indicated that baseballs with lower mass and less stiffness have a reduced potential for injury (99). Additionally, laboratory studies have shown that reduced-impact balls are less likely to result in head injury and skull fracture (100).…”

Measurement of Head Impacts in Youth Ice Hockey Players

“…In addition to recording impact acceleration variables (linear and rotational acceleration), the HIT system also records measures of impact severity. GSI [18] and HIC [49] are biomechanical criteria that can be used to predict the likelihood of brain injury [12] . Both GSI and HIC are severity measures based on weighted integrals of acceleration-time profi les [22] .…”

Physical and Mechanical Properties of Various Field Lacrosse Balls

“…Softer baseballs have been shown to reduce the risk of head injury, eye injury, and commotio cordis (Crisco, Hendee, & Greenwald, 1997;Heald et al, 1994;Link, Maron, Wang, et al, 2002;Vinger, Duma, & Crandall, 1999). The practice ball we tested had a compression load nearly fi ve times less than the regular balls.…”