Mitigation of Linear Accelerations and Shear Forces During Drop Head Simulated Falls

Mitigation of Linear Accelerations and Shear Forces During Drop Head Simulated Falls

Stephen Carlson (Lakehead University, Thunder Bay, Canada), Carlos Zerpa (Lakehead University, Thunder Bay, Canada), Eryk Przysucha (Lakehead University, Thunder Bay, Canada) and Paolo Sanzo (Lakehead University, Thunder Bay, Canada)
DOI: 10.4018/IJEACH.2019070103

Abstract

The danger and risk associated with ice hockey has led to the development of new helmet technologies and testing protocols to minimize the risk of traumatic brain injuries or concussions. Researchers believe that understanding helmet performance across different impact locations and angles during head collisions helps inform helmet manufacturers in the development of helmet testing protocols for brain injury prevention. Based on these beliefs and concerns, this study examined the dynamic interaction of neck compliance, helmet location, and angle of impact in mitigating linear acceleration and shear forces. The results support the hypothesis that an increasing angle of impact decreases peak linear acceleration and increases shear force. Decreasing neck compliance, however, decreases peak linear acceleration and shear force for some helmet impact locations but not all of them. These results add to the literature by implementing a new helmet testing protocol to provide information beyond traditional measures of peak linear acceleration used in current helmet testing standards.
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Background

The sport of ice hockey contains the highest incident of concussion and head injury per participant in all of sports (Kendall et al., 2012). In Canada, for example, 3.78% of sport-related emergency room visits in a year related to head injuries experienced by people while playing ice hockey. Among these head injuries, concussions seemed to be the most prevalent type of head injury (Wennberg & Tator, 2003). A concussion or mild traumatic brain injury (mTBI) is “an alteration in brain function, or evidence of brain pathology, caused by an external force” (Menon, Schwab, Wright, & Maas, 2010, p.1637).

The elevated incident of concussions in the sport of ice hockey relates to the high level of impact forces to the head experienced by individuals while playing the sport (Post, Oeur, Hoshizaki, & Gilchrist, 2011; Wennberg & Tator, 2003). These impacts forces result in either linear or rotational accelerations affecting the brain matter and consequently producing concussions (Meaney & Smith, 2011). Linear acceleration refers to a vector quantity representing the rate of change of linear velocity over time measured in units of g (Gimbel & Hoshizaki, 2008). A g unit signifies a multiple of the acceleration due to gravity (Post, Oeur, Hoshizaki, & Gilchrist, 2011). Angular acceleration, on the other hand, refers to a vector quantity representing the change in angular velocity over time measured in radians per second squared (McLean & Anderson, 1997).

Peak linear acceleration represents the most frequent measure used to assess head injuries and helmet performance in the sport of ice hockey. The magnitude of the linear accelerations seems to indicate the severity of the head injury due to the impact (Gurdjian et al., 1968). The magnitude of the rotational accelerations, on the other hand, seems to be more associated with high levels of tissue strain and brain damage (King, Yang, Zhang, & Hadry, 2003).

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