The influence of centric and non-centric impacts to American football helmets on the correlation between commonly metrics in brain injury research

Concussion has become recognized as an injury which can be a source of long term neurological damage. This has led to research into which metrics may be more appropriate to define risk of injury. Some
researchers support the use of linear acceleration as a metric for concussion, while others suggest the use of linear and rotational acceleration as well as brain deformation metrics. The purpose of this study was to examine the relationships between these metrics using a centric and non‐centric impact protocol. A linear
impactor was used to impact a Hybrid III headform fitted with different models of American football helmet using a centric and non‐centric protocol. The dynamic response was then used as input to the FE model for analysis of brain deformations. The results showed that linear acceleration was correlated to rotational acceleration and brain deformation for centric conditions, but under non‐centric conditions it was not. These results indicate that the type of methodology used will influence the relationship between the variables used to assign risk of concussion. These results also support the use of a centric/non‐centric protocol and measurement of rotational acceleration and brain deformation when it comes to the development of helmet technologies.