Head impact accelerations for brain strain-related responses in contact sports: a model-based investigation

Both linear [Formula: see text] and rotational [Formula: see text] accelerations contribute to head impacts on the field in contact sports; however, they are often isolated in injury studies. It is critical to evaluate the feasibility of estimating brain responses using isolated instead of full degrees-of-freedom (DOFs) accelerations. In this study, we investigated the sensitivities of regional brain strain-related responses to resultant [Formula: see text] and [Formula: see text] as well as the relative contributions of these acceleration components to the responses via random sampling and linear regression using parameterized, triangulated head impacts with kinematic variable values based on on-field measurements. Two independently established and validated finite element models of the human head were employed to evaluate model-consistency and dependency in results: the Dartmouth Head Injury Model and Simulated Injury Monitor. For the majority of the brain, volume-weighted regional peak strain, strain rate, and von Mises stress accumulated from the simulation significantly correlated with the product of the magnitude and duration of [Formula: see text], or effectively, the rotational velocity, but not to [Formula: see text]. Responses from [Formula: see text]-only were comparable to the full-DOF counterparts especially when normalized by injury-causing thresholds (e.g., volume fractions of large differences virtually diminished (i.e., [Formula: see text]1 %) at typical difference percentage levels of 1-4 % on average). These model-consistent results support the inclusion of both rotational acceleration magnitude and duration into kinematics-based injury metrics and demonstrate the feasibility of estimating strain-related responses from isolated [Formula: see text] for analyses of strain-induced injury relevant to contact sports without significant loss of accuracy, especially for the cerebrum.