Head and Neck Response of an Active Human Body Model and Finite Element Anthropometric Test Device During a Linear Impactor Helmet Test

Abstract

It has been proposed that neck muscle activation may play a role in head response resulting from impacts in American Football. The importance of neck stiffness and active musculature in the standard linear impactor helmet test was assessed using a detailed head and neck finite element (FE) model from a current human body model (HBM) compared to a validated hybrid III head and neck FE model. The models were assessed for bare-head and helmeted impacts at three speeds (5.5, 7.4, and 9.3 m/s) and three impact orientations. The HBM head and neck was assessed without muscle activation and with a high level of muscle activation representing a braced condition. The HBM and hybrid III had an average cross-correlation rating of 0.89 for acceleration in the primary impact direction, indicating excellent correspondence regardless of muscle activation. Differences were identified in the axial head acceleration, attributed to axial neck stiffness (correlation rating of 0.45), but these differences did not have a large effect on the overall head response using existing head response metrics (head injury criteria, brain injury criteria, and head impact power). Although responses that develop over longer durations following the impact differed slightly, such as the moment at the base of the neck, this occurred later in time, and therefore, did not considerably affect the short-term head kinematics in the primary impact direction. Though muscle activation did not play a strong role in the head response for the test configurations considered, muscle activation may play a role in longer duration events.

Comparison of Neck Injury Criteria Values Across Human Body Models of Varying Complexity

“…The three dimensional mesh of the intervertebral discs in the M50-O is comprised of material laws for both the annulus fibrosus and nucleus pulposus. The M50-O neck has been validated in linear impact for passive and active musculature (Bruneau and Cronin, 2019), deviation from nominal occupant position postures at the whole body (Gayzik et al, 2018) and tissue level (Shateri and Cronin, 2015), and exhibited close agreement to PMHS data in a study of a frontal, restrained occupant (Schap et al, 2019).…”

Brain response of a computational head model for prescribed skull kinematics and simulated football helmet impact boundary conditions

“…However, the biofidelity of the ATD neck is often cited as a limitation (Elkin et al, 2018) owing to the simplified structure and high stiffness relative to the human neck in some loading scenarios. A novel method to determine head kinematics is by reconstructing helmeted impacts computationally using a detailed human body model (HBM) coupled with a computational helmet model (Figure 1Figure 1b), which can provide additional anatomical detail compared to an ATD (Bruneau and Cronin, 2019). Furthermore, this simulated human body motion (HBM-S) boundary condition can be used as a testbed to make improvements to helmet design by allowing rapid iteration of helmet geometry and properties, and can be used to assess the interaction of effects that may be obscured by using a PK boundary condition.…”

“…Furthermore, this simulated human body motion (HBM-S) boundary condition can be used as a testbed to make improvements to helmet design by allowing rapid iteration of helmet geometry and properties, and can be used to assess the interaction of effects that may be obscured by using a PK boundary condition. It has been shown that the head kinematics of the HBM are comparable to those of the ATD over short time frames (Bruneau and Cronin, 2019); however, it is possible that the neck could have an effect on brain response, which takes longer to reach maximum values relative to the kinematic responses (Sanchez et al, 2018).…”

“…head and neck (Bruneau and Cronin, 2019), or the full body impacts (Darling et al, 2016). These studies have predominantly used the Global Human Body Models Consortium (GHBMC) HBM (Bruneau and Cronin, 2019;Darling et al, 2016;Jin et al, 2017), a modern HBM with extensive experimental validation (Barker et al, 2017;Barker and Cronin, 2020) and a representation of passive and active neck muscle (Bruneau and Cronin, 2019).…”

“…Differing conclusions regarding the effect of neck muscle activation on head kinematics in football helmet impacts have been reported; from increasing head acceleration (Schmidt et al, 2014), to reducing head angular velocity and brain deformation (Jin et al, 2017), or showing no consistent effect on kinematics for varying head impact orientations (Bruneau and Cronin, 2019;Eckersley et al, 2020). Head kinematics at short durations (<40 ms post impact) have been shown to be mostly unaffected by active musculature (Bruneau and Cronin, 2019;Eckersley et al, 2020), but it is possible that the longer timeframe required for brain strains to develop results in active musculature having a larger effect on the brain response. The HBM-S boundary condition has not been widely evaluated in the literature to date, and has not been specifically compared to the PK boundary condition for predicted brain deformations.…”