Comparative dynamic response analysis of the Hybrid III head and neckform against a strength-scaled neuromuscular reference model in American football-relevant impacts

The Hybrid III anthropometric test device (ATD) is the most prominent head and neck surrogate device used for the laboratory testing of head protective equipment for American football, despite being originally designed and validated for an automotive frontal crash scenario. These differing impact conditions have been hypothesized to produce kinematic responses that lack biofidelity, leading to unrepresentative data and misinformed helmet design. This study characterizes the dynamic response of the Hybrid III neckform against a range of strength-scaled HYOID computational models. Blunt head impacts were performed experimentally on the Hybrid III ATD to produce kinematic responses in five directions: Sagittal Plane (SP) Flexion/Extension, Coronal Plane (CP) Right Lateral (RL) Bending, and 45° Off-Center (OC) Flexion/Extension. Impacts were then simulated in OpenSim on HYOID models with maximum isometric strength scaled from 1× to 11× baseline (0%–1000% increase). Results showed that HYOID models required strength increases of 400%–1000% to replicate the angular displacement magnitude observed in Hybrid III ATD impacts. Even under these extreme and non-physiological conditions, HYOID models were unable to reproduce Hybrid III ATD peak kinematic metrics outside of the sagittal plane, averaging an angular acceleration error of −36.48%, −23.93%, and −32.17% for CP RL Bending, 45° OC Flexion, and 45° OC Extension impacts, respectively. These findings highlight current limitations of available ATDs and support the development of sports-specific surrogate neck devices with improved biofidelity to be used in the laboratory evaluation of American football helmets.