Effects of varied stiffness and design asymmetry of neck anthropometric test devices on quasi-static and dynamic loading response to football head impacts

Abstract

Anthropometric test devices (ATDs) are human surrogate models that have been used to represent the response of the human body in the context of compliance and safety testing. Although progress has been made in improving the biofidelity of ATD neckforms for sports-specific impacts, most experiments have been oversimplified and do not consider factors that are important when accurately reconstructing football head impacts. The effects of neckform geometry and neck cable tension on two ATDs were assessed in this study using both static and dynamic testing methods. Three neck cable tensions were included in the analysis: 1.36 ± 0.27 N m (T), reduced by 50% (0.5T), and increased by 50% (1.5T). Static bending was performed in four directions (sagittal, coronal, and ±45° off-center planes) and dynamic impacts were conducted in the six locations specified by the National Football League (NFL) test protocol. Increased cable tension resulted in statistically significant increased neck stiffness and reductions in both static and dynamic range of motion, as well as dynamic kinematic metrics. Neck asymmetry contributed to differences in stiffness, enhancing the effects of cable tension in the loading directions where the neckforms were less stiff. In longer duration dynamic events, neckforms reached large angular displacements after the occurrence of the peak kinematic metrics. Results from this work provide quantitative ATD sensitivity metrics that will aid in future laboratory testing and enhance the design of ATD systems.