Relative Motion Between the Helmet and the Head in Football Impact Test

Abstract

Approximately 1.6–3.8 million sports-related traumatic brain injuries occur each year in the U.S. Researchers track the head motion using a variety of techniques to study the head injury biomechanics. To understand how helmets provide head protection, quantification of the relative motion between the head and the helmet is necessary. The purpose of this study was to compare helmet and head kinematics and quantify the relative motion of helmet with respect to head during experimental representations of on-field American football impact scenarios. Seven helmet-to-helmet impact configurations were simulated by propelling helmeted crash test dummies into each other. Head and helmet kinematics were measured with instrumentation and an optical motion capture system. The analysis of results, from 10 ms prior to the helmet contact to 20 ms after the loss of helmet contact, showed that the helmets translated 12–41 mm and rotated up to 37 deg with respect to the head. The peak resultant linear acceleration of the helmet was about 2–5 times higher than the head. The peak resultant angular velocity of the helmet ranged from 37% less to 71% more than the head, depending on the impact conditions. The results of this study demonstrate that the kinematics of the head and the helmet are noticeably different and that the helmet rotates significantly with respect to the head during impacts. Therefore, capturing the helmet kinematics using a video motion tracking methodology is not sufficient to study the biomechanics of the head. Head motion must be measured independently of the helmet.

On-Field Performance of an Instrumented Mouthguard for Detecting Head Impacts in American Football

“…Previous research examining impact conditions using dummies had demonstrated noticeable differences between helmet and head kinematics which indicates that helmet motion does not necessarily correlate with head motion. 22 While lowering the trigger threshold may help to improve sensor recall at lower severity, the trade-off is potentially filling the sensor memory with spurious events that may limit recording of head impacts of all severities later in the game. Beyond adjustments to the triggering threshold, future system improvements could include increasing memory capacity to reduce the risk of filling memory while improving recall.…”

Sex differences in neck strength and head impact kinematics in university rugby union players

“…The variation in measurement methods and scientific rigour makes the derivation of severity metrics unreliable. For example, inertial measurement unit (IMU) sensors mounted externally to the head, either on the skin or in helmets and headbands, significantly overestimate peak linear acceleration (PLA) and peak rotational acceleration (PRA) (Joodaki et al, 2019;Patton et al, 2020b;Wu et al, 2016). This is due primarily to poor sensorskull coupling and soft tissue artefact (STA), where the skin deforms relative to the underlying bone (De Rosario, Page, Besa, Mata, & Conejero, 2012).…”

Survey on Video-Based Biomechanics and Biometry Tools for Fracture and Injury Assessment in Sports

“…In future studies, a more extensive search for web videos could facilitate the application of the methods presented for other sports. Other biomechanical studies have been considered by tracking in alternative sports, such as American football [35], rugby [39], baseball [6], basketball [33], Gaelic field [37], snowboard [41], skiing [40], among others. However, such mentioned studies are limited to the analysis of the efforts generated on sensors when stepping or making direct contact, or by consensus decision by experts in the area in case.…”