Pilot characterization of head kinematics in grassroots dirt track racing

Abstract

Objective

The objective of this study was to utilize an instrumented mouthpiece sensor to characterize head kinematics experienced by grassroots dirt track race car drivers.

Methods

Four dirt track race car drivers (ages 16–19) were instrumented with custom mouthpiece sensors capable of accurately measuring head motion during racing. Sensors were deployed before races and recorded tri-axial linear acceleration and rotational velocity for approximately 10 min at 200 Hz. Film review was performed to identify data associated with racing laps. For each lap, moving average kinematics were computed and subtracted from the head motion signals to obtain ‘adjusted’ head motion accounting for lower frequency variance due to periodic motion around the track. From adjusted data, linear and angular head perturbations (i.e., deviations from moving average) were extracted using a custom algorithm.

Results

Data was collected during 400 driver-races. A total of 2438 laps were segmented from mouthpiece recordings. The median (95th percentile) peak linear acceleration, rotational velocity, and rotational acceleration of all laps were 5.33 (8.28) g, 2.89 (4.60) rad/s, and 179 (310) rad/s², respectively. Angular perturbations occurred most frequently about the anterior-posterior axis (median lap frequency = 6.39 Hz); whereas linear perturbations occurred most frequently in the inferior-superior direction (7.96 Hz). Nine crash events were recorded by the mouthpiece sensors. The median (95^th percentile) peak head kinematics of these events were 13.4 (36.6) g, 9.67 (21.9) rad/s, and 630 (1330) rad/s².

Conclusions

Mouthpiece sensors can be used to measure head kinematics during active racing. Laps, head perturbations, and crashes may be useful units of observation to describe typical head kinematic exposure experienced by drivers while racing. Subsequent research is needed to understand the associations between repetitive racing exposure and neurological function. Higher magnitude events (i.e., crashes) are not uncommon and may result in concussion or more severe injury. Results represent novel characterizations of head kinematic exposure experienced in a dirt track racing environment. This information may inform evidence-based strategies (e.g., vehicle/seat design) to improve driver safety.

Keywords:

• Motorsports
• auto racing
• mouthpiece sensor
• head kinematics

Acknowledgments

The authors would like to thank the drivers for their participation in this study and acknowledge all members of the research team who traveled to collect data.

Disclosure statement

Authors Joel Stitzel and Jillian Urban have a patent pending on the mouthpiece instrumentation described herein.

Additional information

Funding

This study was supported by Toyota Racing Development USA. Author Tanner Filben is supported by the National Science Foundation Graduate Research Fellowship under Grant No. 2102417. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation.