Sensitivity And Agreement Between Head Impact Monitoring Devices In American Football

PURPOSE: Historically, most head acceleration events in American Football have been measured via accelerometers embedded in helmet padding. Recently, other form factors such as instrumented mouthpieces (IMPs) have been developed, capable of measuring linear and rotational head impact kinematics. We aimed to determine the sensitivity and agreement of these two devices (helmet-based vs. IMP) in a field-based setting. METHODS: We filmed two collegiate offensive linemen across four full-contact practices. Participants were concurrently equipped with an IMP and a helmet-based device [Head Impact Telemetry (HIT) System] to review peak linear acceleration (PLA, g) and peak rotational acceleration (PRA, rad/s2). We recorded the frequency and percentage of head acceleration events recorded by each device confirmed by video. Sensitivities of IMP and HIT System were separately calculated by dividing the number of device-measured impacts by the total number of video-observed events. The systematic bias and relationships between the devices were analyzed by paired samples t-tests and two-tailed Pearson correlation coefficients, respectively. RESULTS: We analyzed 149 video-confirmed head impacts that were either recorded by both devices (n = 61, 40.9%), only the IMP (n = 9, 6.0%), only the HIT System (n = 62, 41.6%), or not detected by either device (n = 17, 11.4%). Overall, the IMP demonstrated a sensitivity of 47.0% in detecting a video-confirmed impact (70 of 149 impacts); whereas, the HIT System demonstrated a sensitivity of 82.6% (123 of 149 impacts). Among the 61 impacts measured by both devices, IMP recorded lower PLA [median (interquartile range); 18.7 (8.1) g vs. 32.6 (13.1) g; p < 0.001], and lower PRA [1149.0 (457.89) rad/s2 vs. 1662.1 (856.43) rad/s2; p < 0.001]. We observed that IMP PRA was moderately correlated with the HIT System’s PLA (r = 0.530) and PRA (r = 0.527) (both p values ≤0.001). CONCLUSIONS: Overall, PLA and PRA were lower with IMP than HIT System when a head acceleration event was recorded by both devices. The IMP was less sensitive than the HIT System by a factor of 1.77, missing a significant portion of video-confirmed head acceleration events. However, its design and opportunities for future integration with existing player monitoring systems makes its further development attractive. This study was partially funded by Football Research Inc. (Award# A22-0340-001). They were not involved in the study conceptualization, statistical analysis, interpretation, or drafting of the manuscript.