Background Wearable sensor systems have the potential to quantify head kinematic responses of head impacts in football. However, on-field use of sensors (e.g. accelerometers) remains challenging due to factors such as poor coupling to the head.
Objective To test the validity of a novel in-ear sensor for quantifying head-impact exposure in youth football.
Design Descriptive laboratory study/validation study.
Setting Youth football.
Participants Six male youth football players (15.3±0.3 years).
Evaluations In step 1, the sensor was mounted to a Hybrid III headform (HIII) and impacted with a linear impactor or football (range: 9–144g). Accelerative forces, including peak linear acceleration (PLA), were obtained from both systems. In step 2, six youth soccer players wore sensors during a structured training protocol including heading and non-heading exercises; in step 3, they completed two regular football sessions. For each recorded accelerative event, PLA outputs were compared to video.
Main Outcome Measurements In step 1, random and systematic error were calculated using HIII as reference. In steps 2 and 3, mean values (±SD) were calculated for (1) all heading and (2) all non-heading events. Receiver operating characteristic curves were used to determine the sensor’s discriminatory capacity in both on-field settings, and cut-off values for predicting outcomes were identified.
Results In step 1, random and systematic error were both 11% for PLA. In step 2, heading events resulted in higher absolute values (PLA=15.6±11.8g) than non-heading events (PLA=4.6±1.2g); area under the curve (AUC) was 0.98. In step 3, AUC was >0.99. A 9g cut-off value yielded a positive predictive value of 100% in the structured training protocol vs. 65% in regular football sessions.
Conclusions The in-ear sensor displayed considerable random error and overestimated head impact exposures substantially. It showed excellent on-field accuracy for discriminating headings from other accelerative events, but secondary means of verifying events are still necessary.
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