Assessing the association between on-field heading technique and head impact kinematics in a cohort of female youth soccer players.

There is concern that exposure to soccer headers may be associated with neurological sequelae. Training proper heading technique represents a coachable intervention that may reduce head acceleration exposure. The objective was to assess relationships between heading technique and head kinematics in female youth soccer players. Fourteen players (mean age = 14.4 years) wore instrumented mouthpieces during practices and games. Headers were reviewed by three raters to assign a technique score. Mixed models and LASSO regression evaluated associations of technique with peak linear acceleration (PLA), rotational acceleration (PRA), rotational velocity (PRV), and head impact power ratio (HIP Ratio) while adjusting for session type and ball delivery. Two hundred eighty-nine headers (n = 212 standing, n = 77 jumping) were analyzed. Technique score (p = 0.043) and the technique score - session type interaction (p = 0.004) were associated with PRA of standing headers, whereby each 10-unit increase in technique score was associated with an 8.6% decrease in PRA during games but a 5.1% increase in PRA during practices. Technique was not significantly associated with any other kinematic metrics; however, peak kinematics tended to decrease as technique score increased. LASSO regression identified back extension and shoulder/hip alignment as important predictors of peak kinematics. Additional research on heading technique and head acceleration is recommended.

Characterization of On-Field Head Impact Exposure in Youth Soccer.

The objective of this research was to characterize head impacts with a validated mouthpiece sensor in competitive youth female soccer players during a single season with a validated mouthpiece sensor. Participants included 14 youth female soccer athletes across 2 club-level teams at different age levels (team 1, ages 12-13 y; team 2, ages 14-15 y). Head impact and time-synchronized video data were collected for 66 practices and games. Video data were reviewed to characterize the type and frequency of contact experienced by each athlete. A total of 2216 contact scenarios were observed; heading the ball (n = 681, 30.7%) was most common. Other observed contact scenarios included collisions, dives, falls, and unintentional ball contact. Team 1 experienced a higher rate of headers per player per hour of play than team 2, while team 2 experienced a higher rate of collisions and dives. A total of 935 video-verified contact scenarios were concurrent with recorded head kinematics. While headers resulted in a maximum linear acceleration of 56.1g, the less frequent head-to-head collisions (n = 6) resulted in a maximum of 113.5g. The results of this study improve the understanding of head impact exposure in youth female soccer players and inform head impact exposure reduction in youth soccer.

Development, Validation and Pilot Field Deployment of a Custom Mouthpiece for Head Impact Measurement.

The objective of this study was to develop a mouthpiece sensor with improved head kinematic measurement for use in non-helmeted and helmeted sports through laboratory validation and pilot field deployment in female youth soccer. For laboratory validation, data from the mouthpiece sensor was compared to standard sensors mounted in a headform at the center of gravity as the headform was struck with a swinging pendulum. Linear regression between peak kinematics measured from the mouthpiece and headform showed strong correlation, with r2 values of 0.95 (slope = 1.02) for linear acceleration, 1.00 (slope = 1.00) for angular velocity, and 0.97 (slope = 0.96) for angular acceleration. In field deployment, mouthpiece data were collected from four female youth soccer players and time-synchronized with film. Film-verified events (n = 915) were observed over 9 practices and 5 games, and 632 were matched to a corresponding mouthpiece event. This resulted in an overall sensitivity of 69.2% and a positive predictive value of 80.3%. This validation and pilot field deployment data demonstrates that the mouthpiece provides highly accurate measurement of on-field head impact data that can be used to further study the effects of impact exposure in both helmeted and non-helmeted sports.