Repeated head loading in sports is associated with negative long-term brain health, and there is growing evidence of short-term neurophysiological changes after repeated soccer heading. The objective of this study was to quantify the head kinematics and effects of repetitive soccer headers in adolescents using an instrumented mouthguard. Adolescent soccer players aged 13-18 years were randomly assigned to a kicking control, frontal heading, or oblique heading group. Participants completed neurophysiological assessments at three-time points: immediately prior to, immediately after, and approximately 24 h after completing 10 headers or kicks. The suite of assessments included the Post-Concussion Symptom Inventory, visio-vestibular exam, King-Devick test, modified Clinical Test of Sensory Interaction and Balance with force plate sway measurement, pupillary light reflex, and visual evoked potential. Data were collected for 19 participants (17 male). Frontal headers resulted in significantly higher peak resultant linear acceleration (17.4 ± 0.5 g) compared to oblique headers (12.1 ± 0.4 g, p < 0.001), and oblique headers resulted in significantly higher peak resultant angular acceleration (frontal: 1147 ± 45 rad/s2, oblique: 1410 ± 65 rad/s2, p < 0.001). There were no neurophysiological deficits for either heading group or significant differences from controls at either post-heading timepoint, and therefore, a bout of repeated headers did not result in changes in the neurophysiological measures evaluated in this study. The current study provided data regarding the direction of headers with the goal to reduce the risk of repetitive head loading for adolescent athletes.
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