• Sophie-Andrée Vinet, Géraldine Martens, Samuel Guay, Amélie Apinis-Deshaies, Johan Merbah, Bertrand R Caré, Laurie-Ann Corbin-Berrigan, Eric Wagnac, and Louis De Beaumont.
• 1Montréal Sacred Heart Hospital Research Center, Montréal, Québec, Canada.
• J. Neurosurg. 2024 Aug 1; 141 (2): 436444436-444.

ObjectiveThis study investigated the association between head impact exposure (HIE) during varsity Canadian football games and short-term changes in cortical excitability of the primary motor cortex (M1) using transcranial magnetic stimulation (TMS).MethodsTwenty-nine university-level male athletes wore instrumented mouth guards during a football game to measure HIE. TMS measurements were conducted 24 hours before and 1-2 hours after the game. Twenty control football athletes were submitted to a noncontact training session and underwent identical TMS assessments. Between-group changes in short-interval intracortical inhibition (SICI) ratios over time were conducted using two-way ANOVAs. The relationship between HIE (i.e., number, magnitude, and cumulative forces of impacts) and SICI (secondary outcome) was also investigated using Pearson correlations.ResultsRelative to controls, the group of athletes who had played a full-contact football game exhibited a significant intracortical disinhibition (p = 0.028) on the SICI 3-msec protocol (i.e., short interstimulus interval of 3 msec) within hours following the game. Moreover, exposure to ≥ 40g hits positively correlated with SICI disinhibition (p < 0.05).ConclusionsAthletes exposed to subconcussive hits associated with Canadian football exhibit abnormal M1 corticomotor inhibition function, particularly when the recorded impact magnitude was ≥ 40g. Given the deleterious effects of decreased inhibition on motor control and balance, systematically tracking head impact forces at each game and practice with contacts could prove useful for injury prevention in contact sports.

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