Objective To examine the relationship between cerebral autoregulation changes and impact exposuresthroughout a season of contact sports (hockey or football).

Design Prospective Cohort.

Setting Laboratory.

Participants 40 male contact sport athletes (19.4±1.2 years); to date, 3 cross-country athletes (20.0±1.0 years) have completed testing (non-contact controls).

Intervention Participants completed testing prior to the start of their athletic seasons (T1), and again after the conclusion of each season (T2). Blood pressure (BP) oscillations were driven by stand-squat manoeuvres at 0.05 and 0.10 Hz. BP and cerebral blood velocity (CBV) in the middle cerebral artery were indexed non-invasively using finger photoplethysmography and transcranial Doppler ultrasound, respectively. RM-ANOVA independent variables included time (2) and frequency (2).

Outcome measures Point-estimates of coherence (correlation), phase (synchronisation), and gain (amplitude buffer) transfer function analysis metrics were calculated. Biomechanical data on head-impact exposure was estimated in a subset of contact-sport athletes (n=29) using the xPatch (X2 Biosystems), affixed to the right mastoid.

Results Significant frequency-time interaction for gain in contact-sport athletes (p=0.048) but not controls (p=0.213). Simple effects analysis revealed a time effect at 0.10 Hz (p<0.001), whereby gain increased at T2 (95% CI: 0.070–0.229%/%). The Δgain _T2-T1 at 0.10 Hz was correlated withestimated cumulativerotational acceleration exposure (r=0.462, p=0.015).

Conclusions These findings suggest cumulative exposure to the rotational component of sustained head-impactsduring participation in a season of contact-sport (hockey or football) impairs the ability of the cerebrovasculature to buffer BP challenges experienced during everyday activities.

Competing interests None.