Objective For both subconcussive impacts and traditionally-defined concussion, neither the number of head impacts nor the magnitude has had a strong correlation to the incidence or severity of injury. Recent modelling work has suggested that impulse may be an important biomechanical factor, and therefore it is hypothesised that it may be a good predictor of subconcussive neurophysiological changes.

Design Observational study.

Setting American high school football team.

Participants Nine male high school football athletes (mean age=16.4, range=15–17) volunteered. All participants were enrolled with parental consent.

Assessment of risk factors Head impacts were monitored at all practices and games with the Head Impact Telemetry System. Baseline neurophysiology was measured prior to contact activity using a functional magnetic resonance imaging (fMRI) visual n-back task protocol. Subjects returned throughout the season and were re-evaluated according to the same protocol.

Outcome measures Kinematic impulse was computed from head impact telemetry. Changes in neurophysiology were determined as the difference in the 2 vs. 1-back contrast. This contrast was determined for 116 anatomically defined regions of interest (ROI).

Main results Stepwise regressions (P=0.05) relating kinematic impulse to ROI-specific changes in neurophysiology yielded significant correlations for 57/116 ROIs. 22/116 ROIs had an R2 value greater than 0.70. Correlations were found bilaterally for 16 anatomical ROIs, including the executive pre-frontal regions, basal ganglia, and thalamus.

Conclusions The relationship between kinematic impulse and fMRI changes reported here are the strongest correlations to subconcussive changes reported to date. Correlations were observed bilaterally in regions associated with concussion symptoms.

Competing interests None.