Current methods of concussion assessment are subjective and vulnerable to error, and a missed concussion diagnosis could increase an athlete’s risk of further injury. An objective method of concussion assessment could provide valuable physiological data about injury severity and duration. The NuroChek system uses a flashing light stimulus to evoke electrophysiological activity, which is measured from occipital electrode sites and used to calculate a signal-to-noise ratio (SNR) and determine the magnitude of activity at the target location. Reductions in this activity are proposed to be associated with dysfunction or damage after concussion; in a previous study, the SNR was shown to decrease after concussion, and then return to baseline strength upon recovery. To examine the utility of the NuroChek system and SNR output in concussion assessment and management, 157 participants were assessed with the NuroChek system as rugby athletes (n = 121), combat athletes (n = 19), or non-athlete controls (n = 17). All athletes were assessed at multiple time points, while the non-athlete control group was only assessed at one time point. All participants completed two trials of the NuroChek headset and at least one cognitive measure. The first study (Chapter 4) examines the acute effects of concussion on the SNR, as well as any SNR changes after injury. Rugby athletes who sustained concussions (n = 21) were tested at multiple time points after their injuries with the NuroChek system and either the King-Devick (K-D) or the Sport Concussion Assessment Tool (SCAT-5). The post-injury and baseline SNR were compared to identify any changes within 3 days of concussion, as well as changes during the follow-up time points that might correspond with concussion recovery (up to 20 days post-injury and mid-season or end-of-season if available). No statistically significant changes were seen after concussion, W = 11.000, p = 0.612, d = -0.099, n = 8. When compared to the non-concussed male rugby athletes, the concussed athletes had significantly lower SNRs than the athletes who sustained regular repetitive impacts by the end-of-season, H(3) = 10.160, p = 0.017, d = 0.135, n = 76. The second study (Chapter 5) examines the different effects that concussion history, age, and sex have on the SNR and its trajectory over time in those experiencing repetitive impacts. While the SNR was not affected by concussion history or age, there was a main effect for sex: male athletes demonstrated significantly higher average SNRs than female athletes at all three time points. Additionally, the SNRs from female participants demonstrated a significantly greater proportion of a harmonic artefact (51.8%, compared to 15.1% of data from male participants) that decreased the quality of the female data. Sex and repetitive impacts were examined for any interaction, but the sample sizes were too small in some subgroups for statistical analysis. A main effect of repetitive impacts on the SNR was also seen in rugby and combat athletes. This could indicate that repetitive impacts lead to higher SNR in athletes over time. Overall, the SNR in this study was not sensitive to changes after concussion or during recovery. No evidence was found to support NuroChek’s use in the assessment or management of concussion in rugby athletes. Additionally, the potential effect of repetitive impacts on the SNR confounds the relationship between the SNR and concussion. Future development of electrophysiological assessment methods for concussion should consider the effects of repetitive impacts and sex.