In addition to the functional sequelae that ensue following this injury, concussion in both the acute and persistent phases is being recognized as a neurophysiological injury. Traditional methods of assessment following concussion place emphasis on subjective self-report and administration of neuropsychological batteries. These assessments are used in an effort to return the youth to activity (i.e school, sport). However, these methods can be unreliable as youth have a high incentive to return to play and neurocognitive resolution does not necessarily equate to pre-injury function. To augment these measures, an objective indicator of neurophysiological stress is needed. Heart rate variability (HRV) is an objective, neurophysiological indicator of autonomic nervous system functioning. HRV is quantified by measuring the time intervals between heartbeats. Increased variability in heart rate (i.e. increased HRV) is seen as healthy neurophysiological function, demonstrating an individual's ability to adapt and be flexible to the demands of the environment. Conversely, decreased HRV is demonstrative of an individual's reduced ability to respond flexibly to their environment. Investigating the impact of persistent concussion symptoms on HRV has the potential to enhance our understanding of autonomic nervous system functioning in the chronic phases of this injury for an understudied population.