Objective: This retrospective pilot study examines the correlation between post-concussive symptoms, neurocognitive performance and the level of exertion after concussion. Methods: Activity level in the first week after concussion was retrospectively reviewed in 51 cases (15.57±2.12 years old) from a sports concussion clinic. The number of on-field symptoms was recorded. Summary composite scores from the ImPACT computerized test battery were utilised. These data were used to compare immediate symptoms reported; intensity of activity between concussion and time of initial evaluation, and performance on neurocognitive tests. Results: A significant correlation was found between the number of immediate symptoms and the intensity of activity after concussion. Those athletes with fewer immediate symptoms had a significantly higher activity level and better performance on visual memory. The data demonstrated significant differences (p = 0.0431) in the number of immediate symptoms between activity intensity groups. Discussion: We theorise that those athletes with a greater number of immediate symptoms are less likely to engage in high levels of exertion after concussion due to a disruption in cerebral metabolism that is worsened by exertion. Cortisol may play a key role in this destructive process as it has been shown to reduce cerebral glucose uptake and glutamate clearance, exacerbate declines in ATP after injury, and it increases in a dose dependent manner with activity. Conclusion: Further research is required to examine the role of post-concussive exertion to formulate an evidenced-based approach in returning athletes to activity following concussion.