The purposes of this study were (a) to determine the reliable change in post-concussion-like symptoms reported following self-selected exercise or sports activities and (b) to explore the potential influence of gender and exercise parameters on post-concussion-like symptoms reported by a non-concussed cohort following exercise/training. A pre-to-post observational design was used. A convenience sample of students aged 18-30 years who visited a university recreation center to engage in their chosen exercise activity and a purposeful sample of men's and women's rugby union players engaged in their regular training sessions were included in the study. All participants reported their symptoms using the symptom scale of the Sport Concussion Assessment Tool 2. The reliable change index was used to determine the change in symptom scores reported from pre-to post-exercise/training. Multiple linear regression analysis was used to model the exercise variables to explain the impact on the reporting of symptoms. A total of 260 participants (146 males and 114 females) completed their self-selected exercise activity or rugby union training. Approximately two-thirds of all participants did not demonstrate a change (increase or decrease) in total symptom score (201/260, 77.9%) and/or symptom severity score (212/260, 81.9%) from pre-to post-exercise/training. The symptom response following exercise or sports training did not change in the majority of participants. Clinicians need to be aware of these findings to make informed decisions on return-to-play following a concussive brain injury.