CONTEXT:Aerobic exercise interventions are increasingly being prescribed for concussion rehabilitation, but whether aerobic training protocols influence clinical concussion diagnosis and management assessments is unknown. OBJECTIVE:To investigate the effects of a brief aerobic exercise intervention on clinical concussion outcomes in healthy, active participants. DESIGN:Randomized controlled clinical trial. SETTING:Laboratory. PATIENTS OR OTHER PARTICIPANTS:Healthy (uninjured) participants (n = 40) who exercised ≥3 times/week. INTERVENTION(S):Participants were randomized into the acute concussion therapy intervention (ACTIVE) training or nontraining group. All participants completed symptom, cognitive, balance, and vision assessments during 2 test sessions approximately 14 days apart. Participants randomized to ACTIVE training completed six 30-minute exercise sessions that progressed from 60% to 80% of individualized maximal oxygen consumption (V˙o2max) across test sessions, while the nontraining group received no intervention. MAIN OUTCOME MEASURE(S):The CNS Vital Signs standardized scores, Vestibular/Ocular Motor Screening near-point convergence distance (cm), and Graded Symptom Checklist, Balance Error Scoring System, and Standardized Assessment of Concussion total scores. RESULTS:An interaction effect was found for total symptom score ( P = .01); the intervention group had improved symptom scores between sessions (session 1: 5.1 ± 5.8; session 2: 1.9 ± 3.6). Cognitive flexibility, executive functioning, reasoning, and total symptom score outcomes were better but composite memory, verbal memory, and near-point convergence distance scores were worse at the second session (all P values < .05). However, few changes exceeded the 80% reliable change indices calculated for this study, and effect sizes were generally small to negligible. CONCLUSIONS:A brief aerobic training protocol had few meaningful effects on clinical concussion assessment in healthy participants, suggesting that current concussion-diagnostic and -assessment tools remain clinically stable in response to aerobic exercise training. This provides normative data for future researchers, who should further evaluate the effect of ACTIVE training on clinical outcomes among concussed populations. TRIAL REGISTRATION NUMBER:ClinicalTrials.gov : NCT02872480.