The overarching purpose of this proposed research is to determine whether BDNF and/or specific miRNAs can serve as biomarkers for recovery from a concussion during prescribed exercise. The investigators hypothesize salivary BDNF and specific miRNA signatures will change in a statistically significant manner as participants proceed from injury to recovery and participants who show recovery in ANS regulation will show significant differences in salivary BDNF and specific miRNA expression. This study also aims to determine if BDNF and/or specific miRNA can serve as biomarkers of the return of ANS function in concussed patients. The basic premise here is that the volume of exercise will significantly affect the rate of change in the expression of salivary BDNF and miRNA from injury to recovery.

• This is a four-arm randomized control trial that investigates the changes in expression of BDNF/ miRNA after prescribed exercise intervention in concussed adolescents. Potential participants will be selected from incoming patients to the University Concussion Management Clinic. For a patient to become a potential participant in the "concussed participant" group, a sports medicine physician must first confirm the diagnosis of an acute concussion within 10 days of injury. Healthy controls will be recruited at local high schools (pediatric) and from the UB Clinical Trial registry (pediatric and adult). Concussion diagnosis is based on history, a concussion symptom questionnaire, and a concussion-specific physical examination. If the participant's medical history and demographic information meet eligibility criteria, they will be asked if they would like to participate. All potential participants will be informed of all study procedures verbally. If participants are willing and eligible to participate, they will be asked to consent/ assent to the study procedure.
• Participants will be asked to fill out the documentation regarding their demographics, concussion symptoms/history (Concussion Symptom Evaluation, Post-Concussion Symptom Inventory), and motivation to exercise (Modified Perceived Competence Scale, Modified Treatment Self-Regulation Questionnaire). Additionally, to determine if participants have any contraindications to exercise, the Physical Activity Readiness Questionnaire (PAR-Q) will be completed by all participants.
• Participants will undergo the Buffalo Concussion Physical Exam (BCPE), a short examination to used determine if a patient is concussed. This examination includes vital signs, a head and neck examination, cranial nerve testing, oculomotor testing, and a balance test.
• A trained examiner will complete an Oral Hygiene Index-Simplified (OHI-S) and will collect saliva. The Oral Hygiene Index is a short evaluation of the calculus and debris on selected teeth to assess the oral hygiene of a participant. Saliva will be collected using a Genotek Swab (miRNA) and a Salimetrics Cryovial (BDNF). Saliva will be collected with a swab (Genotek) and passive drool (Salimetrics) techniques.
• After saliva is obtained, the participant will be asked to complete the Buffalo Concussion Treadmill Test (BCTT). The BCTT is a graded exercise test that is used to determine concussion-related exercise intolerance. Although it is standard for patients from the Concussion Clinic to require a BCTT assessment as a part of their standard visit, participants will be made aware that their BCTT data will be used for this study. During the BCTT participants will be asked to wear an HR monitor (Polar H10) for the collection of HR and Heart Rate Variability (HRV) data.
• After completion of the BCTT, the examiner will use the results of the exercise test to create an individualized exercise prescription. The prescription will be randomized for high and low volumes and even split between male and female participants in healthy and concussed groups.
• Recovery date for concussed participants will be provided by the study clinician after the end of the intervention if concussed participants do not recover during the study time frame.

Inclusion Criteria:

• Adolescent and adult athletes (age 13-18) diagnosed with SRC within 10 days of injury.

Exclusion Criteria:

• Evidence of focal neurological deficit;
• Inability to exercise because of orthopedic or cervical spine injury;
• Increased cardiac risk according to American College of Sports Medicine criteria;
• History of moderate or severe TBI, defined as brain injury with a Glasgow Coma Scale score of 12 or less;
• Current medication treatment for ADHD, learning disorders, depression, anxiety, or other medications that can affect HR;
• Symptom severity score of less than 5 on the initial visit Post Concussion Symptom Scale questionnaire. (7) currently pregnant (8) have any contraindications to exercise (Physical Activity Readiness-Questionnaire)

Self-representation of gender identity

No plan to share IPD currently

It is hypothesized that participants in the concussion group would not different in age, sex, ethnicity, height or weight from control samples.

Adverse events were monitored during the two week intervention.

Adolescents participant condition (concussed or healthy) and intervention (light aerobic exercise) does not constitute a high risk for serious adverse events or mortality.