The use of aerobic exercise treatment in the chronic phase of concussion recovery is well-described in the literature but there are limited existing data on the effect of exercise treatment in the acute phase after sport-related concussion (SRC). This study will compare the outcomes of adolescents with a recent SRC who are randomized to sub-threshold aerobic exercise versus those randomized to placebo stretching to evaluate the effect of aerobic exercise in the acute recovery phase.

Historically, concussion has been described as a cognitive injury and patients have been advised not to engage in any cognitive or physical exertion while symptomatic. More recently, however, concussion has been described as a physiological injury affecting both the heart and autonomic nervous system, and patients suffering from prolonged concussion-related symptoms and deficits have been encouraged to begin aerobic exercise as part of their concussion care. While intensive exercise too soon after concussion has been associated with delayed recovery and used to justify prolonged periods of rest, recent studies have shown that controlled, sub-symptom threshold aerobic exercise may aid recovery by improving autonomic balance and cerebral blood flow auto-regulation after concussion. This study will randomly assign pediatric patients with concussion to a treatment group in which they will complete sub-symptom threshold aerobic exercise or to a placebo group in which they will complete a standardized stretching protocol. All participants will have routine visits that consist of a physical examination and exercise test until the intervention ends at recovery or 1-month post-randomization.

Inclusion Criteria (Case Subjects):

• Sports-related concussion (organized or recreational).
• Physician-diagnosed concussion within the last 10 days.
• Symptom score difference ≥3 on the Post-Concussion Symptom Inventory (PCSI) Current versus PCSI Pre-Injury.
• Parental/guardian permission (informed consent) and child assent.

Inclusion Criteria (Control Subjects):

• No known recent concussion within the past year or still causing active symptoms.
• Parental/guardian permission (informed consent) and child assent.

Exclusion Criteria (Case and Control Subjects):

• Subjects with moderate or severe traumatic brain injury as indicated by a score <13 on Glasgow Coma Scale (GCS), presence of lesion on CT/MRI, and/or focal neurologic deficit consistent with an intracerebral lesion.
• History of more than 3 diagnosed concussions.
• Subjects that sustained an injury involving loss of consciousness for 30+ minutes or post-traumatic amnesia for 24+ hours.
• Inability to exercise because of lower-extremity orthopedic injury, significant vestibular or visual dysfunction, or increased cardiac risk.
• Pre-existing comorbidities, such as chronic pain, cardiac, neurological, or autoimmune conditions, that prevent participation in active testing and/or rehabilitation.
• Currently taking medications that can affect autonomic function.
• Active substance abuse/dependence.
• Unwillingness to exercise or unable to access place to safely exercise.
• Parental/guardian permission (informed consent) not obtainable or not provided
• Cannot understand English.

Exclusion Criteria (Case Subjects Only):

• Additional head injury during the intervention.
• Parents/ guardians or subjects who, in the opinion of the Investigator, may be non-compliant with study schedules or procedures.