The purpose of this study is to examine the effect that blood flow restriction training will have on patients with concussion who demonstrate an intolerance to physical activity. Progressive exercise training has been shown to effectively reduce the effects of concussion and facilitate return to academic and athletic activities. In many cases, exercises intolerance is present in these patients which hinders progression. In musculoskeletal conditions, blood flow restriction training, when combined with low load exercise, has been shown to produce similar gains as high load exercises. If a patient being treated for concussion can tolerate low load exercise without concussive symptoms, then blood flow restriction may increase exercise gains by facilitating autonomic responses similar to high load training. This study will explore this hypothesis in patients between the ages of 14 and 30 who are referred for physical therapy intervention which is the standard of care at Duke Sports Sciences Concussion Clinic. Blood flow restriction training is also used in multiple patient populations at Duke Sports Physical Therapy without adverse events.