In this half day workshop Dr Barry Willer will describe his research and other research that suggest that mild traumatic brain injury (mTBI) and concussion are primarily physiologic in nature. At rest, individuals with mTBI have increased heartrates and decreased parasympathetic responses. During exercise, individuals with mTBI have increased diastolic blood pressure and increased cerebral blood flow. These and other physiologic differences have major implications for diagnosis, treatment and return to activity decisions.