Inclusion Criteria:  Recreationally healthy and active or considered an athletic performer, males and females, to regularly engage in >150 min/week of physical activity. Participants considered an athletic performer if they have history of participating in athletics at the university, amateur, elite or professional level, or are a military veteran. Healthy participants defined as not currently injured, or recovering from an injury within the past 12 months, or undergone surgery within the last 12 months, or with any known history of moderate to severe traumatic brain injury resulting in impaired judgement or inability to make sound decisions within the last 12 months. Post concussion participants are eligible if their last concussive event occurred within a month and up to 5 years of the date of data collection.  Exclusion Criteria:  If younger than 18 or >50 years of age. Current cardiovascular, metabolic, psychiatric, or neurologic disease or cognitive or substance-abuse problems or taking medications that may impair cognition, balance, or functional mobility such as gait.