an objective biological test to measure concussion may provide further insight into a player's decision to return-to-play. protein s100b is a calcium-binding protein that has been studied as a sensitive biomarker of central nervous system injury alter mild head trauma and as a useful predictor of clinical outcome after brain injury. both head trauma and exercise influence disruption of the blood-brain barrier, which causes the release of s100b into the peripheral circulation. serum samples were taken from post-concussed and non-concussed collegiate athletes before and immediately after participation in a maximal aerobic fitness test...