Objectives: Review existing literature on studies involving active humans regarding how the magnitude and the location of impact are factors in determining the tolerance of a brain injury and more accurately determine the risk for concussion.

Method: A review of the literature was conducted analyzing studies involving American football players and brain injury. Previous literature reviews have looked at head tolerance from impacts, but the subjects have either been cadavers, or animals. These studies had significant limitations since traumatic brain injury (TBI) cannot be detected in cadavers and injury thresholds from animal experiments are not directly applicable to humans. More recent studies, however, have involved experiments with the contact sport of American football. These studies have provided more complete data and the results have indicated that, while the injury may not be immediately apparent, significant injuries can be sustained from exposure to a head impact.

Results: The results indicate that brain injury tolerance is expressed in terms of head acceleration and that there is an association between the position of the player and the likelihood of sustaining an injury causing impact. Studies of American football players have made it possible to collect brain injury tolerance data on living human beings. This in turn can help establish more accurate diagnoses of TBI that occur as a result of direct or indirect contact force. However, much more cumulative epidemiological and biomechanical impact data (i.e., positions, direction) needs to be collected in order refine methods to better diagnose both apparent and non-apparent brain injuries.