This paper reviews the studies that have been conducted on the performance of the American football helmet in preventing concussion. The review will also guide us to understand what problems still exist and what research directions we should take. Throughout the history of sports, injuries limiting the career life of the athletes have been the leading concern of the sport authorities. These injuries are more extensive in sports in which athletes are in severe contact with each. Mild Traumatic Brain Injury, concussion, widely occurs in American football because of the frequent strokes to players' heads. Concussion includes several types of neurological dysfunctions such as headache, dizziness, confusion, blurred vision, delayed reaction time and etc. Lots of the studies have focused on understanding the concussion and improving the protective performance of the helmet, so that the dose of the injury in players is reduced. Researches in this area can be classified as two major methods: experimental studies and Finite Element Modeling (FEM) simulations. In experiments, researchers have tried torecord head impacts or reconstruct the severe collisions using the game videos in the laboratory conditions. They have used the Hybrid III dummy in order to study the effects of the different impact parameters such as direction, velocity, region of the head being hit and etc. These studies have been done by analyzing the dynamic responses of head includinglinear acceleration (LA), rotational acceleration (RA), and different head injury criteria like Head Injury Criteria (HIC) and Gadd Severity Index (GSI). Mentioned impact parameters have been also examined using FEM simulations. Researchers have applied the results of experimental tests including linear and rotational acceleration in order to study the brain deformation responses to different types of impacts. In this regards, brain deformation responses like maximum principal strain have been considered and analyzed using the head injury and concussion thresholds. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.