Six Degree of Freedom Head Acceleration Measurements in Football Players

The existing five degree of freedom HITS sensor used to measure head accelerations is incapable of measuring rotational head acceleration about the z-axis. A new six degree of freedom (6DOF) sensor has been developed capable of measuring linear and rotational accelerations for each axis. The 6DOF sensor consists of 12 accelerometers that integrate into football helmets and communicate wirelessly with a laptop on the sideline. An estimation algorithm processes the data from the 12 accelerometers to determine linear and rotational accelerations. The newly developed sensor is capable of accurately recording linear and rotational head accelerations experienced by football players. Twenty (20) players on the Virginia Tech football team will be instrumented with 6DOF sensors during the 2007 season. INTRODUCTION E ach year, there are approximately 1.5 million traumatic brain injuries in the United States (Thurman et al., 1999); 75% of which are mild traumatic brain injuries (MTBI) (Sosin et al., 1996). About 300,000 of these concussions are sustained by athletes playing contact sports, with football having the largest occurrence (Thurman et al., 1998). The high incidence rate of concussions in football provides a unique opportunity to collect biomechanical data to characterize MTBI. Several injury metrics are used to predict head injury; however, all the criteria use limited data from human volunteers. Head injury criterion (HIC), peak acceleration, and severity index (SI) are injury metrics derived from linear head acceleration and are primarily based on cadaver tests with skull fractures. Rotational acceleration injury thresholds are based mostly on primate tests with severe concussion, diffuse axonal injury (DAI), or intracranial bleed.