Profiling position specific head trauma in professional American football based on impact magnitude and frequency

In American football repetitive brain trauma is associated with high risk of neurologic disorders. Head contact is integral to the game, resulting in high frequency of head contacts during a game/season. Low energy impacts that do not manifest signs recognized as injury still present metabolic and/or physiologic changes within the brain. The purpose was to estimate player position specific brain trauma profiles based on strain magnitude and impact frequency. Head impacts from 32 game films of professional football were documented and categorized based on event type, head location, and velocity for 8 positions. Inbound velocity was calculated using Kinovea 0.8.20 software. Events were reconstructed using 50th percentile Hybrid III headform, unbiased neckform, linear impactor (collisions) and monorail drop tower (falls). Maximum principal strain (MPS) within the cerebrum was calculated using UCDBTM. Frequency [p < 0.0005] and magnitude [p < 0.0005] were significantly different between the 8 positions. No significant differences in frequencies between the following; quarterback, wide receiver, and defensive back; running back, tight end, and linebacker; and between offensive and defensive linemen. Approximately 60% of documented impacts were received by linemen and tight end. The magnitudes of impacts experienced by quarterbacks were significantly different to all positions excluding wide receiver and defensive back. Wide receiver experienced significantly different magnitudes than both linemen; and differences were found between offensive linemen and defensive back. Approximately 95% of impacts experienced by linemen were below 17% MPS. Conversely, over 90% of impacts documented for quarterback were above moderate strain magnitudes (>17%). Results show risks of repetitive trauma and injury vary with position; some experience high frequency impacts of low magnitude while others receive lower hit counts of higher magnitudes. Findings showed that tight end and running back are particularly risky with relatively high brain strain magnitudes coupled with high frequency making them susceptible to high trauma loads.