Search

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.

IntroductionLoss of consciousness (LOC) occurs with approximately 8 percent of concussions in professional American football and has been associated with severity of injury (1, 2). However it is unknown how LOC relates to severity of head impact responses. The purpose of this study was to compare the head accelerations and brain tissue deformation between cases of concussions with and without LOC in elite American football to inform prevention strategies.MethodsConcussive injuries with and without LOC from helmet-to-helmet and shoulder collisions as well as falls in elite American football were reconstructed in laboratory using hybrid III headform to obtain peak linear and rotational acceleration and maximum principal strain, cumulative strain damage at 10%, and strain rate metrics in 5 brain regions associated with loss of consciousness.ResultsImpact velocity, peak linear and rotational acceleration were greater in the LOC group than the no LOC group. The brain tissue deformation metrics were greater in the LOC group than the no LOC group. Linear acceleration was most predictive for cases of helmet-to-helmet collisions whereas shoulder collisions were best predicted by rotational acceleration. The best overall predictor was impact velocity.Discussion/conclusionThe presence of a loss of consciousness in concussive impacts is a result of greater magnitude of brain tissue trauma. This was primarily caused by greater impact velocities in head impacts leading to LOC. Rules aiming at mitigating this aspect of the game would decrease the risk of a loss of consciousness in this sport. Each type of events resulted in different values of kinematic data and brain tissue deformation, which suggests that studies evaluating risk of concussions based 1 type of event cannot be generalized.

IntroductionTrauma related neuropathologies including recent reports involving chronic traumatic encephalopathy (CTE) in 8 soccer players have been concerning. Purposeful sub-concussive head impacts, known as headers, are an integral part of the game. The purpose of this study was to describe dynamic head response and brain tissue strains for front ball-to-head impacts in elite soccer.MethodsVideo analysis thirteen (13) Champion's League soccer footage was completed to establish reconstruction parameters of head impact events. Analysis of 5 (5) front ball-to-head events were reconstructed using a Hybrid III 50th percentile headform and a pneumatic linear impactor. The University College Dublin Brain Trauma Model was used to calculate maximum principal strain (MPS).Results and discussionRecorded head impact velocities during elite soccer game play were 3.5–23.0 m/s. Most purposeful head-to-ball impacts occurred on the front-temporal region of the head (66.4%) at 0–15 degrees of cervical flexion. There was an average of 1.5 unintentional head impacts and 62.2 headers per game; 49.6% of headers occurred at an inbound velocity below 10 m/s. The lowest velocity reconstructed was 4.7 m/s, yielding 12.8 g and 604 rad/s2 for peak resultant linear and rotational accelerations, respectively; the MPS for this impact was 0.09. Neurophysiologic changes and functional impairment have been reported in past research on sub-concussive impacts with 5%–15% strain. The mean 0.11 MPS yielded in this study reflects a potential for these changes in elite soccer athletes.ConclusionThe main objective of this analysis was to identify impact characteristics and quantify dynamic cerebral response and brain tissue deformation in elite soccer game play. Further research must include cervical muscle activation, the level of play and player position, inbound ball-to-head velocities during different game play events and appropriate impact characteristics to appropriately characterize risk of injury in the attempts of mitigating risk of head injury during soccer game play.