Head Impact Exposure in Collegiate Football Players

Bioengineering Laboratory, Department of Orthopaedics, The Warren Alpert Medical School of Brown University and Rhode Island Hospital, Providence, Rhode Island 02903, USA.
Journal of Biomechanics (Impact Factor: 2.75). 08/2011; 44(15):2673-8. DOI: 10.1016/j.jbiomech.2011.08.003
Source: PubMed


In American football, impacts to the helmet and the resulting head accelerations are the primary cause of concussion injury and potentially chronic brain injury. The purpose of this study was to quantify exposures to impacts to the head (frequency, location and magnitude) for individual collegiate football players and to investigate differences in head impact exposure by player position. A total of 314 players were enrolled at three institutions and 286,636 head impacts were recorded over three seasons. The 95th percentile peak linear and rotational acceleration and HITsp (a composite severity measure) were 62.7g, 4378rad/s(2) and 32.6, respectively. These exposure measures as well as the frequency of impacts varied significantly by player position and by helmet impact location. Running backs (RB) and quarter backs (QB) received the greatest magnitude head impacts, while defensive line (DL), offensive line (OL) and line backers (LB) received the most frequent head impacts (more than twice as many than any other position). Impacts to the top of the helmet had the lowest peak rotational acceleration (2387rad/s(2)), but the greatest peak linear acceleration (72.4g), and were the least frequent of all locations (13.7%) among all positions. OL and QB had the highest (49.2%) and the lowest (23.7%) frequency, respectively, of front impacts. QB received the greatest magnitude (70.8g and 5428rad/s(2)) and the most frequent (44% and 38.9%) impacts to the back of the helmet. This study quantified head impact exposure in collegiate football, providing data that is critical to advancing the understanding of the biomechanics of concussive injuries and sub-concussive head impacts.

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Available from: Arthur Maerlender, Mar 03, 2014
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    • "To overcome the limitations of GPS, in particular the measurement of brief, high intensity events, inertial sensors have been implemented in a number of sporting applications. The majority of this research has been focused on head impacts and concussions in boxing (Beckwith et al., 2007) and American football (Crisco et al., 2011; Rowson et al., 2009). There was however, research into using inertial sensors in rugby union to automatically detect collisions (Kelly et al., 2012) based on pattern recognition. "
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    ABSTRACT: Athlete performance and monitoring is an area of interest across many sporting codes, for indoor sports however, the primary methods of athlete monitoring are manually recording statistics or video analysis. This paper contains two studies, the first to validate an automatic jump detection method which was developed using inertial sensors and the second to determine the accuracy at which the time of flight (ToF) can be detected using this method. To evaluate the automatic jump detection method both male (n=7) and female (n=5) volleyball players performed a total of 1201 jumps manually identified on video during a typical training session. Of these 1201 jumps, the method correctly identified 1144 (95%) jumps in the inertial data with only 57 (5%) being false negatives and 54 (4%) false positives. The ToF was then found to be underestimated with a mean error of -0.015s ± 0.058s when compared to the ToF obtained from a force plate. Overall the system provided a means to quickly and easily track the number of jumps being performed by each player and the approximate ToF of each jump when compared to existing methods.
    Full-text · Article · Mar 2015 · International Journal of Performance Analysis in Sport
    • "Although our current study did not assess the risk of concussion, our results do indicate that the location of head impact in combination with player anticipation and player involvement may play a significant role in studying impact severity. Studies using surrogate reconstructions of documented concussive hits in the National Football League have suggested that concussion risk is associated with the peak linear acceleration of the head[15,16]. Nevertheless, clinicians should factor in impact location in regards to player anticipation and player involvement when developing injury prevention programs that should include proper tackling instruction . "
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    ABSTRACT: Football accounts for 55% of all concussions in collegiate athletics, and 6.8% of all injuries in collegiate football. The two primary purposes of this study were to 1) examine the effect of body collision anticipation (anticipated vs unanticipated) and involvement (striking vs struck) on head impact biomechanics as measured by linear acceleration, rotational acceleration, and Head Impact Technology severity profile (HITsp), and 2) study the interaction between these same two factors and the location of head impact (i.e. back, front, side, or top). College football players were equipped with accelerometer-instrumented helmets (Head Impact Telemetry System) to collect head impact biomechanics during all games in a single playing season. Multiple camera views were synchronized with the head impact data, and viewable collisions (N = 1408) were evaluated using a standardized criteria rubric to assign player anticipation and involvement. Data were analyzed using separate random intercepts general mixed linear models for each dependent variable, incorporating each individual player as a repeating factor in the analyses. Our findings indicate that struck players experience greater rotational accelerations compared to the striking player, yet no differences were observed for linear acceleration or HITsp. It would appear, based on our data, that all impacts-anticipated or otherwise-produce the same mean severity. However, significant interactions between player anticipation and location of impact, as well as player involvement and location of impact, were observed for all three biomechanical measures. Anticipated collisions to the top of the head (likely indicative of a spearing mechanism) were among the most severe we observed in our study. These data are important for coaches to emphasize proper tackling techniques and skill development with their players.
    No preview · Article · Jan 2014
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    • "In order to understand the biomechanics associated with concussion, numerous studies have been conducted over the last decade to investigate player exposure and tolerance to head impacts in football.3,4,7,9,10,13,16,17,22,23,25–27,31–34 Many of these studies have utilized commercially available helmet-mounted accelerometer arrays (Head Impact Telemetry (HIT) System, Simbex, Lebanon, NH) to measure head kinematics resulting from head impact in real-time during live play. "
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    ABSTRACT: Head impact exposure in youth football has not been well-documented, despite children under the age of 14 accounting for 70% of all football players in the United States. The objective of this study was to quantify the head impact exposure of youth football players, age 9-12, for all practices and games over the course of single season. A total of 50 players (age = 11.0 ± 1.1 years) on three teams were equipped with helmet mounted accelerometer arrays, which monitored each impact players sustained during practices and games. During the season, 11,978 impacts were recorded for this age group. Players averaged 240 ± 147 impacts for the season with linear and rotational 95th percentile magnitudes of 43 ± 7 g and 2034 ± 361 rad/s(2). Overall, practice and game sessions involved similar impact frequencies and magnitudes. One of the three teams however, had substantially fewer impacts per practice and lower 95th percentile magnitudes in practices due to a concerted effort to limit contact in practices. The same team also participated in fewer practices, further reducing the number of impacts each player experienced in practice. Head impact exposures in games showed no statistical difference. While the acceleration magnitudes among 9-12 year old players tended to be lower than those reported for older players, some recorded high magnitude impacts were similar to those seen at the high school and college level. Head impact exposure in youth football may be appreciably reduced by limiting contact in practices. Further research is required to assess whether such a reduction in head impact exposure will result in a reduction in concussion incidence.
    Full-text · Article · Jul 2013 · Annals of Biomedical Engineering
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