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As a service to our visitors, Simbex provides a handy source of publications, references and whitepapers that we believe would be of interest.  Abstracts and/or full publications are not available through this web site or Simbex.  We hope you find this resource useful.  

Publications Related to the HIT System™

Validation of a Noninvasive System for Measuring Head Acceleration for Use During Boxing Competition
Beckwith, Jonathan G.; Chu, Jeffrey J. ; Greenwald, Richard M.
Simbex, Lebanon, NH

Abstract: Instrumented boxing headgear (IBH) for measuring impact severity and location during competition was assessed. The IBH data were processed to determine linear and rotational acceleration at the head center of gravity, impact location, and impact severity metrics, such as the Head Injury Criterion (HIC) and Gadd Severity Index (GSI). When fitted to a Hybrid III (HIII) head form and impacted with a weighted pendulum to simulate common boxing blows, the IBH showed a high correlation with the HIII for peak linear and rotational acceleration, HIC, and GSI. These results, and the mean location error of 9.7 [plus or minus] 5.2[degree], indicated that the IBH is a valid system for measuring head acceleration and impact location.

Journal of Applied Biomechanics v. 23 no. 3 (August 2007)  p. 238-44

Analysis of linear head accelerations from collegiate football impacts.
Brolinson PG, Manoogian S, McNeely D, Goforth M, Greenwald R, Duma S.
Division of Sports Medicine, Edward Via Virginia College of Osteopathic Medicine, Virginia Tech Department of Athletics, Blacksburg, VA 24061, USA.

Sports-related concussions result in 300,000 brain injuries in the United States each year. We conducted a study utilizing an in-helmet system that measures and records linear head accelerations to analyze head impacts in collegiate football. The Head Impact Telemetry (HIT) System is an in-helmet system with six spring-mounted accelerometers and an antenna that transmits data via radio frequency to a sideline receiver and laptop computer system. A total of 11,604 head impacts were recorded from the Virginia Tech football team throughout the 2003 and 2004 football seasons during 22 games and 62 practices from a total of 52 players. Although the incidence of injury data are limited, this study presents an extremely large data set from human head impacts that provides valuable insight into the lower limits of head acceleration that cause mild traumatic brain injuries.

Curr Sports Med Rep.  2006 Feb;5(1):23-8.

Head acceleration is less than 10 percent of helmet acceleration in football impacts.
Manoogian S, McNeely D, Duma S, Brolinson G, Greenwald R.
Virginia Tech - Wake Forest, Center for Injury Biomechanics, Blacksburg, VA, USA.

Sports-related concussions constitute 20 percent of brain injuries each year in the United States. Concussion research has included a variety of instrumentation and techniques to measure head accelerations. Most recently, the Head Impact Telemetry (HIT) System (Simbex, Lebanon, NH), a wireless system that provides real-time data from impacts, is used to measure in-situ head accelerations in collegiate football. The purpose of this study is to compare helmet shell acceleration to head center of gravity acceleration using two measures of linear head acceleration. A study of 50 helmet to helmet impact tests using a pendulum provided a range of head accelerations from 5 g to 50 g. The primary measure of head acceleration is accelerometers mounted at the center of gravity of the Hybrid III head. A secondary measure is the in-helmet HIT System. The series of 50 pendulum impacts included three impact velocities of 2.0 m/s, 3.5 m/s and 5.0 m/s at four different impact locations. The impact locations were on the side, back, top and just above the facemask on the front. By comparing these two measured head accelerations and the helmet acceleration during a pendulum impact, it is shown that the response of the head and the helmet vary greatly and the in-helmet system matches the head and not helmet acceleration. Specifically, head acceleration is less than 10 percent of helmet acceleration in football impacts; moreover, the HIT System is able to accurately measure the head acceleration.

Biomed Sci Instrum.  2006;42:383-8.

Head impact severity measures for evaluating mild traumatic brain injury risk exposure.
Greenwald RM, Gwin JT, Chu JJ, Crisco JJ.
Simbex, Lebanon, New Hampshire, USA.

OBJECTIVE: The aims of this study were to quantify the sensitivity of various biomechanical measures (linear acceleration, rotational acceleration, impact duration, and impact location) of head impact to the clinical diagnosis of concussion in United States football players and to develop a novel measure of head impact severity combining these measures into a single score that better predicts the incidence of concussion. METHODS: On-field head impact data were collected from 449 football players at 13 organizations (n = 289,916) using in-helmet systems of six single-axis accelerometers. Concussions were diagnosed by medical staff and later associated with impact data. Principal component analysis and a weighting coefficient based on impact location were used to transform correlated head impact measures into a new composite variable, weighted principal component score (wPCS). The predictive power of linear acceleration, rotational acceleration, head injury criterion, and wPCS was quantified using receiver operating characteristic curves. The null hypothesis, that a measure was no more predictive than guessing, was tested (alpha = 0.05). In addition, receiver operating characteristic curves for wPCS and classical measures were directly compared to test the hypothesis that wPCS was more predictive of concussion than were classic measures (alpha = 0.05). RESULTS: When all of the impacts were considered, every biomechanical measure evaluated was statistically more predictive of concussion than guessing (P < 0.005). However, for the top 1 and 2% of impacts based on linear acceleration, a subset that consisted of 82% of all diagnosed concussions, only wPCS was significantly more predictive of concussion than guessing (P < 0.03); when compared with each other, wPCS was more predictive of concussion than were classical measures for the top 1 and 2% of all of the data (P < 0.04). CONCLUSION: A weighted combination of several biomechanical inputs, including impact location, is more predictive of concussion than a single biomechanical measure. This study is the first to the authors' knowledge to quantify improvements in the sensitivity of a biomechanical measure to incidence of concussion when impact location is considered.

Neurosurgery.  2008 Apr;62(4):789-98; discussion 798.

An algorithm for estimating acceleration magnitude and impact location using multiple nonorthogonal single-axis accelerometers.
Crisco JJ, Chu JJ, Greenwald RM.
Department of Orthopaedics, Brown Medical School/Rhode Island Hospital, Providence, RI, USA.

Accelerations of the head are the likely cause of concussion injury, but identifying the specific etiology of concussion has been difficult due to the lack of a valid animal or computer model. Contact sports, in which concussions are a rising health care concern, offer a unique research laboratory environment. However, measuring head acceleration in the field has many challenges including the need for large population sampling because of the relatively low incidence of concussions. We report a novel approach for calculating linear acceleration that can be incorporated into a head-mounted system for on-field use during contact sports. The advantages of this approach include the use of single-axis linear accelerometers, which reduce costs, and a nonorthogonal arrangement of the accelerometers, which simplifies the design criteria for a head-mounted and helmet compatible system. The purpose of this study was to describe the algorithm and evaluate its accuracy for measuring linear acceleration magnitude and impact location using computer simulation and experimental tests with various accelerometer configurations. A 10% error in magnitude and a 10 deg error in impact location were achieved using as few as six single-axis accelerometers mounted on a hemispherical headform.

J Biomech Eng.  2004 Dec;126(6):849-54.

Analysis of real-time head accelerations in collegiate football players.
Duma SM, Manoogian SJ, Bussone WR, Brolinson PG, Goforth MW, Donnenwerth JJ, Greenwald RM, Chu JJ, Crisco JJ.
Virginia Tech-Wake Forest Center for Injury Biomechanics, Blacksburg, VA 24061, USA.

OBJECTIVE: To measure and analyze head accelerations during American collegiate football practices and games. METHODS: A newly developed in-helmet 6-accelerometer system that transmits data via radio frequency to a sideline receiver and laptop computer system was implemented. From the data transfer of these accelerometer traces, the sideline staff has real-time data including the head acceleration, the head injury criteria value, the severity index value, and the impact location. Data are presented for instrumented players for the entire 2003 football season, including practices and games. SETTING: American collegiate football. SUBJECTS: Thirty-eight players from Virginia Tech's varsity football team. MAIN OUTCOME MEASUREMENTS: Accelerations and pathomechanics of head impacts. RESULTS:: A total of 3312 impacts were recorded over 35 practices and 10 games for 38 players. The average peak head acceleration, Gadd Severity Index, and Head Injury Criteria were 32 g +/- 25 g, 36 g +/- 91 g, and 26 g +/- 64 g, respectively. One concussive event was observed with a peak acceleration of 81 g, a 267 Gadd Severity Index, and 200 Head Injury Criteria. Because the concussion was not reported until the day after of the event, a retrospective diagnosis based on his history and clinical evaluation suggested a mild concussion. CONCLUSIONS: The primary finding of this study is that the helmet-mounted accelerometer system proved effective at collecting thousands of head impact events and providing contemporaneous head impact parameters that can be integrated with existing clinical evaluation techniques.

Clin J Sport Med.  2005 Jan;15(1):3-8.

In vivo study of head impacts in football: a comparison of National Collegiate Athletic Association Division I versus high school impacts.
Schnebel B, Gwin JT, Anderson S, Gatlin R.
Department of Orthopedics, University of Oklahoma, Norman, Oklahoma, USA.

OBJECTIVE: To compare the frequency and magnitude of head impacts between National Collegiate Athletic Association Division I and American high school football players. The long-term goal is to correlate impact forces with injury patterns, leading to improvements in protective headgear. METHODS: The helmets of football players at the University of Oklahoma (n = 40) and Casady High School (n = 16) were instrumented with the Head Impact Telemetry System (Simbex, Lebanon, NH). Data were collected for practices and games for the 2005 football season and were analyzed by player position and school. Player positions were separated into two groups (skill and line) for analysis. Two case studies of athletes who sustained a concussion are also presented. RESULTS: A total of 54,154 impacts were recorded at the University of Oklahoma and 8326 at Casady High School. College players sustained high-level impacts greater than 98 g more frequently than high school players. The mean linear accelerations for the top 1, 2, and 5% of all impacts were also higher for college players (P < 0.02). Skill position players received 24.6% of all impacts and sustained an impact greater than 98 g once every 70 impacts. In contrast, linemen sustained the highest number of impacts, but most were relatively low-magnitude (20-30 g). Linemen sustained an impact greater than 98 g once every 125 impacts. CONCLUSION: Differences in the frequency and magnitude of head acceleration after impact exist between a Division I college team and a high school team. Compared with linemen, skill position players typically sustain the highest-level impacts. Additional data collection and analysis are required to correlate concussion diagnosis with acceleration magnitude and impact location.

Neurosurgery. 2007 Mar;60(3):490-5; discussion 495-6