Head impact telemetry system
Head Impact Telemetry (HIT) System technology was developed by Simbex (Lebanon, NH) with support from the National Institutes of Health (NIH; R44HD40743 and R01HD048638) to measure and record in vivo head impact exposure (i.e. frequency, location, and kinematics of head impact). Since 2003, the core technology, which includes an array of non-orthogonal accelerometers, data acquisition, RF telemetry hardware, and post-processing software, has been used in a variety of sport and military applications to investigate the relationship between head kinematics and brain injury. This research has enabled and contributed to improved helmet design and testing methods, changes to sporting rules and regulations, and novel approaches to improve player safety. Additionally, HIT System technology is the essential feature of Riddell’s Sideline Response System (SRS) - a real-time monitoring tool used by American football teams to manage an athlete’s head impact exposure.
Head Impact Telemetry (HIT) System technology incorporates an array of non-orthogonal accelerometers (Analog Devices, Inc., Cambridge, MA), data acquisition (1000 Hz over 40 ms time window), and RF telemetry hardware into self-contained inserts placed in commercially available helmets. The broad technology has been tailored to multiple helmet models, including those for: American-style football, boxing, soccer, ice hockey, equestrian, snow sports, and several military applications. While physically connected to the helmet, the instrumented insert acts as an effective spring to maintain contact with the head during impact and to decouple head acceleration from helmet acceleration.
Data collection occurs when any of the six accelerometers exceeds a pre-filtered threshold (8 ms pre-trigger and 32 ms post-trigger). Data is then transmitted wirelessly to a laptop computer where each event is processed and stored within a relational database. Communication range of the system typically exceeds 200 yards; however, in the event of poor communication, each in-helmet sensor array is capable storing up to 100 impacts in nonvolatile memory to minimize the potential for data loss.
Traditional mathematical approaches to calculate head kinematics about the center of gravity (CG), such as those employed in controlled laboratory testing, require precise accelerometer mounting. Because this is not practical for field implementation, the HIT System uses a custom, simulated-annealing optimization algorithm to obtain linear and angular acceleration of the head CG from output of the six head mounted accelerometers. Impact location is then estimated by taking the reflection of the three-dimensional direction vector of peak linear acceleration. The directional vector is then converted to a spherical head coordinate system (azimuth and elevation).
To validate the technology for on-field acquisition of head impact exposure, a multi-phase verification process was conducted which included laboratory testing, video correlation of on-field events, and multi-site field trials.
Research Use and Outcomes
The first on-field use of the HIT System occurred during the 2003 football season at Virginia Tech. Since that time, usage has spread to all levels of play in football (i.e. Professional, College, High School, Youth) and been used to collect head impact exposure data in a wide variety of sporting and military environments. This has generated an exposure database that, as of 2017, includes more than 3.5 million recorded head impacts.
Funding from multiple sources, including the NIH (R01HD048638, R01NS094410, R01NS055020, R01NS092853, and R21NS088781), Centers for Disease Control and Prevention (R01CE001254 and 5R49CE000196), Department of Defense, NOCSAE, and Riddell, has enabled multi-institutional research initiatives to help clinicians, biomechanics, and investigators better understand the relationship between head impact exposure and concussion injury in sports.
Key outcomes from this work, which has involved multiple institutions (Dartmouth, Brown, Virginia Tech, Michigan, North Carolina, Purdue, U Pittsburgh Medical Center, Indiana, and others), include:
- First field use in college football led by researchers at Virginia Tech (2003)
- First field use in high school football led by researchers at the University of Oklahoma (2005)
- Quantified football Head Impact Exposure (HIE – the frequency, magnitude, and location of head impacts) for all playing positions and all levels of play
- Established a relationship between diagnosed concussion and previously sustained head impact exposure, and determined:
- Development of HITsp (HIT Severity Profile) - a novel, composite head impact exposure metric that is more sensitive and specific to mTBI than other single metrics, such as linear acceleration, rotational acceleration, or impact frequency alone
- Established relationships between head impact exposure and signs/symptoms of concussion as identified through neurocognitive testing and advanced imaging techniques
Information from these studies has been used as the basis for:
- Practice rules changes made to limit head impact exposure in at all levels of play - from Pop Warner to College to the NFL – and at the institutional level.
- Development of the Virginia Tech STAR Helmet Ratings to compare performance of commercially available helmets
- Head impact exposure data has guided several generations of new helmet design
- Inspiring an entire market of head impact monitoring systems for both research and commercial use
The HIT System technology is an essential feature of the Riddell (Chicago, IL) Sideline Response System (SRS). The SRS is available for American-style football and is the only HIT System variant marketed commercially.
The Riddell SRS, which was first introduced in 2005, monitors and records head impact exposure during play and alerts sideline personnel that an atypical exposure has occurred. The SRS is not a medical or protective device and does not diagnose concussions or other head injuries. Its intended use is to improve the efficiency and effectiveness of all sideline staff and encourage the consistent application of appropriate sideline practices to identify and reduce head impact exposure.
The SRS software provides several real-time alert options as well as the ability to review and export head impact data retrospectively. Key single impact measures include peak linear and angular acceleration at the head center of gravity, contact location, and acceleration duration. Additionally, the system captures time of each impact, helmet temperature, and computes severity indices such as Head Impact Criteria (HIC), Gadd Severity Index (GSI), and Head Impact Telemetry Severity Profile (HITsp).
For real-time alerting, a local paging system informs sideline personnel of any impact exceeding an alarm threshold for available impact measures. Default alarm thresholds are provided for all impact measures; however, thresholds can be modified for individual players. Additionally, a custom Alerting Protocol is available that identifies players who have experienced atypically high head impact exposure for their skill level (i.e. Professional, College, High School, Youth) and playing position. Atypical exposure is defined for both single and cumulative impacts and derived from the millions of head impacts recorded with the SRS since 2005.
InSite - Next Generation HIE Monitoring
In 2013, Simbex and Riddell partnered to launch a second-generation head impact monitoring system – the InSite Impact Response System – that builds on the research foundations laid by SRS. With support from the National Institutes of Health (R44HD061224), InSite incorporates low power electronics and thin-film sensor technology  to make the benefits of head impact exposure monitoring accessible to teams and leagues at all levels of the sport.
- Beckwith, Jonathan G.; Greenwald, Richard M.; Chu, Jeffrey J. (2011-10-13). "Measuring Head Kinematics in Football: Correlation Between the Head Impact Telemetry System and Hybrid III Headform". Annals of Biomedical Engineering. 40 (1): 237–248. ISSN 0090-6964. PMC . PMID 21994068. doi:10.1007/s10439-011-0422-2.
- Crisco, Joseph J.; Chu, Jeffrey J.; Greenwald, Richard M. (2004-12-01). "An algorithm for estimating acceleration magnitude and impact location using multiple nonorthogonal single-axis accelerometers". Journal of Biomechanical Engineering. 126 (6): 849–854. ISSN 0148-0731. PMID 15796345.
- Duma, Stefan M.; Manoogian, Sarah J.; Bussone, William R.; Brolinson, P. Gunnar; Goforth, Mike W.; Donnenwerth, Jesse J.; Greenwald, Richard M.; Chu, Jeffrey J.; Crisco, Joseph J. (2005-01-01). "Analysis of real-time head accelerations in collegiate football players". Clinical Journal of Sport Medicine. 15 (1): 3–8. ISSN 1050-642X. PMID 15654184.
- Manoogian, Sarah; McNeely, David; Duma, Stefan; Brolinson, Gunnar; Greenwald, Richard (2006-01-01). "Head acceleration is less than 10 percent of helmet acceleration in football impacts". Biomedical Sciences Instrumentation. 42: 383–388. ISSN 0067-8856. PMID 16817638.
- Chu, J.J.; Beckwith, J.G.; Crisco, J.J.; Greenwald, R.M. "A novel algorithm to measure linear and rotational head acceleration using single-axis accelerometers". Journal of Biomechanics. 39. doi:10.1016/s0021-9290(06)85195-x.
- Greenwald, Richard M.; Gwin, Joseph T.; Chu, Jeffrey J.; Crisco, Joseph J. "HEAD IMPACT SEVERITY MEASURES FOR EVALUATING MILD TRAUMATIC BRAIN INJURY RISK EXPOSURE". Neurosurgery. 62 (4): 789–798. PMC . PMID 18496184. doi:10.1227/01.neu.0000318162.67472.ad.
- Beckwith, Jonathan G.; Chu, Jeffrey J.; Greenwald, Richard M. (2007-08-01). "Validation of a noninvasive system for measuring head acceleration for use during boxing competition". Journal of Applied Biomechanics. 23 (3): 238–244. ISSN 1065-8483. PMID 18089922.
- Rowson, Steven; Beckwith, Jonathan G.; Chu, Jeffrey J.; Leonard, Daniel S.; Greenwald, Richard M.; Duma, Stefan M. (2011-02-01). "A six degree of freedom head acceleration measurement device for use in football". Journal of Applied Biomechanics. 27 (1): 8–14. ISSN 1065-8483. PMID 21451177.
- Hanlon, Erin; Bir, Cynthia (2010-11-01). "Validation of a wireless head acceleration measurement system for use in soccer play". Journal of Applied Biomechanics. 26 (4): 424–431. ISSN 1065-8483. PMID 21245502.
- Siegmund, Gunter P.; Guskiewicz, Kevin M.; Marshall, Stephen W.; DeMarco, Alyssa L.; Bonin, Stephanie J. (2016-04-01). "Laboratory Validation of Two Wearable Sensor Systems for Measuring Head Impact Severity in Football Players". Annals of Biomedical Engineering. 44 (4): 1257–1274. ISSN 1573-9686. PMID 26268586. doi:10.1007/s10439-015-1420-6.
- Mihalik, J P; Guskiewicz, K M; Jeffries, J A; Greenwald, R M; Marshall, S W (2008-06-06). "Characteristics of head impacts sustained by youth ice hockey players". Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology. 222 (1): 45–52. doi:10.1243/17543371jset4.
- Brolinson, P. Gunnar; Manoogian, Sarah; McNeely, David; Goforth, Mike; Greenwald, Richard; Duma, Stefan (2006-02-01). "Analysis of linear head accelerations from collegiate football impacts". Current Sports Medicine Reports. 5 (1): 23–28. ISSN 1537-8918. PMID 16483513.
- Wilcox, Bethany J.; Machan, Jason T.; Beckwith, Jonathan G.; Greenwald, Richard M.; Burmeister, Emily; Crisco, Joseph J. (2014-07-01). "Head-impact mechanisms in men's and women's collegiate ice hockey". Journal of Athletic Training. 49 (4): 514–520. ISSN 1938-162X. PMC . PMID 25098659. doi:10.4085/1062-6050-49.3.19.
- Mihalik, Jason P.; Blackburn, J. Troy; Greenwald, Richard M.; Cantu, Robert C.; Marshall, Stephen W.; Guskiewicz, Kevin M. (2010-06-01). "Collision type and player anticipation affect head impact severity among youth ice hockey players". Pediatrics. 125 (6): e1394–1401. ISSN 1098-4275. PMID 20478933. doi:10.1542/peds.2009-2849.
- Mihalik, Jason P.; Bell, David R.; Marshall, Stephen W.; Guskiewicz, Kevin M. (2007-12-01). "Measurement of head impacts in collegiate football players: an investigation of positional and event-type differences". Neurosurgery. 61 (6): 1229–1235; discussion 1235. ISSN 1524-4040. PMID 18162902. doi:10.1227/01.neu.0000306101.83882.c8.
- Schnebel, Brock; Gwin, Joseph T.; Anderson, Scott; Gatlin, Ron (2007-03-01). "In vivo study of head impacts in football: a comparison of National Collegiate Athletic Association Division I versus high school impacts". Neurosurgery. 60 (3): 490–495; discussion 495–496. ISSN 1524-4040. PMID 17327793. doi:10.1227/01.NEU.0000249286.92255.7F.
- BROGLIO, STEVEN P.; SCHNEBEL, BROCK; SOSNOFF, JACOB J.; SHIN, SUNGHOON; FENG, XINGDONG; HE, XUMING; ZIMMERMAN, JERRAD. "Biomechanical Properties of Concussions in High School Football". Medicine & Science in Sports & Exercise. 42 (11): 2064–2071. doi:10.1249/mss.0b013e3181dd9156.
- "National Athletic Trainers' Association". National Athletic Trainers' Association. PMC . PMID 21062178. doi:10.4085/1062-6050-45.6.549. Retrieved 2017-01-30.
- Crisco, Joseph J.; Wilcox, Bethany J.; Beckwith, Jonathan G.; Chu, Jeffrey J.; Duhaime, Ann-Christine; Rowson, Steven; Duma, Stefan M.; Maerlender, Arthur C.; McAllister, Thomas W. "Head impact exposure in collegiate football players". Journal of Biomechanics. 44 (15): 2673–2678. PMC . PMID 21872862. doi:10.1016/j.jbiomech.2011.08.003.
- Crisco, Joseph J.; Wilcox, Bethany J.; Machan, Jason T.; McAllister, Thomas W.; Duhaime, Ann-Christine; Duma, Stefan M.; Rowson, Steve; Beckwith, Jonathan G.; Chu, Jeffrey J. (2012-05-01). "Magnitude of head impact exposures in individual collegiate football players". Journal of Applied Biomechanics. 28 (2): 174–183. ISSN 1065-8483. PMC . PMID 21911854.
- Broglio, Steven P.; Sosnoff, Jacob J.; Shin, SungHoon; He, Xuming; Alcaraz, Christopher; Zimmerman, Jerrad (2009-07-01). "Head impacts during high school football: a biomechanical assessment". Journal of Athletic Training. 44 (4): 342–349. ISSN 1938-162X. PMC . PMID 19593415. doi:10.4085/1062-6050-44.4.342.
- Daniel, Ray W.; Rowson, Steven; Duma, Stefan M. (2012-02-15). "Head Impact Exposure in Youth Football". Annals of Biomedical Engineering. 40 (4): 976–981. ISSN 0090-6964. PMC . PMID 22350665. doi:10.1007/s10439-012-0530-7.
- Daniel, Ray W.; Rowson, Steven; Duma, Stefan M. (2014-07-03). "Head Impact Exposure in Youth Football: Middle School Ages 12–14 Years". Journal of Biomechanical Engineering. 136 (9): 094501–094501–6. ISSN 0148-0731. doi:10.1115/1.4027872.
- BECKWITH, JONATHAN G.; GREENWALD, RICHARD M.; CHU, JEFFREY J.; CRISCO, JOSEPH J.; ROWSON, STEVEN; DUMA, STEFAN M.; BROGLIO, STEVEN P.; MCALLISTER, THOMAS W.; GUSKIEWICZ, KEVIN M. "Head Impact Exposure Sustained by Football Players on Days of Diagnosed Concussion". Medicine & Science in Sports & Exercise. 45 (4): 737–746. doi:10.1249/mss.0b013e3182792ed7.
- BECKWITH, JONATHAN G.; GREENWALD, RICHARD M.; CHU, JEFFREY J.; CRISCO, JOSEPH J.; ROWSON, STEVEN; DUMA, STEFAN M.; BROGLIO, STEVEN P.; MCALLISTER, THOMAS W.; GUSKIEWICZ, KEVIN M. "Timing of Concussion Diagnosis Is Related to Head Impact Exposure Prior to Injury". Medicine & Science in Sports & Exercise. 45 (4): 747–754. doi:10.1249/mss.0b013e3182793067.
- Rowson, Steven; Duma, Stefan M.; Greenwald, Richard M.; Beckwith, Jonathan G.; Chu, Jeffrey J.; Guskiewicz, Kevin M.; Mihalik, Jason P.; Crisco, Joseph J.; Wilcox, Bethany J. (2014-01-31). "Can helmet design reduce the risk of concussion in football?". Journal of Neurosurgery. 120 (4): 919–922. ISSN 0022-3085. doi:10.3171/2014.1.JNS13916.
- Breedlove, Evan L.; Robinson, Meghan; Talavage, Thomas M.; Morigaki, Katherine E.; Yoruk, Umit; O'Keefe, Kyle; King, Jeff; Leverenz, Larry J.; Gilger, Jeffrey W. (2012-04-30). "Biomechanical correlates of symptomatic and asymptomatic neurophysiological impairment in high school football". Journal of Biomechanics. 45 (7): 1265–1272. ISSN 1873-2380. PMID 22381736. doi:10.1016/j.jbiomech.2012.01.034.
- Talavage, Thomas M.; Nauman, Eric A.; Breedlove, Evan L.; Yoruk, Umit; Dye, Anne E.; Morigaki, Katherine E.; Feuer, Henry; Leverenz, Larry J. (2010-10-01). "Functionally-Detected Cognitive Impairment in High School Football Players without Clinically-Diagnosed Concussion". Journal of Neurotrauma. 31 (4): 327–338. ISSN 0897-7151. PMC . PMID 20883154. doi:10.1089/neu.2010.1512.
- McAllister, Thomas W.; Ford, James C.; Ji, Songbai; Beckwith, Jonathan G.; Flashman, Laura A.; Paulsen, Keith; Greenwald, Richard M. (2011-10-13). "Maximum Principal Strain and Strain Rate Associated with Concussion Diagnosis Correlates with Changes in Corpus Callosum White Matter Indices". Annals of Biomedical Engineering. 40 (1): 127–140. ISSN 0090-6964. PMC . PMID 21994062. doi:10.1007/s10439-011-0402-6.
- McAllister, T. W.; Flashman, L. A.; Maerlender, A.; Greenwald, R. M.; Beckwith, J. G.; Tosteson, T. D.; Crisco, J. J.; Brolinson, P. G.; Duma, S. M. (2012-05-29). "Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes". Neurology. 78 (22): 1777–1784. ISSN 0028-3878. PMC . PMID 22592370. doi:10.1212/WNL.0b013e3182582fe7.
- Rowson, Steven; Duma, Stefan M. (2011-05-07). "Development of the STAR Evaluation System for Football Helmets: Integrating Player Head Impact Exposure and Risk of Concussion". Annals of Biomedical Engineering. 39 (8): 2130–2140. ISSN 0090-6964. doi:10.1007/s10439-011-0322-5.
- Rowson, Steven; Duma, Stefan M.; Beckwith, Jonathan G.; Chu, Jeffrey J.; Greenwald, Richard M.; Crisco, Joseph J.; Brolinson, P. Gunnar; Duhaime, Ann-Christine; McAllister, Thomas W. "Rotational Head Kinematics in Football Impacts: An Injury Risk Function for Concussion". Annals of Biomedical Engineering. 40 (1): 1–13. ISSN 0090-6964. doi:10.1007/s10439-011-0392-4.
- Chu, Jeffrey J.; Beckwith, Jonathan G.; Leonard, Daniel S.; Paye, Corey M.; Greenwald, Richard M. (2011-10-13). "Development of a Multimodal Blast Sensor for Measurement of Head Impact and Over-pressurization Exposure". Annals of Biomedical Engineering. 40 (1): 203–212. ISSN 0090-6964. doi:10.1007/s10439-011-0410-6.