An Instrumented Mouthguard for Measuring Linear and Angular Head Impact Kinematics in American Football

Camarillo, David B.; Shull, Peter B.; Mattson, James A.; Shultz, Rebecca; Garza, Daniel

doi:10.1007/s10439-013-0801-y

Cited by 187 publications

(209 citation statements)

References 26 publications

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“…The striking uniformity of impacts oscillating around 20 Hz indicates that a substantial portion of sports head impacts are exciting a mechanical resonance of the skull-brain system and causing amplified skull-brain relative motions. In previous studies using our instrumented mouthguard, we showed that the natural frequency of the mouthguard is around 150 Hz and that head impacts had much higher energy levels at lower frequencies, suggesting that the measured frequency content has not been biased by the instrumentation [30,32]. The above information again prompts the long-ignored question: can mechanical resonance lead to mTBI?…”

Section: Discussionsupporting

confidence: 62%

Resonance of human brain under head acceleration

Laksari

Kurt

et al. 2015

J. R. Soc. Interface.

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Although safety standards have reduced fatal head trauma due to single severe head impacts, mild trauma from repeated head exposures may carry risks of long-term chronic changes in the brain's function and structure. To study the physical sensitivities of the brain to mild head impacts, we developed the first dynamic model of the skull-brain based on in vivo MRI data. We showed that the motion of the brain can be described by a rigid-body with constrained kinematics. We further demonstrated that skull-brain dynamics can be approximated by an under-damped system with a low-frequency resonance at around 15 Hz. Furthermore, from our previous field measurements, we found that head motions in a variety of activities, including contact sports, show a primary frequency of less than 20 Hz. This implies that typical head exposures may drive the brain dangerously close to its mechanical resonance and lead to amplified brain-skull relative motions. Our results suggest a possible cause for mild brain trauma, which could occur due to repetitive low-acceleration head oscillations in a variety of recreational and occupational activities.

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Section: Discussionsupporting

confidence: 62%

Resonance of human brain under head acceleration

Laksari

Kurt

et al. 2015

J. R. Soc. Interface.

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“…5,12 Head impact kinematics in contact sports are investigated using the Head Impact Telemetry system 13,14 and accelerometerembedded mouthguards. 15,16 However, there are substantial knowledge gaps in the relationships between subconcussive impact kinematics and outcome measures. The ocular-motor system orchestrates accommodation and vergence, and their concomitant adjustments enable individuals to visualize an object at various distances and directions.…”

Section: Invited Commentarymentioning

confidence: 99%

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

et al. 2016

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IMPORTANCE An increased understanding of the relationship between subconcussive head impacts and near point of convergence (NPC) ocular-motor function may be useful in delineating traumatic brain injury.OBJECTIVE To investigate whether repetitive subconcussive head impacts during preseason football practice cause changes in NPC. DESIGN, SETTING, AND PARTICIPANTSThis prospective, observational study of 29 National Collegiate Athletic Association Division I football players included baseline and preseason practices (1 noncontact and 4 contact), and postseason follow-up and outcome measures were obtained for each time. An accelerometer-embedded mouthguard measured head impact kinematics. Based on the sum of head impacts from all 5 practices, players were categorized into lower (n = 7) or higher (n = 22) impact groups.EXPOSURES Players participated in regular practices, and all head impacts greater than 10g from the 5 practices were recorded using the i1Biometerics Vector mouthguard (i1 Biometrics Inc). MAIN OUTCOMES AND MEASURES Near point of convergence measures and symptom scores.RESULTS A total of 1193 head impacts were recorded from 5 training camp practices in the 29 collegiate football players; 22 were categorized into the higher-impact group and 7 into the lower-impact group. There were significant differences in head impact kinematics between lower-and higher-impact groups (number of impacts, 6 vs 41 [lower impact minus higher impact = 35; 95% CI, 21-51; P < .001]; linear acceleration, 99g vs 1112g [lower impact minus higher impact= 1013; 95% CI, 621 -1578; P < .001]; angular acceleration, 7589 radian/s 2 vs 65 016 radian/s 2 [lower impact minus higher impact= 57 427; 95% CI , 31 123-80 498; P < .001], respectively). The trajectory and cumulative burden of subconcussive impacts on NPC differed by group (F for group × linear trend 1, 238 = 12.14, P < .001 and F for group × quadratic trend 1, 238 = 12.97, P < .001). In the higher-impact group, there was a linear increase in NPC over time (B for linear trend, unstandardized coefficient [SE]: 0.76 [0.12], P < .001) that plateaued and resolved by postseason follow-up (B for quadratic trend [SE]: −0.06 [0.008], P < .001). In the lower-impact group, there was no change in NPC over time. Group differences were first observed after the first contact practice and remained until the final full-gear practice. No group differences were observed postseason follow-up. There were no differences in symptom scores between groups over time. CONCLUSIONS AND RELEVANCEAlthough asymptomatic, these data suggest that repetitive subconcussive head impacts were associated with changes in NPC. The increase in NPC highlights the vulnerability and slow recovery of the ocular-motor system following subconcussive head impacts. Changes in NPC may become a useful clinical tool in deciphering brain injury severity.

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“…50,51 Linear acceleration, a lin , was not used here because a lin -induced brain strain responses are negligible because of the near incompressibility of the brain. This was confirmed in terms of both maximum principal strain, e ep (using DHIM and an independently developed head model, SIMon 36 ), and WM fiber strain, e n: :…”

Section: Idealized Head Impactsmentioning

confidence: 99%

“…In addition, a pre-computation strategy may also be effective in the context of contact sports, 32,46 because the head's impact temporal characteristics appear largely similar within or across subjects. 50,51 On the other hand, when using realistic head impacts as model inputs, tract-specific injury susceptibility indices could allow assessment of the relative injury vulnerabilities of neural pathways to identify the most vulnerable ones in real-world injury scenarios. These will be the subjects of future investigations.…”

mentioning

confidence: 99%

White Matter Injury Susceptibility via Fiber Strain Evaluation Using Whole-Brain Tractography

Zhao

Ford

Flashman

et al. 2016

Journal of Neurotrauma

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Microscale brain injury studies suggest axonal elongation as a potential mechanism for diffuse axonal injury (DAI). Recent studies have begun to incorporate white matter (WM) structural anisotropy in injury analysis, with initial evidence suggesting improved injury prediction performance. In this study, we further develop a tractography-based approach to analyze fiber strains along the entire lengths of fibers from voxel-or anatomically constrained whole-brain tractography. This technique potentially extends previous element-or voxel-based methods that instead utilize WM fiber orientations averaged from typically coarse elements or voxels. Perhaps more importantly, incorporating tractography-based axonal structural information enables assessment of the overall injury risks to functionally important neural pathways and the anatomical regions they connect, which is not possible with previous methods. A DAI susceptibility index was also established to quantify voxel-wise WM local structural integrity and tract-wise damage of individual neural pathways. This ''graded'' injury susceptibility potentially extends the commonly employed treatment of injury as a simple binary condition. As an illustration, we evaluate the DAI susceptibilities of WM voxels and transcallosal fiber tracts in three idealized head impacts. Findings suggest the potential importance of the tractography-based approach for injury prediction. These efforts may enable future studies to correlate WM mechanical responses with neuroimaging, cognitive alteration, and concussion, and to reveal the relative vulnerabilities of neural pathways and identify the most vulnerable ones in real-world head impacts.

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An Instrumented Mouthguard for Measuring Linear and Angular Head Impact Kinematics in American Football

Cited by 187 publications

References 26 publications

Resonance of human brain under head acceleration

Resonance of human brain under head acceleration

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

White Matter Injury Susceptibility via Fiber Strain Evaluation Using Whole-Brain Tractography

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