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Time Window of Head Impact Kinematics Measurement for Calculation of Brain Strain and Strain Rate in American Football

Instrumented mouthguard and finite element head model components.

Abstract

Wearable devices have been shown to effectively measure head movement during impacts in sports such as American football. The device collects kinematic signals within a predefined time window when triggered by an impact, which are then used by finite element (FE) head models to compute brain strain and strain rate. To identify the minimum sufficient time window for FE analysis, 118 video-confirmed on-field football impacts recorded by the Stanford Instrumented Mouthguard were analyzed. Simulations using truncated kinematics were compared with the original full window. Considering individual differences in brain geometry, six representative brain models were included. Larger brains required longer time windows, but a pre-trigger of 40 ms and post-trigger of 70 ms yielded strain and strain-rate calculations not significantly different from the original 200 ms window. A total duration of approximately 110 ms is recommended for accurate modeling of football impacts.

DOI Source Document
Time Window of Head Impact Kinematics Measurement for Calculation of Brain Strain and Strain Rate in American Football
Predictive Factors of Kinematics in Traumatic Brain Injury from Head Impacts Based on Statistical Interpretation

Feature importance heatmap for traumatic brain injury prediction.

Abstract

This study investigates the predictive power of various rotational kinematic factors for traumatic brain injury by analyzing their relationships with 95% maximum principal strain (MPS95). Using datasets from laboratory tests, American football, MMA, NHTSA crash tests, and NASCAR events, the study evaluates derivative orders, directions, and polynomial powers of rotational velocity and acceleration. Through regression models and statistical interpretation—including zero-order correlation, structure coefficients, commonality analysis, and dominance analysis—the study identifies angular acceleration, magnitude, and first-power features as the most predictive across most datasets, with notable exceptions in MMA and NASCAR impacts. The results highlight that predictive kinematic factors vary substantially across impact types.

DOI Source Document
Predictive Factors of Kinematics in Traumatic Brain Injury from Head Impacts Based on Statistical Interpretation
The Relationship Between Brain Injury Criteria and Brain Strain Across Different Types of Head Impacts Can Be Different

Brain injury criteria and head impact kinematics across datasets.

Abstract

This study evaluates how brain injury criteria (BIC) relate to brain strain across diverse types of head impacts including sports collisions and automotive crash tests. Using linear regression models, the study analyzes 95% maximum principal strain, regional strain metrics, and cumulative strain damage across 18 BIC. Results demonstrate significantly different relationships between BIC and brain strain across datasets, showing that a given BIC value can correspond to different strain levels depending on impact type. These findings highlight the limitations of applying a BIC developed from one impact type to another and emphasize the need for context-specific injury risk estimation.

DOI Source Document
The Relationship Between Brain Injury Criteria and Brain Strain Across Different Types of Head Impacts Can Be Different
Rapid Estimation of Entire Brain Strain Using Deep Learning Models

Predicted whole-brain strain fields from the deep learning head model.

Abstract

This study proposes a deep learning head model for rapid estimation of whole-brain strain during head impacts. A five-layer deep neural network with feature engineering was trained on 2511 head impacts obtained from finite element simulations and on-field measurements in college football and mixed martial arts. The model predicts the maximum principal strain (Green–Lagrange) for all brain elements in less than 0.001 seconds, achieving an average RMSE of 0.022 with a standard deviation of 0.001 across repeated training runs. This approach enables fast, accurate estimation of brain deformation and supports potential clinical use in real-time traumatic brain injury detection.

DOI Source Document
Rapid Estimation of Entire Brain Strain Using Deep Learning Models
A new open-access platform for measuring and sharing mTBI data

Open-access mTBI data workflow and impact-detection pipeline.

Abstract

1 Vol.:(0123456789)Scientific Reports | (2021) 11:7501 | https://doi.org/10.1038/s41598-021-87085-2 www.nature.com/scientificreports A new open‑access platform for measuring and sharing mTBI data August G. Domel1,12, Samuel J. Raymond1,12*, Chiara Giordano1,12, Yuzhe Liu1, Seyed Abdolmajid Yousefsani1, Michael Fanton2, Nicholas J. Cecchi1, Olga Vovk3, Ileana Pirozzi1, Ali Kight1, Brett Avery4, Athanasia Boumis4, Tyler Fetters3, Simran Jandu4, William M. Mehring4, Sam Monga5,6, Nicole Mouchawar7, India Rangel4, Eli Rice4, Pritha Roy4, Sohrab Sami4, Heer Singh4, Lyndia Wu1,8, Calvin Kuo2,9, Michael Zeineh7, Gerald Grant10,11 & David B. Camarillo1,2,11 Despite numerous research efforts, the precise mechanisms of concussion have yet to be fully uncovered. Clinical studies on high‑risk populations, such as contact sports athletes, have become more common and give insight on the link between impact severity and brain injury risk through the use of wearable sensors and neurological testing. H

DOI Source Document
A new open-access platform for measuring and sharing mTBI data
Emergency ventilator for COVID-19

Emergency ventilator prototype and pneumatic design.

Abstract

RESEA RCH ARTICL E A low-cost, highly functional, emergency use ventilator for the COVID-19 crisis Samuel J. Raymond ID 1 *, Sam Baker 2 , Yuzhe Liu 1 , Mauricio J. Bustamante 3 , Brett Ley 4 , Michael J. Horzewski 5 , David B. Camarillo 1,5,6,7☯ , David N. Cornfield 8☯ 1 Department of Bioenginee ring, Stanford University , Stanford, CA, United States of America, 2 Department of Comp arative Medicine, Stanford University , Stanford, CA, United States of America, 3 Department of Electrica l Engineeri ng and Computer Science, UC Berkeley, CA, United States of America, 4 Kaiser Pulmon ology and Critical Care, Fontana, CA, United States of America, 5 O2U Inc., Stanfor d, CA, United States of America, 6 Department of Mechanic al Engineering, Stanford University, Stanfor d, CA, United States of America, 7 Department of Neurosur gery, Stanfor d University, Stanford , CA, United States of America, 8 Department of Pediat rics-Pulm onary Medicine, Stanford University , Stanford, CA, United State

William P. King, Jennifer Amos, Magdi Azer, Daniel Baker, Rashid Bashir, Catherine Best, Eliot Bethke, Stephen A. Boppart, Elisabeth Bralts, Ryan M. Corey, Rachael Dietkus, Gary Durack, Stefan Elbel, Greg Elliott, Jake Fava, Nigel Goldenfeld, Molly H. Goldstein, Courtney Hayes, Nicole Herndon, Shandra Jamison, Blake Johnson, Harley Johnson, Mark Johnson, John Kolaczynski, Tonghun Lee, Sergei Maslov, Davis J. McGregor, Derek Milner, Ralf Moller, Jonathan Mosley, Andy Musser, Max Newberger, David Null, Lucas O'Bryan, Michael Oelze, Jerry O'Leary, Alex Pagano, Michael Philpott, Brian Pianfetti, Alex Pille, Luca Pizzuto, Brian Ricconi, Marcello Rubessa, Sam Rylowicz, Clifford Shipley, Andrew C. Singer, Brian Stewart, Rachel Switzky, Sameh Tawfick, Matthew Wheeler, Karen White, Evan M. Widloski, Eric Wood, Charles Wood, Abigail R. Wooldridge
DOI Source Document
Emergency ventilator for COVID-19
Concussion and the severity of head impacts in mixed martial arts

Article overview for mixed martial arts head-impact measurements.

Abstract

Concern about the consequences of head impacts in US football has motivated researchers to investigate and develop instrumentation to measure the severity of these impacts. However, the severity of head impacts in unhelmeted sports is largely unknown as miniaturised sensor technology has only recently made it possible to measure these impacts in vivo. The objective of this study was to measure the linear and angular head accelerations in impacts in mixed martial arts, and correlate these with concussive injuries. Thirteen mixed martial arts fighters were fitted with the Stanford instrumented mouthguard (MiG2.0) participated in this study. The mouthguard recorded linear acceleration and angular velocity in 6 degrees of freedom. Angular acceleration was calculated by differentiation. All events were video recorded, time stamped and reported impacts confirmed. A total of 451 verified head impacts above 10g were recorded during 19 sparring events (n = 298) and 11 competitive events (n = 153). The average resultant linear acceleration was 38.0624.3g while the average resultant angular acceleration was 256761739 rad/s2. The competitive bouts resulted in five concussions being diagnosed by a medical doctor. The average resultant acceleration (of the impact with the highest angular acceleration) in these bouts was 86.7618.7g and 756163438 rad/s2. The average maximum Head Impact Power was 20.6kW in the case of concussion and 7.15kW for the uninjured athletes. In conclusion, the study recorded novel data for sub-concussive and concussive impacts. Events that resulted in a concussion had an average maximum angular acceleration that was 24.7% higher and an average maximum Head Impact Power that was 189% higher than events where there was no injury. The findings are significant in understanding the human tolerance to short-duration, high linear and angular accelerations.

DOI Source Document
Concussion and the severity of head impacts in mixed martial arts
Validation and Comparison of Instrumented Mouthguards for Measuring Head Kinematics and Assessing Brain Deformation in Football Impacts

Instrumented mouthguard validation setup and devices.

Abstract

Instrumented mouthguards are widely used to measure head kinematics due to the rigid coupling of upper dentition and skull. This study validates and compares five commonly used instrumented mouthguards using pneumatic impacts delivered to a Hybrid III headform. Results show all devices accurately measure peak angular acceleration, angular velocity, and brain injury criteria values. Mouthguards with sufficiently long sampling windows also provide accurate inputs for a convolutional neural network–based brain model to compute brain strain. Measurement accuracy varies with impact location but is largely insensitive to impact velocity.

DOI Source Document
Validation and Comparison of Instrumented Mouthguards for Measuring Head Kinematics and Assessing Brain Deformation in Football Impacts
Dynamic Blood-Brain Barrier Regulation in Mild Traumatic Brain Injury

Blood-brain barrier disruption patterns after repetitive head impacts.

Abstract

Whereas the diagnosis of moderate and severe traumatic brain injury (TBI) is readily visible on current medical imaging paradigms (magnetic resonance imaging [MRI] and computed tomography [CT] scanning), a far greater challenge is associated with the diagnosis and subsequent management of mild TBI (mTBI), especially concussion which, by definition, is characterized by a normal CT. To investigate whether the integrity of the blood-brain barrier (BBB) is altered in a high- risk population for concussions, we studied professional mixed martial arts (MMA) fighters and adolescent rugby players. Additionally, we performed the linear regression between the BBB disruption defined by increased gadolinium contrast extravasation on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on MRI and multiple biomechanical parameters indicating the severity of impacts recorded using instrumented mouthguards in professional MMA fighters. MMA fighters were examined pre-fight for a baseline and again within 120 h post-competitive fight, whereas rugby players were examined pre-season and again post-season or post-match in a subset of cases. DCE-MRI, serological analysis of BBB biomarkers, and an analysis of instrumented mouthguard data, was performed. Here, we provide pilot data that demonstrate disruption of the BBB in both professional MMA fighters and rugby players, dependent on the level of exposure. Our data suggest that biomechanical forces in professional MMA and adolescent rugby can lead to BBB disruption. These changes on imaging may serve as a biomarker of exposure of the brain to repetitive subconcussive forces and mTBI.

DOI Source Document
Dynamic Blood-Brain Barrier Regulation in Mild Traumatic Brain Injury
A theoretical model of the shrinking metal tubes

Axisymmetric profiles and stress contours of shrinking tubes.

Abstract

This study proposes the first theoretical model for shrinking metal tubes. According to the relation between the actual die radius and a critical value determined by tube geometry and conical angle, three deformation modes are identified. Experimental data and numerical simulations across a wide parameter range validate the model. Predictions of compressional force, reduced radius, and equivalent plastic strain agree with FEM results for die angles ≤40° and radius–thickness ratio ≥10. Influences of friction, dynamic effects, unsteady deformation stages, and conical angles are analyzed. Comparisons with expansion tubes reveal that shrinking exhibits higher energy absorption at the same deformation ratio, and an optimization is provided to maximize SEA.

DOI Source Document
A theoretical model of the shrinking metal tubes