impact-mitigation-modern-football-helmets-advances-limitations

Impact Mitigation in Modern Football Helmets: Advances and Limitations of Position-Specific Designs

It has been established that repetitive head impacts lead to the accrual of changes in brain function, structure, and chemistry. The helmet is the primary ...

University of Cincinnati

Research suggests contact sports affect neurological health. This study used permutation-based mediation statistics to integrate measures of metabolomics, neuroinflammatory miRNAs, and virtual reality (VR)-based motor control to investigate multi-scale relationships across a season of collegiate American football. Fourteen significant mediations (six pre-season, eight across-season) were observed where metabolites  mediated the statistical relationship between miRNAs and VR-based motor control (   0.05; total effect  50%), suggesting a hypothesis that metabolites sit in the statistical pathway between transcriptome and behavior. Three results further supported a model of chronic neuroinflammation, consistent with mitochondrial dysfunction: (1) Mediating metabolites were consistently medium-to-long chain fatty acids, (2) tricarboxylic acid cycle metabolites decreased across-season, and (3) accumulated head acceleration events statistically moderated pre-season metabolite levels to directionally model post-season metabolite levels. These preliminary findings implicate potential mitochondrial dysfunction and highlight probable peripheral blood biomarkers underlying repetitive head impacts in otherwise healthy collegiate football athletes.

A preliminary model of football-related neural stress that integrates metabolomics with transcriptomics and virtual reality.

Observations of short-term changes in the neural health of youth athletes participating in collision sports (e.g., football and soccer) have highlighted a need to explore potential structural alterations in brain tissue volumes for these persons. Studies have shown biochemical, vascular, functional connectivity, and white matter diffusivity changes in the brain physiology of these athletes that are strongly correlated with repetitive head acceleration exposure. Here, research is presented that highlights regional anatomical volumetric measures that change longitudinally with accrued subconcussive trauma. A novel pipeline is introduced that provides simplified data analysis on standard-space template to quantify group-level longitudinal volumetric changes within these populations. For both sports, results highlight incremental relative regional volumetric changes in the subcortical cerebrospinal fluid that are strongly correlated with head exposure events greater than a 50-G threshold at the short-term post-season assessment. Moreover, longitudinal regional gray matter volumes are observed to decrease with time, only returning to baseline/pre-participation levels after sufficient (5-6 months) rest from collision-based exposure. These temporal structural volumetric alterations are significantly different from normal aging observed in sex- and age-matched controls participating in non-collision sports. Future work involves modeling repetitive head exposure thresholds with multi-modal image analysis and understanding the underlying physiological reason. A possible pathophysiological pathway is presented, highlighting the probable metabolic regulatory mechanisms. Continual participation in collision-based activities may represent a risk wherein recovery cannot occur. Even when present, the degree of the eventual recovery remains to be explored, but has strong implications for the well-being of collision-sport participants.

Normalized Brain Tissue-Level Evaluation of Volumetric Changes of Youth Athletes Participating in Collision Sports.

Contact sports participation has been shown to have both beneficial and detrimental effects on health, however little is known about the metabolic sequelae of these effects. We aimed to identify metabolite alterations across a collegiate American football season. Serum was collected from 23 male collegiate football athletes before the athletic season (Pre) and after the last game (Post). Samples underwent nontargeted metabolomic profiling and 1131 metabolites were included for univariate, pathway enrichment, and multivariate analyses. Significant metabolites were assessed against head acceleration events (HAEs). 200 metabolites changed from Pre to Post (P < 0.05 and Q < 0.05); 160 had known identity and mapped to one of 57 pre-defined biological pathways. There was significant enrichment of metabolites belonging to five pathways (P < 0.05): xanthine, fatty acid (acyl choline), medium chain fatty acid, primary bile acid, and glycolysis, gluconeogenesis, and pyruvate metabolism. A set of 12 metabolites was sufficient to discriminate Pre from Post status, and changes in 64 of the 200 metabolites were also associated with HAEs (P < 0.05). In summary, the identified metabolites, and candidate pathways, argue there are metabolic consequences of both physical training and head impacts with football participation. These findings additionally identify a potential set of objective biomarkers of repetitive head injury.

Metabolomic response to collegiate football participation: Pre- and Post-season analysis.

Participants in American football experience repetitive head impacts that induce negative changes in neurocognitive function over the course of a single season. This study aimed to quantify the transfer function connecting the force input to the measured output acceleration of the helmet system to provide a comparison of the impact attenuation of various modern American football helmets. Impact mitigation varied considerably between helmet models and with location for each helmet model. The current data indicate that helmet mass is a key variable driving force attenuation, however flexible helmet shells, helmet shell cutouts, and more compliant padding can improve energy absorption.

Design Considerations for the Attenuation of Translational and Rotational Accelerations in American Football Helmets.

Current cartilage repair therapies do not re-create the complex mechanical interface between cartilage and bone, which is critical for long-term repair durability. New biomaterial designs that include hard tissue-soft tissue interface structures offer promise to improve clinical outcomes.

Novel Osteochondral Biotemplate Improves Long-term Cartilage Repair Compared With Microfracture in an Ovine Model.

Intervertebral disc degeneration is the most recognized cause of low back pain, characterized by the decline of tissue structure and mechanics. Image-based mechanical parameters (e.g., strain, stiffness) may provide an ideal assessment of disc function that is lost with degeneration but unfortunately remains underdeveloped. Moreover, it is unknown whether strain or stiffness of the disc may be predicted by MRI relaxometry (e.g.  or ), an increasingly accepted quantitative measure of disc structure. In this study, we quantified  and  relaxation times and in-plane strains using displacement-encoded MRI within the disc under physiological levels of compression and bending. We then estimated shear modulus in orthogonal image planes and compared these values to relaxation times and strains within regions of the disc. Intratissue strain depended on the loading mode, and shear modulus in the nucleus pulposus was typically an order of magnitude lower than the annulus fibrosis, except in bending, where the apparent stiffness depended on the loading. Relative shear moduli estimated from strain data derived under compression generally did not correspond with those from bending experiments, with no correlations in the sagittal plane and only 4 of 15 regions correlated in the coronal plane, suggesting that future inverse models should incorporate multiple loading conditions. Strain imaging and strain-based estimation of material properties may serve as imaging biomarkers to distinguish healthy and diseased discs. Additionally, image-based elastography and relaxometry may be viewed as complementary measures of disc structure and function to assess degeneration in longitudinal studies.

Intervertebral Disc Elastography to Relate Shear Modulus and Relaxometry in Compression and Bending.

This review highlights the biomechanical foundations of braille and tactile graphic discrimination within the context of design innovations in information access for the blind and low-vision community. Braille discrimination is a complex and poorly understood process that necessitates the coordination of motor control, mechanotransduction, and cognitive-linguistic processing. Despite substantial technological advances and multiple design attempts over the last fifty years, a low-cost, high-fidelity refreshable braille and tactile graphics display has yet to be delivered. Consequently, the blind and low-vision communities are left with limited options for information access. This is amplified by the rapid adoption of graphical user interfaces for human-computer interaction, a move that the blind and low vision community were effectively excluded from. Text-to-speech screen readers lack the ability to convey the nuances necessary for science, technology, engineering, arts, and math education and offer limited privacy for the user. Printed braille and tactile graphics are effective modalities but are time and resource-intensive, difficult to access, and lack real-time rendering. Single- and multiline refreshable braille devices either lack functionality or are extremely cost-prohibitive. Early computational models of mechanotransduction through complex digital skin tissue and the kinematics of the braille reading finger are explored as insight into device design specifications. A use-centered, convergence approach for future designs is discussed in which the design space is defined by both the end-user requirements and the available technology.

Biomechanical Considerations of Refreshable Braille and Tactile Graphics Toward Equitable Access: A Review.

The ability of bacteria to sense and respond to mechanical forces has important implications for pathogens during infection, as they experience wide fluid shear fluctuations in the host. However, little is known about how mechanical forces encountered in the infected host drive microbial pathogenesis. Herein, we combined mathematical modeling with hydrodynamic bacterial culture to profile transcriptomic and pathogenesis-related phenotypes of multidrug resistant . Typhimurium (ST313 D23580) under different fluid shear conditions relevant to its transition from the intestinal tract to the bloodstream. We report that D23580 exhibited incremental changes in transcriptomic profiles that correlated with its pathogenic phenotypes in response to these progressive increases in fluid shear. This is the first demonstration that incremental changes in fluid shear forces alter stress responses and gene expression in any ST313 strain and offers mechanistic insight into how forces encountered by bacteria during infection might impact their disease-causing ability in unexpected ways.

Incremental increases in physiological fluid shear progressively alter pathogenic phenotypes and gene expression in multidrug resistant .

 The 2014 American Academy of Pediatrics recommendation for CPAP as an alternative to mechanical ventilation for treatment of neonatal respiratory distress prompted a rapid shift to noninvasive respiratory support. Since most patients receive nasal bubble CPAP a concomitant increase in nasal pressure injuries followed. This prospective observational study aimed to develop strategies to reduce nasal mask pressure injury in neonates by (1) quantifying CPAP mask-interface pressure and (2) assessing placement variability.  A micro-electromechanical systems pressure sensor was modified for contact pressure measurements with silicone embedding and calibrated. The CPAP generator and interface components were sized for a 24-week neonatal simulator. Thirteen neonatal ICU staff placed the simulator on CPAP at 6 cm HO and 8 L/min of flow with no humidification. Pressure was measured at 3 locations (the forehead, nasal bridge, and philtrum) in triplicate (3 measurements/site). Descriptive statistics; a location-specific, one-way analysis of variance with a Tukey post hoc test; and a 2-sample paired  test of the means of the first and last triplicate were performed.  Pressure ranged from 12-377.3 mm Hg. The mean [SD] interface pressure at the philtrum was significantly higher than both the nasal bridge and the forehead (philtrum 173.9 [101.3], nasal bridge 67.8 [28.9], and forehead 79.0 [36.9],  < .001). CPAP fixation varied, including bonnet placement, trunk angle, mask compression, use of hook and loop extenders, and level of vigorous bubble feedback achieved.  This study developed a modified pressure sensor for quantifying the pressure exerted by a nasal mask on facial skin. Maximum pressures were higher than those previously reported. Inter-individual differences were present in both quantitative and qualitative measures of pressure. Reduction of NIV-associated pressure injuries may be achieved through NIV fixation technique training and improved nasal mask stability and size increments.

Neonatal Noninvasive Ventilation Nasal Mask Interface Pressure and the Inter-Individual Variation of Mask Placement.

Osteoporosis is a common metabolic bone disorder characterized by low bone mass and microstructural degradation of bone tissue due to a derailed bone remodeling process. A deeper understanding of the mechanobiological phenomena that modulate the bone remodeling response to mechanical loading in a healthy bone is crucial to develop treatments. Rodent models have provided invaluable insight into the mechanobiological mechanisms regulating bone adaptation in response to dynamic mechanic stimuli. This study sheds light on these aspects by means of assessing the mechanical environment of the cortical and cancellous tissue to in vivo dynamic compressive loading within the mouse tibia using microCT-based finite element model in combination with diaphyseal strain gauge measures. Additionally, this work describes the relation between the mid-diaphyseal strains and strain gradients from the finite element analysis and bone formation measures from time-lapse in vivo tibial loading with a fluorochrome-derived histomorphometry analysis. The mouse tibial loading model demonstrated that cancellous strains were lower than those in the midshaft cortical bone. Sensitivity analyses demonstrated that the material property of cortical bone was the most significant model parameter. The computationally-modeled strains and strain gradients correlated significantly to the histologically-measured bone formation thickness at the mid-diaphyseal cross-section of the mouse tibia.

Computationally derived endosteal strain and strain gradients correlate with increased bone formation in an axially loaded murine tibia model.

Rodent models have offered valuable insights into the mechanobiological mechanisms that regulate bone adaptation responses to dynamic mechanical stimuli. However, using avian models may provide new insights into the mechanisms of bone adaptation to dynamic loads, as bird bones have distinct features that differ from mammalian bones. This paper illuminates these aspects by evaluating the mechanical environment in a novel avian, chukar partridge tibiotarsus (TBT), during fast locomotion and in cortical and cancellous tissue under in vivo dynamic compressive loading within the TBT. We measured in vivo mechanical strains at the TBT midshaft on the anterior, medial, and posterior surfaces during locomotion at various treadmill speeds. The mean in vivo strains measured on the anterior, medial, and posterior surfaces of the TBT midshaft were 154 με, -397 με, and -438 με, respectively, at a treadmill speed of 2 m/s. The mean experimentally measured strains on the anterior, medial, and posterior surfaces of the TBT were 114.7 με, -952.6 με, and -593.7 με under an in vivo dynamic compressive load of 130 N. The study, which employs a micro-computed tomography (microCT) based finite element model in combination with diaphyseal strain gauge measures, found that cancellous strains were greater than those in the midshaft cortical bone. Sensitivity analyses revealed that the material property of cortical bone was the most significant model parameter. In the midshaft cortical volume of interest (VOI), daily dynamic loading increased the maximum moment of inertia and reduced the bone area in the loaded limb compared to the contralateral control limb after three weeks of loading. Despite the strong correlations between the computationally modeled strains and experimentally measured strains at the medial and posterior gauge sites, no correlations existed between the computationally modeled strains and strain gradients, and histologically measured bone formation thickness at the mid-diaphyseal cross-section of the TBT.

Characterization of strains induced by in vivo locomotion and axial tibiotarsal loading in a chukar partridge model.

The development of a collagen-nanoscale hydroxyapatite three-dimensional (3D) in vitro culture system for reproducing osteocyte differentiation and tissue mineralization.

Contact sports affect measures at multiple scales such as transcriptomics, metabolomics, brain function, and behavior, but studies have not yet studied the statistical structure of how they are integrated. This preliminary study, examining collegiate American football players, integrated across-season changes (Δ) from transcriptomic and metabolomic variables (neuroinflammatory miRNAs and metabolites), neuroimaging (resting-state fMRI network ), and virtual reality (VR)-based motor control. These findings were then assessed against head acceleration events (HAE). Using permutation-based moderation analysis (all   0.05  , we observed that (1) Δtridecenedioate, a mono-unsaturated fatty acid, interacted with ΔmiR-505 to predict default mode network (DMN) , meaning the interaction between two molecular biology measures predicted a neuroimaging measure. Further, (2) Δtridecenedioate and DMN  interacted to predict motor control, indicating the interaction of a molecular and a neuroimaging measure predicted behavior. ΔmiR-505 was positively related to HAE and DMN  was negatively related to HAE and reduced relative to non-athlete subjects. These multi-scale, moderating relationships between a potential ROS scavenger, neuroinflammatory miRNA, reduced brain connectivity, and diminished motor control argue that seemingly healthy athletes with frequent HAE may experience chronic neuroinflammation. This  framework using permutation-based mediation/moderation analysis has general applicability for human-animal translational studies.

Integrating multi-omics with neuroimaging and behavior: A preliminary model of dysfunction in football athletes.

Tracheoesophageal fistula (TEF), often occurring with esophageal atresia (EA), presents significant respiratory challenges in neonates. Neither the effect of EA/TEF, nor the effect of post-surgical complications such as tracheomalacia, on respiratory effort has been previously quantified. This study calculates the tracheal resistive component of work of breathing (TR-WOB) to quantify breathing effort pre- and post-surgical repair of EA/TEF. The primary objective of this study was to calculate the TR-WOB before and after surgical repair and compare it to normal values.

Article	Year
A preliminary model of football-related neural stress that integrates metabolomics with transcriptomics and virtual reality. iScience\| PubMed ID: 35106455	2022
Normalized Brain Tissue-Level Evaluation of Volumetric Changes of Youth Athletes Participating in Collision Sports. Neurotrauma reports\| PubMed ID: 35112108	2022
Metabolomic response to collegiate football participation: Pre- and Post-season analysis. Scientific reports\| PubMed ID: 35197541	2022
Design Considerations for the Attenuation of Translational and Rotational Accelerations in American Football Helmets. Journal of biomechanical engineering\| PubMed ID: 36628996	2023
Novel Osteochondral Biotemplate Improves Long-term Cartilage Repair Compared With Microfracture in an Ovine Model. The American journal of sports medicine\| PubMed ID: 37602735	2023
Intervertebral Disc Elastography to Relate Shear Modulus and Relaxometry in Compression and Bending. bioRxiv : the preprint server for biology\| PubMed ID: 37732250	2023
Biomechanical Considerations of Refreshable Braille and Tactile Graphics Toward Equitable Access: A Review. Journal of biomechanical engineering\| PubMed ID: 38421346	2024
Incremental increases in physiological fluid shear progressively alter pathogenic phenotypes and gene expression in multidrug resistant . Gut microbes\| PubMed ID: 38783686	2024
Neonatal Noninvasive Ventilation Nasal Mask Interface Pressure and the Inter-Individual Variation of Mask Placement. Respiratory care\| PubMed ID: 39379162	2025
Computationally derived endosteal strain and strain gradients correlate with increased bone formation in an axially loaded murine tibia model. Journal of the mechanical behavior of biomedical materials\| PubMed ID: 39388844	2024
Characterization of strains induced by in vivo locomotion and axial tibiotarsal loading in a chukar partridge model. Bone\| PubMed ID: 40280253	2025
The development of a collagen-nanoscale hydroxyapatite three-dimensional (3D) in vitro culture system for reproducing osteocyte differentiation and tissue mineralization. Biomaterials\| PubMed ID: 40554221	2026
Integrating multi-omics with neuroimaging and behavior: A preliminary model of dysfunction in football athletes. Neuroimage. Reports\| PubMed ID: 40567291	2021
Tracheal Work of Breathing in Neonates With Tracheoesophageal Fistula Before and After Surgical Repair via Computational Fluid Dynamics Assessment. Journal of pediatric surgery\| PubMed ID: 40907879	2025

Eric A. Nauman

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