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

McIver, Kevin G; Lee, Patrick; Bucherl, Sean; Talavage, Thomas M.; Myer, Gregory D.; Nauman, Eric A.

doi:10.1115/1.4056653

Cited by 4 publications

(4 citation statements)

References 59 publications

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“…Inclusion of a fluid return reservoir may increase the mass of the helmet substantially. Despite this, increased mass has been associated with improved helmet performance in impact testing (McIver et al, 2023), so we do not anticipate that such a modification would have negatively influenced helmet performance. However, it remains unclear how much helmet mass, rather than the physics of the liquid shock absorber, may have contributed to the improved performance of the liquid helmet model relative to the Riddell, Schutt, and Xenith helmet models, which all had lower masses than the liquid helmet.…”

Section: Figurementioning

confidence: 97%

Finite element evaluation of an American football helmet featuring liquid shock absorbers for protecting against concussive and subconcussive head impacts

Cecchi

Alizadeh

Liu

et al. 2023

Front. Bioeng. Biotechnol.

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Introduction: Concern has grown over the potential long-term effects of repeated head impacts and concussions in American football. Recent advances in impact engineering have yielded the development of soft, collapsible, liquid shock absorbers, which have demonstrated the ability to dramatically attenuate impact forces relative to existing helmet shock absorbers.Methods: To further explore how liquid shock absorbers can improve the efficacy of an American football helmet, we developed and optimized a finite element (FE) helmet model including 21 liquid shock absorbers spread out throughout the helmet. Using FE models of an anthropomorphic test headform and linear impactor, a previously published impact test protocol representative of concussive National Football League impacts (six impact locations, three velocities) was performed on the liquid FE helmet model and four existing FE helmet models. We also evaluated the helmets at three lower impact velocities representative of subconcussive football impacts. Head kinematics were recorded for each impact and used to compute the Head Acceleration Response Metric (HARM), a metric factoring in both linear and angular head kinematics and used to evaluate helmet performance. The head kinematics were also input to a FE model of the head and brain to calculate the resulting brain strain from each impact.Results: The liquid helmet model yielded the lowest value of HARM at 33 of the 36 impact conditions, offering an average 33.0% (range: −37.5% to 56.0%) and 32.0% (range: −2.2% to 50.5%) reduction over the existing helmet models at each impact condition in the subconcussive and concussive tests, respectively. The liquid helmet had a Helmet Performance Score (calculated using a summation of HARM values weighted based on injury incidence data) of 0.71, compared to scores ranging from 1.07 – 1.21 from the other four FE helmet models. Resulting brain strains were also lower in the liquid helmet.Discussion: The results of this study demonstrate the promising ability of liquid shock absorbers to improve helmet safety performance and encourage the development of physical prototypes of helmets featuring this technology. The implications of the observed reductions on brain injury risk are discussed.

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Section: Figurementioning

confidence: 97%

Finite element evaluation of an American football helmet featuring liquid shock absorbers for protecting against concussive and subconcussive head impacts

Cecchi

Alizadeh

Liu

et al. 2023

Front. Bioeng. Biotechnol.

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show abstract

“…Energy is the typical metric used to classify impact tests and, for helmet testing, is usually between 18 and 150 J (depending on the sport [95]). Where rigid anvils are used for testing, energies may be lower than those expected during actual sporting collisions and falls, with a view to maintaining similar severities, and acceleration vs. time profiles, to the actual collisions and falls [190,227,229]. Wider ranges of impact velocities, energies, and anvil compliances are used in research studies than in standards [85,95,189,229,234].…”

Section: Helmet Testingmentioning

confidence: 99%

“…As covered in section 2, there is ongoing discussion around the acceleration magnitudes and time profiles that are associated with clinical diagnosis of concussion, which should be resolved before updating standards [95]. As such, metrics are often compared to in-field measures for actual sporting collisions and falls, and those collected with an un-helmeted headform [190,[226][227][228][229].…”

Section: Helmet Testingmentioning

confidence: 99%

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Mechanical metamaterials for sports helmets: structural mechanics, design optimisation, and performance

Haid,

Foster,

Hart

et al. 2023

Smart Mater. Struct.

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Sports concussions are a public health concern. Improving helmet performance to reduce concussion risk is a key part of the research and development community response. Head impacts with compliant surfaces that cause long duration moderate or high linear and rotational accelerations are associated with a high rate of clinical diagnoses of concussion. As engineered structures with unusual combinations of properties, mechanical metamaterials are being applied to sports helmets, with the goal of improving impact performance and reducing brain injury risk. Replacing established helmet material (i.e., foam) selection with a metamaterials design approach (structuring material to obtain desired properties) allows development of near optimal properties. Objective functions based on up to date understanding of concussion could be applied to topology optimisation regimes, when designing mechanical metamaterials for helmets. Such regimes balance computational efficiency with predictive accuracy, both of which could be improved under high strains and strain rates to allow helmet modifications as knowledge of concussion develops. Researchers could also share mechanical metamaterial data, topologies and computational models in open, homogenised repositories, to improve the efficiency of their development.

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The National Football League and traumatic brain injury: blood-based evaluation at the game

Rauchman,

Placantonakis,

Reiss

2023

Concussion

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

Cited by 4 publications

References 59 publications

Finite element evaluation of an American football helmet featuring liquid shock absorbers for protecting against concussive and subconcussive head impacts

Finite element evaluation of an American football helmet featuring liquid shock absorbers for protecting against concussive and subconcussive head impacts

Mechanical metamaterials for sports helmets: structural mechanics, design optimisation, and performance

The National Football League and traumatic brain injury: blood-based evaluation at the game

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