Category Archives: helmet expert

Helmet expert Dr. John Lloyd has served attorneys nationwide for 25+ years in biomechanics, human factors, helmet testing and motorcycle accident expert

Helmets Do Not Prevent Brain Injury?

In a word. No.

A better question might be “Can Helmets Prevent Brain Injury?” Same answer – No.

It is not currently possible to develop a helmet that can protect all persons under all foreseen and unforeseen circumstances. But, given current medical understanding of head and brain injuries as well as 21st Century advanced materials, it is certainly possible to protect most people from life-threattening brain injuries under foreseen circumstances.

Helmets are actually intended to protect against blunt trauma injuries to the head. They are not specifically designed to prevent brain injuries.

The mechanisms which cause head and brain injuries are quite different. Forces associated with linear accelerations are responsible for visible injuries, such as lacerations, contusions and skull fracture. Whereas, brain injuries, including concussions, axonal injury and subdural hematoma are caused by forces associated with angular / rotational accelerations. When the head impacts a surface, the skull may come to an abrupt stop, but inertia acting on the brain will cause it to continue to move This inertia strains the nerves and blood vessels of the brain, causing injuries. The type of injury is dependent on the magnitude of this strain and the time duration over which it acts on the brain.

Helmets may indeed reduce the rotational forces acting on the brain. But since helmets are not currently certified according to their ability to protect against brain injury the level of protection is not standardized. Hence, it is possible to sustain catastrophic brain injuries, even while wearing a helmet.

I have performed extensive biomechanical testing of helmets for various applications, including military, motorcycle, football, skiing / snowboarding and cycling. My testing involves measurement of both linear and angular accelerations, thereby characterizing helmets in terms of their ability to protect against head and brain injuries. Results vary substantially between manufacturers that offer helmets for particular applications and between applications. Based on my testing to date, I can report that certain football helmets seem to outperform helmets in other categories in terms of their ability to protect against head and brain injuries.

Much research has been conducted to understand and quantify biomechanical thresholds for various head and brain injuries, including skull fractures, concussions, axonal injury (damage to nerve fibers in the brain) and subdural hematomas (bleeding in the brain). Why then don’t all helmet manufacturers strive to provide necessary protection?

There are certain intrinsic or personal factors that might increase one’s risk of head and brain injury, but for the rest of us, why do helmets provide inadequate protection against life-threatening head and brain injuries during reasonable or foreseen use?

One example of this is the life-threatening brain injury which former Formula One superstar, Michael Schumaker sustained when he fell while skiing and impacted a rock. It has been reported that Mr. Schumaker was only skiing at about 13mph when he fell and the likelihood of impacting a fixed object while skiing, such as a tree or rock is certainly not unforeseen. So why did his helmet fail to provide necessary protection?

helmet - Dr. John Lloyd

Advanced materials certainly exist to provide required protection for normal persons, including Mr. Schumaker and many other unfortunate victims, under normal or foreseen circumstances. As end-users, we must demand that regulatory organizations require helmet manufacturers meet standards that protect persons who are not otherwise at heightened risk from head and brain injuries due to foreseen circumstances.

NI Week features John Lloyd football helmet expert

Football helmet expert, Dr. John Lloyd,  had the privilege to present his research on football helmets as part of the Keynote address at the National Instrument conference in Austin, TX this week. The audience of 5,000+ attendees learned about Dr. Lloyd’s research into biomechanics of the brain.

It has been said that helmets cannot prevent concussions. I disagree.

As a biomechanist I have dedicated my career to studying the biomechanics of brain injuries. There are two key mechanical forces that give rise to head and brain injuries (1) linear forces, which are responsible for visible injuries, including bruising and skull fractures, and (2) rotational forces, which cause invisible injuries, such as concussion and brain injury.

Since helmets are currently designed to pass testing standards that focus on linear forces only, it is no surprise that helmets have limited benefit in preventing concussions. Through advances in medicine we have learned that concussions can potentially have life-long neurological consequences, including memory impairement and personality changes / behavioral effects.

Over the past years I have developed and validated a testing method to evaluate helmets in terms of their ability to protect against both linear and rotational forces. Using this apparatus I characterized football helmets, results of which have been submitted to Science for publication.

Based on lessons learned from my biomechanical evaluation of various sports helmets, I have devised a matrix of shear-thickening non-Newtonian materials. A prototype helmet was constructed using this matrix liner, results of which show that rotational forces that cause concussion and other brain injuries are reduced by up to 50% compared to a leading football helmet, while also reducing linear forces.sport concussion and sport accident reconstruction expert Dr. John Lloyd

It is my goal and my passion to work with leading helmet companies to make this technology available to players and sports participants of all aged to enhance their protection against brain trauma. I am looking to collaborate with one manufacturer in each sport to offer an exclusive license patent-pending technology.

Testing Proves Motorcycle Helmets Provide Inadequate Protection Against TBI

Motorcycle accident victims account for more than 340,000 fatalities annually, with the United States ranking 8th highest worldwide in the number of motorcycle accident deaths. 75% of all fatal motorcycle accidents involve brain injury, with rotational forces acting on the brain the primary cause of mortality. Current motorcycle helmets are effective at reducing head injuries associated with blunt impact. However, the mechanism of traumatic brain injury is biomechanically very different.

Samples of 9 motorcycle helmet models, representing full-face, three-quarter and shorty designs were evaluated. Helmets, fitted to an instrumented Hybrid III head and neck, were dropped at 13 mph in accordance with DOT motorcycle helmet testing standards.

motorcycle helmet testing

Results show that, on average, there is a 67% risk of concussion and a 10% probability of severe or fatal brain injury associated with a relatively minor 13mph helmeted head impact.

In conclusion, motorcycle helmets provide inadequate protection against concussion and severe traumatic brain injury associated with even relatively minor head impact

New Football Helmet Reduces Brain Injury

John Lloyd of BRAINS, Inc. announced today that football head injuries and concussions can be reduced up to 50 percent with their new helmet safety breakthrough. 

New Helmet Technology Reduces Brain Injuries - football helmet prototype by Dr. John Lloyd | expert

San Antonio, FL – Dr.John Lloyd PhD of BRAINS, Inc. announced their latest breakthrough in football helmet safety today. The unique new helmet technology promises to provide up to 50 percent more protection against football head injuries and concussions. The technology has wide application and can be used in every kind of helmet from baby helmets to military helmets, and for all athletes at risk of concussion and head injuries such as football players, cyclists, skiers, snowboarders, skateboarders, hockey players, baseball players, lacrosse players, boxers, soccer players, equestrian / horse-riding sports, such as polo and horse racing, as well as motorcycle and race car drivers.

Recent medical research documents found that concussions and cumulative head impacts can lead to lifelong neurological consequences such as chronic traumatic encephalopathy, a degenerative brain disease known as CTE and early Alzheimer’s.

The U.S. Centers for Disease Control and Prevention, estimates 1.6 – 3.8 million sport-related brain injuries annually in the United States. Of these 300,000 are attributed to youth football players, some of whom die from their injuries every year – a tragedy difficult for their mothers and families to recover from.

The severity of the issue touching both the nation’s youth and professional athletes has led to thousands of lawsuits and Congressional Hearings. Growing concern has spread to the White House where President Obama recently spoke at the Healthy Kids and Safe Sports Concussion Summit.

The BRAINS, Inc. research team, led by renowned brain injury expert, Dr. John Lloyd, has worked for years on their project to help make sports safer. A controversial subject, some opponents have stated that concussion prevention is impossible. Dedicated to saving lives and preserving brain health, Dr. Lloyd and team persevered with their work leading to this new innovation. “Our results show that forces associated with concussion and brain injury are reduced up to 50% compared to similar testing with a leading football helmet,” said Dr. John Lloyd, Research Director.

“The patent-pending matrix of non-Newtonian materials will not only benefit football, but can be utilized in all sports helmets as well as military, motorcycle and even baby helmets to improve protection and dramatically reduce the risk of brain injuries,” reported Dr. Lloyd.

The materials are inexpensive, and produce a helmet that is considerably lighter and more comfortable than a traditional helmet.   Two additional applications of this new safety technology include medical flooring especially in hospitals and nursing homes or child play areas , as well as vehicle interiors.

About BRAINS, Inc.

BRAINS, Inc. located in San Antonio, Florida, is a research and development company focused on the biomechanics of brain injuries. The company was founded in 2011 by John D. Lloyd Bio, Ph.D., CPE, CBIS, Board Certified Ergonomist and Certified Brain Injury Specialist. He has also provided expert witness services nationwide for over 20 years in the fields of biomechanics, ergonomics and human factors, specializing in the biomechanics of brain injury, including sport and motorcycle helmet cases, slips and falls, motor vehicle accidents and pediatric head trauma. BRAINS, Inc. is open to licensing with manufacturers to bring this much-needed technology to market for the protection of sports participants and athletes of all ages. For additional information visit : http://drbiomechanics.com/sports-helmet-football-helmets/new-helmet-technology/  or call 813-624-8986.

Motorcycle Helmet Standards

Motorcycle helmets were originally developed in the early 20th century and, like most helmets, are modeled after military helmets, the purpose of which is to protect against penetrating head injury. The modern motorcycle helmet, with a hard outer shell and rigid expanded polystyrene (EPS) liner was actually introduced over 60 years ago. The outer shell serves as a second skull, dispersing the impact force over a wider surface area, while the inner shell compresses in an attempt to reduce translational forces. A mechanism to mitigate tangential forces is absent. Since the liner fills the entire inner surface of the shell, tangential forces cannot be absorbed and are transmitted directly to the head and brain. Motorcycle helmet standards focus on reducing the effect of linear impact forces by dropping them from a given height onto an anvil and measuring the resultant peak linear acceleration.

Motorcycle Helmet Standards

In motorcycle helmet testing, the risk of impact loading injuries, such as skull fractures, can be determined by measuring linear accelerations experienced by a surrogate head form in response to impact. Whereas risk of impulse or inertial loading injuries, such as concussion, axonal injury and subdural hematoma can be quantified by measuring impact-related angular accelerations at the center of mass of a test head form.

Unfortunately, the evolution of motorcycle helmet design is not driven by advances in scientific knowledge, but rather by the need to meet applicable testing standards. In the United States, standards include the federal motor vehicle safety standard (FMVSS) #218, commonly known as the DOT motorcycle helmet testing standards, and Snell M2015, while ECE 22.05 and BSI 6658 were adopted in European countries. Test procedures involve dropping a helmeted head form onto various steel anvils at impact velocities ranging from only 5.0 to 7.75 m/s (11-17 mph). Pass/fail is based on the ability of the helmet to provide protection against forces associated with linear acceleration in response to impact.

Current motorcycle helmet testing standards do not incorporate measures of angular acceleration and therefore fail to assess whether helmets offer protection against catastrophic brain injuries. The omission of this critical measure is reflected epidemiologically in the disproportion of closed head injuries in fatal motorcycle accidents.

Helmets Do Not Prevent Brain Injury

Helmets are intended to minimize blunt force trauma to the head, such as skull fracture, lacerations and contusions. Whereas risk of diffuse brain injuries, such as concussion, brain bleeding and axonal injuries are caused when brain tissue, nerves and blood vessels stretch and tear as the head moves suddenly but the brain lags behind. The type of brain injury is dependent on the magnitude of this strain and the time duration over which it acts on the brain.

Risk of focal head and brain injury is measured in terms of peak linear acceleration associated with impact, while risk of diffuse brain injury is measurable in terms of peak angular acceleration.

While helmets can prevent fatalities associated with penetrating head trauma, it may be argued that protection against diffuse brain injury is of paramount importance. After all, cuts, bruises and even bone fractures will heal, but brain injuries often have life long neurologically devastating effects.

Unfortunately, helmet testing standards addresses only the risk of blunt force trauma, not risk of brain injury.

Helmets may reduce the rotational forces acting on the brain. But since helmets are not currently certified according to their ability to protect against brain injury the level of protection is not standardized. Hence, it is possible to sustain catastrophic diffuse brain injuries, even while wearing a helmet.

As a biomechanics researcher, Dr. John Lloyd has dedicated his career to understanding the biomechanics of brain injuries. One objective of which is to develop a new generation of helmets for sports and motorcycling using “intelligent” materials that hold great promise for reducing the risk of traumatic brain injuries.

Dr. Lloyd’s biomechanics laboratory employs a specialized helmet testing apparatus for evaluating the risk of both head and brain injuries. This apparatus has been published in a peer-reviewer journal.motorcycle football sports helmet expertUsing this apparatus, Dr. Lloyd, evaluates the linear and rotational forces associated with specific impact events, such as a motorcycle crash or sports injury, to determine whether an unhelmeted condition, or the type of helmet might have prevented the injury sustained. This apparatus has also been used to investigate whether a particular helmet failed to perform or did not meet scientifically-acceptable levels of protection.

Traditional testing of motorcycle helmets focuses on reducing the effect of linear impact forces by dropping them from a given height onto an anvil and measuring the resultant peak linear acceleration. According to the Federal Motor Vehicle Safety Standard (FMVSS) 218, commonly known as the DOT helmet standard, the test involves dropping a motorcycle helmet onto a flat steel and hemispherical anvil at an impact velocity of 6.0 m/s (13.4 mph).  In general, if the resultant peak linear acceleration is less than 400G, the helmet is considered acceptable. Current motorcycle helmet testing standards do not incorporate measures of angular acceleration and therefore do not address whether any motorcycle helmet can provide protection against diffuse brain injuries, including concussion.

In 1995, the European Commission Directorate General for Energy and Transport initiated a Cooperative Scientific and Technical Research (COST) program to investigate Motorcycle Safety Helmets. Several agencies from Finland, the United Kingdom, France and Germany participated in this study, which compiled and analyzed data from 4,700 motorcycle fatalities in Europe, each year. The COST report [i] documents that 75% of all fatal motorcycle accidents involve head injury. Linear forces were present in only 31% of fatal head injuries, while rotational forces were found to be the primary cause in over 60% of cases.

Dr. Lloyd recently conducted independent testing of various motorcycle helmets utilizing a methodology that has been peer-reviewed [i] and has survived a Daubert motion for exclusion [ii]. The following figure presents peak angular acceleration results of repeated testing of various motorcycle helmets, including: (i) Voss novelty helmet, (ii) Bell shorty helmet, (iii) Daytona shorty helmet, and (iv) Bell full-face helmet, compared with an unhelmeted condition for impacts onto concrete at approximately 20mph. The red horizontal line on the figure indicates the 50% threshold for concussive trauma, as defined by Pellman et al [iii].risk of brain injuries measured by helmet test system - John Lloyd PhD

Results show that while a novelty or DOT approved motorcycle helmet will reduce the peak angular acceleration associated with a head impact relative to an unhelmeted condition, the level of protection is not sufficient to prevent diffuse brain injury in a typical motorcycle accident.

[i]     Caccese V, Ferguson J, Lloyd J, Edgecomb M, Seidi M and Hajiaghamemar M: Response of an Impact Test Apparatus for Fall Protective Headgear Testing Using a Hybrid-III Head/Neck Assembly. Experimental Techniques, 2014.

[ii]     Superior Court, Judicial District of Hartford, CT. Docket Number: HHD-CV-13-6043998-S. Case Caption: SHUMBO, JAKE Et Al v. K2 SPORTS USA Et Al. Order #227.86 regarding: 03/02/2015 Motion to Exclude Expert Testimony. Notice Issued: 07/09/2015

[iii] Pellman EJ, Viano DC, Tucker AM, Casson IR, Waeckerle JF: Concussion in professional football: reconstruction of game impacts and injuries. Neurosurgery 53(4): 799-812, 2003

[iv]     COST-327 report of the European Commission Directorate General for Energy and Transport on Motorcycle Safety Helmets. (1999).

Helmeted Motorcyclist Fatality

Two helmeted motorcyclist were traveling on a rural state road when a tractor-trailer driver failed to see the bikes and made a left turn in front of them to enter a truck stop. The rider in the right track had little time to respond and collided head first into the box trailer. He was pronounced deceased at the scene.

Helmeted motorcyclist fatality refers to the unfortunate occurrence of a motorcyclist dying in an accident despite wearing a helmet, highlighting the limitations of helmet protection in extreme crashes or severe impacts.

The helmeted motorcyclist was wearing a non-compliant or ‘novelty’ helmet, which did not meet DOT motorcycle helmet standards (FMVSS 218). Opposing counsel claimed that had the biker been wearing a DOT-certified motorcycle helmet he may have survived the impact.

The motorcyclist wore a non-compliant 'novelty' helmet, not meeting DOT standards. Opposing counsel argued that a DOT-certified helmet might have increased survival chances
The motorcyclist wore a non-compliant 'novelty' helmet, not meeting DOT standards. Opposing counsel argued that a DOT-certified helmet might have increased survival chances

Motorcycle helmet expert, Dr. John Lloyd, was retained to evaluate and compare the protective performance of DOT-certified and novelty motorcycle helmets.

Based on a comprehensive motorcycle accident reconstruction it was determined that the impact speed of the rider was 45 to 50 miles per hour. Motorcycle helmet certification tests typically involve impact speeds of 13-17 miles per hour. Therefore a dedicated apparatus was constructed to generate higher impact speeds. Using a force-balanced twin pendulum apparatus, Dr. Lloyd was able to generate head impact speeds similar to those specific to the subject crash, yet preserve the standard DOT test methodology, thereby avoiding a Daubert challenge.

Eight DOT and non-DOT helmets were purchased for this study. Each was impacted once in the frontal region while fitted to an instrumented crash test dummy head. High speed data and video were acquired for each test.

Results demonstrate that, although the tested DOT-certified motorcycle helmets outperformed the tested novelty helmets, neither would provide adequate protection against head injuries, such as skull fractures, contusions and lacerations, or brain injuries, including hemorrhages or axonal injury in an impact of this magnitude.

The "Lloyd-helmeted-motorcyclist-case-head-injury-graph" likely shows the relationship between helmet use and head injury severity in a specific motorcycle crash, comparing outcomes for helmeted versus non-helmeted riders.
Graph illustrating the severity of brain injuries in a Lloyd helmeted motorcyclist case, comparing outcomes based on helmet type (e.g., DOT-certified vs. non-compliant helmets) and the extent of brain damage, including concussions, hemorrhages, and axonal injury.

Dr. Lloyd’s prior published motorcycle helmet studies demonstrate that while DOT-certified motorcycle helmets can reduce the risk of traumatic head injuries, typical helmets do not afford any protection against acute brain injury.

Helmets – The Ultimate Protection?

Helmets – The Ultimate Protection? explores the effectiveness of helmets in preventing severe head injuries during accidents, examining their role in reducing the risk of skull fractures, concussions, and other brain injuries.The common belief among riders is that a motorcycle helmet protects the whole head, including the brain. However testing standards in Europe (ECE 22.05) and the US (DOT & Snell), which involve dropping helmeted headforms from heights of 2-3 meters onto a steel plate, only evaluate a motorcycle helmet in terms of its ability to protect against blunt force trauma, such as skull fractures and penetrating head injuries. The mechanism underlying diffuse brain injuries, such as concussions and brain hemorrhages is distinctly different, but is not assessed by current motorcycle helmet testing standards.

Imagine a bowl of jelly, where the bowl represents the skull and the jelly represents the brain. The bowl (skull) serves to protect the jelly (brain) from impact by dispersing forces over a larger surface area. If the bowl were impacted such that the force passes through the center of the jelly, the jelly moves very little. This is called linear force. Whereas, if you rotate the bowl of jelly between your hands you will see that the jelly moves quite a lot, especially towards its center. This is called a rotational force.

In reality, most motorcycle helmet impacts will produce both linear and rotational forces. In the case of head and brain injury, linear forces are responsible for injuries such as bruises and fractures. Whereas rotational forces cause the nerves and blood vessels in the brain to stretch and tear, leading to concussions, injury to the nerve fibers (axonal trauma) and brain bleeding (hematomas).

The human head is designed to protect the brain against typical impacts associated with daily living, such as normal bumps and falls. The skull can be thought of as a helmet to the brain by resisting penetrating injury to the brain. While the scalp glides over the skull to decrease rotational forces, thereby reducing the risk and severity of diffuse brain injuries. However, the forces associated with motorcycle collisions far exceed that which the human skull and scalp was intended to protect. Hence in motorcycling the use of a helmet to reduce the risk of such injuries is typically mandated.

Helmets are designed with 3 principal components – the outer shell, the inner liner and a comfort layer. The shell is typically made of polycarbonate plastics or fiberglass and serves two purposes; to minimize the likelihood that a sharp object might penetrate the head, and to dissipate the impact over a larger surface area. The inner liner is made from EPS foam (polystyrene) and serves to absorb the impact forces. The comfort layer does nothing more than provide comfort between the head and the polystyrene liner. Unfortunately, the polystyrene liner has limited effectiveness at reducing the rotational forces – those responsible for diffuse brain injuries – below safe levels.

A cooperative study was undertaken in Europe in the late 1990s to examine motorcycle accidents and their causes. Based on data from 4,700 helmeted motorcyclist deaths, the study found head injuries accounted for three-quarters of all fatalities. More than 60 percent of which were brain injuries caused by rotational forces, while only 30 percent of fatal head injuries were due to linear forces. This extensive study proves that motorcycle helmets are inadequate in providing necessary protection against diffuse brain injuries.

One might propose that protection against diffuse brain injury ought to deserve a higher priority. After all, the skull will likely heal from trauma, but the brain may not.

The challenge with protective headgear, including motorcycle, military and sports helmets is that, due to the characteristics of the liner materials, the head is directly coupled to the helmet. That is, the head and helmet are effectively joined and move as one. Therefore upon impact, any rotational forces generated on the helmet are transmitted directly to the brain. In fact, due to the size of helmets rotational forces can actually be amplified. The solution lies in de-coupling the head from the helmet, much the way that the scalp is de-coupled from the skull, so that the helmet can have some degree of rotation independent of the head. In this way, the rotational forces are dampened before they are transmitted to the brain, thereby lessening the risk and severity of brain injury.

BRAINS, Inc., of which Dr. Lloyd is the Research Director, is developing a new generation of motorcycle helmets, utilizing a patented composite of shear-thickening non-Newtonian materials. Due to their nature, these advanced materials respond differently to linear and rotational forces, thereby allowing the helmet some independent rotational motion, effectively de-coupling the helmet from the head. This technology was demonstrated at NI Week (http://youtu.be/T591x950oRI) and shows great promise for protection against both blunt force trauma and traumatic brain injuries.

Given the choice of a helmet that protected against skull fracture and one which also provides protection against brain injury, which would you choose?

For more information, please contact John@DrBiomechanics.com

 

Biography:

Dr. John Lloyd holds a PhD in Ergonomics from Loughborough University and is a Brain Injury Specialist. He is an expert in the field of brain injury biomechanics.

As a motorcycle enthusiast, John has clocked more than 250,000 miles and completed numerous training programs. Dr. Lloyd has served as a biomechanics expert on a variety of motorcycle accident cases.

Helmet Testing & Case Studies

motorcycle football sports helmet expert

The following are links to articles and case studies written by John Lloyd on helmet research and testing:

Motorcycle Helmet Testing

Biomechanical Evaluation of Motorcycle Helmets: Protection Against Head & Brain Injuries

What Every Rider Needs to Know About Motorcycle Helmets

Crash-Related Motorcycle Helmet Retention System Failures

Helmets – The Ultimate Protection?

Helmets Do Not Prevent Brain Injury

Motorcycle Helmets Provide Inadequate Protection Against Traumatic Brain Injury

Sport and Football Helmets

Brain Injury in Sports

How Well Do Football Helmets Protect Against Concussion and Brain Injury?

Researchers Discover Objective Indicator of Concussion

New Helmet Technology Reduces Brain Injuries

Case Studies

Helmeted Motorcyclist Fatality

Motorcycle Helmets Provide Inadequate Protection Against Traumatic Brain Injury

Dr. John Lloyd recently conducted a biomechanical study to evaluate motorcycle helmets in terms of their ability to provide protection against traumatic head and brain injuries. Motorcycle helmet testing proves inadequate protection against concussion and diffuse traumatic brain injuries associated.

Motorcycle accident victims account for more than 340,000 fatalities annually, with the United States ranking 8th highest worldwide in the number of motorcycle accident deaths. 75% of all fatal motorcycle accidents involve brain injury, with rotational forces acting on the brain the primary cause of mortality. Current motorcycle helmets are effective at reducing head injuries associated with blunt impact. However, the mechanism of diffuse traumatic brain injury is biomechanically very different.

Samples of 9 motorcycle helmet models, representing full-face, three-quarter and shorty designs were evaluated. Helmets, fitted to an instrumented Hybrid III head and neck, were dropped at 13 mph in accordance with DOT motorcycle helmet testing standards.motorcycle helmet testing

Results show that, on average, there is a 67% risk of concussion and a 10% probability of severe or fatal brain injury associated with a relatively minor 13mph helmeted head impact.motorcycle helmet testing results

In conclusion, motorcycle helmets provide inadequate protection against concussion and diffuse traumatic brain injuries associated with even relatively moderate impact.