Category Archives: sports helmet expert

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

Helmet Expert

Dr. Lloyd’s unique capability as a helmet expert is in the biomechanical  evaluation of helmets, specifically, football, sports and motorcycle helmets. Helmets are designed to reduce the risk of blunt force trauma to the head, however protection against diffuse traumatic brain injury is often inadequate. Dr. Lloyd is often called upon to opine whether the head and brain injuries may or may not have been prevented by head protection.

His work on football helmets has been published in the Journal of Neurosurgery and his work on motorcycle helmets has been printed in Adventure Bike Magazine.

motorcycle football sports helmet expert

As a helmet expert, Dr. Lloyd’s advanced research has lead to several peer-reviewed publications in scientific journals. Specifically, the test apparatus and methods that he employs to evaluate helmet protection was published in a landmark technical article titled “Response of an Impact Test Apparatus for Fall Protective Headgear Testing Using a Hybrid-III Head-Neck Assembly“.

Using this apparatus, helmet expert Dr. Lloyd and neurologist Dr. Frank Conidi of the Florida Center for Headache and Sports Neurology have presented a series of studies at the American Academy of Neurology meetings. Their work was publicized by the AAN in a press-release titled “How Well Do Football Helmets Protect Players from Concussions“. Dr. Lloyd and Dr. Conidi published a scientific article in the Journal of Neurosurgery titled “Brain Injury in Sports“. This article documents the limited protection against traumatic brain injuries afforded by many current varsity football helmets.

Example Motorcycle Helmet Expert Case

motorcycle helmet expert Hamilton crashDr. Lloyd provided biomechanical analysis on a recent motorcycle accident case in which an automobile crossed the path of an unhelmeted rider traveling at approximately 25 miles per hour. The motorcyclist’s head shattered the driver’s side window, leading to catastrophic brain injury


motorcycle helmet expert Hamilton test apparatusDr. Lloyd was asked to opine as to whether or not a motorcycle helmet would have prevented these injuries. A test apparatus was constructed using an exemplar automobile driver’s door and window to measure the forces acting on a crash test dummy head.

The following high speed videos and data were captured showing the helmeted versus unhelmeted conditions.

We learned that, had the motorcyclist been wearing a helmet during the subject collision, he would have most likely sustained fatal neck injuries as the helmet was deflected by the window, producing unsurvivable neck extension, as shown below:

Test results and video documentation were presented at deposition and proved highly valuable.

motorcycle helmet expert Hamilton test results

Please call Dr. Lloyd at 813-624-8986 or email  DrJohnLloyd@Tampabay.RR.com to discuss how he can be of help to you with your case.

Football Helmets

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

Football helmet research presented by John Lloyd, PhD – BRAINS, Inc. & Frank Conidi, MD – Florida Center for Headache and Sports Neurology at the 66th Annual Meeting of the American Academy of Neurology, 2014

YouTube link to video on Biomechanics of Football Helmets

Sports related concussion is the most widely publicized neurological disorder, with football accounting for the highest incidence across all sports. There is a silent epidemic of these invisible injuries across players of all ages from youth through professional, resulting in a 3-fold increase in ER visits among high school players from 2000-2010. It is estimated that a quarter of a million of these injuries each year have long-term consequences. A single moderate to severe brain injury can leave one at risk for early onset dementia, while repeated mild concussions may have the same effects (Giza).

The football helmet became mandatory in the 1930’s to provide protection against catastrophic head injuries. Over the past eighty years there have been significant modifications in football helmet design. Yet despite advances in technology there is still little evidence that helmets offer significant protection against concussion and traumatic brain injury (Giza). hile the widely utilized Simbex HITS system and the Virginia Tech STAR rating system attempt to measure helmet performance, neither offer a direct measure of concussion or brain injury risk.

Methods

According to Holbourn, risk of focal head injury, such as skull fracture and brain contusion, can be expressed in terms of linear acceleration, while the risk of concussion, axonal injury and diffuse brain injury is associated with angular/rotational acceleration. The standard NOCSAE / ASTM helmet tests only measure forces associated with linear acceleration and therefore fail to account for risk of brain injury.

Goldsmith Leatherhead football helmet - sports accident reconstruction expert John Lloyd

A modified test apparatus, incorporating a Hybrid III crash test dummy head and neck, has been validated by Caccese and Lloyd. This method induces a rotational inertia on impact, thereby facilitating measurement of risk of focal head and diffuse brain injuries.

We purchased 60 football helmets, including three samples each of 20 different models.  All helmets were dropped five times from a height of 2.0 meters onto a steel plate, generating an impact velocity of 13.9 mph.

Football Helmet Results

Our findings show that football helmets vary widely in terms of their performance to protect against focal head injury and concussion / diffuse brain injury. All tested football helmets, including the 1930s leatherhead meet the minimum performance criteria of 275G as set by the ASTM F717 standard. However, this standard does not account for duration of impact, which is a critical factor. Moreover, ASTM F717 does nothing to set helmets performance standards in terms of protection against concussion and brain injury.

football helmet testing and analysis Dr. John Lloyd sports accident reconstruction expertBy design, helmets reduce impact force by increasing the impact duration. But, as demonstrated by Depreitere (blue) and Lowenhielm (red) increasing impact duration actually lowers the brain injury threshold.
Head injury risk was calculated with respect to the140g threshold for 7msec impact documented by Ono, wwhile brain injury risk was calculated based on Ommaya’s1700 rad/s^2 tolerance limit for moderate AIS2 brain injury, which concurs with Rowan and Dumas top 25% of sub-concussive impacts.

Results are presented below, where % reduction of head injury risk is shown in red and % reduction of concussion/mTBI is presented in blue.

Bars above the x-axis indicate that the helmet performs better than the documented threshold, while those below the x-axis did not meet our performance thresholds.

Football helmet results by sports accident reconstruction expert Dr. John Lloyd

It is noted, interestingly, that the 1930s Goldsmith leatherhead helmet actually outperformed several contemporary football helmets in terms of protecting against concussion and brain injury, including the Adams a2000 Pro, the Rawlings Quantum and the Riddell 360.

Based on our research, the top 3 varsity helmets are: Xenith X1, Schutt Air XP Pro, and Rawlings Quantum Plus, respectively. The top 10 helmets are presented below, based on their protection against traumatic focal head injuries and diffuse brain injuries:

Football helmet top 10 results from testing and analysis by sports accident reconstruction expert John Lloyd PhD

Conclusions

None of the football helmets on the market today offer what most would consider adequate protection against concussions and traumatic brain injuries. A shift in thinking towards lighter high-tech materials for helmets, teaching proper hitting and tackling techniques, pre and in-season isometric and isokinetic cervical strengthening programs, and continued concussion awareness and education are the best means of protecting athletes of all levels from the consequences of concussion and traumatic brain injury.

Future Research

It is hypothesized that oblique impacts present even longer impact durations, which may explain why such seemingly innocuous impacts cause increased incidence of concussion.

Embracing the findings from testing of the 1930s Goldsmith leatherhead,  a new generation of soft football helmets is proposed, utilizing today’s advanced non-Newtonian materials, which we anticipate might outperform contemporary helmets in terms of protection against both traumatic head and brain injuries.

References

1. Caccese V, Lloyd J, F et al (2014). An Impact Test Apparatus for Protective Head Wear Testing Using a Hybrid III Head-Neck Assembly. Experimental Techniques.
2. Depreitere, B. et al. (2006). Mechanics of acute subdural hematomas resulting from bridging vein rupture, J Neurosurg, 104; 950–956.
3. Holbourn, A.C.H. (1943). Mechanics of Head Injuries. The Lancet p438-441
4. Giza CC, Kutcher JS, Ashwal S, et al. (2013) Evidence based guideline update: Evaluation and management of concussion in sports. Report of the Guideline Development Subcommittee of the American Academy of Neurology. Epub March 18.
5. Lowenhielm, P. (1974). Strain Tolerance of the Vv. Cerebri sup. (. Z. Reehtsmedizin 75, 131-144
6. Ommaya A. (1985). Biomechanics of Head Injury – Experimental Aspects. In Nahum A M & Melvin J (Eds). The Biomechanics of Trauma. 
7. Ono K. (1998) Human head impact tolerance. In Yoganandan (Ed). Frontiers in Head and Neck Trauma: Clinical and Biomechanical. IOS Press, Amsterdam. Appleton-Century-Crofts publishers, Norwalk, CT.
8. Rowan S. & Duma S. (2013). Brain Injury Prediction: Assessing the Combined Probability of Concussion Using Linear and Rotational Head Acceleration. Annals of Biomedical Eng. 41, (5): 873–882

Why all head protection is in need of a redesign

The humble helmet dates back nearly 3000 years and though it has been used prolifically in warfare, it is now most commonly used to provide head protection outside the combat arena. 

However, although applications might have diversified, it is still fundamentally designed and used to provide the same thing.

So when this most traditional of objects is combined with modern sensor technologies, greater test data resolution and analysis, there is bound to be fresh insight.

And this is the case for many conventional designs where sensors, test and measurement technologies are changing conventional thinking into how something has been designed, to how it should be designed.

It sets the scene and means helmet design is on a collision course for further impact protection, specifically in preventing serious brain injury by giving helmet designers greater clarity in to the mechanical forces at play in any particular scenario.

It was this, along with a lifetime of comprehensive knowledge, which enabled biomechanist Dr John Lloyd, research director of BRAINS, to start up a company dedicated to improving current helmet technology and ultimately improve protection for wearers. He aims to shed new light on helmet design, and improve protection against the fundamental causes of concussion and brain injury.

“There are two key forces at play during a head impact,” said Dr Lloyd, speaking at this year’s National Instruments Week in Austin, Texas. “Firstly there are linear forces, these are the ones that cause visible injuries such as bruising and skull fractures. However, the second is the rotational forces. These are the ones that cause invisible injuries such as concussion and brain injury.

“Current helmet testing technologies measure the linear forces. However, at this time, they do not measure the rotational forces, so consequently we have helmets for many sports that do not test against their ability to provide protection against concussions and brain injury.”

Whether it is for riding a bike, horse riding, skiing or indeed for the soldier in the field, the effect of rotational movement is the same. Yet, it is rarely tested for, and even less frequently measured, to see how effective any helmet is in rotation force protection.

Dr Lloyd modified the standard apparatus used for testing helmets (see the rig on page 28), where a head section is raised 2m on a rig and dropped under gravity before it hits a striking plate with an impact force in the region of 4500N. However, instead of using a standard head form, Dr Lloyd replaced it with a standard automotive crash test dummy head and neck section. This way, when the head impacts the striking plate at the bottom of the test rig it will rotate, and the movement measured.

“We had multiple sensors embedded in the centre of mass of this head form,” explained Lloyd. “So, during the impact we were able to measure the linear acceleration as well as the angular motion of the head.

“My measuring apparatus includes sensors from several manufacturers.. The angular rate sensor, for example, that is used to measure the rotational forces is a highly specialised sensor. And, as a result, has its own data acquisition hardware and software.”

Simplifying synchronisation
Trying to integrate all this data from different sensors was a challenge at best. And to make matters more complicated, the peak linear acceleration and peak angular acceleration actually happen at different points in time.

“So while you can just line up the data,” he said, “there is a lag between them. So we need to measure that lag, which is a critical measurement in the research.”

To resolve the problem, Dr Lloyd uses both the National Instruments LabView graphical software and a CompactDAQ to interface with the sensors and provide the necessary synchronisation between the various sensors.

Dr Lloyd modified his apparatus for testing helmets used by American footballers in the National Football League (NFL), to develop understanding of the how spinal and head injuries are caused and improve the design of the standard helmet.

“The results are pretty alarming in terms of how little protection they provide against concussions and traumatic brain injuries,” he said.

“Based on lessons learned from that study, I have developed a new ‘football’ helmet prototype. This uses a patent pending matrix of non-Newtonian materials and when we tested the prototype helmet, on the same apparatus, the result blew me away. Not only did these materials reduce the linear forces but compared to the standard football helmet they actually reduced the rotational forces that cause concussion and brain injury by an amazing 50%.”

The non-Newtonian materials Lloyd has in mind are inexpensive and produce a helmet that is considerably lighter and even said to be more comfortable for those wearing them.

Dr Lloyd is now expanding the concept of reducing rotation forces in helmets in every application and said it can be applied to almost any helmet design to help reduce concussion and brain injuries from sports to leisure and even back to warfare.

Building a rig and conducting the test
A modification to the US National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was used by Dr John Lloyd, research director of US helmet research start-up, BRAINS.

He developed and validated a new helmet test rig to measure the impact of protective headwear to include measurements of both linear and angular kinematics. This apparatus consists of a twin wire fall test system equipped with a drop arm that incorporates a 50th percentile Hybrid III head and neck assembly from HumaneticsATD crash test dummy, as used in the automotive industry.

The aluminium fly arm runs on Teflon sleeves through parallel braided stainless steel wires, which are attached to mounting points in the building structure and anchored into the concrete foundation. The anvil, onto which the head drop systems impacts, consists of a 350mm x 350mm steel based plate.

Both the standard Riddell Revolution Speed US university football helmet, and the prototype BRAINS helmet that incorporates a non-Newtonian matrix, were dropped from a height of 2m onto a flat steel anvil, in accordance with American Society for Testing and Materials (ASTM) standards. This generated an impact velocity of 6.2 m/s (13.9 mph).

Instrumentation: 
A triaxial accelerometer from PCB Piezotronics and three DTS-ARS Pro 18k angular rate sensors (Diversified Technical Systems) were affixed to a tri-axial block installed at the centre of mass in the Hybrid III head form. Data from the accelerometer and angular rate sensors were acquired using National Instruments compactDAQ hardware.

Analysis: 
Data from the analogue sensors were acquired at 10,000Hz, per channel, using LabView and then filtered in Matlab using a phaseless 4th order Butterworth filter with a cut off frequency of 1650Hz. Angular acceleration values were derived from the angular velocity data based on a 5-point least squares quartic equation.

Result:
The result of the new helmet design shows significant improvement in rotational acceleration exerted on the head and neck, cutting the overall force by nearly 50%.

Author
Justin Cunningham

– See more at: http://www.eurekamagazine.co.uk/design-engineering-features/technology/why-all-head-protection-is-in-need-of-a-redesign/66493/#sthash.6Tv5duXE.dpuf

Research article “Brain Injury in Sports” published in Journal of Neurosurgery

Dr. Lloyd is pleased to announce that his research article  on Sports Brain Injury, co-authored with Dr. Frank Conidi has been published in the Journal of Neurosurgery:

Lloyd - Sports Brain Injury

OBJECT
Helmets are used for sports, military, and transportation to protect against impact forces and associated injuries. The common belief among end users is that the helmet protects the whole head, including the sports brain injury. However, current consensus among biomechanists and sports neurologists indicates that helmets do not provide significant protection against concussion and sport brain injury. In this paper the authors present existing scientific evidence on the mechanisms underlying traumatic head and sports brain injury, along with a biomechanical evaluation of 21 current and retired football helmets.

METHODS
The National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was modified and validated for impact testing of protective headwear to include the measurement of both linear and angular kinematics. From a drop height of 2.0 m onto a flat steel anvil, each football helmet was impacted 5 times in the occipital area.

RESULTS
Skull fracture risk was determined for each of the current varsity football helmets by calculating the percentage reduction in linear acceleration relative to a 140-g skull fracture threshold. Risk of subdural hematoma was determined by calculating the percentage reduction in angular acceleration relative to the bridging vein failure threshold, computed as a function of impact duration. Ranking the helmets according to their performance under these criteria, the authors determined that the Schutt Vengeance performed the best overall.

CONCLUSIONS
The study findings demonstrated that not all football helmets provide equal or adequate protection against either focal head injuries or traumatic brain injuries. In fact, some of the most popular helmets on the field ranked among the worst. While protection is improving, none of the current or retired varsity football helmets can provide absolute protection against brain injuries, including concussions and subdural hematomas. To maximize protection against head and brain injuries for football players of all ages, the authors propose thresholds for all sports helmets based on a peak linear acceleration no greater than 90 g and a peak angular acceleration not exceeding 1700 rad/sec2.

http://thejns.org/doi/abs/10.3171/2014.11.JNS141742