Category Archives: sports helmet testing

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

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

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