Tag Archives: skateboard helmet testing

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

Biomechanics Laboratory

I employ state-of-the-science biomechanics resources in my evaluations, as depicted in the following figure. This biomechanics laboratory includes various certified biofidelic mannequins, dedicated test apparatus, data acquisition hardware, software and calibrated sensor instrumentation, professional photography and high speed and videography equipment.

Dr. John Lloyd-biomechanics laboratory

Much of my research and work for civil law suits focusses on biomechanical evaluation of helmets, in particular sports helmets, including football and ski helmets.

Dr. John Lloyd-biomechanics laboratory helmets

For helmet testing, we have a standard NOCSAE (National Operating Committee for Standards in Athletic Equipment) head drop system

Dr. John Lloyd-biomechanics laboratory NOCSAE test

However, the standard NOCSAE system only measures forces associated with linear acceleration, which are attributed with focal head injuries, such as skull fractures. This system has a rigid neck and therefore cannot measure rotational or angular accelerations, which are associated with traumatic brain injuries, such as concussion and subdural hematomas. We have a modified helmet drop test system, developed in collaboration with the University of Maine, Advanced Manufacturing Center, validation of which has been published in a peer-reviewed journal.Dr. John Lloyd-biomechanics laboratory modified helmet test

The following image shows both the NOCSAE and modified helmet test systems in parallel.

Dr. John Lloyd-biomechanics laboratory modified helmet test

Recent research shows that standard linear impact tests may not fully account for impact forces as they do not incorporate angular velocity. Therefore, I have created an inverted pendulum system, which is more representative of a standing fall

 Dr. John Lloyd-biomechanics laboratory inverted pendulum

Additionally, the biomechanics laboratory is equipped with the following resources:

  • Monorail head drop assembly
  • Twin wire guided drop system (NOCSAE)
  • Weighted pendulum impactor
  • Linear bearing table
  • Height-adjustable, eletromagenetically-controlled freefall drop platform
  • 20,000N impact force plate
  • 880lb ceiling mounted lift system
  • Certified biofidelic adult headforms
  • CRABI12 biofidelic infant mannequin
  • Hybrid III 3-yr old biofidelic mannequin (KSS)
  • National Instruments 32 channel USB-6343 X-series data acquisition system
  • LabView 2009 data acquisition software.
  • Calibrated sensors, including Kistler and PCB Piezotronics tri-axial accelerometers, MEMS triple axis digital gyroscopes, and PCB Piezotronics uni-axial and tri-axial load cells.
  • Selection of flooring materials, including carpeting, wood and laminates as well as concrete and wood sub-flooring surrogates
  • Professional still photography equipment
  • Normal speed and high speed (up to 1kHz) videography equipment
  • Photography flash and ‘hot’ lighting

Brain Injury in Sports

Dr. Lloyd’s research article “Brain Injury in Sports”, co-authored with Dr. Frank Conidi has been published in the Journal of Neurosurgery.

Please email me at DrJohnLloyd@Tampabay.RR.com  if you would like to receive a full copy of the published article.

Abstract

BACKGROUND
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 brain. However, current consensus among biomechanists and sports neurologists indicates that helmets do not provide significant protection against concussion and brain injuries. In this paper the authors present existing scientific evidence on the mechanisms underlying traumatic head and brain injuries, 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.

Brain Injury in Sports - apparatus

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.

Brain Injury in Sports - results

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.

 

Please call Dr. Lloyd at 813-624-8986 or email  DrJohnLloyd@Tampabay.RR.com if you would like to receive a full copy of the published article “Brain Injury in Sports”

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.