Tag Archives: helmet
The U.S. Consumer Product Safety Commission, which is charged with protecting the public from unreasonable risks of injury or death associated with the use of thousands of types of consumer products under the agency’s jurisdiction, has announced that Head USA, of Boulder, Colo., will recall its snowboard helmets because of the head injury risk.
“The helmets do not comply with the impact requirements of safety standards for helmets, posing a risk of head injury,” according to the Commission.
The recall involves six models of HEAD ski and snowboard helmets: Agent, Alia, Andor, Arise, Arosa and Avril. They were sold in sizes M/L and XL/XXL in black, blue, green white and yellow, with straps in a variety of colors. HEAD, the model name, size and “Production Code: Dec. 2014” are printed on stickers that can be found by lifting the lining above the right earpiece. The helmets were sold at specialty ski and snowboard shops and online from January 2015 through December 2015, for between $80 and $120.
“Consumers should immediately stop using the recalled helmets and contact Head USA to receive a free replacement helmet,” according to the Commission.
More detais can be found at: http://www.cpsc.gov/en/Recalls/2016/Head-USA-Recalls-Ski-and-Snowboard-Helmets/#remedy
A shock-absorbing football helmet system being developed at the University of Michigan could blunt some dangerous physics that today’s head protection ignores.
The engineering researchers making the system, called Mitigatium, were recently funded by a group that includes the National Football League. Their early prototype could lead to a lightweight and affordable helmet that effectively dissipates the energy from hit after hit on the field. Current helmets can’t do this, and that’s one of the reasons they aren’t very good at preventing brain injury, according to the university.
“Today’s football helmets are designed to prevent skull fractures by reducing the peak force of an impact,” said Ellen Arruda, U-M professor of mechanical engineering and biomedical engineering. “And they do a good job of that. But they don’t actually dissipate energy. They leave that to the brain.”
Sports like football present big challenges for the designers of protective head gear. To dissipate energy, a helmet typically has to deform, like the bike version cracks in a collision. And disposable helmets aren’t practical for football players.
When a bike helmet breaks, it’s absorbing what’s called “impulse”—a secondary effect of an initial force. Impulse, which gives objects momentum, is what transmits kinetic energy through a system. It takes into account not just force, but also how long that force was applied. To calculate impulse, you multiply the average force by the length of time it was exerted on the subject.
For head protection to be most effective against the speeds and weights of players on a football field, these researchers say it has to block impulse.
They’re not the first to say this. They’ve found medical studies from 70 years back that blame impulse for damage from football-style, quick impacts. Yet today, helmet makers and health researchers alike tend to rely on other factors. For example, new helmet designs are approved based solely on the peak force they can withstand.
“Everyone is focused on the force of an impact and only the force,” Arruda said. “But they’ve found that when they measure peak force on the surface of the skull, they can’t correlate that with brain injury. The reason is that force is only part of the story.”
Scientists and doctors don’t fully understand how a blow to the head translates to brain injury, but the U-M researchers say impulse is a big factor. Arruda and her colleagues have demonstrated this.
They’ve taken one of the first close looks at the mechanical features of impacts and blasts and how helmets and other armor might be designed to do a better job protecting sensitive structures. o do that, they built two-dimensional mock cross-sections of materials that stood in for the brain and skull in various helmet shells. Then they use a table-top collision simulator to test the different samples. They compared how much energy was transmitted through to the brain-type layer in their own helmet system and the status quo. They used a high-speed camera to help them observe how the brain model deformed in both systems.
“Some of the insight we got from this analysis was subtly different from how the helmet community thought about design, although we found examples in old medical literature that were consistent with our understanding,” said Michael Thouless, the Janine Johnson Weins Professor of Engineering in mechanical engineering and materials science and engineering.
In their experiments, the current helmet model did little to block impulse. The researchers could tell this by how much the speckled pattern on their brain layer distorted. The Mitigatium prototype, however, reduced impulse to just 20 percent of what got through to the brain model in the conventional helmet. Mitigatium reduced peak pressure to 30 percent. It lowered both by an order of magnitude, Arruda said.
Here’s how it works: It’s made of three materials that amount to more than the sum of their parts. The first layer is similar to the hard polycarbonate that’s the shell of present-day helmets. The second is a flexible plastic. Together these substances reflect most of the initial shock wave from a collision—most of the initial force. They also do something else unique and important: They convert the frequency of that incoming pressure wave to a frequency that the next layer can, in essence, grab ahold of and dissipate by vibrating. This third “visco-elastic” layer has the consistency of dried tar.
“We’ve come up with a totally new concept of how to make efficient impact-mitigating structures that could dissipate energy without being damaged,” Thouless said. “And we used basic concepts of mechanics to develop a fundamental understanding of how to protect delicate structures such as the brain.”
Late last year, the U-M team was one of five winners of the Head Health Challenge III, a competition to support the development of materials that better absorb or dissipate impact. Aside from the NFL, sponsors are Under Armour, GE and the National Institute of Standards and Technology. The U-M researchers received $250,000 to take their technology to the full prototype stage. Doctoral candidate Tanaz Rahimzadeh is also contributing to this project.
The researchers also point out that their system is extremely flexible, in that different materials could be used to tune different incoming pressure waves. They envision their approach to have applications for the military and other protective gear, as well as for playground surfaces.
A paper on some of these findings, titled “Design of armor for protection against blast and impact,” is published in the Journal of the Mechanics and Physics of Solids. Rahimzadeh is the first author.
To reduce the risk of concussion, researchers and others have sought ways to improve helmet technology as a way to resolve the problem.
A better solution may be to ditch the helmets altogether, according to a new study in the Journal of Athletic Training, the National Athletic Trainers’ Association’s scientific publication. Researchers investigated the effectiveness of helmetless tackling to reduce head-impact exposure in an NCAA Division I football program.
The study, partially funded by the NATA Research & Education Foundation, showed a 28 percent reduction in head impacts during practices and games. To review “Early Results of a Helmetless-Tacking Intervention to Decrease Head Impacts in Football Players,” please visit:
“Given proper training, education and instruction, college football players can safely perform supervised tackling and blocking drills in practice without helmets,” said Erik E. Swartz, PhD, ATC, FNATA, lead author of the study and professor and chair, Department of Kinesiology, University of New Hampshire. “This intervention also eliminates a false sense of security a player may feel when wearing a helmet. Younger players with less experience may require modifications to this intervention to realize a positive effect. While more research is needed, our results do show a reduction in head impacts during our one season of testing.”
The findings are from the first year of a two-year study in which 50 NCAA Division 1 football players at the University of New Hampshire were assigned to an intervention (25 athletes) or control (25 athletes) group. The intervention group participated in five-minute tackling drills without their helmets and shoulder pads as part of the Helmetless Tackling Training (HuTT) program. Drills occurred twice per week during preseason practices and once per week throughout the competitive season (16 weeks). The control group performed noncontact football skills with no change to their routine. All athletes were provided head-impact patch sensors worn on the skin and new helmets. Both groups were supervised by members of the football coaching staff. At the end of the season, the intervention group experienced an average 30 percent fewer impacts per exposure than the control group.
The notion of removing the football helmet for discrete and regular periods during practice to reduce head impact is counterintuitive to the sport, wrote the authors. “These findings elucidate the risk-compensation phenomenon and may help explain the behavior of spearing and the rise in catastrophic neck and head injuries that followed,” they added. “A football helmet is designed to protect players from traumatic head injury, but it also enables them to initiate and sustain impacts because of the protection it affords. While improving protective equipment in and of itself will not resolve the risk of concussion and spine injury in football, the solution may be found in behavior modification.”
High school and college football players can each sustain more than 1,000 impacts in a season, while individual youth players may sustain 100 during that same timeframe according to the study. “The extent to which this intervention may yield similar outcomes in younger players with less experience is still unknown. We are currently in the first year of a high school study focused on four high schools in New Hampshire,” adds Swartz.
“Should future research replicate our findings, the eventual adoption of helmetless-tackling training may improve public health and decrease the associated economic burden by reducing football-related head and neck injuries and the risk of long-term complications.”