By Chris Gorski, Inside Science -- Hard-shelled football helmets first emerged nearly 80 years ago to protect against catastrophic head injuries like skull fractures and brain hemorrhages, and they have evolved over the decades to offer better protection. Recently, public attention has increasingly focused on other consequences of hits to the head, including concussions and long-term degenerative diseases such as chronic traumatic encephalopathy.

But not all players suffer the same array of impacts. Now researchers, equipment makers and the NFL have begun working to design helmets optimized to serve players based on the position they play. In 2016, the NFL and partners announced what they call an Engineering Roadmap, a $60 million, five-year effort to spur innovation in safety equipment. The program aims to make a better overall helmet in three years, and position-specific models in five.

"We know there are some differences in the type, severity and frequency of impacts each position would experience on field," said Jeff Crandall, chairman of the NFL's engineering committee and the director of the Center for Applied Biomechanics at the University of Virginia in Charlottesville. "If we could get something like a position-specific helmet, you can consider that you could truly optimize a helmet for a given position."

The success of the effort likely depends on the quality of the data researchers can obtain and on how they apply it in designing new helmets. And even if the investment is likely to pay off in the form of better protective equipment, it might take longer than five years and it might not result in a helmet designed for every position on the field, according to experts interviewed by Inside Science.

Just as the game of football will likely never eliminate the violent tackles and repetitive collisions that can cause brain injuries, it's unlikely that anyone will ever invent a helmet that prevents all brain injuries. Although efforts to improve absorption and mitigation of impacts are spurring innovation, they probably won't completely solve the problem.

"I'm not convinced that we'll ever come up with a concussion-proof helmet," said Steve Broglio, head of the NeuroTrauma Research Laboratory at the University of Michigan in Ann Arbor. "I'm not convinced that that's possible."

What helmets protect against -- and what they don't

While helmets do protect against cuts, broken noses and skull fractures, they can't stop the brain from moving within the skull, which is a key problem in addressing concussion.

Concussions can result from impacts to the head or other events that jar the brain, such as whiplash. A player may lose consciousness, but often does not. Other symptoms may include headaches, confusion, sensitivity to light, and nausea. Such a disparate suite of symptoms can complicate efforts to define exactly what a concussion is.

"There [are] 45 or so different definitions of the injury floating around in the literature," said Broglio. He believes the field is moving toward diagnosing the injury with degrees of probability, such as possible concussion, probable concussion and definite concussion.

And as UCLA neuroscientist Chris Giza told Inside Science earlier this year, some experts contend that concussions act like an umbrella for what may actually be a spectrum of injuries that affect different people in different ways.

Even less understood are the degenerative brain conditions associated with repetitive impacts to the head, including chronic traumatic encephalopathy, which is characterized by tangles of a protein called tau in the brain and the loss of healthy brain structures. It can result in memory loss, impulsive behavior and dementia, among many other symptoms, although currently it can only be diagnosed after death.

In a study released this summer in the medical journal JAMA, all but one of the 111 deceased NFL players in their sample were found to have had the disease, based on examinations of their brains. The study's authors stressed in their paper and to the media that their sample was not likely representative of all NFL players, since family members who suspected that their loved ones had exhibited cognitive issues were probably the most likely to donate their loved one's brain for research. Despite that, the statistics suggest that the potential link between football and chronic traumatic encephalopathy is well worth continued research.

Studies have even suggested that chronic traumatic encephalopathy can develop in people who never had a concussion, but instead experienced repeated smaller subconcussive impacts that resulted in negligible symptoms when they occurred. Because relatively little is known about the cause of the disease, it's not clear what kind of impact reduction and absorption would reduce the risk of developing it.

This is the kind of uncertainty researchers and engineers are up against as they try to develop better helmets. They tend to focus their efforts on mitigating the force of impacts and directing the protection where it's most needed, but even helmets that excel at absorbing certain kinds of force don't necessarily stop concussions if they don't absorb and mitigate impacts that twist the brain inside the skull.

When a player is hit, the impact can generate movement in multiple directions. So a helmet has to absorb more than simply the energy of a direct linear impact.

"We know now that [concussion] is primarily a rotational injury," said Blaine Hoshizaki, who directs the University of Ottawa's Neurotrauma Impact Science Laboratory in Canada. "So if your helmet's not being tested for its capacity to mitigate the rotational acceleration, then you really don't know how well your helmet is working for protecting against concussion."

"It's a complex problem," said Kristy Arbogast, a biomechanical engineer at the Children's Hospital of Philadelphia and the University of Pennsylvania. She also represents the NFL Players Association on the NFL Engineering Committee. "For the engineering side, we're really just focusing on this mindset that less is better."

A custom helmet for every position

In recent years the NFL has developed what they call an Engineering Roadmap to improve head protection for its players. In 2016, they pledged to spend $60 million over five years to spur innovations in protective equipment and helmet technology. The NFL's five-year position-specific helmet initiative is part of that effort.

Protective equipment designed for the specific dangers associated with each position could, in theory, increase player safety, but the effort may be hampered by a lack of specific data on what makes each position unique.

Image credit: peter castleton via flickr. Image License: CC BY 2.0

The Helmet Safety Paradox

Behavioral scientists have found that people sometimes react to safety equipment by engaging in riskier behavior, such as following cars more closely when driving with anti-lock brakes or skiing faster when wearing a helmet. They call the phenomenon risk compensation. A similar issue can arise when people begin driving a fuel-efficient car, or purchase an energy-efficient air conditioner. Studies show that increasing energy efficiency can actually result in an increase in total consumption.

Applied to football, risk compensation would mean that having a helmet that dampens the impact of hitting the head could lead a player to subtly adjust behavior in a way that could increase the risk of head injury.

"It's an important aspect that we engineers can't be the only ones looking at this issue," said Kristy Arbogast, a biomechanical engineer with the Children's National Hospital of Philadelphia at the University of Pennsylvania and a safety consultant for the National Football League Players Association. "We need to bring in our behavioral science and public health colleagues to really understand those issues of risk compensation, because it really is part of the whole story."

For years, players at some high schools and colleges have had sensor systems embedded in their helmets to track impact magnitude and frequency, such as the Riddell InSite Impact Response System. Such sensors have been used to conduct studies related to both injuries and the impact profiles of different positions. The NFL and NFLPA are still weighing factors such as sensor performance, ergonomics and player privacy, and hasn't yet put instruments inside the helmets players wear on the field.

Nevertheless, information captured from high-level college football may provide data that's relevant to addressing safety at the NFL level, said Sam Browd, a pediatric neurosurgeon at Seattle Children's Hospital and the co-founder of the football helmet-maker VICIS. "They're playing at a very high level and I think you can certainly learn from those groups together."

That means that studies done at Virginia Tech and North Carolina, among other schools, might help influence the development of customized helmets for NFL players.

Researchers are still seeking better data straight from the NFL, and that has led to some creative approaches. The NFL may decide to use a sensor integrated into a different piece of safety equipment.

"We believe that the balance of accurate data and something that would be acceptable to players, that they would actually use, would be a mouthguard-based sensor," said Arbogast. "Implementing sensor electronics within some sort of mouthguard, mouthpiece, ensures that you're kind of as close to the skeletal structure as possible, since the upper mandible is attached to the head."

Arbogast has been working with others from the NFL and NFL Players Association to review existing sensors for both their accuracy and ability to work with existing safety equipment. For the players there is another important variable: privacy. The Players Association in particular wants to make sure that any data collected is kept confidential and secure.

"Players don't want employers making decisions on their future employment based on collection of research data that's intended to improve the health and safety of the game," said Sean Sansiveri, vice president of business and legal affairs for the NFL Players Association. "It's not going to be used for other purposes."

While they work to select and implement sensors to directly collect impact-related data during games and practices, the NFL relies on an elaborate video-based system to study and reconstruct impacts that happen on the field.

Engineering committee chair Jeff Crandall and the team working on the Engineering Roadmap recently announced an analysis of the 459 player concussions detected during the 2015 and 2016 seasons that included data from meticulously reconstructing the collisions from multiple angles.

"We want to have a better understanding of what players are experiencing on the field in terms of impacts," said Crandall.

The NFL's effort gathers statistics about a number of details, such as whether the injured player's helmet hit another helmet, another part of the body or the ground. They calculate the linear and rotational accelerations, compare the results by position and also reconstruct the impacts with crash test dummies.

Omitted from the effort are impacts that didn't result in a diagnosed concussion.

"We're sort of basing it on identifying the injury event, and then studying that," said Arbogast. "You aren't necessarily studying high severity impacts that don't lead to injury."

Stefan Duma, a Virginia Tech biomechanical engineer who developed the STAR system that gives helmets a rating from 1 to 5 stars based on their ability to reduce brain acceleration, acknowledged that companies could produce position-specific helmets, potentially at very high cost. But he pointed out that the NFL's current data may not be sufficient.

"We can tell you what a running back exposure looks like versus a wide receiver. We can do that for college because we've had all the players instrumented," he said. "The NFL doesn't have that data, because they don't have the instrumented response data from the NFL players."

One benefit of instrument-based data over the NFL's video review data is that it would include more impacts, including those that didn't result in diagnosed concussions.

From data to protection

Multiple experts told Inside Science that they are generally optimistic that current efforts will result in additional improvements to general-purpose helmets. Enhanced protection could help address the needs of a given position or grouping of positions.

Football helmet with a visor atop a grassy football field

Image credit: Dzimitry1991 via shutterstock

Better Helmet Testing

Companies will need to test any position-specific helmets they develop. To do so, they may also have to define an appropriate array of tests that evaluate those helmets against the needs of each position. Multiple groups, including the NFL, already evaluate helmets and provide feedback on their ability to mitigate impacts, but those tests don't take position-specific risks into account.

"One can envision that you would come up with a battery of tests and conditions that represent a particular position of player, and you would go through and say, 'I'm going to evaluate this particular helmet as a running back helmet,'" said Jeff Crandall, chairman of the NFL's engineering committee, and the director of the Center for Applied Biomechanics at the University of Virginia in Charlottesville. "So the variety of tests and the velocities and the impact locations could be tailored toward what that player experienced on field in our annual evaluation ranking."

Such an approach could be akin to customizing a car's crash test rating according to how a person drives. But for helmets, those tests might not be simple to develop, according to Grant Goulet, vice president of product innovation at Xenith, a sports equipment company.

"I think as we try and broaden that out to a position specific test standard that is relevant for in-game impact scenarios, it becomes very challenging from a standards perspective to develop those tests," he said.

"A lineman helmet might be enhanced in the front, but I don't see where they're going to neglect the back and the sides," said the University of Michigan's Steve Broglio. "It's like saying we're going to put in front air bags, but take out seat belts."

Although many predict that research and development efforts will produce substantial safety improvements, it's possible that going beyond fine-tuning the helmets and really improving protection in a large and substantial way will require new material innovations or design strategies.

"When you look at the modern football helmets, especially the top group that we have five-star rated, I say those are about 95 percent as good as a helmet's ever going to get," said Duma. Absent a newly invented padding material or other new system, he said, "there's not a lot of room for improvement."

Hoshizaki said that although it is true that different positions present different trauma profiles, some positions, especially cornerbacks, may present inconsistent profiles that make it difficult to develop a single optimized helmet for the position. Players who play multiple positions might require multiple helmets -- or perhaps some positions would have to be grouped together.

Browd thinks that the first step in developing position-specific helmets may be designing one helmet for linemen and one for players at the skill and speed positions. "I don't think you're going to have 10 or 15 helmets, at least initially, out on the field," he said.

As researchers study the hits players at different positions face and consider the best way to enhance protections, helmet companies are developing their own customization strategies. Some of them are focused on fit, and others on developing architecture that could be tuned to address needs based on position.

The companies that make helmets highlight different strategies to improve player protection. Among other strategies, Riddell is focusing on fit. This is the company that developed the first plastic shell helmet in 1939 and is now using a custom light scanner to map the contours of a player's head in order to develop customized padding for individuals. Xenith, founded in 2006, employs what they call a floating shock suspension system intended to allow the head and helmet's shell to move independently. VICIS, founded in 2013, uses a layer of columns under a soft shell to mitigate both linear and rotational forces.

C Watts via flickr. CC BY 2.0

Moving innovations beyond the NFL

Regardless of when position-specific helmets arrive and in what form, a helmet designed and built for NFL players is by definition a specialty product. Some experts say they won't directly serve the vast majority of other football players.

"More people would be affected by an age-specific helmet than a position-specific one," said David Camarillo, a bioengineer at Stanford University in California. "The NFL is trying to solve the NFL's problems; they're not trying to solve football's problems, which is a mistake in my opinion."

Just as NASCAR drivers are protected by different safety systems than daily commuters, there are differences between the helmet that provides the best protection to an NFL player and the helmet worn by a youth player.

"I think age or skill level-specific helmets is at least equally important because the types of impacts that a junior high school player receives and the number and intensity of those impacts [are] certainly different than what a high school player would see or a college player would see," said Thad Ide, senior vice president for research and product development at the sports eqiuipment company Riddell.

Arbogast said she hopes the research will stimulate "those innovations in material science, innovations in structural design that we can then think about how to translate to other age groups."

The NFL-funded research and other projects may also lead to innovations in the turf, other equipment and other components that affect the game, which all may contribute to increased safety. These efforts may make the game safer for NFL and even youth players, but it's difficult to predict how far they can go.

"We're seeing a bunch of innovation in every component of the helmet, or even surfaces that the head might hit," said the NFL Players Association's Sansiveri.

Leagues have also changed rules and norms. In recent years, the NFL reduced contact in practice, changed rules to penalize helmet-to-helmet hits and moved kickoffs to encourage touchbacks to reduce collisions. The Canadian Football League and college's Ivy League, among others, have also made meaningful changes to reduce dangerous impacts.

Although experts express a range of opinions regarding when position-specific helmets will arrive and how much additional protection they will provide, all share the goal of making equipment better.

Arbogast said meeting the five-year goal of the project greatly depends on how many different helmets they want to make. Grant Goulet, vice president of product innovation at the sports equipment company Xenith, sees value in the efforts, even if position-specific helmets turn out not to be the right approach. "I think it's exciting to see innovation in the space, especially given what's going on with head health these days and the importance of protecting the athletes and ensuring the success and survival of the game that we all love," he said.

Riddell's Ide said he doesn't find the timeframe "overly optimistic or ambitious." He suggested that as data collection becomes more widely integrated into helmets, it may become possible to go one step further -- to optimize helmets for individual players.

For Browd, from VICIS, this complex landscape is part of the challenge. "This is sort of the way science works, right?" he said. "We're learning and the technology is adapting to the best state of medical and scientific knowledge as it stands today."

Reprinted with permission from Inside Science, an editorially independent news product of the American Institute of Physics, a nonprofit organization dedicated to advancing, promoting and serving the physical sciences.