The NFL says Guardian Caps make football safer. The science isn’t so sure

After enduring four concussions in his first three NFL seasons, Chris Olave decided he could no longer justify prioritizing swag over safety.

The New Orleans Saints receiver has begun wearing a Guardian Cap over his helmet on game days in hopes that the cartoonishly bulky, foam-padded covering offers better protection against blows to the head. 

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“Shoot, I got kids now,” Olave told reporters earlier this month after his team’s season opener against Detroit. “I want to live a regular life after I’m done with football. I love my kids to death. So, I don’t really care how it looks no more. I just got to throw it on.”

For football players, the dangers of strapping on a helmet and stepping between the white lines have never been clearer. Scientists have demonstrated that the cumulative effect of repeated blows to the head is the most reliable predictor of what could cause someone to suffer from the degenerative brain disease known as chronic traumatic encephalopathy, or CTE. 

At least 1 in 4 former NFL players who died from 2016-2021 had CTE, according to a recent study published in the British Medical Journal, and researchers say that 25% estimate represents a conservative floor. The prevalence of CTE among deceased former NFL players has only further ratcheted up the pressure on the league to show that it’s proactively hunting for answers.

Since 2022, the NFL has touted the innovation of a mom-and-pop duo as a potential solution. NFL officials have cited lab tests showing that the Guardian Cap cushions the impact of hits to the head by at least 9%. They also point to a roughly 50% reduction in concussions when players wear the extra layer of padding over their helmets during practices.

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Those figures are the NFL’s rationale for requiring players to either wear a Guardian Cap during contact practices or one of the handful of helmet models that have performed best during safety tests. The league has also permitted the use of Guardian Caps during games since the start of the 2024 season, though Olave is one of just a few dozen players who have risked social media ridicule by wearing one on a game day.  

“We think it has been a step forward for player safety overall,” said Jeff Miller, the NFL’s executive vice president for health and safety initiatives. 

And yet not all independent neurologists and neuroscientists support America’s most powerful and visible sports league throwing its weight behind the Guardian Cap. Some expressed concern that Guardian Caps give athletes a false sense of security without meaningfully reducing the risk of CTE. Others cited a 2025 study involving the NFL’s top medical official that poked holes in the league’s claim associating Guardian Caps with a decrease in concussions.

Providing further fuel for criticism is the fact that the Guardian Cap NXT model worn by NFL and Division I college players is not the same as the product marketed to the masses. The lighter-weight XT model, which sells for as much as $89.99, has less padding than the NXT. Impact tests conducted by multiple different laboratories have shown that the XT model may be less effective than the NXT at protecting the head and reducing injury risk.

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“The jury is out on whether the Guardian Cap is helping NFL players,” said Chris Nowinski, co-founder of Boston University’s CTE Center and one of the world’s most renowned figures in brain injury research. “We have no reason to believe it’s helping high school and college players. 

“We’ve created a sort of nightmare scenario where people strap these things on their kids’ helmets and believe they’re now safe from concussions and CTE. Nothing could be further from the truth.” 

‘It was crickets all day’

The story of the Guardian Cap actually begins about a quarter century before its invention. 

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In fall of 1987, an industrial designer from Erie, Pennsylvania, was watching a college football game and witnessed a particularly brutal helmet-to-helmet collision. The jarring hit inspired Bert Straus to try to devise a product capable of cushioning the impact of such blows. 

Several years of tinkering produced the Pro Cap, an energy-absorbing, half-inch foam shell that attached to the top of a conventional football helmet. Former Buffalo Bills free safety Mark Kelso credited the Pro Cap for extending his NFL career by a few years. So did former San Francisco 49ers left tackle Steve Wallace. 

Unresolved questions about the Pro Cap’s effectiveness contributed to the NFL never fully embracing it, as did pushback from players reluctant to wear a bulky, goofy-looking product. The concept gradually faded from football despite repeated attempts from Straus to revive it. 

By 2010, Straus sought help developing a helmet with a soft, energy-absorbing exterior capable of withstanding repeated hits without cracking or becoming ineffective. Straus approached Lee and Erin Hanson, an Atlanta couple whose material sciences company specialized in developing custom polyurethane formulations for anything from body shields for the U.S. Army to the outer layer of golf balls. 

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For Erin Hanson, helmet safety was an issue that felt deeply “personal.” The mother of five had a son who had started playing football. Her father was a coal miner’s son who used football to earn a full ride to Purdue and hoist himself out of poverty. 

“In my family, football is everything,” Hanson said. “There are so many benefits to having kids involved with football, but I wanted to find a better, safer way to do it.”

At the onset of the NFL’s concussion crisis, with the league facing criticism over its callous approach to brain injuries, commissioner Roger Goodell organized a summit of helmet safety experts to discuss possible reforms. Straus and Erin and Lee Hanson traveled to a hotel ballroom in Manhattan in December 2010 to pitch their product in front of Goodell and members of the NFL’s head, neck and spine committee.

The presentation, Erin Hanson admits, was not well-received. The soft-shell helmet prototype was “too ahead of its time,” she said.

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“We were told that this will never fly, that we were taking the sound out of the game,” Hanson added. “That made sense to people who wanted to hear the sound of helmet shells cracking, I guess, but I really did not want to hear my son playing like that.”

The failure to gain traction only made the Hansons more determined. They struck out on their own, convinced that the best market opportunity lay not with redesigning the football helmet but with creating a protective add-on that addressed some of the most frequent complaints about Straus’ Pro Cap. 

The Guardian Cap was lighter weight and designed to fit any helmet because it attached with clips or straps. It also shifted and slid atop a helmet rather than affixing directly to it, redirecting impact without increasing neck torque, according to laboratory tests that the Hansons paid for to vet their product.

“We knew that we could make a difference if someone would give it a try,” Erin Hanson said, but early believers were hard to find. Entire days would pass at football trade shows or sports medicine conventions without the Hansons’ booth attracting more than a few visitors.

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Potential customers were especially scarce at one 2013 conference in Destin, Florida. 

“It was crickets all day Friday and all day Saturday,” Erin Hanson recalled. “On Sunday, Lee and I said, ‘We’re just going to walk into the town and get lunch because nobody’s coming to our booth.’ “

Shortly after the Hansons returned to pack up and head home, a man approached their booth and said, “Well, that makes perfect sense.” That man was orthopedic surgeon Jeffrey Guy, team physician for the University of South Carolina athletic department. His enthusiasm was the breakthrough the Hansons had long been seeking. 

The NFL hops on board … but not the players

At Guy’s recommendation, Jadeveon Clowney and the rest of the South Carolina football team started wearing Guardian Caps during their 2013 summer practices. Then in-state rival Clemson followed suit. Before long, Guardian Caps were showing up on high school and college practice fields across the country, and the NFL was displaying newfound interest. 

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In April 2017, the Hansons received a grant of $20,000 from the NFL to support testing of the Guardian Cap at Biocore, an NFL-funded biomechanics and injury prevention research lab in Charlottesville, Virginia. The lab tested the lone existing version of the Guardian Cap at the time — the one the Hansons were selling to high school and college programs — but the seven-ounce XT model scarcely reduced the severity of impacts experienced by NFL players. 

“They didn’t really withstand much more force, if any, than helmets alone,” said Miller, the NFL’s executive vice president for health and safety initiatives. “Now they may work for other levels of the sport, but they certainly weren’t working at the speeds and forces that NFL players are subjected to.” 

The Hansons responded by creating the more heavily padded NXT version of the Guardian Cap, which fared considerably better in testing. Biocore attached the 12-ounce Guardian Cap NXT to a variety of different helmets, placed the helmets on the head of a crash-test dummy and fired a mechanical impactor into it at different angles and speeds. The NXT model decreased head impact severity by 9% compared to just the helmets alone. When both dummies wore the NXT model, the force of a helmet-to-helmet collision was nearly 20% less severe.

Encouraged by those results, the NFL permitted the use of Guardian Caps in practice in 2020 and mandated their use by certain position groups two years later. On September 8, 2024, Steelers guard James Daniels and Patriots safety Jabrill Peppers became the first players to wear the protective helmet covering in a regular-season game.

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To say that the Guardian Caps were unpopular among fashion-conscious NFL players is a massive understatement. Miami Dolphins linebacker Jordyn Brooks described Guardian Caps as “UFO caps.” Arizona Cardinals defensive end JJ Watt told reporters, “You feel like a bobblehead.” Philadelphia Eagles center Jason Kelce protested by showing up to his first 2022 training camp practice with bubble wrap around his helmet.

Among the few players who endorsed the change was offensive lineman Justin Pugh, who tweeted, “Let’s laugh at how dumb we look but increase our chances of remembering our kids’ names.”

The barrage of jokes about the clunky-looking Guardian Caps hasn’t prevented the Hansons from cashing in on the NFL’s endorsement of their product. Sales for Guardian Caps have surged the past few years, with over 500,000 athletes worldwide now wearing the protective helmet covering.

To Erin Hanson, those sales figures are a success story. To others, they’re something else entirely. 

Researchers: The NFL’s math isn’t mathing

If the NFL marketed the Guardian Cap as a way to slightly improve a player’s odds of avoiding a brain injury, Nowinski insists he wouldn’t put up a fuss. 

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The former Harvard defensive lineman and advocate for football safety says he only began speaking out when Roger Goodell repeatedly trumpeted the product as having “reduced concussions by 50%” despite evidence to the contrary. 

In 2024, a group of researchers, including NFL chief medical officer Allen Sills, reviewed league surveillance footage to analyze the impact of Guardian Cap use on the concussion rate during preseason practices from 2018 to 2023. They reviewed video of every concussion to determine which players were involved in the collision and whether the cause was a blow to the helmet shell.

The results of the study suggest to Nowinski that the NFL was premature in giving the Guardian Caps credit for reducing the concussion rate by 50% rather than considering the potential role of other variables. When only concussions involving helmet shell impact were considered, the study found that “there was no longer a significant relationship between Guardian Cap use and the incidence of concussions.”

“When the peer-reviewed study showed that it wasn’t the Guardian Cap that was reducing the rate of concussions, the NFL didn’t do anything to correct itself,” Nowinski said. “How unethical is it to go trumpet this massive reduction in concussions that sells half a million Guardian Caps to kids, giving them a false sense of security of concussion prevention, and then not correct yourself when the study comes out?”

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The company that designs and manufactures Guardian Caps stands behind their effectiveness in reducing the impact of hits to the head but makes no claims about concussions. On the Guardian Sports website, the Hansons include a disclaimer that reads in part, “No helmet, headgear or chin strap can prevent or eliminate the risk of concussions or other serious head injuries while playing sports or otherwise.”

The NFL’s stance remains largely unchanged. While Miller says the NFL endorsed the Guardian Cap because of its ability to decrease the severity of head impact, he did not shy away from the league’s previous concussion-related claims. 

“Look, the players who wore the Guardian Cap saw the concussion reduction and those that didn’t [wear the Guardian Cap] didn’t,” Miller said. “So I have to attribute at least some of the concussion reduction to the Guardian Cap.”

How effective Guardian Caps are at insulating football players from other dangers is also a complicated topic. 

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In 2024, researchers at Virginia Tech’s helmet-testing laboratory found that players who wear the Guardian Cap’s NXT model experience an 8% decline in linear accelerations and a 14% decline in rotational accelerations. That suggests to Virginia Tech helmet laboratory director Steve Rowson that the NXT model “may be helping a little.”

“It’s really hard to quantify the effect in the real world,” Rowson said, “but when we’re starting to see reductions over 10%, that stands out.”

The benefits were significantly less from the Guardian Cap XT version worn by youth and high school players. The average reduction in linear acceleration was just 3% and in rotational acceleration was just 5%.

Decreasing the severity of blows to the head by such a small amount “isn’t meaningfully reducing the risk” of CTE, according to Daniel Daneshvar, chief of brain injury rehabilitation at Spaulding Rehabilitation Hospital and associate professor at Harvard Medical School. In fact, the way Daneshvar sees it, the NXT model’s head impact figures “aren’t going to make a huge difference” either.

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The average force of a routine blow to the head in a high school football game is 27 times the force of gravity, according to Daneshvar. An 8% reduction, Daneshvar points out, is still nearly a 25G impact. A 3% reduction is still an impact of more than 26G.

“You’re much better off taking that 27G impact and making it a 0G impact by modifying the way that you practice,” Daneshvar said.

Multiple brain injury experts expressed concern that neither the Hansons nor the NFL is doing enough to clarify that the version of the Guardian Cap worn by professional football players is not the same as the model available for the public to purchase. 

“I would guess that less than 1% of people realize that,” Nowinski said. 

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When asked if he found that problematic, Miller said the NFL’s focus “has always been developing a model that works for us and sharing that data.”

“I can’t say that we’ve spent time testing other versions of the Guardian Cap at speeds that the lower levels of the sport engage in,” Miller added. “I guess that would ultimately be a question for the company to see what they’ve done in that regard.” 

Erin Hanson pushed back against the notion that the NXT model of the Guardian Cap is a “completely different product” than the XT. 

“It’s got an extra layer so it’s a little bit heavier,” she said, “but it’s doing the same reduction of impact at NFL speeds that we’re getting with our product at lower speeds for the youth level.”

Are the Guardian Cap’s days numbered?

Since Lee and Erin Hanson first came up with the design for the Guardian Cap 15 years ago, helmet technology has steadily improved. Instead of having biomechanical engineers test whether helmets met a minimum safety standard, the NFL began asking labs to assess which helmets reduced impact severity the most. 

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The byproduct has been a competitive marketplace in which a helmet that was once considered state-of-the-art could be substandard within a few years. Newer helmets feature flexible or deformable shells, multiple layers and densities of foam and position-specific padding designed to protect players where data suggests they get hit the most. 

“It wasn’t until helmets started getting rated, both by us and the NFL, that manufacturers were incentivized to try to make the best performing helmet possible,” Rowson said. “These evaluation systems really accelerated innovation in the helmet space. Helmet manufacturers, rather than relying on their own data, could then point to independent data to show why their helmet is better at reducing risk.”

Top-performing helmets are already performing well enough that Rowson wonders if there will be a market for the Guardian Cap or other helmet shell add-ons in 5-10 years. The advantage to strapping a Guardian Cap to a top-tier helmet today is far more marginal, Rowson said, than it was just a few years ago. 

That’s a stance the NFL and NFLPA shares. Already the league is incentivizing players to pick the safest available helmets by telling them they’ll no longer have to practice in Guardian Caps as a result.  

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“I see the Guardian Cap as a transitional piece of equipment,” Miller said. “Meaning that if the technology in the helmets continues to improve at the pace that it is right now, that will push players to the better-performing helmets, as opposed to the Guardian Cap.

“Now that said, Guardian Cap could come up with a new device that adds much more benefit. I’m sure they’re working on that but the helmet manufacturers are making great strides at a really rapid pace. Therefore we’re very comfortable encouraging players to wear those helmets where the Guardian Cap becomes optional.”

To Nowinski, the Guardian Cap may have already outlived its usefulness. He has friends who regularly ask him if they should buy one for their kids. 

“I always say no,” Nowinski said. “There is no evidence they make your kids safe.”