This is why Kansas City Chiefs players have been wearing special foam caps over helmets

It’s possible fans who have seen photos from the Kansas City Chiefs’ training camp in St. Joseph noticed something unusual.

Some players are wearing foam coverings over their helmets, giving the impression they have comically large heads. In reality, they are wearing Guardian Caps as part of an NFL mandate, which was passed in March, per ESPN.

Here is more about the caps, including why they’re in use in Chiefs camp and around the league.

Who’s wearing them?

The Sporting News said linemen, tight ends and linebackers must wear the caps, although the entire Steelers team will use them.

“In essence, the NFL is trying to reduce head injuries from constant head trauma in the trenches,” the Sporting News reported.

An NFL.com story said those position players were required to wear the soft-shell cushion because “they do the most hitting during those full-contact training camp practices.”

How long will they be worn?

The ESPN story said the designated players will wear Guardian Caps for “every preseason practice between the start of the training camp contact period and the second preseason game.”

Kansas City’s second preseason game, which is against the Washington Commanders, is Aug. 20.

The NFL.com story said that particular time period was chosen because it’s the start of high-contact practices, and there are more players on the field because it’s before roster cuts are made.

NFL teams must reduce their rosters to 85 players by Aug. 16, then cut the number to 80 by Aug. 23.

How do the caps work?

If you’ve watched a NASCAR race, specifically a crash, you may have an idea of how the foam cushion works.

Here’s an explanation from the Guardian Cap website: “Physics say that an outer ‘soft’ material of the proper density, stiffness and energy absorbing properties reduces the initial severity of the impact. The hard shell then has lower forces transmitted to it, and in turn conveys lower forces to the interior soft helmet padding and then lower forces to the head. Very similar to a NASCAR driver and the soft wall technology that tracks have adopted or even automobiles and the soft bumpers and airbags that are now required. The Guardian serves the same purpose for an athlete’s head — a soft shell barrier between it and impact.”

According to the NFL, wearing the cap wearing the cap results in at least a 10 percent reduction in severity of impact if one of the players is using it and 20 percent if two players in the collision are wearing it.

What do the Chiefs think about the caps?

Defensive tackle Chris Jones is ready to ditch his.

“As soon as I’m able to take it off, I will,” Jones said.

Left guard Joe Thuney wasn’t quite as dismissive.

“If it helps reduce head injuries, that’s really good,” Thuney said, but he isn’t sure he’ll continue to wear it beyond the required time.

“I’ll have to see how it’s going after we put the pads on,” Thuney added.

Here are Chiefs defensive linemen Frank Clark and Jones wearing the caps on Thursday (video from KSHB’s Hayley Lewis).