Why are NFL players wearing padding on helmets at training camp?

Bengals linemen, linebackers and tight ends wore Guardian Caps at training camp after the NFL required the padding for some position players this preseason.

What in the world are those weird-looking helmets the Saints are wearing in camp?, Rod Walker

Why are NFL players wearing padding on helmets at training camp?

NFL's use of Guardian padded helmet caps in camp draws support and

Guardian Cap Use a Concern for Watt, Saleh Early in Training Camp - Sports Illustrated

What are those helmet pads Chicago Bears offensive linemen have been wearing at practices? – Chicago Tribune

What Pros Wear: Guardian Caps What are Those Helmet Covers Being

Have you seen the strange helmets Cowboys players are wearing in camp? Here's the story

Puffy Guardian Caps Could Reduce NFL Player Concussions

nfl helmets training camp

NFL Mandated Guardian Caps: Controversial Change - Sports