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.

Eagles training camp: 'We look a little goofy:' Philly players on wearing the new Guardian Cap – The Morning Call

NFL Players Seen Sporting Futuristic New Helmets During Training Camp (PICS)

nfl helmets training camp

Guardian Cap debuts during minicamps in effort to reduce avoidable head contact

NFL training camps: Guardian Cap players are wearing over helmets, why

NFL exec suggests Guardian Caps worn to protect players during practices could one day debut in games

NFL training camps: Guardian Cap players are wearing over helmets, why

The story behind those soft-shell puffy Guardian Caps players have been wearing

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

NFL Training Camp: 12 photos of players wearing the new Guardian Caps