Oakland Raiders wide receiver Antonio Brown has spent much of training camp on the non-football injury list due to some gnarly looking blisters on his feet. Brown had shared some disgusting photos of his feet a few times over the past week, and really, his feet didn't look good at all. It had many wondering what possibly could have caused the foot ailments. Well, according to "PFT Live" co-host Chris Simms, Brown's feet didn't appear to be blistered but rather they were showing signs of frostbite. Simms went on to report — citing someone close to Brown — that the former Steelers wide receiver sustained frostbite from using a cryotherapy machine without proper footwear. Via ProFootballTalk : Simms got word from someone with knowledge of the situation that Brown burned his feet by entering a cryotherapy machine without the proper footwear, and his feet were frostbitten. Full-body cryotherapy is a popular recovery method used by athletes like LeBron James. Basically, you stand in a cryotherapy chamber for roughly three minutes as temperatures drop as low as minus-110 degrees Celsius (minus-166 degrees Fahrenheit). But anyone who has used whole-body cryotherapy before knows that you don't stand in the chamber barefoot. Simms didn't detail what exactly Brown was wearing on his feet, but whatever it was, it obviously wasn't suited for such low temperatures. Follow For The Win 's Andrew Joseph on Twitter @AndyJ0seph . If you love talking football, we have the perfect spot for you. Join our Facebook Group, The Ruling Off the Field , to engage in friendly debate and conversation with fellow football fans and our NFL insiders.