Reports out of China state that woman suffered at least one ruptured breast implant after lying on her stomach for four hours and gaming. According to Chinese news reports, Xiao Ai (a pseudonym) had recently got into an iOS app called Dragon Summon and was often staying up late to play the game. Earlier this month, she was in bed, playing the app for a long session, when she felt a pain in her chest.
Ai was rushed to the hospital, and Xinhuanet reports that the hospital's doctor said she was in a bad position for an extended period of time, putting pressure on the implants and causing the rupture. (The Chinese news sources do not specify if both implants, which she got five years ago, were affected.)
Implants or not, it's always a good idea to take breaks while gaming -- stand up and change your posture. This is important stuff. Don't forget.