Real Madrid players have been seen training in unusual blue masks that resemble oxygen equipment designed to replicate high altitude training. But they are, in fact, very different. And Madrid performance manager Antonio Pintus, whose main role is to oversee the players' physical conditioning, is the person behind the idea. The equipment is understood to be worn during stress tests, with Pintus telling Real Madrid TV that they are 'designed to find out the players' aerobic and anaerobic threshol