You're breaking my speed on flat ground by a bit, and, seriously dude, running that fast on a treadmill is bad mojo. A 6 minute mile like OP is risky enough, breaking into the sub-5-minute range is just asking for injury. One thing goes wrong and that's a whole lot of pointy plastic and metal waiting to jack your shit up. Even in the winter I felt safer running laps around our camp's LZ than trying to push the treadmills at my 5:20-5:30/mile pace. Find an indoor track or run outside. Your face will thank us later.