I thought this was so funny, had to share. I have heard of some really interesting ways of high altitude training and have jokingly said to just sleep with a wet sock in your mouth, which would probably kill you by the way, but check this out. In fact, when first reading, I thought he might have died or something, but . . .
According to Hoang, the mask he wore was designed to restrict breathing to simulate training at high altitude. A vest he also wore to the post office was packed with ten pounds of weights. CBS 5 News