Today, in beautiful weather, I ran a 6:45 paced 4-mile tempo. Awesome. I did have to switch to 2-1 breathing pattern at around 1.25 miles into the fast part, which is somewhat scary, because I'm not sure how long I can breathe that fast, but maybe OK. In fact I should be happy that I can sustain high oxygen intake for longer and longer. Maybe those years of smoking are to blame for destroying enough of my lung tissue?