I intended to go outside to walk 2 miles, despite my back being pretty tight still. Leaving the gym, I had to decide whether I wanted to bring my iPod Classic (arm band) and phone with me (no pockets). Doing so would have guaranteed that I wouldn't have run. However, I left both behind.
I started out at a nice trot, just enough to roll the feet forward for a smooth transition. By the 0.2 mile mark, I was down to an average pace of 8'53". By the end of the first mile, I was down to an 8'37" pace. My second mile was at an 8'14" pace. My limiting factor quickly became aerobic capacity with lungs and heart. Much more than 2 miles and I would have hit a pretty hard wall.
Now that I'm finished with the run, my back (and lingering sinus infection) actually feels better than before.