I did another 30 minute run yesterday when I was in Edmonton. I figure it was about 5km again. It was cool out but I didn't have any trouble breathing while I was running.My legs felt great and I think I could have gone further if I'd wanted to. Then when I got home, cooled off, and had a shower, I started coughing for about 45 minutes. Since then, my lungs hurt (a little) when I take a deep breath. I used my inhaler before I left. I guess my lungs just don't like the colder dry air...