When you say that you run, are you running around a track or just on a treadmill? Both are very different, as you might know.

I've just started running around here outside, and it's been pretty nice. I run downhill for about 10-11 minutes, and then uphill for about 10-11 minutes. My goal is to be able to run for 30 to 45 minutes without stopping and with ease. Maybe get the runner's 'high'.