I've been "running" on the treadmill at the gym lately. I'm not sprinter nor marathon runner nor do I hope to be, but being able to run to the aid of my co-workers and not be a waste due to not being able to breathe would be outstanding. Saturday I did 1.25 miles jogging .75 of it. It's not much, but for me, it's excellent. Hell, I'm surprised by my level of endurance thus far. I've only been doing this for about a month now as opposed to the lifting I've been doing for about 3 months.
Congrats!! I recommend using a program that varies the incline on treadmill.
