I do a 5 minute warm-up, usually starting about 2.5 or 2.6 mph, increasing every minute til I'm up to 3.6, which is about as fast as my short legs will let me "walk." Then I do another 5 minutes there. Then for 15 minutes - on my best days
- I do intervals of running 1-2 minutes at 4.8 or higher alternating with walking 2-3 minutes or however long it takes to breathe easier.
I end with a 5 minute cool down, going down from 3.6 to 2.6 or so, decreasing every minute. I'll go longer at the slow pace if my heartrate isn't under 120 (or if what's on the gym TV is good
) My goal is to be able to run that whole middle 15 minutes and then work to increase that.