[mosesbotbol]

A close friend of mine is one most sought after trainers in the city, what he does with clients is as follows:

3 minutes at 3.5 mph, 0 elevation
1 minute at 3.5 mph, maximum elevation

Repeat in the same cycle. Your flat speed can be faster, but the elevation speed is not as critical as you'll be working it. This ratio is also done between a few sets instead of sitting around between body parts. It's important to keep a minimum intensity level for the entirety of your workout with peaks (like weight lifting sets and maximum elevation stints on treadmill) and steady state (flat 3.5 mph).