I love my treadmill workout! With mp3 in hand (or should I say ear) I start off with a speed of 2.0 for 5 mins as a warm-up. Then I bump it up to 2.5 for 5 mins and down to 2.0 for 5 mins. I do this in increments on the high end until I reach 3.5 mins.
At that point, I do 2 mins of 2.0 and 3 mins of 3.3, etc until I reach 3.9 That's as fast as I've been able to reach so far. After doing my intervals at this pace for awhile, I start working my way down, making sure the last 5 mins are at 2.0 I feel the intervals really give me a workout