Interval intensity on treadmill
On the treadmill would be very similar. Start out at a moderate intensity. It should be moderately difficult, but you can still talk and are breathing essentially normally. You can increase the intensity by either increasing the speed each minute, or by increasing the incline. When I used the treadmill, I did it by bumping up the speed, like 3.0, 3.5, 4.0, 4.5, 5.0, 3.0, and then the last minute before cool down 6.0
As you get stronger and faster, you just bump up your start point. But you could very easily leave the machine at the same speed and increase the incline each minute. That really doesn't matter. What matters is that you're going from a moderate intensity to an intense intensity, and the last minute before cool down you give it all you have.
When I am on the most intense level, my respiratory rate is usually 60, and my heart rate is between 165-185. When you are at your 90 and 100% levels, you should not be able to say more than one word. I certainly would not suggest you try to hit my levels. I don't want to be responsible for your cardiac arrest. You have to be really in touch with how your body feels and what your capable of.
There is a standard formula for what your heart rate should be for maximum cardiac benefits. 220 - (your age)x 0.8= your target pulse. So lets say your 40yrs old. 220 - 40=180x 0.8= 144. You want to get your heart rate up high enough that it stays slightly elevated for several hours. Then you're getting a metabolic benefit on top of a cardio-aerobic benefit.
Good luck! Let me know how it goes.