I wouldn't get that technical with it. Try going as hard and fast as you can for 30 seconds and then a jogging pace for 60 to 90 seconds. Then repeat a few times. Then maybe try to add another interval every week. If you can work up to 15 intervals of 30 seconds max and 60 seconds jogging, that's pretty good.
I agree that you don't want to get too technical about it. However, gauging your intensity allows you to know where you are and how you are doing.
The best tool for that is a heart rate monitor. It permits you to measure the intensity of your workout.
The Karvonen Formula
[http://exercise.about.com/cs/fitnesstools/g/karvonen.htm] allows each individual to customize it for them.
Intensity is the key to success. However, one can only push so hard for so long. There is an inverse relationship between time and intensity.
Time and intensity are on opposite sides of the see saw. When one goes up, the other goes down.
So, higher intensity levels are reached when high intensity sprints are kept short, 30 seconds or less. Even with 30 seconds sprints, you'll find the amout of work you are doing will diminish as you near the 30 sccond mark.
As you recommended, 60 to 90 second jogs (low intensity recovery sets) work. The Sprint 8 program in the book "Ready, Set, Go" recommends this method.
Another thing is in performing these sprint sets, work up to your maximum effort as you would with a weight training program.
The first sprint being about 50% of your maximum, take your recovery job. The next sprint is performed at about 60% of you maximum effort.
Keep pushing the intensity up with each sprint. The last sprint should be performed with everything you've got.
We track our weight training program by how much weight we push/pull. To track your interval sprint progress, track your heart rate.
The last set of your weight training exercise should be the most you can do. It's the same with your high intensity sprint set. Your highest heart rate reading will be with your last sprint.