These may have been answered before but sometimes I need a little more clarification.

Here is what I was doing on a treadmil. 1min run with 2min fast walk. From the link posted in the HIIT thread I should be doing much shorter and more intense runs. Say maybe a 10 to 15 second sprint, but how much time before I sprint again? If I only wait 30 seconds or so before I spint again, I'll only be good for maybe 3 or 4 minutes. Is that long enough? Any suggestions on a routine for treadmil. BTW, I tried this last night and it seemed to work ok on the treadmil. I'll do it outside when the weather is a little better.

What about leg fatigue, heart rate, and resparitory rate. By the time I started the 3rd run, my legs were starting to burn, and my chest was pumping hard. Not to sound stupid, but is that what I am shooting for?

Thanks again,
Jerry