The 8/12 Gut Buster

Last week Kris posted a blog entry about what I am calling the 8/12 exercise system.
This week I started trying it out, I started on Monday with 15 minutes on the stationary bike and while it certainly made me sweat more, it felt like time went faster as I was focussed on keeping to the 8 seconds intense and then 12 seconds reduced exercise.
On Tuesday I used it while I did my normal run along the beach, this I really felt. Normally I jog along the beach at a reasonable pace. On an intensity scale of 1 to 10, where 1 is sleeping and 10 is throwing up, I normally jog along at a 7 or 8. Using the 8/12 technique on the beach on Tuesday I felt like I got to a 9.9, no throwing up but it was a close thing.
I think this must work, it certainly makes me work harder, and that has got to be a good thing.

What do you do to keep fit?