6/9: This is the method used in the Australian study referenced above, and this is what I personally recommend. The numbers stand for seconds, and in this case, "6/9" means you would sprint all out for 6 seconds, then slow to about 50-60% for 9 seconds. Of course, you would continue repeating this cycle for as long as you can (you didn't think you'd be done in 15 seconds did you?!).
For example, hop on the exercise bike and warm up for 2-3 minutes at about 40-50% of your maximum effort. Once you hit the end of your warmup session, BAM!, launch into a full out sprint for 6 seconds. Then, slow to about 50-60% for 9 seconds, and BAM!, full out sprint for another 6 seconds. So, each full 6/9 interval lasts 15 seconds, or 4 intervals per minute. Keep repeating this cycle for as long as you can, but be sure that you are going as hard as possible for each 6 second sprint interval. It's OK if you can only last a few minutes the first few times. Your endurance will build up, as your waist shrinks down!
