Simple enough, 20 seconds on, 10 seconds off for multiple four minute intervals. Should probably be done at the completion of a workout to get the most out of it. http://www.tabataprotocol.com/ Variants, are out there. Can do this with multiple exercises that include resistance band work, pushups, dumbells, burpees, pretty much whatever you can think of that you could go all out at for 20 seconds. Interestingly, this sort of workout, somewhat reflects a tough round of boxing, requires some explosive energy as well as endurance if you do the sort of one I do, with pushups, pullups (2nd set assisted), shoulder presses with some dumbells, and burpees. I'm still not used to this, it gasses me every time.
Then how is it good for fat burning? The whole point of interval training is not to gas yourself. To push yourself as hard and as fast as you can then back off recover and do it again.
The recovery periods in HIIT(high intensity interval training) are designed to go longer than if you didnt have them, but by no means you can do HIIT training as long as steady state endurance training. You ARE supposed to gas yourself, you want to perform the high intensity intervals at around 85-95% of maximum effort. The big strain you put on yourself during the high intensity intervals, trains your anaerobic system and recovery systems much better than endurance type training. As for weight loss, doing 1 hour of endurance training burns more calories than 20 minutes of HIIT. However, 20 minutes of HIIT burns more than 20 endurance. This is mainly becuase of the afterburn effect of HIIT; it raises your metabolism for a long time after the workout. HIIT allows you to improve faster than steady state endurance training when it comes to muscle growth, strenght, cardiovascular fitness and therefor surprisingly endurance. Personally I like to combine the two types of training. When I'm doing my daily laps in the pool and i have say 1.5 hours to work out, I start with an hour of freestyle at around 3.5 miles an hour, then I rest for say 5 minutes and start doing HIIT by alternating between 2 stretches almost full effort sprints and one very slow breast stroke stretch. It gases me out completely and after around 20 minutes I feel like puking, then i end with 5 minutes of cooling down. Worked miracles to improve my endurance strength and weight loss when compared to 1.5 hours just doing endurance.
Fat burning isnt the goal of tabatas. It is known for very effective anaerobic gains, while also having the benefit of providing aerobic gains. If one is concerned primarily with burning fat, focus on putting less food in your mouth daily with whatever cardio workout you come up with.
Dont let anyone sell you on after burn or more correctly EPOC(exercise post oxygen consumption). EPOC is the calories burned(more correctly oxygen used) to return the body to its pre-exercise state. The drgree of EPOC is a function of intensity and time. Not just intensity. The highest EPOC occurs at around 75% VO2 max(intensity) for a long duration of around a hour and a half. Quickly gassing yourself doesn't equate to a high EPOC. Gassing occurs because you are expending energy faster than the body can process the lactate waste, the body is operating above the maximum lactate steady state. You operate above this maximum and you will quickly have to slow down or drop. However, the amount of actual energy you have burned might not be that much. EPOC is a function of many things only one of which is the processing of lactate out of the body. The body has to rebuild ATP stores, oxygen stores and normalize other functions. All of this takes energy. This energy is EPOC. If all you have done is hit your lactate threshold then the required energy for the other parts of EPOC is low. All that said maximum EPOC will only be about 150 Cal. Your 20 min HIIT is probably not exceeding 50.
You're right, the effect on EPOC is minimal, still it's there. I might have worded things a little more careful, my assumption was that doing HIIT for 20 mins burns about as much as an average 20 min endurance workout. The difference between them would then be in the higher EPOC with HIIT. Even though the benefits of HIIT for weight loss are debatable, this doesn't take away the many other benefits of HIIT though (higher lactate tolerance, faster recuperation (i.e. getting rid of lactate,rebuilding ATP etc), more cardiovascular benefits and muscle growth. I think that for people that have little time to work out and time efficiency is a big issue HIIT is good to try, also for weight loss. For me, I just enjoyed getting my 100m time under a minute in a non standard 20m size lap pool. I found a sharp improvement after i started doing HIIT along with my endurance training.