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Interval Training

Ok hopefully someone can clarify this for me. How exactly does interval training burn fat. I’m a 1st year ex phys student and from what i’ve learned thus far interval training utilizes the anaerobic energy system which does not use fat as a source of energy. Since you’re constantly changing intensities your body never switches over to the aerobic system which does use fat as a source of energy. I’m all up for trying new things, but I’m not clear on how exactly HIIT is a superior fat burning activity. Any thoughts?

Well, I’ll start off by saying the research supports HIIT as an excellent fat burning tool.

2)Which substrate you burn during exercise is not really that important, except for very specific situations.

3)HIIT seriously stresses the aerobic system also. The aerobic system is constantly working as the base mechanism for creating energy and you are adding stints of high intensity phosphocreatine and glycolytic work on top of it.

4)HIIT creates a large EPOC (excess post-exercise oxygen consumption) leading towards extra energy expenditure to maintain homeostasis.

5)Regardless of what substrate is used, HIIT creates a large energy expenditure and while “cals in = cals out” is not the whole story by any means, it is a major portion of it.

That’s just a start. I figure several others can add more.

Interval Training puts your body in a state of oxygen debt. So even though the amount of calories burned during actaul activity may not appear as high as a 30 minute aerobic session (depends on the length of interval session), the calories continue to burn during the recovery period as the body works to return to its baseline state.

Once an aerobic training session is completed so is the calorie burning.

Tree was right - Intervals burn fat/energy for a much longer period than does normal cardio. Once you stop a low intensity cardio session, you basically stop burning calories. There is no deprivation of oxygen and not much lactic acid build up. Interval training creates an oxygen deficit, which creates lactic acid, which releases the growth hormones. Growth hormones burn fat while building muscle.

Coincidentally, high intensity cardiovascular work in general has much the same benefits. It just so happens that interval training is easier.


Unless the high intensity cardiovascular work is anaerobic in nature, it will not have the same effect. As long as oxygen is being burned as the major source of fuel, no oxygen debt is created, and thus once the exercise has finished, so has the calorie burning.

In an interval workout the body goes anaerobic during the high intensity periods, and then gets some recovery, but not enough recovery to bring the body back to homeostasis.

Cardiovascular work in long bouts with no recvoery built in will not produce the same effects.

I’ve never done an interval workout that was easy.

Interval training is hard, but so is hiit cardio style. It’s just that you can go harder during the intense times of interval training, therefore keeping cardio time to a minimal amount.

Don’t forget about the metabolic machinery and more efficient metabolism that you’ll build with prolonged, dedicated training, HIIT-style.

You’ll be developing more mitochondria (especially in Type II fibers) and more capillary density. Therefore, you’ll be more efficient at burning fat at rest.

It’s already been mentioned that the elevated metabolism in the period following HIIT (i.e. EPOC) is a source of fat-burning. However, it’s also known that HIIT elevates your metabolism for a time greater than just the few hours afterwards–similar to the response of weight training.

Addditionally, right after a bout of HIIT, there is a drastic increase in lipolysis and the appearance of fatty acids in the blood (i.e. from adipose tissue). Therefore, some low-intensity activity right afterwards will contribute to elevated fat oxidation.

Aerobic training at lower intensity burns a higher percentage of calories from fat- However higher intensity exercise will burn more calories overall-therefore you can use more fat calories for energy

It surely is unfortunate that this is very much representative of the content of undergraduate curriculum in our field and the resultant degree holders.

The reason for this dumbing-down of science, I cannot explain. Perhaps it is in an effort to appeal to the general public. Truly unfortunate.

I think we are touting the same things. HIIT is interval training.

High Intensity Interval Training.


You should have seen my 3000 level nutrition class.

Actual test question:
“Which billboard contained the catchphrase, ‘Cute Anorexic Chicks?’”

I should have saved my money and read T-mag. I should have saved my money and read T-mag. I should have saved my money and read T-mag.

Any way that I can get college credit for reading T-mag?


The Dog Child…It surely is of paramount concern to me. It’s very frustrating to know that our profession (well, my profession-to-be) is littered with mis-information.

However, I will say that if you take your game (or schooling) to the next level (i.e. a solid graduate program), then you can surely depart from the rest; and this is where you’ll definitely see how much is not covered or mis-covered in undergraduate exercise physiology and kinesiology departments.

Fortunately, we’ve also got T-Mag and the Forums to distribute proper knowledge. It’s a comfort to me.

Tree Rollins…HIIT and Interval Training aren’t necessarily the same. For example, the latter would be applied to athletes for improving performance via improving the energy systems specific to the sport. In Interval Training, athletes often do not give maximal efforts (very close to it though) during the interval portion. In addition, during the recovery portion, athletes are encouraged to attain full recovery such that the interval portion can be of the same intensity from the first to last “sprint.” These charactersitics are not necessarily required of HIIT when it’s applied to physique athletes.

I would disagree with your statements about post graduate education. As someone who has a masters degree, the information is a little better, but still not great. Almost everything comes from self study and researching things on your own.

Most text books contain information thats a minimum of 5 years old. The info was current at the time of writing but the amount of time it takes to get a book published is so long that science has changed.

Unless you get a professor who stays current and uses a book for mere reference its tough to get the real scoop.

I can see it now- " The phyilosphy of T-Mag"- TM450. The class meets Friday Nights for 3 hours. A variety of guest speakers each week. Credit hours- 3.

As far as the definition of interval training. Anything that has timed periods of varying intensity is interval training.

HIIT- stands for High Intensity Interval Training.

The work to recvoery ratio is up to you, and will vary from athlete to athlete depending on training experience, level of conditioning, and goals.

Most sprinters typically would make good “physique athletes”, and they do quite a bit of interval training.

Great to see how many informed people are actually out there. Being an ex phys major you generally tend to believe everything you’re taught by your professors, its a shame how much they leave out. I’m with dogchild I should have saved my money and just read t-mag.

I’m a biology major, and the stuff is so dumbed down for us, it’s ridiculous. I only truly learn when I read scientific publications. Only then can I put 2 and 2 together and get 5. Oh wait, that’s not right, damn professors…

I hope to instill this in you now. When I was in college, my exerc physio professor ranted and raved on about slow intensity cardio and how it will pave the way for ultimate fat loss. We even did experiments measuring VO2 and VCO2. He also looked pregnant and complained of aches and pains all the time. Then in the football offseason, I do track workouts with some teammates, and end up losing about 25 lbs of fat. We did versions of CT’s Running Man, with some other sprints as well. Needless to say, not everything is what it seems on the surface

As a former phys of ex student with a BS I can say that A phys of ex degree is about as worthless as they come. Much of what is taught is either dated or not applicable to the real world. I remember learning very little that could actually be appiled to strength training and conditioning. I remember sitting in nutrition class andlearning about the food guide pyramid and how i was eating way too much protein and it was potentially dangerous. And we wonder why so many trainers suck.


As much as I’d like to take my game to the next level, I think it’s going to be the next-self educated level, as my undergraduate education has had little-to-nothing to do with science. I’m graduating this fall with a degree in Philosophy, so I’m lacking about 3-4 years of the hardcore science it would take to get into a good graduate program. So you can see my dilemma. Of course, Louie Simmons is self educated, and Dr. Fred “Squat” Hatfield has a degree in Psychology, I believe, and no one doubts their training credentials.

Anyways, I’m off the board for a while. I’m going to St. Paul to get my RKC certification.


The Dog Child…It can definitely be done (i.e. self-edumacation). That’s how I really took my game to the next level in undergrad. I spent my weekends, for the most part, in the stacks at the library reading the real science and just getting a hold of as much as possible.

Good luck (with your certification) and in the future, Dog Father!