I understand the benefits of elevated metabolism post cardio that come from HIIT, they've been well documented on every bodybuilding site on the internet. However, I don't understand why it is necessary to train in intervals to achieve these benefits. Is the argument that intervals are necessary for a session to be truly "high intensity" for any worthwhile length of time? There seems to be so grey area here.

For example, 3 miles in twenty minutes. Surely the heart rate is elevated well beyond the run itself for most people-thats a tough run. But its "steady state," as well. Why does the designation of "steady state" automatically=no post cardio metabolic boost?

I've always wondered this. Thanks.

I've always wondered why HIIT is supposed to be better. I think if you do an intense run it might lead to muscle loss whereas HIIT won't .

It's the difference between a marathon and a sprint.

Did you do wind sprints when you were a kid? Doing enough wind sprints might equal a long distance but it's totally different then walking the same distance or even running it.

It's the difference between a marathon and a sprint.

Did you do wind sprints when you were a kid? Doing enough wind sprints might equal a long distance but it's totally different then walking the same distance or even running it.

I don't think you're addressing the OP's question. He's asking the difference between sprinting around a track the whole way, and doing interval or "wind" sprints around that track.

To answer the OP as best I can, I think that it's only possible to achieve the high intensity (> 90 or 95% of MHR) for short periods of time, less than a couple of minutes at most. If you are able to maintain "high intensity" for longer than that, then it's not high intensity for you, and you would probably be able to be even more intense in a shorter period of time.

People get hung up on defining intensities based on comparisons to fellow exercisers and even compared to their estimated MHR, which can often be off by a lot and this can skew their ideas of high intensity and low intensty by quite a bit.

Something that doesn't fail for me, is that if it's high intensity, after 1:30 or 2:00, I should be unable to continue unless I cycle back down to my "rest" interval. If I could do more, I need to make the "work" interval more intense.

i've lost quite a bit of weight myself and i haven't done HIIT once. some min/max'ers may disagree and that's ok. i have no desire to break up my concentration and pace like that. so i looked at some other methods of weight loss.

look at what the military does, reduce calories and run. can't stop, runnin'. right now i run 2 miles twice a day and go for a long 6 mile on the weekends. is that a lot of running? hell yeah, but I feel no pain and it works for me and i'm losing fat like crazy. no other organization has made more chubby people lean as far as i know.

plus i find that there is a psychological edge in knowing you can run, a lot if need be, and for long distance. a lot of people nowadays can barely run a mile and when your knocking out 4, 5, and 6 at a time it's a good feeling.

You never really hear on these boards or T-Nation or other places people just advocating going on a run. To run as far as you can and as fast as you can for 30 minutes. I know that bodybuilders and other pros have reasons for HIIT and LISS depending on what part of the season they are in, but, for the most part, people are here for general fitness.

For fat loss, it still comes down to the amount of calories in vs. the amount of calories out. If you're consistantly lifting and aren't about to go on the show Survivor, I can't imagine that, for the average person, muscle loss is going to be significant.

Although, you do see some less than lean people running marathons. I've wondered about that as well. Why aren't they more lean if they've just finished training for a marathon? I know they are doing 10 minute miles, but still ....

Although, you do see some less than lean people running marathons. I've wondered about that as well. Why aren't they more lean if they've just finished training for a marathon? I know they are doing 10 minute miles, but still ....

I'm gonna guess that they eat too much/not well.

Personally I don't like doing HIIT as I have to constantly adjust the speed on the treadmill. Also I have never met anyone who does it - maybe it's just an American/Canadian thing.

I know in the Singapore army they make overweight recruits run round the island each day until they're in shape. But there are very few overweight recruits as fitness standards start in Primary 3 and to get the primary 6 leaving certificate a pupil has to be able to run 3 kms in 15mins as well as do a lot of other exercises. But then HIIT is for fat loss not for people who just want to lose weight (which most likely includes muscle loss) - so I am told.

I do HIIT because I do martial arts like muay thai and jiu jitsu, with the eventual goal of doing MMA. HIIT improves both aerobic and anaerobic capacity, and fighting is an anaerobic activity. HIIT workouts, like Tabata drills, leave me feeling much more used, from head to toe, than steady state cardio does. I still do steady state once or twice a week, but it's just not a useful activity for me, generally. I need that sudden burst of full body effort, and then a short break, again and again, to emulate a fighting situation.

And honestly, I feel like my conditioning is just vastly improved over what it was when I was just running, and without putting so much wear on specific parts of my body (namely my right hip, which basically no longer likes it when I run more than 2 miles).

And in the end, HIIT leaves me more exhausted in less time. I have things to do!

I don't think you're addressing the OP's question. He's asking the difference between sprinting around a track the whole way, and doing interval or "wind" sprints around that track.


You can't sprint all the way around the track. Over 200 meters. I guess maybe 400 meters it's no longer a sprint.

HIIT intervals are all out or fairly close to it.

HIIT also builds with each interval. First interval doesn't push you that close to the edge. You recover a little but not all the way to resting. The next interval builds on this level pushing you further. This repeats. By the time you're done your body needs longer to recover from this elevated state. My guess is that is why the post workout calorie burn adds up. You can do steady state for hours and then stop. You won't find yourself needing to recover the same way.

However, I don't understand why it is necessary to train in intervals to achieve these benefits. Is the argument that intervals are necessary for a session to be truly "high intensity" for any worthwhile length of time? There seems to be so grey area here.

Yes, you can't really go all out for long, unless your all isn't all that much.

When you train your lactate threshold, you can get it up to about 95% of your VO2max, and the lactate threshold will be how hard you can go for any length of time. But a hard interval is typically well over the VO2max - you go instantly into oxygen debt. The hard interval should be completely impossible to keep up for two minutes, it should be seriously difficult to do it for over a minute.

If you can keep your hard interval going for a few minutes, then you are not doing HIIT; you are doing some other sort of interval training.

There are lots and lots of useful interval workouts. There's nothing wrong with doing longer hard intervals. There is also nothing wrong with doing longer easy intervals or even resting on them. These are just different variations on the same idea. All HIIT means is that the hard interval is as hard as you can do.

You can't sprint all the way around the track. Over 200 meters. I guess maybe 400 meters it's no longer a sprint.

HIIT intervals are all out or fairly close to it.

Yes, that's basically what the rest of my post went on to say ;)

Personally, I do both HIIT and medium-intensity long runs (10 km in about 40+ minutes). I think it keeps my body guessing, allowing less adaption to either short or long distances. The HIIT helps me with anaerobic activities (I play a lot of squash), and the MISS helps me with endurance in all the sports I play.

For fat loss, I think both are fine, but HIIT is probably more efficient.

I love being able to get all I need to do on the treadmill done in 15 minutes. I do my longer runs outdoors, it gets too boring on a treadmill for 45 minutes...

I'm gonna guess that they eat too much/not well.

Or they eat that way on purpose because less weight = less weight to carry each mile.

Makes it a bit easier to run long marathons. Although there are a lot of people 180-210 lbs who run marathons too.

look at what the military does, reduce calories and run.

Oddly enough the military isn't concerned with the most efficient way to train for long runs. They are concerned with getting people into good condition and imposing disciplines of various sorts. Yes, just running will get you into good condition. So will the other thing that the military likes to do - load you with weight and have you walk over hills.

But if you want to get into the best condition that you can, these methods, although not bad, are not the best. Intervals are more efficient at getting you to run long distances, and high intensity intervals are part (although not all) of that picture.

The advantage of the intervals is that they use less glycogen and burn more fat than steady state; they trigger more metabolic pathways, but don't deplete as much, as other forms of exercise.

Now I myself do like to use long hard steady intensity work, but that is because intervals do not deplete glycogen. Depleting glycogen is for training your liver to have a higher glycogen capacity. Just like anything else, the adaptation is pretty specific to the stress; the liver only responds if you push on it. The reason I do this is because the capacity for extending high intensity work which requires glycogen is increased.

So oddly enough, intervals are efficient at increasing endurance at low intensities, and hard steady work is efficient at increasing high intensity endurance.

Sounds backwards in a way, but it's not. What happens is this:

The interval training uses carbohydrate metabolism, and the body adapts by increasing the cardiovascular capacity which increases the intensity at which you can burn carbs. But since that cardiovascular capacity is also used in burning fat, then this adaptation increases the ability to burn fats as a side effect. But since the overall glycogen used is small the liver is more or less untouched by this. So the intervals increase the rate at which you can burn carbohydrates, but not the total amount of carbohydrates that you store.

The long steady hard work does deplete glycogen. And this is why body builders don't really care for it - the high glycogen cost means that for the same fat Calories burned, a higher carbohydrate cost must be paid - so it is not anywhere near as efficient at triggering fat burning as intervals. But, it is the only way to deplete the muscle and liver glycogen. This is the efficient way to get the body to store more glycogen when it can. It is quite subtle how this burns fat, but its worth mentioning. By having a high glycogen store, you can work out harder and longer without running into trouble. And more of the carbohydrates you eat get stored as glycogen instead of turned into fat, so your nutrition doesn't have to be timed quite as closely. It also means your weight goes up and down a lot more from workouts though.

So it's not like there is no value from the long steady hard work. But a lot of guys want to burn fat most of all with their cardio. And for that, the cardio with the most time spent at low heart rates is the answer. That either means LISS (which burns Calories at a pretty low heart rate while you do it) or HIIT (which burns Calories at as low as possible a heart rate when you stop doing it). That's why body builders focus on HIIT or LISS.

And of course, you can do your HIIT while you lift - just use intense sets and short rest. That's what the guys who do "no cardio" are doing. That is the most time efficient method, and it also means that on the rest day, they fully rest. That is more of a muscle building consideration, but body builders are concerned with that.

Sounds backwards in a way, but it's not. What happens is this:...

Wow! Cool info, Zen! This stuff is eye-opening about whats been going on with my training.

Oddly enough the military isn't concerned with the most efficient way to train for long runs. They are concerned with getting people into good condition and imposing disciplines of various sorts. Yes, just running will get you into good condition. So will the other thing that the military likes to do - load you with weight and have you walk over hills.

But if you want to get into the best condition that you can, these methods, although not bad, are not the best. Intervals are more efficient at getting you to run long distances, and high intensity intervals are part (although not all) of that picture.

The advantage of the intervals is that they use less glycogen and burn more fat than steady state; they trigger more metabolic pathways, but don't deplete as much, as other forms of exercise.

Now I myself do like to use long hard steady intensity work, but that is because intervals do not deplete glycogen. Depleting glycogen is for training your liver to have a higher glycogen capacity. Just like anything else, the adaptation is pretty specific to the stress; the liver only responds if you push on it. The reason I do this is because the capacity for extending high intensity work which requires glycogen is increased.

So oddly enough, intervals are efficient at increasing endurance at low intensities, and hard steady work is efficient at increasing high intensity endurance.

Sounds backwards in a way, but it's not. What happens is this:

The interval training uses carbohydrate metabolism, and the body adapts by increasing the cardiovascular capacity which increases the intensity at which you can burn carbs. But since that cardiovascular capacity is also used in burning fat, then this adaptation increases the ability to burn fats as a side effect. But since the overall glycogen used is small the liver is more or less untouched by this. So the intervals increase the rate at which you can burn carbohydrates, but not the total amount of carbohydrates that you store.

The long steady hard work does deplete glycogen. And this is why body builders don't really care for it - the high glycogen cost means that for the same fat Calories burned, a higher carbohydrate cost must be paid - so it is not anywhere near as efficient at triggering fat burning as intervals. But, it is the only way to deplete the muscle and liver glycogen. This is the efficient way to get the body to store more glycogen when it can. It is quite subtle how this burns fat, but its worth mentioning. By having a high glycogen store, you can work out harder and longer without running into trouble. And more of the carbohydrates you eat get stored as glycogen instead of turned into fat, so your nutrition doesn't have to be timed quite as closely. It also means your weight goes up and down a lot more from workouts though.

So it's not like there is no value from the long steady hard work. But a lot of guys want to burn fat most of all with their cardio. And for that, the cardio with the most time spent at low heart rates is the answer. That either means LISS (which burns Calories at a pretty low heart rate while you do it) or HIIT (which burns Calories at as low as possible a heart rate when you stop doing it). That's why body builders focus on HIIT or LISS.

And of course, you can do your HIIT while you lift - just use intense sets and short rest. That's what the guys who do "no cardio" are doing. That is the most time efficient method, and it also means that on the rest day, they fully rest. That is more of a muscle building consideration, but body builders are concerned with that.

as i stated earlier, from a min/max approach i'm sure HIIT is superior, I really don't care. my overal thesis in that regard is that I, and others, don't like HIIT and simply won't do it. i stated earlier i enjoy the clear, concise objective able to be understood by others, like I just ran 5k in less than 20 minutes. and i know a lot of people that run pretty quick marathons that don't focus on HIIT much at all, maybe once a week or every other.

as i stated earlier, from a min/max approach i'm sure HIIT is superior, I really don't care. my overal thesis in that regard is that I, and others, don't like HIIT and simply won't do it. i stated earlier i enjoy the clear, concise objective able to be understood by others, like I just ran 5k in less than 20 minutes. and i know a lot of people that run pretty quick marathons that don't focus on HIIT much at all, maybe once a week or every other.

:confused: Most marathon training includes a weekly intervals session as well as maybe a tempo run (MISS/HIT). It is considered a crucial part of the training programme. More than once a week would be too much with all the other training. For fitness and fat loss a mixture of HIT, HIIT and LISS is probably ideal, but you aren't going to continue with stuff you hate doing!

Very interesting stuff zenpharaohs. Just out of curiosity, does MISS cardio cause one to burn calories after finishing the exercise? Or is it like LISS cardio, which only burns calories during the exercise itself?

Very interesting stuff zenpharaohs. Just out of curiosity, does MISS cardio cause one to burn calories after finishing the exercise? Or is it like LISS cardio, which only burns calories during the exercise itself?

All exercise burns Calories after the exercise, but with LISS it's a tiny amount not worth considering.

The amount of post exercise Calories is linear in the volume of exercise. In other words if you do the same workout for twice as long, then you double the amount of post exercise Calories.

The amount of post exercise Calories grows faster than linear with increasing intensity of the exercise. So if you do the same workout at twice the intensity, then you much more than double the amount of post exercise Calories.

These two principles have been verified in careful studies. You can also check them yourself with a heart monitor.

Post exercise Calories are almost all from fat; because the carbs are kept in reserve as soon as you start resting.

Most questions about the various cardio strategies can be answered by using these two principles.

Suppose you want to understand how HIIT "works". Well, take a LISS workout, and do it for half as long, but at twice the intensity. Then you will have generated more post exercise Calories in the shorter, more intense workout. So now if you can, double the intensity and halve the duration again. Well, that will be even more post exercise Calories, and so on. You will be having a great fat burn if only you can increase that intensity. But everyone has a limit. So what you end up with for HIIT is a very short workout at the highest possible intensity, which gets a high amount of post exercise Calories from intensity, and then as short a rest as possible, and the repetition of that. The repetitions increase the post exercise Calories by volume. Note that the exact same reasoning applies to any exercise which is in short bursts of intensity, like barbell complexes, etc. Your metabolism is like a gas tank and fuel pump. They don't care what the engine is driving, they just care how much fuel and how fast.

LISS is the other way around. You increase the volume and decrease the intensity, so you end up with a minimal amount of post exercise Calories.

Steady exercise at higher intensity falls somewhere in between. And it's a fair question "what is this for?". Well, LISS and HIIT are both ways to conserve glycogen; LISS because it doesn't burn it fast, and HIIT because it doesn't burn it for long. So when you want to deplete the glycogen, LISS and HIIT are the wrong answer. Getting up to a pretty hard pace and keeping it is the answer. And this can be with traditional highly repetitive cardio style work, or it can be with anything else. The reason to deplete glycogen? To train the metabolism to have a higher capacity. "Efficient" training does not do this.

There is also a use for very long LISS, which does not draw down glycogen much, but which puts pressure explicitly on the fat burning metabolsim; most other forms of exercise do not. Endurance athletes use this (very long runs, rowers call it the "long paddle") to clean up the parts of their fat burning metabolism which are not stimulated in high intensity work which increases the parts of the fat burning metabolism which overlap with the carb burning metabolism.

Ok:
I trained with weights for 13 years.... while I played high school and college (D1) lacrosse. I was a machine then. Used HIIT... not that we had named it back then...

Then I moved to Cali... and I started running. 13 years ago, I ran the western states 100, and in the 3 years before that 17 marathons. While I trained for this stuff, I only lifted with my upper body. Big mistake. I was the fittest skinny fat person I knew. I could run for 26 hours, but, my body and my butt were flabby.:moon:

Once I started training with weights/super sets and HIIT again, I got my fit look back. I can no longer run 100 miles... butt (pun intended) I look alot better- dispite my age.

HIIT- like Zen says- leaves your body burning for a long time. Long, medium intensity stuff... not so long. AND: it shears muscle. For women- this can be deadly. So much of our muscle mass and metabolism relies on our lower body- yes- those glutes... not using them is realy detrimental to progress.

HIIT with Weight training/super setting is where it's at- if what you want is the most bang for your buck metabolically... beautiful strong muscles that burn that- oops- ice cream from last night...

no one's perfect!

Nice Discussion...

Dr. Jen

There are a lot of people on here that eat basically anything they want and simply burn it off with weights and HIIT.

I can't wait till winter....as I'll be starting HIIT again. I did it in grade 8....and I lost 40 lbs while basically eating whatever I wanted.

Amazing.

Yeah,
me too... but I like fresh raw fruits and vegetables, fish, brown rice, whole grains... and ice cream!!!!

Train with HIIT for a while, and you'll see that your indiscretions won't appear on you...

Ok:
I trained with weights for 13 years.... while I played high school and college (D1) lacrosse. I was a machine then. Used HIIT... not that we had named it back then...

Then I moved to Cali... and I started running. 13 years ago, I ran the western states 100, and in the 3 years before that 17 marathons. While I trained for this stuff, I only lifted with my upper body. Big mistake. I was the fittest skinny fat person I knew. I could run for 26 hours, but, my body and my butt were flabby.

Yeah my neice was recruited to an Ivy League school as a cross country skiier. She did well for the first season but didn't get on with the coach, so she switched to rugby, where she plays hooker. She looks fitter, even though she was nationally competitive in the pure endurance sport previously.

woah to the 'sheering muscle' comment earlier.

i believe i experienced this recently. as i've lost weight (from 369 to 230lbs.), i've felt the drive to do more and harder cardio. in addition to lifting heavier, etc.

i think that the medium intensity cardio in addition to getting a bit sloppy in my diet led to me losing more muscle than fat. bah.

medium intensity stuff... not so long. AND: it shears muscle


My experience tells me that this isnt true for everybody. I eat all natural whole foods. Meat, fish & green veggies.

I could also be classified as an endomorph (muscled....tough to take off fat)... eating that diet & lifting never changed my body to a lean muscled physique.

I started walking & jogging (Not to compete in a 100 miler) just for 2-5 miles per day.
(131-151 bpm I think that could be classified as MISS )

The fat percentage finally tumbled down quickly.

Now LISS works for me as well, but HIIT by itself does not allow me to lose much fat. It builds my cardio capacity quickly & my resting heartrate drops quickly.... but I lost a lot of time focusing solely on HIIT.

I totally agree that that circuit training & supersets can work wonders for fatloss....but wearing my Polar & looking at months of BPM charts tells me that my buddies & I are just barely hitting avg 150 bpm (including 30 sec rest periods) when supersetting that way.

So I guess I have to consider that about the same intensity as MISS.
(It certainly feels less intensity wind-wise compared to HIIT | Lactic acid buildup could possibly make it seem harder if you are a go to failure type trainer).

It doesnt seem like it could really be considered HIIT which in my mind is
like going to 90% of your max & rest + repeat for 12-20 minutes.

For me I have 2 problems with HITT.....

1) Mental burnout which leads to consistency problems.
2) Does not burn enough calories for my metabolism (During or After)
+ if there are consistency problems that really limits my calorie burning.

Medium Intensity should not be associated with muscle shearing if you are training a mild amount (Not marathons) & your diet is in order. (Adequate protein & limit your sugar)

Obviously medium intensity cardio (running | jogging) is not going to build muscle by itself... so if you want lean sleek shape you have to be doing tracked progressive resistance exercise to retain or muscle up.

At least from an endomorphs point of view. : )