HIIT vs. lower intensity -what's happening, dude?

morningstar

morningstar

Cathlete
Hey guys,

As some of you know, I am fairly new to cardio for the most part. As such, I decided to hook up my HRM for my non-strength workouts for the next while to see what I could see. So this morning I did Jillian Michael's No More Trouble Zones and then did my own Cardio Coach premix for a walk/run to work.

Now, in 56 minutes, the NMTZ only burned 281 calories, my HR max was 73% and my average HR was 60%. The shorter 36 minute CC premix burned 357 calories, my max HR was 96% and my average HR was 84%.

The thing that gets me is that apparently I burned 60% fat doing the low intensity NMTZ (and it really is low intensity - as a matter of fact, I am going to use it as an abs workout from now on), and I burned 30% fat for the CC premix. I assume that I am burning carbohydrates the rest of the time, am I right?

Here's my question: why is high intensity interval training considered to be so good for fat burning, if I'm burning a higher percentage of fat at a lower intensity? Is EPOC longer or greater with HIIT than with low intensity?

Any light that people can shed on this would be great. I know a lot about weight lifting, but I'm still in the learning stages for effective cardio training.
 
I've always wondered about this too!! I did the 6-wk body makeover a few years ago and he recommended low intensity cardio to burn body fat, however I believe HIIT burns more calories. I would really like someone to shed light because it's always baffled me too.
 
Okay, I'm going to attempt to explain a few things, but please be aware that I know this through researching things on my own, not through formal education!

Burning fat through exercise happens in many different ways, only one of which is during the actual act of exercising. No matter what source the burned calorie comes from, creating a deficit between calories in and out will cause your body fat to be used for fuel. So, higher calorie burn is very important.

High intensity cardio does use more carbohydrates for fuel during the workout, but consistant high intensity over time teaches your body to become more efficient in those zones, which raises the amount of fat burned during the exercise. This is what people are talking about when they refer to making your body better at burning fat. Working out with low intensity does use a greater ratio of fat calories to carb calories, but you are not teaching your body to burn more fat when you work out there. Did that make sense? :)

High intensity training does have a much greater EPOC, like you both mentioned above. In fact, steady state cardio may only raise your metabolism for as few as 10 minutes after exercise, where as Hiit and metabolic training (think kettlebells--things where weighted movements raise your heart rate high for a cardio effect) can raise your metabolism for a whole day or more. So says the research I read :)

Bottom line, a safe defecit between calories in and out will result in body fat reduction, which can be achieved in much less time with high intensity cardio, as well as benefit the fitness of your cardiovascular system and metabolism.

HTH,

Kelly
 
You answered your own question by bringing up EPOC and asking about burning carbs. :)

If you burned 60% fat during a workout the rest (40%) is supposed to be muscle glycogen (a complex carbohydrate stored in the muscles and liver that is the body's preferred source of fuel).

Low intensity exercise burns more % fat calories during the workout because the presence of oxygen is required for the body to access its fat stores for fuel. When you are anaerobic, the body will rely on glycogen.

Depending on which research study you want to believe (and whether you want to believe it at all) EPOC effect of HIIT keeps you stoked for 24 to 38 hours after your HIIT session. The fat burn effect happens mostly in the 4 to 6 hours immediately after the HIIT session supposedly when your body will break down fat to replace the glycogen that the HIIT depleted from your muscles. When you do HIIT you also need nerve / muscle recovery / repair from the demands you made on your body during the high intensity phases. This recovery process raises metabolism during the 24 to 38 or so hours post the workout. So HIIT is touted as better because of the fat you burn AFTER the workout.

Take the vice versa effect for steady state cardio (less glycogen replacement needs, less recovery time and needs) and you have the full picture.

However, some experts believe the studies of EPOC are not conclusive because of shortcomings with research methodology and sample size. They also say there is no exact science to predict precisely when the body is dipping into glycogen versus fat stores.

Moreover, some people believe a calorie is a calorie. If you burned 1 calorie of glycogen, there is that much less for your body to convert and store as fat if it is not consumed (say if you choose instead to be sedentary).
 
But, you burned TWICE the calories in the same amount of time, and given the length you worked out, the same number of calories from fat.

The first w/o came to 5 calories per minute. In an hour you'd burn 300 calories, and 180 would be from fat.

The 2nd w/o came to almost 10 calories per minute. In an hour you'd burn 600 calories, and 180 from fat. Those 300 calories still count in weight loss, no matter where they came from.

I heard it explained this way: Would you rather have 5% of Bill Gates' money, or 100% of mine? :p
 
In the big picture it also all still boils down to total calories in vs out at the end of the day/week. If you're in a deficit you'll lose weight/fat. If you're at maintenance you'll stay the same. If in a surplus you'll gain. You still burned more total calories in the shorter workout than you did in the long less intense one.

Diana
 
I read it also has to do with the after burn, you will continue burining more calories after HiiT. After low intensity I read you go back to our normal everyday calorie burining.

Has anyone lost more weight weight with one or the other?
 
nightowl81 said:
Has anyone lost more weight weight with one or the other?
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I had been doing steady state cardio until it came out of my ears with little or nothing to show for, other than growing frustration. When I started Cardio Coach workouts without changing my diet at that time, my weight came down initially very quick and then steady.

Since starting Cardio Coach / HIIT last year in July I have lost 89 lbs, my endurance increased (whereas I couldn't jog for more than 20 sec. when I started, I am now running 10 miles), my resting heart rate went from the low 80s to 55 to 60.

In what they claim to be my fat burning zone at 115 I don't even break a sweat :eek: However, everyone is different and needs to find what works for them.

LOL Govtgirl, I think I'd prefer 5 % of Bill Gates' money :D I thought that was a great explanation. Just because the you are burning a higher fat percentage on steady state doesn't mean you are losing more fat.
 
I'll take Bill Gates' money because I bet his 5% is more than your 100%. ;)

Vee, you gave a great explanation! Thanks for all of the details -- you made it pretty easy for me to understand.
 
Vee said:
If you burned 60% fat during a workout the rest (40%) is supposed to be muscle glycogen (a complex carbohydrate stored in the muscles and liver that is the body's preferred source of fuel).

Low intensity exercise burns more % fat calories during the workout because the presence of oxygen is required for the body to access its fat stores for fuel. When you are anaerobic, the body will rely on glycogen.
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Vee, this is why many trainers tell you to avoid hiit in a fasted state or if you are on a low carb diet. Makes perfect sense.
I now use SS if I'm doing cardio first thing in the morning with no food.

You have a great way of explaining:)
 
I think the "fat burning zone" on various cardio machines, HRM's, etc is very misleading. Just because you are burning a higher percentage of fat does not mean you are burning MORE fat. A high percentage of a small number is still a small number. A smaller percentage of a much higher number can easily equal or pass that.

It may be a marketing ploy to appeal to those who those who want to convince themselves they've picked the most effective workout, then they enjoy the added benefit of not have to put too much effort/intensity into it (raising your heart rate slightly is more "comfortable" than raising it significantly). There's certainly nothing wrong with PICKING lower intensity for a number of reasons (lighter day in between heavier workouts, slightly sick or run down, better than no exercise at all, part of social/talking activity, etc). But when the "fat burning zone" makes people pick that over a higher heart-rate, higher intensity workout simply because they think they will burn more fat, they are the unsuspecting victims of this unfortunately named zone.

As others have already pointed out, you can easily burn more calories (total AND fat calories) in an equal or shorter amount of time by doing higher intensity. Considering that most people don't have lots of spare time, being efficient is a decided advantage. Then there are the added benefits of burning more after the workout. Also, many strength/muscle building programs recommend HIIT as a complementary workout that enhances the overall program. Odds are that most Cathe fans, especially STS-er's, would be more interested in this type of cardio (even if they don't necessarily "enjoy" it).

If someone prefers the comfort of the lower heart rate/intensity and has lots more time, the same number of calories can also be reached. Extended low intensity cardio can be counterproductive to a strength program, but it all depends on what your personal goals are. Some people simply like long, slow jogging, enjoying the outdoors, etc.
 
I found higher intensity

To be more effective with my body over time. I used to be careful not to work too hard because I was afraid it would not work. I was very careful to not work too hard. Then, I decided I wanted to run and I began the couch to 5k rotation. I decided to ignore how hard it was because I thought I would adapt and my body would become more fit. Also, I thought, in the first week its only 60 seconds of running anyway, how hard could this be? I discovered that the interval style of training is what I should have been doing all along in order to improve my cardiovascular output. I had always been the kid who couldn't run a lap without stopping. I didn't know to just push through that feeling. People always told me to slow down because I have a red face when I work out. Bright red. I'm Irish, its normal to have a ruddy face. Now, I can jog a lot farther and without a side stitch. Ok. Enough about the success story.

I feel hot for several hours after a hiit workout or a weight training workout. I don't really feel that way after a steady state workout. I still do steady state, just not everyday. I am mixing them now. I do 30 minutes steady state and then an interval run/walk for twenty minutes. Both involve hills and I'm always above 150 but for my intensity intervals I aim for 185.
 
I do 30 minutes steady state and then an interval run/walk for twenty minutes.
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I have read that doing your intervals, stopping for a while (5 min), and then doing your steady state is more beneficial for fat loss. I wish I remembered the article... but I thought I would throw that out there.
 
curltess said:
I have read that doing your intervals, stopping for a while (5 min), and then doing your steady state is more beneficial for fat loss. I wish I remembered the article... but I thought I would throw that out there.
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Alywn Cosgrove recommends this type of training in Warp Speed Fat Loss.
 
Thank you! I thought it was Alwyn... but didn't want to say so. I was planning on doing some research tonight.

Thanks again :D
 
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