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d'Anconia
03-09-2006, 09:49 PM
So I was looking over some of the older threads because I had a question about HIIT. Basically I was wondering how many calories in general you guys think are burnt during certain HIIT sessions, and how many of those calories do you think are coming from burnt fat?

I read in the 'More Reasons Why HIIT Rules' thread a quote from a study saying that 9x as many calories are coming from fat as regular aerobic fitness sessions (although total calories burnt was lower in HIIT sessions). But that still isn't very specific.

I personally did about 10 repetitions of 100m sprints when I was doing HIIT last year and am planning on starting up again. Naturally I was wondering about some of the mathematics and stats that are involved.

I understand that my questions are kinda vague but I suppose starting off with how many calories are burnt from fat vs. other sources during regular aerobic fitness is a place to start. If anyone could help me out it'd be appreciated, especially if they could point me in the way of a nice published study or something.

Thanks in advance.

The13ig13adWolf
03-10-2006, 08:43 AM
i don't think you're gonna find a specific number here. energy expenditure is much greater during interval training v. endurance type cardio leading to more burned calories in the post period. this is due to excess post-exercise oxygen consumption (EPOC).

Berardi makes some points here you may find useful:

The Benefits of Training The Anaerobic Energy Systems

While training the anaerobic energy systems is clearly be of benefit for enhancing athletic performance, there are many other non-athletic benefits as well:

1) This type of training is very calorie expensive. Short, 30-minute workouts can burn in excess of 400kcal during the exercise. While carbohydrates provide much of the fuel used during the high intensity interval, fat is also burned preferentially during the low intensity aerobic recovery period between the high intensity intervals.

2) The post exercise calorie expenditure is huge with this type of exercise. In some studies the resting metabolic rate remains elevated (by 15% or more) up to 24 hours after the workout. Interestingly, after exercise the body preferentially burns fat so this elevated metabolism is burning predominantly fat.

3) This exercise leads to an up regulation of aerobic, anaerobic, and ATP-PC enzyme activity. This means that all the energy systems of the body will operate at higher levels and become efficient at burning calories and generating energy.

4) The muscles used during this type of exercise will change their composition, shifting toward an increased percentage of fast twitch fibers. This increase in power-producing fast fibers comes at the expense of the weaker slow twitch ones. The shift is desired as the fast fibers grow more easily than the slow fibers.

5) There is an increase in specific muscle cell organelles (i.e. the sarcoplasmic reticulum). This leads to a better calcium balance and contractile ability.

6) There are short-lived increases in blood testosterone (38%) and growth hormone concentrations immediately after exercise. While this is debatable, these changes may contribute to an anabolic state in the body.

ArchAngel777
03-10-2006, 09:39 AM
Anthony (Uber Mod?) really changed my mind on this type of training. I back it up pretty well now.

Basically, Anthony gave several references back in this (http://www.wannabebigforums.com/showthread.php?t=75212&page=2) thread. Enjoy... :D

d'Anconia
03-10-2006, 04:58 PM
Thanks ArchAngel for the link. There was a lot of info in it.

K I've been reading around and I'm starting to think that HIIT just might not really burn that many calories in general, even if there is a higher portion from fat. I mean HIIT isn't something I can do every single day, in fact I think I'd only be able to do it once every two days. I mean I don't think I'd really burn more than 1000 calories from a sprinting session with HIIT and remember those aren't all from fat.

Doing the math it seems like I'd have to do quite a bit of sessions just for a decrease of 1% bodyfat (~2 lbs of fat for me).

Bleh... maybe I should just stick with the diet.

Edit: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9013436&query_hl=7
ie this study is saying that women who did 40-45 minute sessions 4x a week lost (on average) ~5% bodyfat (of course there are differences that need to be taken into account for bodyweight and the intensity of their exercises and calories burnt during them, etc) after 16 weeks (although it says the first 4 weeks were 'control', I don't know exactly what that means). That means each session probably reduced bodyfat by ~.1% bodyfat.

ArchAngel777
03-11-2006, 10:57 AM
Not sure I understand you correctly (my attention is low right now, because I am pumped for my workout) however, this is how it works out, for the most part.

The session itself burns less calories, that is true. But where HIIT really shines is in the "after affect" so to speak. Your body rebuilts itself and since your heart rate during that period is at an all time low (resting, or slightly above) you will burn the majority of your calories from fat and for up to the next 24 hours.

HIIT or Weightlifting can to some extent be alternated. Because of the nature of HIIT, you are stressing the muscle and thus causing some growth. It is quite different than your standard endurance training.

Personally, I use HIIT for two reasons...

1) To increase my athletic ability. Being able to sprint, or near sprint for a minute at a time is great stuff... It only gets better too. Additionally, when training very high intensity, the lower intensity gets easier as well. So if running at 7.0 for 20 minutes was nearly impossible, training sprints and raising the bar for the next several weeks will yield better results on the low end as well. Thus, 7.0 run for 20 minutes WILL be easier...

2) To suppliment my fat loss. This really is secondary for the most part. I don't view the HIIT as a means to burn my fat, because I believe Weightlifting already does this for me... But I think this does help, because I am pretty strict on my diet.

ArchAngel777
03-11-2006, 11:00 AM
I love this part in your link above


CONCLUSION: High heart rate intensity exercise training without dietary manipulation resulted in a decrease in body fat, but not weight change, as well as a decrease in the intake of saturated fat and cholesterol in normal weight young women. These changes were not observed after low heart rate intensity training.

Jorge Sanchez
03-11-2006, 11:32 AM
I love this part in your link above

I wonder why that is.

Edit: the conclusion that is, not your love for it.

The13ig13adWolf
03-11-2006, 11:38 AM
K I've been reading around and I'm starting to think that HIIT just might not really burn that many calories in general, even if there is a higher portion from fat. I mean HIIT isn't something I can do every single day, in fact I think I'd only be able to do it once every two days.
HIIT burns more calories in the recovery period and throughout the day than you'll get from SS. i don't understand what you mean by "HIIT might not burn that many calories in general".

why on earth would you want to do it every day? IMO it shouldn't be done more than twice a week.

if you want to decrease your bf%, focus more of your attention on your diet rather than cardio.

The13ig13adWolf
03-11-2006, 11:48 AM
The session itself burns less calories, that is true. But where HIIT really shines is in the "after affect" so to speak. Your body rebuilts itself and since your heart rate during that period is at an all time low (resting, or slightly above) you will burn the majority of your calories from fat and for up to the next 24 hours.

HIIT or Weightlifting can to some extent be alternated. Because of the nature of HIIT, you are stressing the muscle and thus causing some growth. It is quite different than your standard endurance training.

Personally, I use HIIT for two reasons...

1) To increase my athletic ability. Being able to sprint, or near sprint for a minute at a time is great stuff... It only gets better too. Additionally, when training very high intensity, the lower intensity gets easier as well. So if running at 7.0 for 20 minutes was nearly impossible, training sprints and raising the bar for the next several weeks will yield better results on the low end as well. Thus, 7.0 run for 20 minutes WILL be easier...

2) To suppliment my fat loss. This really is secondary for the most part. I don't view the HIIT as a means to burn my fat, because I believe Weightlifting already does this for me... But I think this does help, because I am pretty strict on my diet.
nice post.

d'Anconia
03-11-2006, 12:46 PM
HIIT burns more calories in the recovery period and throughout the day than you'll get from SS. i don't understand what you mean by "HIIT might not burn that many calories in general".

why on earth would you want to do it every day? IMO it shouldn't be done more than twice a week.

if you want to decrease your bf%, focus more of your attention on your diet rather than cardio.

I'm not quite sure what you mean by SS. The calories burned throughout the day after a session of HIIT is what I'm looking for too. I'm just trying to find out roughly how much fat in general is burned as a result of HIIT. I was saying every other day or so since every day would cause some serious problems and make it hard to ever do a weight training workout for legs.

And yes I focus more on my diet than I do about cardio. As for now I'm not looking to decrease bodyfat but more to slow down the fat gain during a bulk.

Built
03-11-2006, 01:34 PM
If you're looking to slow down the fat gain on a bulk, look to your diet.

HIIT should probably be limited to twice a week at the most. Otherwise, as you said, it will likely interfere with your training.

Anthony
03-11-2006, 02:11 PM
I'm just trying to find out roughly how much fat in general is burned as a result of HIIT.

There's no magic way to predict this. Try both methods and measure everything like you're obsessed.

Three things to remember:

1) diet is key
2) hiit is like a supplement - everything else has to be in order to maximize benefits
3) hiit is better than steady state cardio for everything - fat loss, vo2 max, lactate threshold, muscle preservation, performance, etc.

The13ig13adWolf
03-11-2006, 04:44 PM
I'm not quite sure what you mean by SS. The calories burned throughout the day after a session of HIIT is what I'm looking for too. I'm just trying to find out roughly how much fat in general is burned as a result of HIIT. I was saying every other day or so since every day would cause some serious problems and make it hard to ever do a weight training workout for legs.

And yes I focus more on my diet than I do about cardio. As for now I'm not looking to decrease bodyfat but more to slow down the fat gain during a bulk.
SS = steady state cardio. like Built said, minimizing fat gain on a bulk is directly related to diet.

Tarendol
03-13-2006, 01:02 PM
I havea a question about this too. How does post-HIIT nutrition change the hightened metabolism throughout the rest of the day? I have been taking my normal post-workout nutrition, including dextrose, but it has occured to me that the insulin spike might stop all fat oxidation. Is this correct? There was some discussion of this on another thread but I didn't see a conclusion.

PowerManDL
03-13-2006, 05:00 PM
The magic of HIIT is rooted in a nifty little biochemical called AMPk.

AMPk works as a cell's energy thermostat, as it were. When the cell has energy, AMPk is off and the cell does its little thing. When the cell is energy depleted, AMPk kicks on and neat things start to happen.

Firstly, protein synthesis is directly inhibited by AMPk. Now, this may send you into alarm, but don't worry. It more than compensates.

Secondly, and this is where it's important for fat-burning, you get the cell primed to 1) store circulating glucose as glycogen and 2) start oxidizing all those free fatty acids for energy. AMPk works to protect the cell overall, and having low glycogen levels isn't a good thing from a survival standpoint. So while it's replenishing glycogen, the FFAs are providing energy.

What does this mean? Well, the upregulation of fatty acid oxidation in the cell makes the cell more efficient at it. In fact, that study by Tremblay that got the whole HIIT craze started showed a marked increase in the factors responsible for fatty acid oxidation, but without the drawbacks of a true aerobic adaptation.

This is also why lifting shows effects on body comp. It works to increase muscular insulin sensitivity; basically any intensive anaerobic work like this will cause a preferential shuttling of calories in general towards muscle.

So, in essence, that means that blood sugar (within limits, non-enhanced physiologies can only handle so much) will be stored in muscle while allowing continued fat oxidation. This in fact is the entire principle behind UD2.0, to those of you familiar with it.

The rationale behind limiting HIIT to 1-2 sessions a week is a good one though. HIIT is pretty demanding on both the muscles and the CNS, and isn't the best for the joints if you're sprinting.

russianwol
03-30-2006, 05:01 PM
Here is a nice write up about "Training Effect" http://en.wikipedia.org/wiki/Training_effect

Explains the resting metabolism and athletic training.