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Joe Black
04-29-2003, 06:43 AM
ok I have a few questions about cardio intensity, glycogen stores and fat :)

1. Generally which is better for fat loss, high intensity for shorter periods or longer periods that are a lower intensity?

From my reading it seems that the main energy source in longer periods, at lower intensity is fat. (up to 50% VO2max)

Now when performing more intense and shorter period cardio, it seems muscle glycogen comes into play, as much as 50% when using 50-70% VO2max intensity levels.

2. So am I right in saying that the shorter, more intense periods would burn more lean muscle (I assume muscle glycogen = lean muscle) ?

Whereas performing lower intensity over a longer period would burn more fat?

3. Now when I refer to fat and glycogen stores, does that mean bodyfat and lean muscle respectively?

4. Also for my last question how does HIIT then make for optimal fat loss in a nut shell? I will do some more reading on HIIT, but I am curious to if there is someone that can sumarize the mix of intensity in terms of effecient fat burning?

5. Lastly, in the big picture of things say these 2 instances were performed:

7k per hour x 40 mins = 4.6k total distance
12k per hour for 30 mins = 6k total distance

Now which one would burn mor fat? Surely on the above info number 1 as up to 50% could be muscle loss at the 2nd type of intensity? However based on the total calorie burning I would expect the 2nd instance would burn more right?

So in the big picture of losing weight which would be better?

lol sorry for the mass of questions but I am starting my sports nutrition course and I want to clarify some of the first chapter :)

GhettoSmurf
04-29-2003, 07:54 AM
i know of a really good thread on another bodybuilding forum that has LOADS of info on HIIT and what it exactly does. when i get home from school ill post it. its a bit of a long read, but i think it will answer most if not all of the questions.

Ja113
04-29-2003, 08:22 AM
Before getting into this...I don't claim to be an xpert or anything like that....If I mess up, somebody please tell me! Also please note that I don't do a ton of cardio myself as fat loss has never been a huge issue with me (well, except for when I was wrestling...but that's a whole other story)


1. Generally which is better for fat loss, high intensity for shorter periods or longer periods that are a lower intensity?

From my reading it seems that the main energy source in longer periods, at lower intensity is fat. (up to 50% VO2max)

Now when performing more intense and shorter period cardio, it seems muscle glycogen comes into play, as much as 50% when using 50-70% VO2max intensity levels.

** I have read similar things. But it does make sense that the lower/longer method would burn more fat as there's a point your body has to get to before it gets into fat burning mode. Also, your body will burn glycogen first before turning to fat as a fuel source (hence the notion of doing cardio before breakfast in the morning...although I don't know if I totally agree with that). However, if you do shorter periods of cardio, your body may not get to the point of fat burning or if it does, you won't be in the fat burning zone for as long a period.

2. So am I right in saying that the shorter, more intense periods would burn more lean muscle (I assume muscle glycogen = lean muscle) ?

Whereas performing lower intensity over a longer period would burn more fat?

** I don't think so as the operative word is shorter! If you did intense cardio for long periods of time then I'd say the likelihood of losing lean muscle mass would be pretty high! However shorter periods I don't think would kill you. Case in point...look at marathon runners...you don't see too many big marathon runners or even cyclists (well, except their legs). Also, whether you do short or longer periods of cardio...you're going to burn glycogen regardless as that's the first fuel source. What you need to be concerned about burning is amino acids as a fuel source as those are the building blocks for protein which in turn build muscle. If you burn those...then yeah...you're going to have a problem with gaining muscle mass.

3. Now when I refer to fat and glycogen stores, does that mean bodyfat and lean muscle respectively?

** Yes and no....I know what you're trying to say but it's not totally correct from a technical/scientific point of view. When you're burning fat and go on a limited or no carb diet, once your body gets rid of all its carbohydrates then it will turn to bodyfat as its main fuel source. Glycogen in your case means muscle glycogen (I think)...which is obviously found in muscle. You can also find glycogen in the liver and your brain! Anways, the point is that glycogen is actually a carb (glucose) stored in a polymer form that your body uses as its first energy source.

4. Also for my last question how does HIIT then make for optimal fat loss in a nut shell? I will do some more reading on HIIT, but I am curious to if there is someone that can sumarize the mix of intensity in terms of effecient fat burning?

** Wow...that's a tall order as there's lots involved. I can't speak about HIIT as I haven't done that particular type of routine but for general resistance training. When you work out...you deplete your muscle glycogen, cause micro tears in your muscles etc etc etc. Through your diet, your body replenishes its muscle glycogen stores and through rest your body repairs the muscles. Studies have shown that trained atheletes tend to replenish muscle glycogen faster and in more quantity than untrained people....so people who work tend to have more muscle glycogen which means they can train longer and harder than untrained people (ie more intense workouts). The body repairs the muscle tears caused by your workouts and because the body adapts, it will add more muscle in preparation for the next workouts....Because you're adding muscle, that also helps your body burn fat as it is metbolically active...so if you have more muscle, you'll burn fat even when you're resting. I hope that kinda answered your question.

5. Lastly, in the big picture of things say these 2 instances were performed:

7k per hour x 40 mins = 4.6k total distance
12k per hour for 30 mins = 6k total distance

Now which one would burn mor fat? Surely on the above info number 1 as up to 50% could be muscle loss at the 2nd type of intensity? However based on the total calorie burning I would expect the 2nd instance would burn more right?

** It would depend on how fast your body gets into the fat burning zone and how long you stay in that zone. Remember, your body is going to use glycogen first before it hits the fat. But from a general point of view, the longer but moderate method would probably burn more fat as you'll probably stay in the fat burning zone longer than shorter periods of cardio. However, if you go too long then you run the chance of also burning amino acids...for a bodybuilder that's not the best thing in the world.

So in the big picture of losing weight which would be better?

** OK..again...big time overview but in my humble opinion. Short, infrequent but intense weight training coupled with low to moderate cardio for 'longer' periods of time (although we're only talking like 20-60minutes).

Once again....if I messed up....someone please edit!

Hope this helps!

PowerManDL
04-29-2003, 02:17 PM
Originally posted by Hulk
ok I have a few questions about cardio intensity, glycogen stores and fat :)

1. Generally which is better for fat loss, high intensity for shorter periods or longer periods that are a lower intensity?

From my reading it seems that the main energy source in longer periods, at lower intensity is fat. (up to 50% VO2max)

Now when performing more intense and shorter period cardio, it seems muscle glycogen comes into play, as much as 50% when using 50-70% VO2max intensity levels.

You're right. The ratio of oxidation to glycolysis decreases in proportion to exercise intensity. The harder you're going, the less oxidation is occuring.

2. So am I right in saying that the shorter, more intense periods would burn more lean muscle (I assume muscle glycogen = lean muscle) ?

Whereas performing lower intensity over a longer period would burn more fat?

Not entirely. Using glycogen != using muscle, at least assuming the glycogen stores aren't empty.

Yes, you will burn more fat as a percentage during the session by doing lower intensity work for a longer period.

However.....you'll burn more total calories with a higher-intensity workout......and there are also metabolic factors to consider that may not make distance work the most optimal when viewed in the big picture.

3. Now when I refer to fat and glycogen stores, does that mean bodyfat and lean muscle respectively?

Fat you're talking about triglycerides.....which are mobilized from body fat stores. Glycogen is referring to the stored form of glucose; which isn't the same thing as muscle tissue. As I said above, muscle tissue is only catabolized when glycogen is exhausted.

4. Also for my last question how does HIIT then make for optimal fat loss in a nut shell? I will do some more reading on HIIT, but I am curious to if there is someone that can sumarize the mix of intensity in terms of effecient fat burning?

When you're doing HIIT, during the intensive interval you're burning glycogen. This does several things: Firstly, it causes a dramatic rise in heart rate and VO2 (ok, not the glycolysis itself, but the intensive activity). Secondly, due to the intensive activation of glycolysis, it creates a large accumulation of lactate in the blood.

During the resting interval, the body re-synthesizes the lactate back into pyruvic acid for use in the Krebs cycle. This process is oxygen-mediated.

My current thinking is that this is what is largely responsible for the increase in beta-oxidation, which has been observed to increase in most of the HIIT studies I've seen; the pyruvic acid is quickly and easily converted to aceytl-Co-A, which is a fundamental catalyst for beta-oxidation. Since glycogen levels are lowered and heart rate is heightened, the "resting state" is being provided with its primary fuel-- triglycerides. And it has plenty of free, readily available substrates with which to oxidize them.

So, basically, you're using more total calories, and the energy deficit created is replenished via triglycerides, which is not the case in distance work. Not only that, but the muscle tissue is adapting to use fat more efficiently; this is key because the muscle tissue itself is given no stimulus to catabolize nor undergo any sort of negative (for our purposes) fiber-type shift as would be the case in long-term endurance training.

5. Lastly, in the big picture of things say these 2 instances were performed:

7k per hour x 40 mins = 4.6k total distance
12k per hour for 30 mins = 6k total distance

Now which one would burn mor fat? Surely on the above info number 1 as up to 50% could be muscle loss at the 2nd type of intensity? However based on the total calorie burning I would expect the 2nd instance would burn more right?

So in the big picture of losing weight which would be better?

Given a choice I'd choose the second option purely because more calories are being burned. However, an interval approach incorporating short sprints and either rest or low-intensity work for 45-120 seconds would be "better" for fat loss efforts.

GhettoSmurf
04-29-2003, 04:42 PM
http://web.ask.com/redir?bpg=http%3a%2f%2fweb.ask.com%2fweb%3fq%3dteen%2bbodybuilding%26o%3d0&q=teen+bodybuilding&u=http%3a%2f%2fwww.teenbodybuilding.com%2f&s=a

heres a good thread about HIIT, a long read, but well worth it IMO

Ironman8
04-29-2003, 06:12 PM
Cool. That's a good read Smurf.

Budiak
04-29-2003, 11:49 PM
Hey Powerman, is the lactate re-synthesis done most efficiently when the slower portions of HIIT are done at a walk or a jog?

I do intervals of 60/30 jog/run and I never seem to run out of steam- though I wouldnt have the gall to call it easy.

What'cha think?

Sayiajin Prince
04-30-2003, 07:54 AM
:hump: this is a good thread. good info

galileo
04-30-2003, 09:19 AM
I typically don't trust Canadians, but here's something following the general idea of this thread and what Powerman has said.

Impact of exercise intensity on body fatness and skeletal muscle metabolism.

Tremblay A, Simoneau JA, Bouchard C.

Physical Activity Sciences Laboratory, Laval University, Ste-Foy, Quebec, Canada.

The impact of two different modes of training on body fatness and skeletal muscle metabolism was investigated in young adults who were subjected to either a 20-week endurance-training (ET) program (eight men and nine women) or a 15-week high-intensity intermittent-training (HIIT) program (five men and five women). The mean estimated total energy cost of the ET program was 120.4 MJ, whereas the corresponding value for the HIIT program was 57.9 MJ. Despite its lower energy cost, the HIIT program induced a more pronounced reduction in subcutaneous adiposity compared with the ET program. When corrected for the energy cost of training, the decrease in the sum of six subcutaneous skinfolds induced by the HIIT program was ninefold greater than by the ET program. Muscle biopsies obtained in the vastus lateralis before and after training showed that both training programs increased similarly the level of the citric acid cycle enzymatic marker. On the other hand, the activity of muscle glycolytic enzymes was increased by the HIIT program, whereas a decrease was observed following the ET program. The enhancing effect of training on muscle 3-hydroxyacyl coenzyme A dehydrogenase (HADH) enzyme activity, a marker of the activity of beta-oxidation, was significantly greater after the HIIT program. In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation.



http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8028502&dopt=Abstract

Raj
04-30-2003, 09:41 AM
This has got to be a sticky..........................

PowerManDL
04-30-2003, 10:00 AM
Gal, that study is actually the "originator" of the concept; I've used it several times, and its quite telling.

Budiak: The lactate clearing happens when enough oxygen is present to allow it to happen. Depending on your work capacity, that could be a walk, a jog, or straight rest.

galileo
04-30-2003, 10:38 AM
Ace. I have more that I'm not sure if you've used. [edited because it had terrible formatting]

Ultrastructural modification of human skeletal muscle tissue with 6-month moderate-intensity exercise training.

Suter E, Hoppeler H, Claassen H, Billeter R, Aebi U, Horber F, Jaeger P, Marti B.

Institute of Social and Preventive Medicine, University of Zurich, Bern.

The study was aimed at investigating if endurance training of moderate intensity and longer duration, intended to promote health rather than performance, evokes ultrastructural changes in
skeletal muscle tissue comparable to those observed after high-intensity protocols. Twenty healthy, middle-aged men enrolled in a 6-month, home-based jogging program of 120 min/wk at 75%
VO2max. Only 12 men showed a sufficient exercise adherence over the 6 months (> or = 60 min/wk on average) and were included into statistical analysis. Their average training activity was 105 +/- 31 min/wk. The results revealed significant increases in VO2max (+8.4%, p < 0.01) and submaximal power output (+18.1%, p < 0.01). Total mitochondrial volume density in M. vastus lateralis increased by 20% (p < 0.05) with a larger increase in subsarcolemmal volume compared to central
volume (50% vs 15%). No changes in volume of intracellular lipid droplets, capillary density, capillary per fiber ratio, fiber mean cross-sectional area and muscle fiber
type could be observed. Body composition analysis showed a decrease in trunk fat mass (-7.3%, p < 0.05) and an increase in trunk lean mass (+1.7%, p < 0.05), while changes in the legs
were not significant. It can be concluded that a moderate- ntensity, health oriented endurance
training beneficially affected cardiovascular and muscle oxidation capacity as well as body composition in the trunk
area. No adaptations in capillaries or lipid metabolism could be
demonstrated. The results support the hypothesis of thresholds for induction of adaptation processes in muscle keletal tissue
depending on the intensity of the exercise

pusher
04-30-2003, 10:53 AM
Powerman:

I was under the impression, that you burn LESS overall calories from doing HIIT work, but that a larger proportion of them come from fats.

The science you stated would indicate that during an HIT training session, depleting glycogen stores, and LA going to PA etc, creates the subtrates to promote fat oxidation, IN PREFERENCE over lean body tissue(muscle mass). I believe this is the main reason that it is favoured by bodybuilders, because it is a way to promote fat as a fuel(= fat burning, not muscle), and preserve muscle tissue.

In longer, low intesnity training, the aim is to deplete glycogen in your body, in order to then burn fat, although your body will quite likey burn LBM as well. - at least this was the reasoning behind this training for years.

If we are talking about a ten minute HIIT session, than I propose that you will burn less OVERALL calories, when compared to a longer low-intensity workout, but proportionately more of that energy will come from fat as a fuel source.

But, to address what Hulk was inquiring about, a longer and higher intensity workout(not HIIT), would burn more calories, but NOT preferentially fat. Although lets say a 1 hour high-intensity cardio session could burn more fat than a 1 hour low-intensity session, you will be metabolizing more muscle tissue along with that fat, which no one really wants.

Remember also, that for HIIT to work, you have to follow a precise schedule of work and rest intervals. I remember reading that the intervals used in the studies where 6/9 or somewhere around that, but I presume that a small variance, say 10/20 will still be effective in creating the HIIT fat-burning environment. But, a 1 minute sprint followed by a 3 minute rest will not likely generate the results we are looking for...

Would you agree Power?


Tremblay et al (23) performed the most notable study which demonstrates that high-intensity exercise, specifically intermittent, supramaximal exercise, is the most optimal for fat loss. Subjects engaged in either an endurance training (ET) program for 20 weeks or a high-intensity intermittent-training (HIIT) program for 15 weeks. The mean estimated energy cost of the ET protocol was 120.4 MJ, while the mean estimated energy cost of the HIIT protocol was 57.9 MJ. The decrease in six subcutaneous skinfolds tended to be greater in the HIIT group than the ET group, despite the dramatically lower energy cost of training. When expressed on a per MJ basis, the HIIT group's reduction in skinfolds was nine times greater than the ET group.

PowerManDL
04-30-2003, 11:13 AM
Originally posted by pusher
Powerman:

I was under the impression, that you burn LESS overall calories from doing HIIT work, but that a larger proportion of them come from fats.

The science you stated would indicate that during an HIT training session, depleting glycogen stores, and LA going to PA etc, creates the subtrates to promote fat oxidation, IN PREFERENCE over lean body tissue(muscle mass). I believe this is the main reason that it is favoured by bodybuilders, because it is a way to promote fat as a fuel(= fat burning, not muscle), and preserve muscle tissue.

Basically, which I explained above.

In longer, low intesnity training, the aim is to deplete glycogen in your body, in order to then burn fat, although your body will quite likey burn LBM as well. - at least this was the reasoning behind this training for years.

Yup. Its taking a sledgehammer to a problem that only requires tweezers.

If we are talking about a ten minute HIIT session, than I propose that you will burn less OVERALL calories, when compared to a longer low-intensity workout, but proportionately more of that energy will come from fat as a fuel source.

I think I worded it poorly above; but its the total cals per unit of time that is relevant, not so much the overall calories consumed. Just like a 30 minute weight-training session will burn more cals than a 30 minute session of light jogging, so will HIIT.

If you'll note in the Tremblay study that gal was nice enough to post, the HIIT group burned up a substantial bit of fat with half the energy consumption of the endurance group.

So with that in mind, you're correct, the total cals used aren't directly that important. Its more the acute deficit and metabolic changes that it induces.

But, to address what Hulk was inquiring about, a longer and higher intensity workout(not HIIT), would burn more calories, but NOT preferentially fat. Although lets say a 1 hour high-intensity cardio session could burn more fat than a 1 hour low-intensity session, you will be metabolizing more muscle tissue along with that fat, which no one really wants.

I agree. If you're not continually moving above the lactate threshold then backing off to recover, you're not getting the optimal effect.

Remember also, that for HIIT to work, you have to follow a precise schedule of work and rest intervals. I remember reading that the intervals used in the studies where 6/9 or somewhere around that, but I presume that a small variance, say 10/20 will still be effective in creating the HIIT fat-burning environment. But, a 1 minute sprint followed by a 3 minute rest will not likely generate the results we are looking for...

That's not entirely true.

The only requisites here are that the lactate threshold be reached, which is simply a matter of exceeding the body's ability to clear the accumulating lactic acid. This can be done in a short amount of time, or over a longer period. And then a rest interval must be given to allow for the lactate to clear; any protocol that utilizes those concepts will achieve the fat-loss effect.

aka23
04-30-2003, 11:31 AM
Originally posted by pusher
In longer, low intesnity training, the aim is to deplete glycogen in your body, in order to then burn fat, although your body will quite likey burn LBM as well. - at least this was the reasoning behind this training for years.

I disagree. You do not need to deplete the body of glycogen to burn fat. When your body is resting, the primary fuel source is usually fat. When you are reading this post, your primary fuel source is probably fat. And you are burning fat througout the low intensity cardio, whether or not your glycogen stores have been depleted. It is true that a larger portion of energy comes from fat as glycogen stores decrease.

You also burn some protein (can be muscle protein) during most types of exercise. This amount is usually insignificant, both for low intensity and high intensity. It usually only becomes significant when glycogen stores are very low as might occur after a long, high intensity session; when working out in the morning on an empty stomach; or when on certain diets.

big
04-30-2003, 11:45 AM
I have a question(might have been answered): I just don't buy that you burn more fat on low intensity then high (maybe no one has said that, but I get that impression whenever I read about cardio). I'm thinking the fat/muscle loss is better on low then hi-intensity but not that you burn more fat.

So am I right or what?

Severed Ties
04-30-2003, 12:44 PM
I would agree with that statement big.

Cardio choice directly depends on glycogen stores as well as how much muscle a person is carrying on their frame in my opinion.

If cardio is performed later in the day after sufficient carbs have been consumed then HIIT is the way to go.

When cardio is performed first thing in the morning or on carb restricted days low-intensity is prefered.

I've also noticed HIIT seems to impact strength levels in a negative fashion. Weather this is due to loss of muscle mass or fiber conversion I'm undecided on.


ST

PowerManDL
04-30-2003, 12:47 PM
Really? I haven't noticed that problem.

Sprinting would be least likely to cause negative fiber-type conversions, especially when compared to endurance work.

aka23
04-30-2003, 02:06 PM
Originally posted by big
I have a question(might have been answered): I just don't buy that you burn more fat on low intensity then high (maybe no one has said that, but I get that impression whenever I read about cardio). I'm thinking the fat/muscle loss is better on low then hi-intensity but not that you burn more fat.

So am I right or what?

I will assume you are comparing lower intensity traditional cardio to higher intensity traditional cardio, like Hulk did in question 5. HIIT is a different story and does not apply to what is written below:

As intensity decreases, a larger portion of fuel comes from fat. As intensity increases, calories are burned at a faster rate, so more total fat calories may be burned. Fat tends to be burned at the highest rate around 65-80% MHR, depending on many factors including previous training, genetics, and fuel stores.

For example walking a mile at 40% MHR would probably burn more fat than jogging a mile at 75% MHR. But walking 20 minutes at 40% MHR would probably burn less fat than jogging 20 minutes at 75% MHR, since more distance is covered in the jogging and more total calories are burned.

A related graph is below. This graph displays data from a study, which found that the highest rate of fat burning occurred at 74%MHR (64% VO2Max).

http://www.thefactsaboutfitness.com/images/fat_zone.gif

Fat/muscle loss is a different issue from fat burned during traditional cardio. Other things such as calorie balance and weight training factor in.

aka23
04-30-2003, 05:25 PM
Originally posted by Severed Ties
I've also noticed HIIT seems to impact strength levels in a negative fashion. Weather this is due to loss of muscle mass or fiber conversion I'm undecided on.

Some possible explanations include overtraining and cutting. I have found that HIIT requires a good amout of recovery time. If HIIT was done too close to leg day or too close to other HIIT sessions, it might result in overtraining and hindered recovery/growth.

When a lot of people do HIIT, they are in a cutting cycle with low calories/carbs. It is possible that the strength loss is more related to the cutting and low calories than to the HIIT.

I doubt that muscle fiber conversion would be a significant factor in such a strength change.

PowerManDL
04-30-2003, 05:28 PM
Hehehee! Not me! I use HIIT as an excuse to eat like a pig.

And I still lean out!

Go me!!!!1

powerhalf
04-30-2003, 06:13 PM
Yikes, some of this stuff is pretty confusing. I guess this has made me re-think my approach to HIIT and cardio in general. Typically when I do HIIT I'd stretch first and then sprint as hard as I possible can for 10 or so seconds, then walk for about 20. I'll do that 6 -8 times, then sit and drink some water and then do it again. I guess it would depend on one's individual goals, whether or not HIIT or a more traditional lower intensity cardio would work better. My goals are basically to keep cutting until I'm satisified with the way I look. Obviously this involves retaining muscle during the cut. I also enjoy the act of sprinting, and I used to do a lot of it in past athletics. And I won't be doing early morning cardio like ST mentioned was an option. I think HIIT would be the best option for me. Any thoughts? :help:

Severed Ties
04-30-2003, 07:48 PM
Originally posted by aka23


Some possible explanations include overtraining and cutting. I have found that HIIT requires a good amout of recovery time. If HIIT was done too close to leg day or too close to other HIIT sessions, it might result in overtraining and hindered recovery/growth.

When a lot of people do HIIT, they are in a cutting cycle with low calories/carbs. It is possible that the strength loss is more related to the cutting and low calories than to the HIIT.

I doubt that muscle fiber conversion would be a significant factor in such a strength change.

I considered the possibilites you've mentioned however since I find the problems with strength resolve themselves if I switch someone from HIIT to a low intensity cardio I've come to the conclusion that it is a direct result of HIIT.

My reasoning behind this is simply that sprinting requires a high amount of glycogen. When carbs are depleated, especially liver glycogen stores, glycogen can only come from muscle glycogen and muscle catabolism for gluconeogenesis. Both of which would severely impact strength levels.

I'm skeptical about the muscle fiber conversion but in a few cases I've found people can lose a significant amount of strength while maintaining the same arm and leg measurments despite dropping bodyfat. I kinda go back and forth on this one but someones prior cardiovascular conditioning would be another contributing factor to consider.


ST

PowerManDL
04-30-2003, 07:50 PM
Originally posted by Severed Ties
My reasoning behind this is simply that sprinting requires a high amount of glycogen. When carbs are depleated, especially liver glycogen stores, glycogen can only come from muscle glycogen and muscle catabolism for gluconeogenesis. Both of which would severely impact strength levels.

That's why you gotta get your carb on, whitey!

I don't ever recommend HIIT while in a carb-depleted state.....and I always eat afterwards just like a weight workout.

WeakSauceAsian
04-30-2003, 08:16 PM
Powerman

iI you didn't know it by now, you do a service to us all. Thanks.

wsa

galileo
04-30-2003, 10:54 PM
What magic causes one to have low glycogen in the morning?

pusher
05-01-2003, 01:13 AM
I disagree. You do not need to deplete the body of glycogen to burn fat. When your body is resting, the primary fuel source is usually fat. When you are reading this post, your primary fuel source is probably fat. And you are burning fat througout the low intensity cardio, whether or not your glycogen stores have been depleted. It is true that a larger portion of energy comes from fat as glycogen stores decrease

This sounds wrong to me. The body preferentially gets its energy(ATP) from glycolysis. Lipolysis (oxidative phosphorylation of fats) occurs yes, but not a majority of the time as you are suggesting. Fats are only burned when the body needs to because it is not as bioenergetically favourable as glycolysis is. Your body gets its energy firstly from carbs, then proteins and then fats, although the latter two do occur on a minimal level all the time. I wish it were true that by sitting here, I will burn fat primarily...this is just not true, otherwise we need not be breathing either(oxygen);)

pusher
05-01-2003, 01:19 AM
galileo: I believe the magic is that the carbs you eat(glycogen), as I've stated earlier, continue to be metabolized into energy as you sleep to keep you alive, since you do not eat during sleep. Thus when you wake up, the carbs in your body have been depleted. This is the reasoning for cardio in the morning on an empty stomach, when the goal is to burn fat preferentially over carbs, since the carb levels are already lowered, you are simply taking advantage of the state of you body.

aka23
05-01-2003, 03:48 AM
Originally posted by pusher
This sounds wrong to me. The body preferentially gets its energy(ATP) from glycolysis. Lipolysis (oxidative phosphorylation of fats) occurs yes, but not a majority of the time as you are suggesting. Fats are only burned when the body needs to because it is not as bioenergetically favourable as glycolysis is. Your body gets its energy firstly from carbs, then proteins and then fats, although the latter two do occur on a minimal level all the time. I wish it were true that by sitting here, I will burn fat primarily...this is just not true, otherwise we need not be breathing either(oxygen);)

Fat only metabolizes in the presence of oxygen. Glycolysis can occur with or without oxygen. If the body has no oxygen available it cannot burn fat and is forced to depend on other pathways, such as anaeorbic glycolysis.

When at rest the average person gets about 65% of calories from fat and 35% of calories from carbs (glycogen/glucose). The exact ratio depends on many factors such as diet, training, and genetics. Fat is the primary source of fuel for most of your daily activities such as watching TV, reading, etc. As intensity of activity increases, this balance shifts and an increasing portion of calories comes from glycolysis.

Some references can be found below:

http://www.ivillage.com/diet/experts/wlcoach/articles/0,,222000_7216,00.html
"All other things being equal, it doesn't like to burn protein, so that leaves fats and carbohydrates (more technically, fatty acids and glucose). At rest, the "average" person burns about 70 percent fat and 30 percent carbs. As one moves from rest to activity, the percentage of fuel coming from fat decreases and the percentage coming from carbs increases. The more intense the exercise, the more carbs and the less fat in the mix, until you reach the point called the "anaerobic threshold" where you're going at about your intensity limit. At that point, 99 percent or more of your fuel is pure carbohydrate and 1 percent or less is coming from fat. "

http://www.cardiacrehabindia.com/exercise_myths.htm .
"As explained above, the body uses a mixture of fuels to obtain energy. Even at rest, about 60% of the energy is derived from fat. So it is untrue to think that fat burning starts only after some time. "

http://www.exrx.net/Nutrition/Substrates.html
"At rest, 33% of the body's energy comes from carbohydrates, or glycogen, stored within the muscles and liver. 66% comes from fat. "

PowerManDL
05-01-2003, 09:48 AM
To add, muscle in particular burns fat as the largest share of its resting energy supply. Glycogen used at rest is going to fuel other processes.

That's one reason why added muscle tissue is so important for changing body composition.

powerhalf
05-01-2003, 09:54 AM
This is pretty heavy stuff. It's entirely possible that I'm not understanding this completely, but it sounds like we have people preferring a lower intensity, more jogging-type cardio over HIIT. With all this being said, which do you prefer?

PowerManDL
05-01-2003, 09:58 AM
HIIT all the way.

Severed Ties
05-01-2003, 10:04 AM
Yo powerman you skinheaded mofo


Originally posted by Severed Ties

Cardio choice directly depends on glycogen stores

We're saying the same thing, it's just not getting through your white supremasist head.:rolleyes:

When someone has the proper carb intake I prefer to use HIIT, however their are times when I use carb restictions or rotations to get bodyfat levels even lower. During these times since the necessary carbs are not available for HIIT I prefer low-intensity, long duration cardio so that muscle is preserved.


ST

pusher
05-01-2003, 10:39 PM
Thanks for clearing that up for me AK, and Power, I had it all wrong.:thumbup:

But one more question, where are the fatty acids that are being metabolized at rest coming from (in what proportion)...are they being mobilized from adipose tissue?

Joe Black
05-02-2003, 02:28 AM
Damn, lots of responses. Thanks guys.

Iím at work right now, but I am going to have a good read of it this evening!

powerhalf
05-02-2003, 02:43 PM
I've also heard that sprinting can be good for quad development, this may be another factor influencing one's decision to do one or the other.