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View Full Version : How much Cardio is TOO much cardio if trying to lose weight/fat?



GrindingOut
04-03-2004, 09:19 PM
I was doing about 30 mins of basketball to kind of warm up

30 mins on the Reebok Body Peak cardio machine

Then lifting for like 20 mins

Then doing a mile on the treadmill in like 15 mins

Is this too much cardio?

Today, I shot around (b ball) for like 40 mins

Did 30 mins on Reebok Body Peak

Then weight lifted, circuit training for 30 mins and cut out the extra mile on the treadmill.

I was reading an article on The Rock and he was talking about how when he was cutting...when he was working 1-2 body parts a day...he just wasn't using enough of his body to burn enough calories to burn fat...

So today when I lifted,,,i did leg presses 3 sets,,,bench press 3 sets,,,dips 3 sets,,,lat pull downs 3 sets. I felt more winded after circuit training than before when i'd weight train 1 or 2 body parts w/out circuit and doing another mile on treadmill. Is keeping this up a good idea? Am I better off cutting out SOME of the cardio and just circuit training 4 body parts when lifting?

I work out 4 times a week by the way...

i'm 5'8" 238lbs...used to be a little over 300lbs so i've already dropped a nice amount...but obviously it's getting harder and harder to lose. My goal is between 190-200 but i have a lot of body fat to lose. Mostly from my mid section and chest. Waist is about 44.

Andy P
04-04-2004, 08:43 AM
1. Do weight before cardio. Even better weights on diff day.

2. Over 45mins is way too much. I prefer HIIT and blast it for only 15min.

3. Get a diet sorted. thats the most important in loosing fat.

IMO cardio should only be used to ensure a negative calorie balance. & too much cardio can be catabolic. IE loose muscle. make sure u get plenty of protein after workouts. HIIT imo opinion is better suited for me. as i hate cardio and getting to over with ASAP is what im after. + the benifits of HIIT over slow/long cardio are massive. IE increased metabolism after cardio.

GrindingOut
05-22-2004, 01:48 PM
1. Do weight before cardio. Even better weights on diff day.

2. Over 45mins is way too much. I prefer HIIT and blast it for only 15min.

3. Get a diet sorted. thats the most important in loosing fat.

IMO cardio should only be used to ensure a negative calorie balance. & too much cardio can be catabolic. IE loose muscle. make sure u get plenty of protein after workouts. HIIT imo opinion is better suited for me. as i hate cardio and getting to over with ASAP is what im after. + the benifits of HIIT over slow/long cardio are massive. IE increased metabolism after cardio.

What are some good HIIT cardio exercises?

wleon
05-22-2004, 01:55 PM
yes you are doing way to much cardio

Dedicated
05-22-2004, 02:39 PM
If your goal is to lose weight my best advice to you is to count your calories, you cannot fail if you do this. If you are already doing this and still having difficulties ask yourself this, are your calories too low? If they are, have a refeed day once a week. This will allow you to bring your calories back up, most likely to the level you were eating when you started your cut. Rinse and repeat, you will lose as much weight as needed like this.

About your cardio I do not think it is too much, but I think the order is not optimal. I think you should make an effort to seperate the weight and cardio sessions. Doing weight training and cardio on the same day is fine but seperating the sessions by several hours would be ideal. If you cannot seperate the sessions make sure you do not work out on empty stomach, and then after your weight training have a fast digesting carb/protein, and then do your cardio. Again it is ideal to seperate the two activities but it can be difficult depending on your schedule.

As for HIIT that is fine but make sure it does not interfere with your lifting. Typically HIIT is much more high impact. Do not rely on this for weight loss, you will just run in circles forever if you do.

Again let me emphasize that you should rely on manipulating your caloric intake to lose weight. The weight training, cardio, and HIIT are just there to let you burn a few extra calories, help with nutrient paritioning, and help you maintain/possibly add a little muscle if your training is in check. Goodluck.

Ebu
05-22-2004, 03:24 PM
He's saying he wants to loose a lot of body fat, never did he mention he wants to gain a lot of muscle. No, your not doing too much cardio.

GrindingOut
05-22-2004, 04:49 PM
If your goal is to lose weight my best advice to you is to count your calories, you cannot fail if you do this. If you are already doing this and still having difficulties ask yourself this, are your calories too low? If they are, have a refeed day once a week. This will allow you to bring your calories back up, most likely to the level you were eating when you started your cut. Rinse and repeat, you will lose as much weight as needed like this.

About your cardio I do not think it is too much, but I think the order is not optimal. I think you should make an effort to seperate the weight and cardio sessions. Doing weight training and cardio on the same day is fine but seperating the sessions by several hours would be ideal. If you cannot seperate the sessions make sure you do not work out on empty stomach, and then after your weight training have a fast digesting carb/protein, and then do your cardio. Again it is ideal to seperate the two activities but it can be difficult depending on your schedule.

As for HIIT that is fine but make sure it does not interfere with your lifting. Typically HIIT is much more high impact. Do not rely on this for weight loss, you will just run in circles forever if you do.

Again let me emphasize that you should rely on manipulating your caloric intake to lose weight. The weight training, cardio, and HIIT are just there to let you burn a few extra calories, help with nutrient paritioning, and help you maintain/possibly add a little muscle if your training is in check. Goodluck.

Great info...

I posted in another thread about how I was consistantly losing 1-2 pounds a week for like 2 months...then I stopped losing...i saw somewhere on here where someone who had the same problem should reset their metabolism by getting off their usual diet and doing a refeed for a couple of days...i did this...basically having 3 days of cheat meals each day...then went back on my diet and dropped like 3 lbs that week (this was last week). So i'll most definetly keep doing that ever 6 weeks or so and cheat still like once a week.

Yes, I want to lose fat and gain some muscle as well which I know is hard, but my main priority is burning fat. I'm already a pretty stocky guy.

I eat about 2000 calories a day. I'm 5'8" 230. My ideal weight is around 190-200. I still want to be big...just more muscular. I'm hearing my calories is too low, but i'm worried about putting on weight if I eat more than that.

ryuage
05-22-2004, 05:22 PM
Im gaining muscle and a good rate while performing cardio at least 5x a week..

Podium Kreatin
05-22-2004, 08:33 PM
sorry to burst ur bubble, but excercise isn't that effective in losing fat. it does contribute, but u'll lose protein and blood sugar and creatine FIRST, before fat oxidation starts! the reason being is fat is not designed to be for rapid muscle contractions, but for metabolic functions (BMR). this is why cardio in the morning, before breakfast, is preferred if u want to lose fat, b/c right when u wake up, u lost a lot of blood sugar.

NOTE: altho the actual cardio doesn't really lose much fat, doing cardio consistently can indirectly help u lose fat by directly boosting BMR by strengthening ur heart, increase slow twitch muscle, and increase the size of ur mitochondria (the organelles involved in oxidizing fat). if u want to lose fat by cardio, u should not do it so that ur super exhausted (imo, the amt of time that u do for cardio varies a lot depending on ur endurance), but rather, follow a consistent schedule that allows u to recover before the next session of cardio. if u do cardio til ur super exhausted, it usually means u lost a lot of muscle.

snow
05-22-2004, 11:55 PM
u go to ohio state?

Pacificmonarch
05-23-2004, 01:26 AM
I personally think there is no such thing as too much cardio. However, depending on what your goals are maybe it is.

What Podium Kreatin said is true and false. If you want to lose weight, the best way is to work out on an empty stomach right after wake up. It will increase your metabolism and studies have shown that fat is burned much fast - up too 300% faster when you exercise in the morning as opposed to in the afternoon. Not only that, if your main goal is to lose weight, after you do cardio wait an hour before eating. After you do some "high intensity cardio" your metabolism is reved up some time after working out, burning extra calories.

Podium said "but excercise isn't that effective in losing fat" I totally have to disagree. Excercise is a totally effective way of losing fat. It is true that you have to watch what you eat(basically you have to burn more calories then you consume), but without exercise people would not be able to lose weight(unless they take some kind of pill which I am totally against). Like I said before, by exercising in the morning you dip into you energy store(fat) because your blood suger is low. That's when you start to use up your excess calories you stored away. However, working out for too long can definitely do more harm then good. It can eat away at your hard earned muscles.

You should just maybe do 20 mins of cardio at high intensity. This a good method i read in a book. First warm up for 2 min at a intensity level of 5. 1 being the least(like lifting a fork to your mouth), 10 being near death. Then after that bring it up to a 6 intensity for a min. Then after that bring it up to a 7 intensity for a min, then a 8 intensity for a min, then a 9 intensity for a min, then bring it back to a 6 min. Do this cycle 3 times. On the last one after the 9 intensity, you give it everything and do an all-out 10 intensity(you should be having a near death experience :-) for a min. Then bring it back to a 5 intensity and your done. The workout plan the books suggests is to lift mon, wed, fri and do cardio for tue, thrus, sat. Sun be a cheat day only.

It think this a good balence of cardio. It's not to long and it won't tax your hard earned muscles. I don't know how intense the cardio you were doing, but if it is intense, then I think you're doing to much cardio.

No matter what, consistancy is key.
Do whatever it takes!
Good Luck.

KingJustin
05-23-2004, 09:33 AM
"2. Over 45mins is way too much. I prefer HIIT and blast it for only 15min."

Not that HIIT is a bad idea, but running for an hour is a great way to burn an awful lot of fat as your body begins to oxydize(?) fat for fuel (I believe that's what happens, at any rate it targets fat) after 20 minutes of increased heart rate.


"I personally think there is no such thing as too much cardio."

This is blatantly wrong. I ran cross country 4 years, track a couple and I see people overtraining with just running all the time. They would simply run too much and it would cause them to get slower.


"What Podium Kreatin said is true and false. If you want to lose weight, the best way is to work out on an empty stomach right after wake up"

Yeah, that's great if you want to lose muscle. Have at least a protein shake (with water) and maybe a banana before you run if it's in the morning.


"It will increase your metabolism and studies have shown that fat is burned much fast - up too 300% faster when you exercise in the morning as opposed to in the afternoon."

I'd be interested in seeing the study.


Anyways, I agree that you should be doing cardio, but not before weights for sure. You need to make sure that after running you have gone into caloric deficit. Running for around 45 minutes to an hour or doing HIIT should probably be what constitutes most of your cardio, as it will help target fat..

GrindingOut
05-23-2004, 10:29 AM
u go to ohio state?

No. Are you in Columbus?

Pacificmonarch
05-23-2004, 10:29 AM
The book I got all the infomation from is call Body-for-Life by Bill Philips. I don't know if he's the best fitness expert in the world, but he definitely has transformed many people within 12 weeks. I personally don't follow everything he says, but he does have proven methods that work. I didn't notice till recently, but there are lots of people who follow his book and have really achieved a "Body-for-Life".

"It will increase your metabolism and studies have shown that fat is burned much fast(er) - up too 300% faster when you exercise in the morning as opposed to in the afternoon."

This is a quote from his book. He doesn't supply the data but I don't think he's lying.

"I personally think there is no such thing as too much cardio."
The reason I said this was because of an interview I saw on tv. It was on some public access channel in Hawaii and they had just finished some big marathon. They were interviewing this old guy who just finished. The interviewer was asking him question on how the run was and stuff like that and the guy(runner) was talking all incoherently and stuff. Then finally, the interviewer asked the guy how old he was, and he said he was 100. That there was definitely motivation for me to run more often.

snow
05-23-2004, 10:46 AM
No. Are you in Columbus?

yeaaaaaaaaaaaaaaaaaaaah i got 2 o state.

GrindingOut
05-23-2004, 11:37 AM
yeaaaaaaaaaaaaaaaaaaaah i got 2 o state.

LOL

I go to Franklin

GrindingOut
05-23-2004, 11:49 AM
yeaaaaaaaaaaaaaaaaaaaah i got 2 o state.

Funny journal...you most def sound like an OSU student...I like to kick it down there...(Ole School, Lidos, Alcatraz a couple times)

KingJustin
05-23-2004, 12:13 PM
"The reason I said this was because of an interview I saw on tv. It was on some public access channel in Hawaii and they had just finished some big marathon. They were interviewing this old guy who just finished. The interviewer was asking him question on how the run was and stuff like that and the guy(runner) was talking all incoherently and stuff. Then finally, the interviewer asked the guy how old he was, and he said he was 100. That there was definitely motivation for me to run more often."

There's no doubt that being thin and reasonably active and taking care of yourself will increase longevity...


"It will increase your metabolism and studies have shown that fat is burned much fast(er) - up too 300% faster when you exercise in the morning as opposed to in the afternoon."

I'd be interested in a famous Aka reply on this one but at the least even if fat is burned faster in the morning you still can't run on an empty stomach if you want to keep your hard earned muscle. It is just catabolic. I recall a study performed on rats where one was fed whey protein, one slow digesting protein and one nothing and all performed cardio in the morning. The rat with the whey protein had lost significantly less muscle than the other rats.

aka23
05-23-2004, 12:36 PM
I believe that this thread has lots of incorrect and/or misleasing information. I do not have time to address everything right now, so I will start will the things I consider most important.


sorry to burst ur bubble, but excercise isn't that effective in losing fat. it does contribute, but u'll lose protein and blood sugar and creatine FIRST, before fat oxidation starts! the reason being is fat is not designed to be for rapid muscle contractions, but for metabolic functions (BMR).

Your body is almost always burning a mixture of fat and glucose/gylcogen. When at rest the average person gets about 65% of calories from fat and 35% of calories from glycogen/glucose. Your body also burns a mixture of glucose/glycogen and fat througout aerobic exrcise, whether you are working out an empty stomach or not.

When glycogen stores decrease as the exercise continues, the body utilizes a larger portion of fat as fuel. Costill's studies of treadmill running at 65% VO2 max found fat oxidation accounted for 39% of the energy at the start of the exercise and 67% of the energy 2 hours later. Ahlborg found similar results of increasing fat usage when the exercise continued for 4 hours (at a lower intensity). One could expect a similar fat burning increase if the aerobic cardio followed weightlifting of the glycogen-depleting type (long sets, short rest).



but u'll lose protein and blood sugar and creatine FIRST
if u do cardio til ur super exhausted, it usually means u lost a lot of muscle.

A small portion of energy comes from proteins, but this amount is usually insignificant. It usually only becomes significant when glycogen levels get very low or in certain other special situations.

The risk of catabolism is dependent on exercise intensity, exercise duration, diet, when exercise is performed, and previous training, among other things. I believe that there is little risk of muscle catabolism as a result of exercise unless the exercise is done in extreme conditions. Protein is generally not a significant source of fuel in exercise. It may become significant in extreme conditions that deplete glycogen levels, especially liver glycogen. Liver glycogen levels fall in a more linear manner than muscle glycogen. Muscle glycogen levels do not drop as quickly at lower levels, as fat usage increases.

This might include exercise done when initial glycogen levels are low (for example in morning on empty stomach or after glycogen depleting type weight training); several hours of continuous moderate intensity exercise; or HIIT in which sprints totaled roughly 30 minutes to an hour, depnding on many factors such as intensity. I believe Hultman & Bosch's research suggested roughly 50% muscle glycogen depeltion after 6+ hours at 50% VO2Max, ~2hours 40min at 70% VO2Max, ~1 hour 40 min at 75% VO2Max, ~1 hour at 85% VO2Max, ~30 minutes at 120%VO2Max (sprint HIIT), and ~15 minutes at 150% VO2Max (sprint HIIT). Even under conditions of complete muscle glycgoen depletion, protein still only accounts for a small portion energy usage during exercise. The study http://www.ncbi.nlm.nih.gov/entrez/query.f...5&dopt=Abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=80204005&dopt=Abstract) at 60% VO2Max for 1 hour under complete CHO depletion estimated ~10% of energy usage was from protein. It is important to note that protein usage does not equal muscle catabolism. Much of the protein comes from other sources. In short, I think there is little to worry about unless the exercise is done in unusual conditions such as after fasting, or while on a low-carb diet.

During the first 4 months of my jounal on this site, I did cardio every day while bulking for a median duration of 1 hour. In this period I averaged ~0.75lb LBM gain per week, made large strength gains including on legs/calve exercises, and lost a small amount of body fat.


If you want to lose weight, the best way is to work out on an empty stomach right after wake up. It will increase your metabolism and studies have shown that fat is burned much fast - up too 300% faster when you exercise in the morning as opposed to in the afternoon. Not only that, if your main goal is to lose weight, after you do cardio wait an hour before eating. After you do some "high intensity cardio" your metabolism is reved up some time after working out, burning extra calories.
Doing "high intensity cardio" on an empty stomach is a recipe for muscle catabolism. Protein usage as fuel is closely tied to low glycogen levels, especially liver glycogen. Working out in the morning on an empty stomach is about the worst possible conditions other than extended fasting, in terms of catabolism. After an overnight fast, your liver glycogen levels may be nearly depleted. Your muscles may have a lot of glycogen left, but your brain cannot cannot use the muscle glycogen, so there is an increased risk of the body catabolizing muscle to get fuel for the brain. The amount of this risk depends on the type of cardio among other things. Higher intensity or longer duration increases risk because there is a greater demand for glycogen. Total fat loss (not just during activity) increases with the intensity or duration of the cardio. After an overnight fast, you are likely to have reduced endurance and more fatigue so both intensity and duration may decrease. If your goal is to lose fat while preserving muscle, then doing cardio on an empty stomach or any other time when glycogen levels are low (for example immediately after weightlifting) is probably a bad idea.

If your goal is to get rid of that last little bit of stubborn fat, then the increased fat mobilization related to the low glycogen levels may be beneficial. Many pro bodybuilders do empty stomach type cardio in conjuction with various supplements that also increase fat mobilization. If you choose to workout in the morning, then such effects could be lessened by eating something beforehand, reducing intensity, and/or drugs/supplements.


"It will increase your metabolism and studies have shown that fat is burned much fast(er) - up too 300% faster when you exercise in the morning as opposed to in the afternoon."

This is a quote from his book. He doesn't supply the data but I don't think he's lying.

The quote sounds like nonsense. Earlier I stated that Costill's studies of treadmill running at 65% VO2 max found fat oxidation accounted for 39% of the energy at the start of the exercise and 67% of the energy 2 hours later. 300% faster would mean deriving 148% of the energy from fat at the start of the exercise and 268% of the energy from fat 2 hours later. Obviously no more than 100% of energy can come from a paticular source. If the 300% quote is based on a real study, then I expect that it involved unusual conditions, such as comparing an empty stomach to immediately after a meal. If I have some time, I will search for real numbers later. I would not be surprisd if the 300% quote was based on a study that found 30%.

In any case, I think total fat loss is more important than fat loss during the activty. Total fat loss closely tied to calorie balance. If you burn a larger portion of calories from fat during the cardio, then you usually burn a smaller portion of calories from fat later in the day. Similarly if you burn a larger portion of calories from glycogen during the cardio, then you usually burn a larger portion of calories from fat later in the day. In this way calorie balance becomes the primary factor that determines fat loss.

The increased metabolism is closely tied to intensity. I would not expect much of an increase in metabolism unless the exercise is done at a high intensity. One study came to the conclusion, ""light exercise could be expected to lead to burning an extra 5-10 calories afterwards; moderate to an extra 12-35 calories. In contrast, strenuous exercise was shown to increase post-exercise energy burning by a huge 180 calories."" You will still get a post exercise burn whether you do the exercise in the morning or afternoon.

snow
05-23-2004, 01:43 PM
u don't post on SOHH, do u?

GrindingOut
05-23-2004, 02:09 PM
u don't post on SOHH, do u?

Possibly hahaha

Ebu
05-23-2004, 03:05 PM
aka23, PLEASE tell me you copy and pasted that...

aka23
05-23-2004, 03:21 PM
aka23, PLEASE tell me you copy and pasted that...

Most of it was cut and pasted from other posts I have written on this forum. You can find the earlier posts with the search function.

Beast
05-23-2004, 03:27 PM
aka knows his ****.

GrindingOut
05-23-2004, 03:31 PM
aka knows his ****.

Yea but I really didn't understand most of that...

Still confused on the best time of day, intensity and duration that I should do cardio to increase fat burning...

Allyrulez
05-23-2004, 03:35 PM
Aka laid the smack down

Ebu
05-23-2004, 04:02 PM
I know aka23 knows his stuff, its just that there was a LOT there, and it would have taken FOREVER to type it up.

Podium Kreatin
05-23-2004, 11:30 PM
a flaw, i believe, i see here is that ppl assume that BMR energy sources and muscle-tissue energy sources go by the same rules. they don't. ok, since there is a lot to quote, i'll just add to what i put:

the ranking for energy source for BMR (resting metabolism, from non-muscle cells):
aerobic glycolysis>fat oxidation>>gluconeogenesis. non-muscle cells do not use creatine nor are capable of anaerobic glycolysis

the ranking for energy source for EXCERCISE (muscle cells):
creatine phosphate>anaerobic glycolysis>gluconeogenesis (protein conversion into glucose)>aerobic glycolysis and oxidation>fat oxidation

here is why excercise differs in energy usage than BMR

BMR uses little fuel per unit of time, b/c of mitochondria. mitochondria can use oxygen and harness 16x the energy (ATP) from glucose than w/o mitochondria (muscle-cells), adn are capable of harnessing energy from fat. however, "oxidative phosphorylation" is very slow, b/c it involves the mitochondria performing "slow, controlled explosions" w/ the oxygen to harness the energy in glucose and fat. u can think of this as a "hot-potato" idea, where oxygen is passed from one protein to another, until it gets to the end. this involves many enzymes and is a lot of oxygen is used

excercise, however, uses the skeletal muscles, which differ in composition than non-muscle cells. this includes: very little or no mitochondria (limited fat oxidation), capable of anaerobic processes, and low oxygen reception relative to other types of tissue.

we can all agree that cardio can boost BMR, which is effective in burning fat. but, in terms of the cardio session itself, longer is not better. this is b/c aerobic processes (aerobic glycolysis and fat oxidation) are TOO SLOW for running and other excercises (muscle-twitch burns more energy per unit of time than anything else).

from aka's website link
It was concluded that protein is utilized during exercise to a greater extent than is generally assumed and that under certain conditions protein carbon may contribute significantly to exercise caloric cost.
the thing about running before breakfast: our blood sugar is low at this point, and u "force" ur body to use fat and protein. but, u will lose protein, b/c our bodies always try to keep a steady level of blood glucose. however, u always lose protein when u are losing fat from excercise, b/c fat is always gonna be the least preferred energy source for excercise, right under protein.

CLARIFICATION: i didnt' say that "cardio isn't effective in losing fat." i'm saying, the cardio session isn't effective in losing fat, and longer is not better, which was to answer the question of this thread. if u do cardio and lose weight effectively, it is more of the BMR energy usage, not the excercise energy usage. here's my summary:
cardio is effective in boosting BMR, which will help lose fat and spares proteins. but doign longer cardio isnt' gonna do much better, b/c the longer cardio session itself isn't effective in burning that much more fat, and won't boost BMR that much.

aka23
05-24-2004, 01:18 AM
the ranking for energy source for EXCERCISE (muscle cells):
creatine phosphate>anaerobic glycolysis>gluconeogenesis (protein conversion into glucose)>aerobic glycolysis and oxidation>fat oxidation

I think you are calling something similar to the order of energy production during maximal exercise "the ranking for energy source." During near maximal exercise (sprint portion of HIIT or weight training), the body first uses intramuscular stores of ATP and posphocreatine (PCr). At maximum intensity exercise, they are only the dominant energy source for about 7 seconds. After ~7 seconds, oxygen-independent glycolysis becomes the dominant energy source. In this process glycogen is used as fuel and lactate is generated. This energy process is sometimes called anaerobic glycolysis, suggesting that it only occurs when oxygen is not available, such as when one is out of breath while sprinting. It actually can occur whether oxygen is present or not. Lactate accumulation is more associated with effort and hormonal release than lack of oxygen. Within a couple minutes of maximal exercise (by this point pace is slowed down significantly), oxygen-dependent glycolysis becomes the dominant energy source. Lypolysis generates energy from fat and also requires aerobic conditions. It is not involved much during the work portion of short periods of near-maximal intensity exercise (It is involved in the rest/recovery periods between sprints.). However, several studies suggest that sprints may be superior to traditional cardio for fat loss. One such study is described at http://www.exrx.net/FatLoss/HIITvsET.html. As I described earlier, fat burned during the activity does not equal total fat loss. Total fat loss is more closely related to calorie balance.

The above "ranking" of energy systems relates to short sprints of near maximal intensity exercise. Traditional aerobic cardio is very different. During aerobic conditions, energy is continually being derived from three main sources: fat, blood glucose, and muscle glycogen. Fat is being used at the start and fat is being used at the finish. The proportion of energy derived from fat is closely tied to intensity. In one study, GA Brooks found the following approximate ratios of energy derived from fat to carbs near the start of exercise at various intensities:

Rest -- 65% Fat / 35% Carbs
20% VO2 Max -- 60% Fat / 40% Carbs
40% VO2 Max -- 45% Fat / 55% Carbs
60% VO2 Max -- 25% Fat / 75% Carbs
80% VO2 Max -- 0% Fat / 100% Carbs

The final case at 80% VO2Max is the near maximal intensity case discussed earlier. Note that at the higher intensities, calories are being burned at a much faster a rate, so the maximum rate of fat oxidation occurs when far less than 50% of the calories are coming from fat. The graph at http://www.biochemsoctrans.org/bst/031/1270/bst0311270f01.htm?resolution=HIGH
shows how rate of fat oxidation varies with intensity of exercise. The study depicted in the graph found the maximum rate of fat burning at slightly below 65% VO2 Max. If I remember this study correctly 65% VO2 Max correlated with ~75%MHR in this study.

Other factors affecting the proportion of fuel from fat include exercise duration, dietary composition including recent meals, training history, environmental conditions, hormones/gender, and supplements/drugs. The paper at http://www.biochemsoctrans.org/bst/031/1270/bst0311270.htm gives a good summary how these factors come into play and how fat oxidation is affected diet, aerobic exercise, and environment.

Notice that protein is not mentioned in the discussion above. As stated earlier, protein is generally not a significant source of fuel in exercise. This makes sense from both an evolutionary perspective and a biochemical perspective. It does not make sense that the body would prefer using protein to fat as fuel in typical conditions, as your posts suggests. Protein stores are limited, and it does not seem logical that the body would evolve to catabolize large amounts of muscle in typical exercise. The process of using protein for energy is also waistful, compared to fat. Protein generally only becomes significant in extreme conditions, when carbs are not available and fat cannot substitute. This might include in the morning on an empty stomach. Liver glycogen is nearly depleted. It is used to supply fuel to the brain. Ignoring special situations like ketosis, fat is not an adequate substitute, so the body is forced to resort to protein. Another example, might be high-intensity exercise done in low-glycogen conditions. Fat cannot supply energy at a fast enough rate for high intensity exericse, so the body must increase the proportion of energy from carbs. If carbs are limited, the body is forced to increase protein usage. This final example is similar to the study I linked to earlier, which found 10% of energy derived from protein under condtions of nearly full glycogen depletion. These extreme conditions of the study explain the quote you listed above: "under certain conditions protein carbon may contribute significantly to exercise caloric cost." This is further supported from the paper I linked to earlier in this post,

"the quantitative contribution of branched-chain amino acids to energy expenditure is usually minimal (<1%). Even in extreme conditions (i.e. prolonged exercise in fasted conditions) amino acid oxidation only represents a relatively small fraction of total substrate utilization (<10%)."

I do not have time to address the other issues, such as the BMR (Basal Metabolic Rate) discussion right now. I may post more tomorrow morning.

aka23
05-24-2004, 11:44 AM
a flaw, i believe, i see here is that ppl assume that BMR energy sources and muscle-tissue energy sources go by the same rules. they don't. ok, since there is a lot to quote, i'll just add to what i put: the ranking for energy source for BMR (resting metabolism, from non-muscle cells):
aerobic glycolysis>fat oxidation>>gluconeogenesis. non-muscle cells do not use creatine nor are capable of anaerobic glycolysis.

BMR stands for basal metabolic rate. It indicates energy used at rest during processes such as respiration, digestion, and brain function. In resting conditions, most organs (muscle, liver, kidneys) use fatty acids as their primary fuel. The brain and red blood cells do not have the necessary mitochondria to use fatty acids as fuel, so they are forced to use glucose during resting conditions. The brain has a significant fuel requirement. It usually requires approximately 150g of glucose/day or ~20% of total energy requirement. When you wake up in the morning your liver glycogen stores are nearly depleted because the brain uses these stores for fuel (via blood glucose) while sleeping. As stated earlier ~65% of energy comes from fat and about 35% of energy comes from carbs during resting conditions. Most of this 35% carbs are used by the brain as stated above.

Aerobic glycolysis is a process in which energy (ATP) is derived from glucose and oxygen. During resting conditions (BMR), fat oxidation is favored over aerobic glycolysis. Fat oxidation's major disadvantage is that cannot supply energy at as fast a rate as glycolysis, so as intensity increases and fat oxidation cannot keep up with energy demand, an increasing portion of energy is derived from aerobic glycolysis.

aka23
05-24-2004, 12:43 PM
excercise, however, uses the skeletal muscles, which differ in composition than non-muscle cells. this includes: very little or no mitochondria (limited fat oxidation), capable of anaerobic processes, and low oxygen reception relative to other types of tissue.

There are several types of skeletal muscle. Type I muscle fibers have a high mitochondrial density and primarily use triglycerides (fat oxidation) for fuel. Type IIa also have a high mitochondrial density, but not as high as Type I. They primarily use glycogen as fuel and can function in aerobic conditions. Type IIb fibers have very low mitochondrial density and poor aerobic capacity. Recent research suggest that these fibers are not present in humans and only exist in animal models. Type IIx fibers fall between IIa and IIB. They are present in human models.

Podium Kreatin
05-24-2004, 01:24 PM
i already mentioned what BMR was, but some thigns u said were incorrect; our brain uses glucose AND ketones, and our RBCs do not use glucose, it only uses BPG (bisphosphoglycerate, a waste product of glycolysis which is only used by blood).


the quantitative contribution of branched-chain amino acids to energy expenditure is usually minimal (<1%).
i didn't disagree w/ this, i'm saying that fat burning is less than protein, and this is always goign to be true for muscle cells.


Rest -- 65% Fat / 35% Carbs
20% VO2 Max -- 60% Fat / 40% Carbs
40% VO2 Max -- 45% Fat / 55% Carbs
60% VO2 Max -- 25% Fat / 75% Carbs
80% VO2 Max -- 0% Fat / 100% Carbs
this follows my "ranking" accordingly. as u rest (BMR), u prefer fat and some carbs as sources of calories, but as u excercise, u use very little fat, and prefer sugars (despite the rise in oxygen delivery)! this is why more cardio isn't gonna be better for burnign more fat, b/c fat burnign is relatively too slow.
i also have to add that aerobic glycolysis and fat oxidation uses the same process in the mitochondria: they wil compete, and ur body will prefer to use oxidative phosphorylation (generation of ATP w/ oxygen) by burning sugar, b/c it diffuses into cells better. fats, again, require many conversions, before it can get to the mitochondria, where it is reconverted as acetyl CoA (fat in adipose-> fatty acid -> acetyl CoA -> blood -> muscle cell -> mitochondria, ithink :))


Fat oxidation's major disadvantage is that cannot supply energy at as fast a rate as glycolysis, so as intensity increases and fat oxidation cannot keep up with energy demand, and increasing portion of energy is derived from aerobic glycolysis.
i can partially agree on u on this, but imo, aerobic glycolysis slows down too as anaerobic glycolysis rates go up. lets refer to the previous quote w/ the VO2 chart: that "100%" carbs include anerobic glycolysis.



the body first uses intramuscular stores of ATP
ur body cant' store ATP! once it is generated, it is used immediately, b/c it is very unstable (ATP-> ADP + Pi + energy). PCr is the only phosphate storage that ur muscles use, and it works by regenerating ATP from ADP (PCr + 3 ADP--creatinekinase--> Cr + 3ATP)


Lactate accumulation is more associated with effort and hormonal release than lack of oxygen.
how is this hormonal (which hormones are involved)? lactic acid accumulates in two ways that i know of: lack of blood flow away from the muscles (venous return by muscle contractions, this is why u have to warm down after running for a long time, and the liver is waht cleans out lactic acid, and this'll give u cramps if there's too much lactic acid in the liver), and lack of blood flow to the muscles.

also, as long as u feel the "burn" from any excercise, u are generating lactic acid, b/c that burn is caused by lactic acid, so u can't tell me that aerobic respiration is gonna dominate over anaerobic glycolysis, b/c our bodies ONLy generate lactate when there is oxygen deficiency! and where lactic acid is present (via the burning sensation in muscles), then fat oxidation is not occuring, b/c that too, requires oxygen, adn aerobic glyolysis is gonna be preferred over fat oxidation, again, referring to the VO2 quote above.

i mean, our bodies will PREFER IDEALLY to use oxygen for all processes, but this is not possible w/ muscle contractions, b/c muscle contractions demand the most ATP per unit of time, and our bodies must use less efficient mechanisms (anaerobic mechs) to generate a butt load of ATP.

think about this analogy: if u want a 700hp/600lb-ft car to go 0-60 in 3 seconds, u need a V8 to burn a buttload of gasoline, w/ an (in)efficiency of less than 8% energy extraction (the horsepower u get is less than 8% of the hydrocarbon bond energy in gas, while 92% is released as heat, exhaust, and monoxide). u can't generate that much torque and horsepower w/ a fuel efficient gas-electric hybrid (where u can use more than 12% of the hydrocarbon bond energy in gas). of course, this is compromise, cuz if u are running away froma lion, then u gotta make sacrifices

clarifications (again): i didn't say u won't do aerobic glycolysis during excercise, or almost zero. i agree that oxygen delivery goes up during excercise (via bohr effect), but i'm talking abour RELATIVE fuel source preferences. all sources of fuel will be burned at a higher rate, of course, but at differetn proportions.

we seem to agree on BMR.

aka23
05-24-2004, 03:47 PM
some thigns u said were incorrect; our brain uses glucose AND ketones, and our RBCs do not use glucose, it only uses BPG (bisphosphoglycerate, a waste product of glycolysis which is only used by blood).

The medline medical encylopedia at http://www.nlm.nih.gov/medlineplus/ency/article/003482.htm states
“.Some cells (for example, brain and red blood cells), are almost totally dependent on blood glucose as a source of energy”

The university biochemistry page at http://www.lsmsa.edu/MKhandoker/biochemistry/Introductory%20biochemisty/Carbohydrate%20metabolism/Carbohydrate%20metabolism%20fact%20sheet.htm states
“In addition to brain, glucose is also the most important fuel for the red blood cells and is normally obtained from the diet.”

I am well aware that the brain can substitute ketones as fuel in special situations, such as ketosis or severe starvation. Note that I wrote: “Liver glycogen is nearly depleted. It is used to supply fuel to the brain. Ignoring special situations like ketosis, fat is not an adequate substitute.”



ur body cant' store ATP! once it is generated, it is used immediately, b/c it is very unstable (ATP-> ADP + Pi + energy). PCr is the only phosphate storage that ur muscles use

The muscle cells store approximately 6 mmol of ATP per kilogram of muscle (Noakes, 1991). This ATP can sustain about 1 second of sprinting (Noakes, 1991).



how is this hormonal (which hormones are involved)? .

Epinephrine (a hormone) infusion increases blood lactate levels, while norepinephrine (a hormone) decreases levels. http://www.ncbi.nlm.nih.gov/entrez/query.f...t_uids=97236534 (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Abstract&list_uids=97236534) . Several studies have found a close correlation between epinephrine and blood lactate levels. If "anaerobic" glycolysis was primarily dependent on oxygen levels rather than hormones, then exercise in low-oxygen conditions at high elevation would generate more blood lactate. Instead the opposite is true.

I am busy at work now and do not have time to address the rest of the your post.

aka23
05-24-2004, 06:19 PM
“"the quantitative contribution of branched-chain amino acids to energy expenditure is usually minimal (<1%). Even in extreme conditions (i.e. prolonged exercise in fasted conditions) amino acid oxidation only represents a relatively small fraction of total substrate utilization (<10%)."

i didn't disagree w/ this, i'm saying that fat burning is less than protein, and this is always goign to be true for muscle cells.
The quote above from the paper "Modulation of carbohydrate and fat utilization by diet, exercise and environment" that you responded to says protein oxidation represents less than 10% of substrate utilization in extreme conditions involving prolonged exercise while fasting and less than 1% in normal conditions. You are saying that fat oxidation accounts for less than this 1% of substrate utilization in normal conditions and this is always going to be true for muscle? I have already provided many examples where this is not the case. For example Costill's studies of treadmill running at 65% VO2 max found fat oxidation accounted for 39% of the energy at the start of the exercise and 67% of the energy 2 hours later. If fat oxidation accounts for 67% of the energy, then it is the dominant energy source, certainly more than protein. The referenced paper mentions a study in which 90% of energy was found to come from fat during exercise. This fat oxidation is primarily occurring in the muscle cells. The referenced paper states, “At rest and during exercise skeletal muscle is the main site of oxidation of FA (fatty acids).”



this follows my "ranking" accordingly. as u rest (BMR), u prefer fat and some carbs as sources of calories, but as u excercise, u use very little fat, and prefer sugars (despite the rise in oxygen delivery)!
You ranked aerobic glycolysis highest in non-muscle cells at rest. The listed study found that fat oxidation was the dominant source of energy at rest, not aerobic glycolysis. You ranked creatine phosphate, anaerobic glycolysis, and gluconeogenesis highest for muscle cells during exercise. I did not list anything to suggest that these play a significant role during traditional aerobic exercise. The study found that fat was the dominant source of energy at the start of lower intensity exercise, and the proportion of energy from fat decreased as intensity increased. The proportion of energy from fat would increase significantly above all these values, if we compared later portions of the exercise. For example Bosch did a study at a very high intensity in which only 6% of energy came from fat oxidation at the start of the exercise. After 3 hours at this intensity, the proportion of energy from fat had increased by more than 7x to 43% Note that this fat oxidation was occurring in the muscle cells. Repeating the early quote, “At rest and during exercise skeletal muscle is the main site of oxidation of FA (fatty acids).”



this is why more cardio isn't gonna be better for burnign more fat, b/c fat burnign is relatively too slow.
Rate of fat burning increases significantly as duration increases. I have given many examples. Calories burned increases as duration increases, and calorie balance primarily determines fat loss, not fat burned during the activity.



i can partially agree on u on this, but imo, aerobic glycolysis slows down too as anaerobic glycolysis rates go up. lets refer to the previous quote w/ the VO2 chart: that "100%" carbs include anerobic glycolysis. .
Exercise at near-maximum intensities in which nearly 0% of the energy is derived from fat are the work portion of sprints that cannot be continued for more than a minute or two. These sprints are primarily dependent on the so called “anaerobic” pathways – ATP, CP, and "anaerobic" glycolysis. Fat oxidation and aerobic glycolysis are the primary sources of energy during traditional aerobic exercise, which occurs at a lower intensity.

Podium Kreatin
05-24-2004, 07:57 PM
Rate of fat burning increases significantly as duration increases. I have given many examples. Calories burned increases as duration increases, and calorie balance primarily determines fat loss, not fat burned during the activity.
i didn't say this wasn't true. i said, u will burn relatively less fat than any other fuel source, and that cardio boosts BMR, which THEN burns fat effectively.

as u burn more fat, u also burn more sugar and protein w/ it. hence, longer cardio isn't "efficient" for burnign mroe fat (like the car analogy; u can burn tons of gasoline to yeild tons of energy (excercise), but only <8% efficiency. but if u drive at slow acceleration (BMR), u burn less fuel, but u have a higher yield b/c u allow more oxygen to go assist gasoline combustion. this is the same for excercise, b/c oxygen delivery increases up to a point, and that's it.
so, think about this: most oxygen u use is for BMR, b/c that's the top priority. u burn "1800kcal/day" just by standing still all day, and the rest is other thigns liek excercise. if u run, do u think ur body is gonna take away significant amt of oxygen out of ur BMR? of course not, cuz then, u'll die running [this is why reptiles only can sprint, they can't run for that long b/c they dont' have that much mitochondria])


The muscle cells store approximately 6 mmol of ATP per kilogram of muscle (Noakes, 1991). This ATP can sustain about 1 second of sprinting (Noakes, 1991).
this ATP comes from creatine, its not like u "store" ATP b/c is not a storage molecule. if u consider a radioactively labelled ATP (w/ labelled phosphate), and inject it into a muscle cell, u can take a "snapshot" about 10 minutes later; ur msucle cell still will have "6 mmol of ATP per kilogram of muscle," but none will be radioactively labelled, b/c it won't be the same ATP that u injected ( the labelled ATP* will be hydrolyzed into ADP*)


Epinephrine (a hormone) infusion increases blood lactate levels, while norepinephrine (a hormone) decreases levels

Lactate accumulation is more associated with effort and hormonal release than lack of oxygen.
that report said epi and norepi had correlation, but it didn't say it regulated lactic acid. u implied that the principle mech for controlling lactate were these two hormones, which was not what that report concluded. (u can inject nitrites or monoxide into the blood and ur blood lactate would go up too, and this DIRECTLY relates to lack of oxygen delivery, and doesn't involve change in hormone levels)

even if adrenalin affects lactic acid is significant; u do not release epi and norepi during excercises such as cardio. hormones wouldnt' explain why ur muscles feel a "burn," b/c as i said, ur body prefers aerobic all the time, and only releases lactic acid when it needs to make ATP quickly b/c there isn't enough O2 going to the muscles (which is the case when u run)

in terms of cardio, oxygen delivery goes up b/c of the elevated pCO2/carbonic acid detected by the brain and heart, and the medulla then triggers an immediate effect by changing breathing rate, and vagal stimulation of the heart. elevated pCO2 in the blood also triggers the bohr effect. however, despite the increased oxygen delivery, we still generate lactic acid! why? b/c oxygen delivery is insufficient.


Fat oxidation's major disadvantage is that cannot supply energy at as fast a rate as glycolysis, so as intensity increases and fat oxidation cannot keep up with energy demand, an increasing portion of energy is derived from aerobic glycolysis.
so, we agree our bodies prefer glucose over fat oxidation, right? this is why our bodies will burn protein as a source of glucose. however, the major disadvantage is NOT that the fat goes through a different pathway than aerobic glycolysis, b/c it DOES go through the same process.
http://www.accessexcellence.org/AB/GG/Acetyl_CoA.html
question: ok, so fat AND glucose in presence of O2 becomes acetyl CoA, so why is fat slower, when it yeilds 9kcal/g and glucose yeilds 4kcal/g in aerobic conditions?
answer: b/c, the rate-limiting step is the conversion from fats to fatty acids. BUT, conversion of protein into glucose is very fast.
http://web.indstate.edu/thcme/mwking/cori.gif
look at this: lactate is converted back into glucose, and this uses a LOT of energy (6ATP to regenerate glucose?). despite it being horribly inefficient, u also generate a lot of glucose very fast! this is why protein conversion into glucose (glucogenesis) is higher than fat.

remember that its not about inefficiency. BMR is about efficiency. excercise is "release tons of ATP as fast as possible, no matter what the long term cost is, b/c the long term effect is that u'll be eaten by the bear if u don't run far enough!"

check this out: our bodies have all the enzymes it needs to convert 18 of the 20 amino acids into glucose. why? cuz, its fast. and its preferred during cardio over fat.

fat metabolism, from what i've learned, not preferred b/c it is too slow. first, blood flow to adipose tissue (the cells that store fat) is very limited (this is why ur skin is cold). second, fat is hydrophobic and cannot be transported into the blood. ur body has a set of enzymes just for converting it into soluble compounds (fatty acids), and when it gets into the destinations, involves other enzymes to reconvert it into other compounds (acetyl CoA). it takes a long time to change the chemistry of a highly hydrophobic molecule into a soluble fatty acid. when u eat fat, it takes a long time to go into ur fat cells b/c of the same problem in its chemistry (bile, lipase, chylomicrons, etc. only to be converted back into straight chains when it arrives in the adipose). fat requires long range circulation to reach the muscles, but protein and glycogen (ur muscles do not use liver glycogen) is local, and stored IN the muscles.

(yea yea, ur prolly gonna say, but fat cells are right next to muscle cells, its not that far, and circulation isn't that slow! BUT, remember why spot-reduction doesn't work...)

Podium Kreatin
05-24-2004, 08:02 PM
as for the ranking system, i may be off b/c i'm basing everything on memory, and one year difference in textbooks makes a lot of differences. but, i know for a fact that fat oxidation is the slowest in excercise

Podium Kreatin
05-24-2004, 08:20 PM
ok, since there is a lot of quotes u'll quote me from to make ur argument, try to answer these qs:
1) if low intensity cardio prefers fat as a usage of fuel, then why do we feel a burn in our muscles? fat yields more than twice as much ATP than glucose, so why would our bodies resort to anaerobic glycolysis, which only yields a measly 2 ATP? (remember, i'm talking about low intensity cardio)
2) how come sprinting (high intensity) gives a big burn in the legs, if VO2 is so high (80%)? should'nt oxygen delivery prevent lactic acid production?
3) why do ppl get sore muscles from low intensity running?
4) why do ppl get sore from HIGH intensity running?
5)why do ppl cramp up when they run long distances (low intensity) if, according to u, aerobic glycolysis and fat oxidation is the choice of fuel? (crampign is caused by too much lactic acid from lack of oxygen going to that muscle site)
6) why do ppl's leg or butt cramp up when they sprint (not talking about charlie horse) hard (high intensity)?

aka23
05-24-2004, 09:29 PM
u will burn relatively less fat than any other fuel source

This statement suggests that you always derive a greater portion of energy from both protein and carbs than fat. Research suggests otherwise. One example is listed in the study at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3967777 . It states,

“With light prolonged exercise there is a progressively greater use of fat until it can contribute up to 80% of the total caloric expenditure.”

If fat can contribute up to 80% of the total caloric expenditure, then conditions must exist in which more energy is derviced from fat than protein or carbs. I have referenced studies and quotes from texts that show this the case in post after post. I have explained logically why protein is not a significant fuel source under usual conditions and listed studies that support this. I see no point to repeat the same information over and over.

Lets take an example of medium intensity aerobic exercise, the kind of exercise that you frequently see people doing at the gym. Do you have any evidence that implies more energy would be “burned” from protein than fat? A quote from a text book? A study? Any reliable source of real information? Lets take an example of low intensity exercise done for a very long duration. Do you have any evidence that fat would not be the dominant fuel source? Again reliable information, such as textbook or study. This does not include feelings of soreness or lactic acid burn. This does not mean chemical equations showing that fat burning does not provide "fast" (high-intensity exercise) energy, just a simple quote from a study or textbook that supports your statement.



cardio boosts BMR, which THEN burns fat effectively.

Again I am repeating the same information over and over. Lets look at how much cardio boosts BMR.

The study http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2706222 found that
“Average BMR in the control period was 5.91 (SE 0.39) MJ/24 h and was not changed with activity. There were no changes in OMR (5.71 (SE 0.27) MJ/24 h in the control) nor in SMR (5.18 (SE 0.27) MJ/24 h in the control), nor in BMR, OMR or SMR when expressed per kg body-weight, or per kg fat-free mass. 6. These results do not support the suggestions that there is a sustained increase in BMR following exercise that can usefully assist in weight-loss programmes.“

The study http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3409854 found that
“Aerobic exercise did not significantly stimulate the 24-h resting metabolic rate of either the post-obese (3 per cent, 50 kcal) or lean controls (2 per cent, 30 kcal), nor was there any significant stimulation over shorter periods “

Again BMR not elevated much unless the exercise is done at a high intensity. Bahr found that moderate intensity exercise, like is typically done by persons at the gym only increases BMR by 12-35 calories.

Lets say BMR does increase. Why does that burn fat more effectively than the cardio? If you burn glycogen during the cardio, then glycogen stores decrease. This signals the body to increase fat oxidation. The fuel mixture at rest is altered, so that more fat is oxidized and the limited glycogen is spared. Burning carbs during the exercise causes fat burning to increase after the exercise is complete. . It is not the possible, small BMR increase that burns fat, it is the calorie deficit.

I do not see the point to wasting my time continuing this discussion and repeating the same information over and over.