I STOLE THIS FROM ANOTHER BOARD...but its very interesting...
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whats up everyone, well i can safely say im a member of alot of different fitness forums also, and a couple months back i stumbled on this article. its very interesting and a new way to look at fat loss. its written by a comp b.b.
please read and let me know how u feel about this issue.
part1:
The day you decide that you want to get ripped, what is the first thing (besides a diet) that comes to mind? CARDIO!! I know we all dread it. It is the necessary evil that we must endure to get that shredded look we want.
Who wants to ride a stationary bike and stare off into space for 45 minutes to an hour? Or jog on a treadmill until your shins feel like they have nails in them. Well RC, I am going to change the way you think of carido. I am not saying that I will make it fun. I am not saying I will make it more likeable. I am saying that you will never look at cardio the same.
First let me say that I will not bore you with scientific jargon, or research dated back to the days of Arnold and Lou. I will use analogies, and metaphors that will paint a picture to help you understand the basics. I am thinking that this may be the beginning to a series of posts. But this will be the fire starter.
I have worked with many athletes, and I am a strait shooter. I tell no lies, and I speak my words exactly as I think them. I do not intend to offend anyone, but if I do I appologize. Now... time to rethink some things.
We have all heard that if you do carido on an empty stomach you will burn more fat than glucose or glycogen . Well my friends this is false. If you are expending energy, via cardio, weights (or even sex), you are burning glucose (blood sugar). Average blood sugar in a healthy individual is 80-100. That is enough fuel to do moderate to high intensity expendature for about 12-15 minutes. After that, your body turns to it's reserve fuel stores. Where does this reserve come from?? Muscle glycogen. Your body basically "leaks out" this excess storage of glucose that has been put in the muscle at an earlier time.
Once your body uses the glucose, and converts to using glycogen it can now run for about 18-24 HOURS, before switching to another fuel source (Protein Ketones, or fat in the form of glycerides). I know none of you do carido for 18-24 HOURS! So none of us are going to "burn fat while doing carido". Even on an empty stomach, all it is going to do is kick over to glycogen usage a little sooner, and Rob your poor muscles of their hard earned glycogen. Wich leads me to my next point. Cardio length.
As I have stated above, you would have to do carido for 18-24 hours to even possibly touch fat storage. I also mentioned that after 12-15 minutes your body kicks over to glycogen useage. We do not want this to happen. 1 molecule of glycogen holds 2 molecules of water. So if we tap into this reserve, our fuel and our cellular water will be used up. To do switch to this mode of fuel usage, our body mut release catabolic hormones. This is exactly what we do not want. No one want's to loose their hard earned muscle. When you loose glycogen, and water... you are basically "loosing muscle" volume. So I recommend doing cardio for 12-15 minutes. This time duration does not allow our body to tap into muscle stores. It only uses residual glucose. We can insure that we will only be using residual glucose by elevating it pre cardio. That is where the pre cardio meal/shake comes in. Dextrose taken about 15 minutes before cardio would increase residual glucose, and give us a cushion of time before we tap muscle stores.
Another common misconception, is that doing cardio at a meduim pace burns more fat than high intensity. This falacy was derived from the FACT that when we are at rest, our body's main fuel source is fat. That is a FACT, but only when we are not exerting ourselves. I don't care how low the intensity, if you spin the pedals on the bike you are going to burn glucose PERIOD. But we can use this phisiological fact to enhance our daily usage of fat. Look for this in part 2 of this series. Why high intensity/ short duration cardio is the secret to burning more fat, and why medium intensity long duration is almost counter productive.
Part 2:
For you to understand what I am babbling about, you may want to read my first blurb on cardio. With that said, I am going to continue.
Short duration/ high intensity vs. long duration/ low intensity.
Science tells us that our main source of fuel during our regular daily activities is from fat. If we exercise we use glucose (blood sugar) then after 12-15 minutes once glucose is used up, our body leaks out excess glucose (glycogen) from the muscle cells. Now I know you all have heard that doing cardio at a medium intensity will burn more fat. The basis of this idea comes from the above reasoning (aerobic vs. anaerobic oxidative cycles). However this again is not true. Your body is still using glucose as it's fuel source. For both variations of cardio, glucose IS the fuel source. Now once your cardio session is done, and you are going about your daily business your body switches back to aerobic oxidation. The main source of fuel becomes fat again. So we want to take advantage of this phisiological FACT, and burn more fat. Longer cardio will only mean more glycogen loss. We want to minimize glycogen loss and maximize fat loss... here is how it is done.
Pick your poison! I mean pick your cardio. For this article we will assume that we are using a stationary bike.
You must ride this bike at full out intensity. You must take your body to the limit, where it hates to be. Two ways to increse intensity, 1) Increase the resistance. 2) put resistance at a lower level, but pedal AS FAST AS YOU CAN. I prefer the first one. Now ride the bike for 12-15 minutes. This short duration will only allow for your body to use residual glucose, and it will leave glycogen stores alone. This short "burst" of cardio at maximum intensity will put your metabolism (basal body temp) throught the roof. You will sweat your ass off in 12-15 minutes, and long after you are done (or you are not going hard enough). When that 12-15 minutes is up, you need something to restore residual glucose otherwise your body will still "leak" glycogen. Dextrose will do the trick. Now remember, we did not burn ANY fat in that 12-15 minutes. We also did not tap into muscle either. So our first goal has been accomplished (not to use muscle glycogen). I hear the talk already, "hey man, I did not burn any fat in 15 minutes". You are correct, but even if you did cardio for 18-24 more HOURS you would not burn a single bit of fat! The fat burning takes place AFTER THE CARDIO IS OVER. Now this is where high intensity/ short duration cardio wins again.
Here is an analogy:
"Take a pot of water, and put it on the stove. Now bring it to a slow simmer. Let it simmer for about 10 minutes. Now take the pot off of the heat, and place it to the side. Set a timer and see how long it takes before the pot is cool enough to touch. It won't take long, maybe a couple of minutes.
Now take out another pot. Identical to the one used before. Put the same amount of water in it. This time turn the heat (intensity) up ALL THE WAY. As soon as that pot starts to boil, remove it immediately. Now time this pot and see how long it takes to cool... ALOT LONGER.
That is the whole idea of the short duration/ high intensity cardio. It will keep our metabolism elevated MUCH longer after cardio is over. This is very important because remember, our body uses fat for fuel AFTER cardio is over. In essence we burn more fat by bringing our metabolism to a "boil". In the hours after cardio, while our metabolism is "cooling", we are burning more fat.
So we accomplished both goals. We burned MORE fat, and we lost LESS muscle. So like I said, doing cardio for a long time (30, 45 min, an hour) at low intensity is actually counter productive. Doing cardio this way will tap into muscle, and our metabolism "cools" down much faster wich means less fat burn after cardio. Well I hope this was an understandable read. Please feel free to ask any questions. I will be happy to answer anything.
Thanks
ADAM
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personally- I couldnt run 400m intervals in the AM..Im more a late afternoon sprinter.. so timing isant as important as intensity imho 
