"*** O.k, instead of throwing theories around why don't we talk some phisiology and see if we can make something out of this whole thing."
Great Idea.
"To deplete glycogen one would need to do a lot more than doing a intense weigth training session followed by some cardiovascular exercise."
Each set you perform depletes your muscles of ATP. During heavy productive weight training, the ATP comes from the anaerobic glycolysis mechanism, therefore time is needed for glycogen stores to replenish. In order for protein synthesis (muscle growth) to take place, it needs an energy source. You guessed it, this energy source is ATP. If you deplete ATP and glycogen stores then you are impeding your muscles ability to grow! Additionally, other enzymes crucial to the muscle building process are also depleted with every weight training set. It's clear that you want to stimulate as much muscle growth as possible, with the smallest amount of glycogen and ATP depletion, which means that you should train as little as possible, while still achieving the desired results. Now, after weight training is a highly anabolic time, where protein synthesis rates are increased up to 400%! This increase will slowely start to decrease with levels returning to normal levels approximately 3 hours post training. When we do cardio after weight training what we are doing is depleting more ATP and glycogen than is necessary which inhibits growth in itself, and we are missing the largest opportunity the natural trainee has to increase protein synthesis! Cardio after weight training is very detrimental to the muscle growth response.
"Supreme, I would reccomend searching through the archives of "Supertraining"( since you are a member) and see what Dr Siff and others have to say about this. I do believe some members touch on this breifly."
I'll check into that, i don't really like the way the site is set up, confuses me, so i have a hard time finding what I'm looking for.
"When you talk about Glycogen being depleted you need to be more specific as glycogen is stored in the muscles, liver and is found in the blood ( blood glucose)."
Muscle glycogen is the main thing I'm talking about here.
"ATP can be utilized by one or a combonation of 3 different pathways. I wont delve further because I'm lazy!"
Just for informational purposes:
*By the phosphagen system - the chemical breakdown of phosphocreatine (PC) - an anaerobic mechanism.
*By anaerobic glycolysis - an anaerobic mechanism.
*By oxidative phosphorylation (Kreb's cycle and electron transport) - an aerobic mechanism.
Certain fibers are optimized to use each method of energy production, as shown below:
Type I - Oxidative phosphorylation mechanism.
Type IIA - Both the phosphagen system and the anaerobic glycolysis mechanisms.
Type IIB - Phosphagen system.
"During intense exercise muscle glycogen stores wil decrease and blood glucose will become more of the primary source. Since Rose is doing 30-40 mins it will not be a great workrate that he will be exercising at. This means there will be blood glucose (depending on how much is avaliable and if it is low, then liver glycogenolysis is stimulated) Plasma free fatty acids and muscle tryglycerides are going to be used as the primary sources. This is assuming that that the workrate is around 65-85% V02 max."
Let's not assume what VO2 Max he will be working at, let's ask him - Rose?
"Protein is rarely mentioned when it comes to this topic because the amount used as fuel is very small, it can range anywhere from 2% on activities lasting under a hour and going as high as 15% with activities lasting longer than a hour. Keep in mind that the individual is consuming a balanced diet."
Are you sure about this? Here is my understanding - Muscle glycogen stores are replenished primarily by blood glucose, while the liver (which also requires large amounts of glycogen) can make glycogen from fructose, lactates, alanine and other substrates. Some confusion usually exists because of the liver's need for glycogen also. The body, indeed, places priority on this task; preferentially replenishing liver glycogen before muscle glycogen. This would imply that when liver glycogen is depleted consumed glucose would first be consumed by the liver, with only the excess going to the muscles. This, however, appears not to be the case. Because the liver has several paths by which it can manufacture glycogen, most of the glucose absorbed from the gut actually travels through the liver without being absorbed and is, therefore, "reserved" for muscle glycogen production. The downside of the liver's demand for glycogen is that when it runs out of glycogen it takes alanine, and the other substrates, from the muscles (atrophy!) in order to make more.
"To deplete ATP you would need to be exercising for extended periods of time(past 2 hours) and even then fatigue would set in acting as a protective function when ATP mechanisms can't keep up with ATP use. The cell does not run out of ATP which would result in a depletion, rather the factors that caused the fatigue wil reduce the rate of ATP utilization faster than the ATP generation so that ATP concentaion is maintained. This is aimed at minimizing changes in cellular homeosatsis with a continued stimulation. Another point is that if ATP were to be depleted muscular contractions would not be possible to preform."
Ok, even though muscle ATP levels are only decreased to roughly 70% of normal resting levels, the 30% that is depleted is the most important! 70-80% of the sarcoplasmic ATP is restricted to the mitochondria and is, in fact, unavailable for cross-bridging. This means that while sufficient ATP is actually inside the cell, it is not located where it could be used to 'fuel' muscle contraction. So high intensity exercise may cease due to ATP depletion in the specific areas of cross-bridging, but total sarcoplasmic ATP concentrations may still remain relatively high (at ~70%). This is known as 'ATP compartmentalization'.
Good arguements, Maki
------------------
Complex problems have simple, easy to understand, wrong answers.
<font size="1">
[This message has been edited by TheSupremeBeing (edited 06-06-2001).]</font>
