Rayn
07-27-2007, 05:03 PM
The following is a repost of mine from school I post on regarding cellular metabolism and how your body uses fats/sugars for fuel. Perhaps someone would enjoy the read ... FOR SCIENCE!! http://www.omginter.net/smilies/eng101.gif
... your muscles store glycogen. At the beginning of exercise, you metabolize the glycogen and it will give you your first bit of energy. This is anaerobic metabolism. The amount of glycogen in your muscles is pretty small, though, and its used up very quickly. At that point, the muscles release enzymes that tell your body to start burning A LOT MORE fat. The fat cells then release fatty acids - which are metabolized in AEROBIC respiration - and are inexhaustible supplies of long term energy. Glycogen is like gunpowder. Fat is like a slow burning candle.
It's interesting to note that in athletes the fat is released from its depots more readily than it is in fat people. It's as if the fat cells in a fat person say, "Ah, heck, why hurry? He'll sit down in a minute." Out of shape people need to exercise persistently in order to train their body to give up the fat.
Both glycogen and fat both 'burn' down to pyruvic acid which is consumed in the Kreb's cycle, but fat requires oxygen. Calories come from both the glycogen in your muscles (produced by the liver) and the fat stores in your body. You have to exercise long enough to enter aerobic respiration to burn fat effectively. That doesn't mean that you have to exercise for at least 30 minutes to start burning fat. You are ALWAYS burning fat in a continual trickle and are burned constantly in muscles in small amounts whether you are sitting, sleeping, standing, or walking -- but the minute you start exercising, the muscles sends signals to the fat which basically say " RELEASE THE GREASE " - depending on your level of fitness your body will respond within 20 - 30 minutes of this. At this point the fatty acids are gush on out into the bloodstream to meet the demand. The sudden peak does not mean that muscles are just beginning to burn fat, however.
As far as consuming muscle ... that's a symptom of overtraining and not an excuse not to run. If you are running multiple times a day intensely, you will burn up your glycogen constantly and enter a place where everytime you go for a run your muscle glycogen is marginal. When this happens the Kreb's cycle is threatened because the muscle isn't getting the sugar that keeps it going. Now, these runners are burning a ton of fat because of that - 80 of their energy is coming from fat - but eventually your muscles are going to need glucose because they want to store glycogen, but there's just not enough in the system due to overtraining.
At this point, the liver improvises and decides to grab some amino acids and remove their nitrogens. It kind of looks like a glucose molocule and its substitute kindling for the Kreb's cycle. The problem is those amino acids were supposed to be doing something else - usually protein construction - so the body is going to act as if it is lacking in protein no matter how much protein is in the diet. Somewhere in the body, a protein dependent tissue is going to suffer. The areas affected first will be muscles that are not used very often (typically the upper body).After I'm done working out or on my last set I start drinking my recovery shake which is creatine with lots of simple sugar and 2 scoops of whey. WHy do I feel like absolute hell for about 2 hours after consuming this? I know I'm causing an insulin spike which is favored for anabolism, but why does it bring you down so?Sure I can talk about insulin ...
When you take your 'recovery drink' after your workout, you're looking to spike your insulin levels, as you know. Now, we already covered above how the muscles burn up all their glycogen during exercise. We further covered that if you are working out consistently, its important to restore these glycogen levels regularly and quickly to avoid have the liver start sending the muscles amino acids that weight lifters want used for muscle building.
So, you increase your blood sugar level with a bunch of simple carbs. Your pancreas responds by secreting a ton of insulin. The purpose of insulin is to open up the pores in the membranes of the muscles cells wider so glucose can get into the muscle. Glucose can get in there normally, but its a bit tight, so to speak, so the absorption rate is significantly slower. Restoring glycogen in your muscles is very important to them because your body wants to make sure you have emergency power.
After you exercise, our body reacts like its in an emergency - the sugar you eat starts going into the muscles very quickly and your blood sugar level drops dramatically - this make you feel kind of like crap!
ADditionally, your muscles are full of glucose, but they need to convert it to glycogen, and that takes energy. Normally this energy comes from ATP in the muscle cell (that's why you're taking the creatine in your recovery shake, by the way) You've been exercising hard for a while now, and you don't have much ATP left in there. So, its time to make some ATP and for that we're going to have to metabolize fat. So, during recovery, you're breaking down fat in order to convert glucose into glycogen.
... your muscles store glycogen. At the beginning of exercise, you metabolize the glycogen and it will give you your first bit of energy. This is anaerobic metabolism. The amount of glycogen in your muscles is pretty small, though, and its used up very quickly. At that point, the muscles release enzymes that tell your body to start burning A LOT MORE fat. The fat cells then release fatty acids - which are metabolized in AEROBIC respiration - and are inexhaustible supplies of long term energy. Glycogen is like gunpowder. Fat is like a slow burning candle.
It's interesting to note that in athletes the fat is released from its depots more readily than it is in fat people. It's as if the fat cells in a fat person say, "Ah, heck, why hurry? He'll sit down in a minute." Out of shape people need to exercise persistently in order to train their body to give up the fat.
Both glycogen and fat both 'burn' down to pyruvic acid which is consumed in the Kreb's cycle, but fat requires oxygen. Calories come from both the glycogen in your muscles (produced by the liver) and the fat stores in your body. You have to exercise long enough to enter aerobic respiration to burn fat effectively. That doesn't mean that you have to exercise for at least 30 minutes to start burning fat. You are ALWAYS burning fat in a continual trickle and are burned constantly in muscles in small amounts whether you are sitting, sleeping, standing, or walking -- but the minute you start exercising, the muscles sends signals to the fat which basically say " RELEASE THE GREASE " - depending on your level of fitness your body will respond within 20 - 30 minutes of this. At this point the fatty acids are gush on out into the bloodstream to meet the demand. The sudden peak does not mean that muscles are just beginning to burn fat, however.
As far as consuming muscle ... that's a symptom of overtraining and not an excuse not to run. If you are running multiple times a day intensely, you will burn up your glycogen constantly and enter a place where everytime you go for a run your muscle glycogen is marginal. When this happens the Kreb's cycle is threatened because the muscle isn't getting the sugar that keeps it going. Now, these runners are burning a ton of fat because of that - 80 of their energy is coming from fat - but eventually your muscles are going to need glucose because they want to store glycogen, but there's just not enough in the system due to overtraining.
At this point, the liver improvises and decides to grab some amino acids and remove their nitrogens. It kind of looks like a glucose molocule and its substitute kindling for the Kreb's cycle. The problem is those amino acids were supposed to be doing something else - usually protein construction - so the body is going to act as if it is lacking in protein no matter how much protein is in the diet. Somewhere in the body, a protein dependent tissue is going to suffer. The areas affected first will be muscles that are not used very often (typically the upper body).After I'm done working out or on my last set I start drinking my recovery shake which is creatine with lots of simple sugar and 2 scoops of whey. WHy do I feel like absolute hell for about 2 hours after consuming this? I know I'm causing an insulin spike which is favored for anabolism, but why does it bring you down so?Sure I can talk about insulin ...
When you take your 'recovery drink' after your workout, you're looking to spike your insulin levels, as you know. Now, we already covered above how the muscles burn up all their glycogen during exercise. We further covered that if you are working out consistently, its important to restore these glycogen levels regularly and quickly to avoid have the liver start sending the muscles amino acids that weight lifters want used for muscle building.
So, you increase your blood sugar level with a bunch of simple carbs. Your pancreas responds by secreting a ton of insulin. The purpose of insulin is to open up the pores in the membranes of the muscles cells wider so glucose can get into the muscle. Glucose can get in there normally, but its a bit tight, so to speak, so the absorption rate is significantly slower. Restoring glycogen in your muscles is very important to them because your body wants to make sure you have emergency power.
After you exercise, our body reacts like its in an emergency - the sugar you eat starts going into the muscles very quickly and your blood sugar level drops dramatically - this make you feel kind of like crap!
ADditionally, your muscles are full of glucose, but they need to convert it to glycogen, and that takes energy. Normally this energy comes from ATP in the muscle cell (that's why you're taking the creatine in your recovery shake, by the way) You've been exercising hard for a while now, and you don't have much ATP left in there. So, its time to make some ATP and for that we're going to have to metabolize fat. So, during recovery, you're breaking down fat in order to convert glucose into glycogen.