Sports Nutrition Bible

[ono]

How is energy produced?

The body has 3 main energy systems in which it can call upon depending on which type of physical activity is being undertaken. These are...

The ATP-PC system

The Anaerobic glyolytic/Lactid Acid System

and...

The Aerobic System


The ATP-PC System

This system uses ATP (as explained before) and phophocreatine (PC, hence the name 'ATP-PC') that is stored in the muscle cells, to generate energy for maximum bursts of strength and speed which last up to around 6 seconds. 20m sprint or near max lift at the gym are examples of maximum bursts.

Phosphocreatine (PC from here on...) is formed when creatine (which is a protein as it happens) is linked to a phosphate molecule. The job of PC is to regenerate ATP rapidly. When the creatine and the phosphate seperate, the free phosphate bond transfers to a molecule of ADP (remember the daddy long legs with only 2 legs). Once this happens, a new ATP molecule is formed (The daddy long legs with 3 legs, curtosy of the added phosphate bond).

Unfortunately the ATP-PC system is in very limited supply. Infact it can only provide around 4 calories of energy. After this, ATP must be produced from other fuels. When this happens other systems take over....

Anaerobic Glycolytic System

This system is activated as soon as you start high intensity activity. It dominates in events lasting upto 90 seconds. 400m-800m sprint is an example of this type of activity.

Anyway, in order to meet sudden large demands for energy glucose bypasses the energy producing pathways that would normally use oxygen. Hence the term 'anaerobic.'

After 30 seconds of this type of exercise, this system contributes up to 60% of your energy output. After around 2 mins, it's contribution falls to around 35%

This system uses carbs in the form of muscle glycogen or glucose as fuel. Glycogen is broken down into glucose, which because of the lack of oxygen present, quickly forms ATP and lactic acid. This is quite ineffective as muscle glycogen dwindles away quite rapdily. Fatigue will also set in due to the build up lactic acid.

lactic Acid and the 'burn'

Just to dispell a myth, it's not actually the lactic acid that causes the 'burn' feeling you can get during or after maximal exercise. The feeling is actually caused by the build up of Hydrogen Ions and acidity. Nice
I'll go into lactic acid later on at some point.....i'm sure


The Aerobic System

This is quite similar to the anaerobic one except ATP is generated from the breakdown of carbs and fats in the presence of oxygen. The process is slower (which means ATP isn't produced as rapidly) but it can produce larger amounts so it's all good.

The aerobic system comes into play after the previous 2 in this topic have pakced in, which only takes a couple of minutes. So after a few minutes energy supply dwitches to the aerobic system.

Basically without going into too much detail, the aerobic system provides the energy required for sub maximal, prolonged exercise.

Fats can be used to produce energy in this system.One fatty acid can produce as much as 200 ATP molecules which makes fats an even more efficient energy source than carbohydrates (glucose can create upto38 molecules of ATP in the same conditions). However fats can only broken down under aerobic conditions when energy demands are quite low. Carbs are more versatile in the sense that they can be broken down in anaerobic conditions.

[ono]

Creatine

So i talked about Phosphocreatine earlier on. I explained that PC consisted of a phosphagen molecule and creatine. So,although most of you have probably supplemented or at least heard of creatine, i'd like to give you a brief breakdown of what the compound actually is.

So....What is Creatine?

It's basically a compound that's made naturally in our bodies to supply energy. It's mainly produced in the liver from 3 amino acids:- glycine, arginine and methionine. From the liver it's transported in the blood to the muscle cells where it is combined with phosphate to make phosphocreatine. Just like magic.

The muscle cells turn over around 2-3g of creatine a day. Once PC is broken down into ATP (energy, remember) it can be recycled into PC or converted into a naother substance called creatinine, which is then removed via the kidney in the urine (pee )

Creatine is typically obtained (in diet) from beef, fish and pork. The typical person stores around 120g of creatine. 60-70% is stored as PC while the remainder is sotred as free creatine.

Supplementation

While i'm on the subject, i might aswell go into the supplementation of creatine. I'm sure most of you have tried creatine monohydrate before, or CEE maybe...Probably with decent results.

The most common course of action is to saturate your muscles with a loading phase of creatine, followed by a maintenance phase. This method is effective, but it's not actually the best way of doing things. In fact it's quite a costly way of getting creatine into your muscles.

What should i do then?

Seen as though around two-thirds of this creatine (20g per day) actually ends up in your urine (wee) with only the remaining one-third ending up in your muscle cells.

To reape maximum benefits of creatine supplementation, a better idea would be to take smaller doses spaced throughout the day. The key is to try to slow down the absorption from the gut. This gives the maximum chance of all the creatine ending up in your muscle cells and not in your urine. To do this, try taking only 6g daily (instead of the 20g - for the loading phase), but instead of consuming it at once, in shake format, sprinkle it on your food. Sprinkle 1g at a time over the course of 6 meals which would give you a total of 6g per day. This will actually produce effects equivalent to taking 20g a day. After that, maintenance should only be 2g per day.

Not only will this method save you money, it will also produce less water retention which can only be a good thing. This loading strategy can be repeated every 8-12 weeks.

Cycle length

The maximum effectiveness, it's proposed that creatine is best taken is cycles lasting 3-5 months, followed by one month off cycle.

[ono]

Lactic Acid - The Lactic Acid Shuttle

Contrary to popular belief, lactic acid produced by the muscles is not a wasted by-product. Infact it constitutes a valuable fuel (once exercise intensity is reduced).

Once intensity is reduced or stopped completely, lactic acid has two possible fates. Some may be converted into pyruvic acid, when then can be broken down into ATP (in the presence of oxygen). So basically lactic acid produces ATP and can be a valuable fuel for aerobic exercise.

The other fate is....

lactic acid may carried away from the muscle (in the bloodstream) to the liver where it can be converted back into glucose, released back into the bloodstream or stored as gylcogen in the liver. This mechanism for removing lactic acid from the muscle is called the lactic acid shuttle

This also explains why the muscle soreness brought on by hard training is not due to lactic acid. In fact, the lactic acid is usually cleared within 15 minutes of exercise.

[ono]

When i initially started this thread i was originally going to dive straight in at the deep end and explain the importance of carbohydrates, protein and fat. In the end i decided to give my best explanation of how the body's energy system works. This hopefully will give you a better understanding of why nutrients are important.

So now i think i have pretty much covered everything i wanted to go through so i'll move on to talk about carbohydrates. I get a feeling this chapter is going to be quite long so i'll try complete it in stages...

to be continued......

[Salty]

I think you've got the lactate shuttle a little wrong mate, the way I understood it worked was...

1. Pyruvate (pyruvic acid) is formed when glycogen and glucose are being broken down at high rates in your muscles (called glycolysis which is the conversion of these into pyruvate). Pyruvate is then converted to Lactate (lactic acid) as it increases in the muscles.
2. Lactate is now formed and transported away from the muscle cells into surrounding tissue and blood. This allows glycolysis to persist and thus continuing the supply of energy to our muscles.
3. The muscle cells which the lactate is transported to can cause the lactate to be broken down to fuel (mainly ATP) or can be used to build glycogen.

[ono]

Yeah sorry i missed out how pyruvic acid accumulates. Anyways i'll give it a go...

When pyruvic acid accumulates in our muscles (which normally occurs after a slight increase in exercise intensity) lactic dehydrogenase(spelling) converts it into lactate. Under moderate-to-high exercise intensity, lactate is converted back to pyruvic acid, which then can be broken into ATP (in the presence of oxygen, of course).

As far as i am aware, pyruvic acid does convert to lactate, but lactate can also be converted back into pyruvic acid.

I hope that explains it a little better...i was rushed for time trying to finish the chapter before my dinner ended at work :-)

[ono]

Carbohydrates

In a an age where low carb-high protein diets are 'the shit' one can be forgiven for not realising that carbohydrates play an essential part in everyday nutrition. The scary thing is, they play an even more important part in sports nutrition.

I say scary because an awful lot of fitness magazines give you allsorts of crazy advice about carbohydrates...

'don't eat fruit, it's full of sugar'

'carbs before bed will make you fat'

In this chapter i'm going to try to explain the importance of carbohydrate. I'm going to try to explain proper glycogen replenishment and why it's vitally importance. I'm going to go into 'carb loading'

I'm also going to go into the GI index, as well as touch upon pre and post exercise carbohydrate.

Finally i'll explain how to work out, how much carbohydrate you need for your particular sport while hopefully dispelling a few myths along the way.

to be continued....


ps, my pc isn't available for me to use at home so this thread may be slow for a few days. Please be patient

[Trainer Monkey]

I think you've got the lactate shuttle a little wrong mate, the way I understood it worked was...

1. Pyruvate (pyruvic acid) is formed when glycogen and glucose are being broken down at high rates in your muscles (called glycolysis which is the conversion of these into pyruvate). Pyruvate is then converted to Lactate (lactic acid) as it increases in the muscles.
2. Lactate is now formed and transported away from the muscle cells into surrounding tissue and blood. This allows glycolysis to persist and thus continuing the supply of energy to our muscles.
3. The muscle cells which the lactate is transported to can cause the lactate to be broken down to fuel (mainly ATP) or can be used to build glycogen.

Everything Ive read says its Hydrogen,but keep in mind,those findings were only published a couple of years ago

[ono]

Post Exercise - carbohydrates



Glycogen Depletion

Intensive training severley depletes your body's glycogen stores. Just how much they're depleted depends very much on the intensity of the training session/event and the duration of it. Another factor that comes into it is - how full your glycogen stores were before exercise. For example, if you commenced training without adequately refuelling from the previous days exercise, you will reach glycogen depletion much more rapidly - as would a car that was running on half a fuel tank, as opposed to a car running on a full on. Simple.

The higher the intensity, the more glycogen you use. For example, explosive activities such as sprints, jumps or lifts and high intensity activities such as running will deplete glycogen stores much more quickly than low intensity exercise would.

The duration also has a bearing on how much glycogen is used. For example you would use more more glycogen running for one hour than you would if you ran at the same pace for only half an hour.

[Salty]

I think you've got the lactate shuttle a little wrong mate, the way I understood it worked was...

1. Pyruvate (pyruvic acid) is formed when glycogen and glucose are being broken down at high rates in your muscles (called glycolysis which is the conversion of these into pyruvate). Pyruvate is then converted to Lactate (lactic acid) as it increases in the muscles.
2. Lactate is now formed and transported away from the muscle cells into surrounding tissue and blood. This allows glycolysis to persist and thus continuing the supply of energy to our muscles.
3. The muscle cells which the lactate is transported to can cause the lactate to be broken down to fuel (mainly ATP) or can be used to build glycogen.

Everything Ive read says its Hydrogen,but keep in mind,those findings were only published a couple of years ago

You are right, although the definition of an acid is that it is a H+ donator. The strength of an acid is how easily it gives up a H+ ion, the stronger they are the more ions they give up. I think what you have read may be in regards to muscle failure where there is a drop in pH? Although I have read articles which say where the lactate is distributed depends on the concentration of the H+ however can't really remember too much.