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Wednesday, 20 June 2012

Training Zones for not quite Dummies.

There are lots of attempts to explain Heart Rate Zones.  Most try and come up with a simple explanation of what your body uses for fuel but by over-simplifying the explanation this tend to create confusion and assumptions (and marketing tools for nutrition companies).

When looking at fuel systems it is best to look at 3 basic questions and then equate those to your training goals.

1.  How much of the fuel source exists

2.  How quickly is it converted to energy by the body

3.  How long does it take to reload or refill this source.

But first lets start with a basic explanation of energy production. A muscle contraction is created using 3 types of fuel - Adenosine-5'-triphosphate (ATP), Creatine Phosphate (CP) and adenosine diphosphoribose (ADP) so at any final point in energy production these need to be produced.

These can be sourced from 4 different sources

1. ATP itself.
2. Glycogen
3. Glucose
4. Body Fat.

So going back and applying our original three questions.


1. How much of the fuel source exists.

Not much - about 10 to 12 seconds worth

2. How quickly is it converted to energy by the body

Incredibly quickly - it's already present in the muscle

3.  How long does it take to reload or refill this source.

Around 120 seconds although it is mostly (81%) refueled within 60 seconds.

So ATP is primarily used for very short explosive outputs such as lifting weights.


Glycogen is converted to ATP through a process called Glycolysis. It is stored within the body in the liver and muscles.

1.  How much of the fuel source exists

If your glycogen levels are 100% topped up you may have as much as two hours worth of Glycogen stored in the liver and muscles.  This level is rarely the case though so it is more like 1:40:00 - 1:50:00

2.  How quickly is it converted to energy by the body

Very quickly - it is already in the muscles and gets in the blood stream quickly via the liver

3.  How long does it take to reload or refill this source.

Glycogen is created from Glucose through a process called gluconeogenesis.  This can take from several hours to days.  The obvious down size if that if you run out of glycogen (commonly called bonking) it will take sometime to reload these stores.  Reloading of Glycogen is commonly what is referred to as Carbo Loading.  The levels of muscle glycogen measured after 24 hours of Carb Loading do not significantly increase if this load time is increased so extended Carb loading sessions arent really necessary and can cause a feeling of bloating.


Blood glucose is controlled through Insulin (lowering blood sugar) and Glucagon (raising blood sugar).  Glucose is converted to ATP through glycogenesis.  It should be noted that there are only 3 different 'natural' sugars - glucose, fructose and galactose.  Any other sugar that you ingest - eg maltodextrin, requires conversion by the body.  The maximum amount of any of these 3 sugar types that your body can convert is about 15g per 15 minute period

1.  How much of the fuel source exists

Not a lot.  In a 75kg person with normal blood sugar levels there is only about 5g of glucose in the blood.

2.  How quickly is it converted to energy by the body

Very quickly - the issue is actually how quickly your body can convert ingested carbs into blood sugar

3.  How long does it take to reload or refill this source.

See comment above - you can reload about 60g an hour which is only about 270 calories worth..

Body Fat

Body Fat is converted to ATP through a process called Lipogenesis.  Body fat is also by far the most abundant fuel supply in the body.

1.  How much of the fuel source exists

A LOT.  1g of fat realises 9 calories.  And incredibly lean Tour De France still has 60(kg) x 0.06(BF) x 9000 (calories per gram) = 32,400 calories. which is enough for 32 hours of hard riding.

2.  How quickly is it converted to energy by the body

Not very quickly

3.  How long does it take to reload or refill this source.

Given the volume in even a lean athlete this isnt really an issue.

For those that like pictures..

So your body burns fuel based on most to least abundant (fat to stored ATP) balanced by the rate at which it can be converted.  This is governed by exertion levels which are measured, as a correlation, by heart rate. Your body, at low levels of exertion, uses Body Fat. As energy requirements (exertion) increases your body switches to blood sugar and then, as requirements increase, glycogen.

Most diagrams show this as a  stacked bar with clear lines between the zones but it doesnt quite work that way.  It is more like

There are two very important take aways from this graph

1.  Your body, even when burning fat, needs a small amount of carbohydrates.  Think of an internal combustion engine - it primarily runs on petrol but still needs a spark for consumption.

2.  At the highest level of exertion your body is using Glycogen which is limited (around 1-2 hours) and takes an extended time to refuel so any form of exercise that extends greater than 1:45:00 (Marathon, Olympic - Ironman Triathlon) CANNOT use glycogen as the primary fuel source.  Of course the flip side is that for shorter events like a Half Marathon or Sprint Distance Triathlon you CAN use glycogen as your fuel source

BTW - The issue with heart rate is that it is an approximation of what fuel source is being used.  The actual percentages can be determined using an exercise metabolic test which involves a mask over the face to measure the amount of oxygen being consumed but also what the 'exhaust' products are.  Each fuel source creates different bi-products so measuring these can determine

a) what fuel source is being used - Fat, Glucose, Glycogen.

b) what amount in calories is being burnt.  In other words - fuel consumption..

Monday, 18 June 2012

Autovation and Discipline

This morning the alarm went off at 5am.  I listened and heard the sound of steady rain outside.  I also had a REALLY busy day ahead with lots to do.  A perfect combination of excuses.

So I put on my cycling gear and went out riding with four other people who got up at the same time and who had the same busy days.

Some would say this is a sign of motivation.  I would say it is a sign of AUTOVATION.  The term 'auto' comes from the greek meaning 'self' or 'ones own'.  By the way - you probably wont find Autovation in the dictionary, I made it up but it makes a lot more sense to me..

The point is that motivation is not something that others provide you.  Motivation (or autovation) is something that needs to come from within - a desire to meet or achieves ones goals.

It is not the coaches job to provide motivation.  The coach brings the skills, science and experiences to combine with the athletes Autovation to help them rapidly achieve their goals - to give the person options and alternatives when things such as injuries or 'life' gets in the way. The coach provides accountability but if the person doesnt want to do it there isnt much the coach can do.

An athlete with no motivation finds excuses.  An athlete with autovation finds a way.

It's Raining and Dangerous        -      Get on the trainer
The pool is closed                      -      Get in the gym
I have a bad ankle/achilles         -      Get in the pool or do some core.

I often hear the term Discipline but what does that mean ?  Is a person that gets home at 7:30 every night to watch (insert favorite reality show here) any more disciplined than someone that leaves work to get to the pool at 7:30 ?  Not really.  The difference is in the choices they make and the autovation they have.

If you dont have autovation to train or achieve a physical goal that is OK - not everyone does.  How many people join gyms in the first week of the year and then stop going ?

Being fit and healthy and comfortable in your clothes is over rated anyway ;)

Tomorrow - set the alarm for 5 minutes earlier. Then when it goes off ask yourself WHY are your doing this, what is your goal and why you want to achieve it.