We will use an example from daily life to explain what happens to our bodies when we do some physical work whether we call it activity, work or exercise. We will describe the building blocks of physical exercise; load, rest and progression (LRP) in combination with the theory of over compensation and overload.

The body’s ability to adjust, or the doctrine of adaptation is explained with a simple example. We also present the natural law of “moderation” where we show the relation between effort and benefit in any field. If we overdo something the result is most often that the level of the activity declines.

We will describe the 4 different energy systems or engines our body has available for different situations. The knowledge and understanding of the aerobic and anaerobic energy systems is, in general, not very well known. You will therefore understand training much better if we are successful in explaining these systems for you. The basics about physical exercise and its building blocks will finally determine how we build up a training program. The training program can be on a weekly basis or, with training periodization, over several weeks or months.

An example from daily life

Imagine that you are working with some type of hand tool (axe, spade or a manual lawn mower) in the garden (without gloves). After a while your “office hands” get sore and if you work enough, you get blisters or even perhaps hand wounds. After the work your hands get a few days of rest, and then what happens?

Our body understands that your hands need some maintenance, and it starts a repair and maintenance process of the worn down parts of your hands. The garden work has been a training, or load, on the skin if we use exercise terminology. This phase of the training process is really a breaking down process in the short time perspective.

But our body is very intelligent for it not only builds up again the worn down skin areas in the hands, it also overcompensates for this wear and tear. This means that it makes sure that the skin will become a bit stronger and thicker than before the workload. This is what we call the overcompensation principle in physical exercise terminology.

The overcompensation principle is the basis of life of all living organisms on earth. All external and internal influence, i.e. stress, on any organism makes it stronger and tougher; this is the reason it survives. If it had not been for the overcompensation principle, all life on earth would probably have died out long ago.

The work you have done with your hands has, after enough rest time, resulted in stronger and thicker skin on the palm of your hands. You took a number of days off from manual work after the first work session; you rested to use the training terminology. In the rest phase your hands started on a maintenance process to repair the tear and wear.

If you start a new work session after a few rest days, your hands will probably be able to work a bit more than the first time before blisters develop. If you do exactly the same amount of work as the first time, you will most probably not get blisters again at all. Your load is then the same both times.

If you continue to do the same amount of work with the same rest between the workloads, you will be able to maintain and keep the same strength and thickness of your skin, but the skin will not be any thicker. To become stronger you have to overload relative to the last work session. This means you have to work a bit harder either in intensity and/or in volume.

The overload principle is another of the main concepts of exercise physiology. The consequence of the overload principle is that you need a progression, an increase or growth in your workload if you want to improve or get stronger.

This example of blisters in your hands is something most people are familiar with. It can, however, be translated to many other phenomena of daily life including all the different types of physical work and exercise you can think of.

We have now covered the basic concepts of physical exercise:

Load/work or physical activity/exercise which make “blisters” on all stressed tissues in body parts such as muscles, organs and the circulatory system.

By giving the body rest, or restitution, it starts a repair and maintenance process of all these “blisters”. But the body is not satisfied with just simple repair and maintenance, because it is “automatically programmed” to make sure it gets a bit stronger than before. It overcompensates, another of the major concepts in physical exercise.

To get stronger you have to increase either your work or exercise volume and/or intensity. This is simply because of the overload and overcompensation principles. If there is no overload there is no progression in your activity. If there is an overload there is a progression and then there is something to overcompensate relative to the previous workload. Your activity, training or exercise need progression if you want to get stronger.

Physical exercise consists of three building blocks:

  • The Load or work, also called catabolic phase. This is actually a break down process due to the stress the load put on the body.

  • The Rest or restitution, also called the anabolic phase. This is a build up process to repair and maintain all wear and tear from the catabolic phase. In addition to the build up the body is overcompensating, it makes sure to get a bit stronger than before the latest load or work.

  • Progression in the training or work is necessary to get an even overload over time. A Progression in the overload gives a Progression in the overcompensation, – with an improvement as a result. The Progression is not as important for a recreational jogger who want to keep fit, but is very important for a top athlete who continuous works for better results and improvements.

The figure below describes schematically what happens in this case with the skin in your hands after a workout with your bare hands. We start the job from the “Starting point” and let us say we are working an hour or two. Be aware of that the time axis does not have any scale, it is only demonstrating a principle.

The hand work breaks down your skin, and after some time your hands are soar. The skin thickness is reduced. We call this the Load phase, also called the catabolic phase (break down). In the Rest phase, also called anabolic phase the hands get rested, and the body mobilize to build up the skin again. We can see the skin thickness being gradually built up again, and then happens this very unique thing, the body does not only build the skin thickness up again to the level before the work, the body want an extra “safety margin”, it overcompensates and makes sure to make the skin thickness a bit thicker and the skin strength a bit stronger than before the work.

The hands and skin are ready for a new attack. The concept of overcompensation is the major foundation for training and exercise. You should also note that the result of the workout does not last forever. After a while you start loosing your skin thickness again; there is no free ride here.

The effect you gained will gradually be lost if you stop using your hands: the process is reversible. The ideal timing for a new physical activity or workout will be when the overcompensation is at its highest level, before the reversible phase starts to reduce the skin thickness. This type of precision is of course not possible in real life, but the curve describes how the body responds in theory.

The other figure below describes two jobs in the garden with a rest time between them. We start the first job at point 1. We can see how the job breaks down the hands and the skin to point 2. The first rest phase starts building up the hands and skin again, and we can see how the body overcompensates to point 3. As we can see, the skin thickness has now increased relative to the starting point 1.

A new garden job starts again at point 3, let us say some 2-3 days after the first job (there is no scale on the time axis). After the second garden job we end up at point 4. You can see this job was a bit tougher than the first one. It goes a bit “deeper” than the first job since we have included some progression, or growth, in the garden work in terms of volume and/or intensity. We have put in some overload relative to the first job.

We rest again as we did after the first job, and we end up at point 5. You can now see that point 5 is a bit higher than point 3 which again is a bit higher than point 1, the starting point. We have thus succeeded with our objective. Our hands have become stronger and the skin thicker after the two garden jobs.

Again, we have to stress that this is a simplification of very complex processes, but it should be a clear and simple example of the principles of physical work or training. You should realize that exercise physiology is not an exact or accurate science. We all have our individual talents and conditions, so all general theory has to be individually adjusted and tailored to how much, how often and how hard etc. for the Load, Rest and Progression.

This simple model is valid for all physical exercise. Irrespective of what we do, under exercise or physical work there will be microscopic tears in stressed tissues in muscles, tendons, bones and in organs like the heart, lungs etc. If you do too much relative to the latest workout, this tear can end up as a injury instead of just a microscopic tear.

If you overdo the overload phase too much, you may become forced to take a very long rest to get healed. The end result of this is that very often you will lose your fitness level or form or, as in our example, the skin in your hands gets thinner.

The body’s adaptation

Our simple example with blisters in the hands describes the body’s adaptation to stress. It is this adaptation which is the basis for all physical training and exercise. It is responsible for the change and strengthening of body cells, tissue and organs as a response to internal or external strain, influence or load above rest level.

This adaptation or body adjustment takes place, as mentioned, on the cell, tissue and organ level (morphologic adaptation). At the same time there is another adaptation in the interaction and teamwork between different organs and muscles (functional adaptation). Because of the body’s adaptation, the human race has survived external stress and hazards by becoming stronger and tougher. In prehistoric times people were constantly exposed to many threats so just surviving was a tough job, in addition to all the work needed to secure enough food.

So-called modern people of today do not have the same physical dangers and stress. This confuses the adaptation our body has taken thousands of years to develop. To compensate for this we developed new phenomenon such as physical exercise and training. All the cells in or bodies have a very unique characteristic which is to save energy and not use more than necessary.

If some of the cells in our body are seldom used or stressed, then they automatically start to build themselves down ( training is reversible) If you have been doing a lot of hard work and have built up very strong skin in your hands, this will not last forever. If you stop using your hands, then the skin in the hands will lose its strength and thickness.

Body cells are just as strong as they have to be. This means they make sure they are strong enough to withstand the stresses and wear and tear they are exposed to. This balance is called homeostasis (the balance between the catabolic and the anabolic processes) in medicine. This is one of the major paradoxes in the so-called progress in the modern western world. Physically, we are using our bodies less and less; we are building them down.

The big challenges with our bodies is that they receive too much food relative to their needs. This surplus food goes to the safety storage; it is stored in our body as fat in case of an “emergency” in the food supply.

This fact has created a lot of new businesses like weight loss industry, health clinics and challenges for the health care system of the so-called welfare diseases.

Even if it sounds negative, physical training or exercise puts a needed load, strain or stress on our body. A more positive expression would be that the training is an external stimulation of the modern human being. The body’s response to this stimulation is that it protects itself by making sure it gets stronger in order to guard itself for eventual new “attacks”. This stimulation is what the so-called modern person needs to take care of his body and health; if not, the body will “fall asleep” and build itself down and while getting weaker and weaker.

We all respond different to events in life, and this is also valid for physical strain or stress. We have to make individual adjustments. The degree of training, stimulation and adaptability will be different from person to person, and it will also vary individually among many different abilities like endurance, strength, resilience, speed, oxygen capacity etc. All of these different talents do have their individual degree of adaptation, and this mix of talents was a gift from our parents. How much each person can train is dependant of both internal as external factors, like:

Internal factors (endogenous) Sex and age, prehistory of physical exercise.

External factors (exogenous) Dosages or volume of exercise or training in quantity and intensity. How much and how you rest, mental and social relations, and relation to natural factors from the nature like climate, light, and sound/noise and other stimulus from nature.>

The “natural law” of moderation

The figure below reflects the “natural law” of moderation, simply because the curve describes relations that seems to be valid in most relations/situations in life.

The curve expresses:

  • If you do nothing or little, then the result will be the same, little or nothing (effort in point a gives a minimal outcome or result, point 1). We are within a lazy and easy going area of the curve.

  • A reasonable effort, point b gives a good outcome in point 2, the result is as expected and deserved. We are within a stimulating area of the curve.

  • There is an optimal point on the curve where you get maximum outcome of your effort. Very good effort, optimal, gives a maximum outcome in point 3. This is a result that very often gives the feeling that it is too good to believe it is true, and it is very often difficult to understand.
    You are devoted to your activities, but you also have the ability to know when enough is enough. You know to give yourself praise and is not controlled by guilt. You are in the most optimal stimulating area of the curve.

  • You are very motivated and devoted, and to be sure you do a bit more than really necessary in many situations, you have a tendency to overdo or exaggerate things, – just to be sure. When it comes to the body’s physical adaptation this can give very confusing effects, the more is not always the better, and the harder is not always the better.

    Suddenly you are not rewarded by doing a bit extra or harder. Your excellent effort in point d “too much” gives only a limited outcome, point 4.
    Very unfair and frustrating! You are very motivated and devoted, but you do not have the ability to know and feel when enough is enough. Your eagerness exceeds your body’s adaptation, and after some time your body have to use other mechanism to protect itself. To stop you, your body either get injured, or you lose your energy and willpower and in the worst case you become ill.

    We are in the over stimulating area in the curve. If you are not able to interpret the feedback your body is giving you, and your exaggeration becomes a chronic situation, then you will gradually move down to the burn-out area of the curve. You should take notice of this and be reflected of what happens with the personalities that really want to achieve the most.

    The most interested, conscientious and hard-working person is most vulnerable for exaggeration relative to the “natural law” of moderation. Most often it is again the feeling of guilt that starts the whole process. It might be that your training program says you should do this and this, and even if you are totally worn out, you follow the program instead of your inner instincts. Girls often lose their period, if they continue to push on they can end up with a hormone chaos with side effects like amenorrhoea, osteoporosis, eating disorders and/or obsessive-compulsive disorders (OCD).

Relative to physical exercise the natural law of moderation curve indicates the body’s adaptation. We have used the example with blisters in the hand, and if we continue to work, – the blisters can easily end up as flesh wounds, we will end up at point 4 in the curve, the wound can then end up with an infection or a scar.

Again we have to emphasize that we are describing very complicated conditions with very simplified explanations, but our major objective is to express that there is no meaning in overdoing physical exercise. It is important to be focused to all feedback our body is giving us, in other words, the internal focus on how we feel.

When you for example are jogging or running you are challenging a lot of tendons, muscles and organs, and all of these body parts do have their own “natural law” of moderation curve. Such a simple activity as jogging is very dependant of a lot of single factors and how they work and co-operate. If we then use the chain model, this activity is not stronger than the weakest chain.

Normally it is the weakest chain or chains we feel when we challenge our body with a physical activity, it can be a blister on the heel, stiff legs, you feel you are loosing your breath or the pulse is very high even with an easy load. If you are conscious and rational in your interpretation of these feedback, you have a very good tool to control your activity, the most important is not to overdo. We also call this weak chain a bottleneck in your total system, it is the total system you are developing with your training.

The bottleneck is limiting your capacity, and at the same time, the bottleneck is easiest to overload since it is the weak chain or point. Of course, it is not dangerous or uncommon that we overload ourselves or a weak chain now and then, it is only when the overload situation is becoming a chronic state it is becoming dangerous and unhealthy.

Our body is much smarter that we are aware of, and it has a very clear first priority:

To protect your life and health.

If you overdo you training too long, the body starts a lot of processes with one clear objective, to stop you from self destruction. Some of the body’s actions are: feeling of pain, you lose your general feeling of well being, you lose your energy, you lose your mood and get moody, you lose your delight of training and finally in a worst case you are not able to move your body.

The final result of your exaggeration is the total opposite of what was the intention with the training, you lose fitness and your wellness. The body’s actions to stop you for your own protection is very hard for most people to understand. We called the law of moderation a natural law, simply because this relation of effort and outcome in most situations/relations seems to follow this curve.

Y-axis   OutcomeX-axis    Effort
Improved runningVolume training
Improvement in soccerIntensity in training
Examination marksHours with studies/reading
Alertness and spiritHours of sleep
ProductivityTotal work hours per week
PerformanceStress level
Body weightFood intake

All these different examples can be used in the curve of moderation. It is clear that the meanings and relations of the curve are in many different situations true. Now, it is up to your creativity to find other situations in life that can also be used in combination with this curve. Remember that whatever you do, if you overdo it, the outcome normally declines relative to the effort put into it.

This “natural law” which we have just presented has not been scientifically proved, but we hope you understand what we mean because it is also called common sense. The challenge is that this is easy to say, but much more difficult to put into practice:

When is enough, – enough?

The moderation curve describes the body’s adaptation. When we are physically active and exercise, we get stronger only when we do it the right way. This means that the moderation curves for each detail and body part are always in motion: the curves are dynamic. They will go up or down or be stable. They are all dependant of how you live and on the individual factors in your own life. Our goal is that you will become aware of the moderation curve and be conscious and focused on this “law” in all areas of your life.

Did you know that our body has 4 energy systems or engines, always ready and standing by for action, day and night!

“Do I need to know this?” you might ask. This is certainly a relevant question since you can very well live and train without knowing this because the body is in full control of itself. But it would give you an extra competitive edge if you had this knowledge. In the information age it is always a great advantage to have some basic knowledge which can use to filter or stop wrong messages, false statements and doubtful commercial advertising etc.

In addition, you will understand how your body responds to physical loads, you will more easily know what to do, when to do it, how to do it, and how much to do. The energy systems work together in demanding situations, and there is always one aerobic system on duty, day and night. One of the aerobic system is always working because it takes care of the basal metabolism necessary to keep you alive.

The aerobic systems are therefore always working in a steady state mode, even when you are working hard. When the aerobic systems are too slow to respond to a sudden change or too weak to support a demanding situation, help is supplied by one or both of the anaerobic systems. This extra help only has the capacity to help for a short time, but it has a great deal of power to offer during this time. The anaerobic systems are not very stable systems, precisely because of this very limited “burning time” capacity.

The anaerobic systems also put a lot of stress on us when we use them, like hyper-ventilation, high pulse rates, and pain from lactic acid. They also put a lot of strain on the aerobic systems, since these systems are responsible for recharging the anaerobic systems and for cleaning up the “mess” after a hard workout.

Aerobic energy systems

One of the aerobic systems is always functioning to keep us alive. Aerobe means that these systems use air, or more correctly oxygen, in the metabolism or “burning”. We have two types of aerobic systems. The difference between the two being what type of fuel is dominant: fat or carbohydrates. Very often the two types of fuels are used simultaneously; the situation decides what type of fuel is dominant.

At rest, fat is the dominant fuel. Fat is a bit slow to “burn”, and is therefore dominant in easy and resting situations. People with very good endurance have developed their fat burning capacity which means that they are able to have fat as dominant fuel in rather demanding work loads such as in a marathon or in a 50 km cross country skiing race.

Normally, carbohydrates will be more and more dominant the more physical demanding the situation is. Our body has very limited storage capacity of carbohydrates with most of the storage in the muscles and some in the liver. As a rule of thumb, we have carbohydrates for about 90 min of hard work, and that is the reason it is so important to pinch and scrape carbohydrates when a competition lasts more than this.

As previously mentioned, well trained athletes are able to use more of a “fatty” mixture of fat and carbohydrates even at a high workload, and are able to finish a marathon, for example, before hitting the wall.

Anaerobic energy systems

Normally the two anaerobic energy systems are “sleeping”. This means that they are on stand by, but not working. These systems are not dependent of air (oxygen). The system most people are familiar with is the lactic acid system. This system supports the aerobic systems when they are not able to supply what the body demands.

A typical situations is when you start a physical exertion suddenly and the aerobic systems are too slow to make the immediate transition to harder activity. The disadvantage with this system is the lactic acid, a low energy by-product that can give you some trouble. The disadvantage with this anaerobic system is its lactic acid, a low energy by-product that can cause trouble. Lactic acid is a normal product always present in our blood stream, but the concentration increases when we use this energy system.

The other energy system is the creatine-phosphate system. This system only starts in more demanding situations such as when you get scared, shocked or when you activate larger muscle groups in explosive or extreme sport situations.

Our energy systems are like a 4-stage rocket.

Imagine that you are quietly walking along a path in the woods and suddenly an angry dog attacks you. Instinctively you will react in a tenth of a second with a fight or flight response. You are igniting the first stage of your rocket engine, your anaerobic creatine-phosphate system. This engine has the shortest reaction time, it gives us enormous power; this system is always standing by to protect you.

The limitation in the engine is the burn time; it has fuel to burn on full speed for only 5-8 seconds. If you still have to run away from the angry dog, the second stage of your rocket engines ignites when the first stage has run out of fuel. Your lactic acid engine is now in action; this is your second anaerobic engine. The power of this engine is less than the first one, but the burn time is longer. On full speed you should have fuel for about 2 minutes. If you use less speed you can probably burn several more minutes.

While this stage is running, you feel more and more pain, and you will gradually feel your breath go over to hyperventilation. Lactic acid, a by-product of this engine, is the reason for this feeling. If the dog is still after you, you have to slow down a lot when you have burned out your first two stages of you rocket engines. The aerobic engine, with dominant carbohydrates as the dominant fuel, is now taking over.

There is always an aerobic engine running in the background when one of the anaerobic engines are running, but now the aerobic engine is supporting more than the vital life functions; it is now taking over the muscles that need energy for your escape. Even if you will feel totally worn out, you will still be able to escape, but now with a dramatically reduced power. You will have fuel to go for about 90 minutes. When this tank is empty, you will gradually switch over to fat dominant aerobic burning, this means you have to slow down even more.

To be able to continue you have to get water during your flight, without water everything will stop. Our dog escape is of course hypothetical; hopefully you get rid of the dog in a minute or two.

If you however are competing in a 2 hours endurance competition, the use of the energy systems are probably turned upside down, you will probably start with the carbohydrate dominant aerobic engine the first minutes to the first half hour, if you are well trained the fat burning will be dominant the next 90 minutes. (You are burning a mix of fat and carbohydrates where the carbohydrates are igniting the slow igniting fat)

The last 30 minutes will always be tough; it all depends if there are more carbohydrates left. If you have some left, you will probably be able to start your lactic acid engine the last 5 minutes, and if you are lucky, you are able to ignite your creatine-phosphate engine the last 50 meters in the final sprint to the finish line. If there are no carbohydrates left, your last 30 minutes will simply go very slow, and your willpower will be low, this is because our brain only burns carbohydrates, and when the supply is small you will get a “never mind” attitude.

In most of the world there is seldom any need to secure our life because of external danger (dangerous animals), but it was because of this unique characteristic of our energy systems our ancestors survived. Today some parts of the world have a problem to “survive” because people simply never use more than their 4 stage of the “rocket engine”, dominant aerobic fat burning (rest metabolism).

The other energy systems lie more or less fallow if you are physical inactive. We learned in the paragraph of adaptation that all cells in our body are programmed to save energy. If cells, muscles and organs never are challenged physically, then these cells, muscles and organs are building themselves down to the level required to “survive” daily life.

All cells in our body are simply adjusting to the need required, this is called homeostasis in the medicine. It is because of this down building or decay we need physical exercise or training in a sedentary or physical inactive lifestyle.

The energy systems do their work in the muscles. The knowledge about how, where and when they function will give you a competitive edge relative to those with no knowledge about this. Our muscles are made up of different types of muscle fiber, all of them are tailor made for each energy system. We will come back to the description of these muscle fibers later.

The type of sport you are involved in will be decisive for the energy system you have to train and develop. The types of sports can be divided into those who:

  • >Mainly use the creatine-phosphate system, explosive sports like jumpers, throwers and weight lifters. This system is also used in shock, panic and other extreme situations. The duration this system works is from tenth of a second and up to maximum 5-8 seconds, then the “battery” or energy supply is empty.

  • Use a mixture of the creatine-phosphate and the lactic acid system, like sprinters. Duration from 10-60 seconds.

  • Use a mixture of the creatine-phosphate system, lactic acid system and the aerobic system with dominant carbohydrate fuel. Typical for ball sports where there are a broad variation of both intensities and duration of rushes. Other sports with duration from 10 seconds and up to two minutes where there is almost full speed the whole time, like middle distance running.

  • Primarily aerobic energy demand, “main engine” a mixture of fat and hydrocarbons, with fat or carbohydrate as dominant fuel. Endurance sports like long distance running, cross country skiing, soccer and cycling.

What happens when several of the energy systems are in action at the same time?

If you exercise, train correctly and perform in future competitions the right way, these systems will support and help each other. If you do all these things wrong, the same systems will interfere with each other and limit your potential.

The most important point for an endurance athlete is not to “start” the lactic acid engine too soon. In other words, it is very important not to begin too fast relative to your fitness level. You should not push over into your anaerobic threshold too soon. If you do so too early, the lactic acid will change the working environment in the working muscles and blood stream. This environment will become more acidic (lower pH), and this will interfere with the main engine’s efficiency (the aerobic system)

Aerobic work load with carbohydrate as dominant fuel (main engine, alactic).

This is the engine you use most often when you are physical active and exercising. The power produced by this engine for a person in top physical condition can be up to 300-400W (Watts). This is power under steady state conditions, and it can “run” up to 90 minutes at peak power. Typical training sessions with this engine running are long easy runs, intervals and fartleks, but it is very important that the intensity not be too high. This is the engine endurance athletes should concentrate on (in competition lasting up to 90 minutes)

We are now probably covering one of the most misunderstood topics of physical endurance training: the intensity of your endurance training you do.

When you perform your aerobic endurance training correctly, the main engine (your aerobic energy system) will be able to do the work by it self. When you push your training to the limit, you enter the area of your anaerobic threshold. This is the hardest you can push your aerobic energy system without help from other energy systems or engines.

If you push a little bit more, your main engine is not able to give more without getting assistance from the anaerobic lactic acid system. A new situation develops when you pass the anaerobic threshold because now you have two energy systems working simultaneously. You are actually pushing you aerobic system harder but, at the same time, the lactic acid from the anaerobic lactic acid system starts accumulating in the working environment for both energy systems: in the working muscles and later in the blood stream. This working environment becomes disturbed, and the conditions for improving your level of endurance are not optimal any longer.

In most parts of the world it is customary to get an extra reward when doing your work, lessons etc. well, and this tradition is often also brought over into the physical exercise. To be sure you are a “good” girl or boy when training, you push a bit extra, just in case.

The result is that you disturb the environment in the working muscles with too high a level of acidity, and this will interfere with, as we have mentioned, optimal growth conditions for endurance. The training effect will be reduced and, in the worst case, the training itself will lower your endurance.

The challenge is to be found in finding the correct working environment of our muscles while realizing that the optimal conditions will always be different from person to person. A stable steady state condition in the muscles means a lactic acid concentration of between 1-4 mmol/l  (dependant on the equipment and measuring standards)

Lactic acid is also produced under pure aerobic work, but the body is able to break it down as it is produced. This is therefore called a steady state or stable condition. A workload up to the anaerobic threshold is the maximum load that has a steady state condition.

When you go over your threshold, the body is not able to break down all the lactic acid produced, and it then starts accumulating in the body. You have now recruited more of the “help engine”, or the lactic acid energy system, since you are demanding more than the aerobic system is able to support. You are now in a non-steady work state.

Lactic acid is a substance that is totally normal in our bodies and is therefore not dangerous for us. If the concentration gets too high, however, we suffer various degrees of discomfort. If your objective is to develop your endurance, then the challenge is to make sure to give your body the best possible properties for endurance growth.

Our experience shows that accumulating lactic acid too often, and in too high concentrations (more than 4-6 mmol/l), can be detrimental for endurance growth. This amount of lactic acid can have a negative influence on us both mentally and physically.

Lactic acid in high concentrations gives us a feeling of pain (a negative emotion) and discomfort, and can very easily contribute to negative learning (experience). It also gives physical effects like:

  • A feeling of thick legs and arms

  • Painful muscles

  • Heavy breathing – hyperventilation

  • Coordination, you feel clumsy and stiff.

  • You get forced to stop very soon

These high concentrations influence the environment in the muscles, which by becoming more acidic. (i.e. lower pH), can disturb, reduce or damage the aerobic enzymes (chemical substances that work like catalysts by increasing the metabolism in the muscle) This result of all this is that training which is too intense actually gives you less aerobic capacity. An acidic environment in the muscles can also damage the muscle cell wall, and fat metabolism capacity is also reduced.

The production and regeneration of creatine-phosphate is delayed and reduced in an acidic muscle because the recharging time is increased and the level of charging is lowered. This will have a great influence on the performance in ball games and in endurance sports.

The risk of injuries is higher with high concentrations of lactic acid in the muscles.

You get muddle-headed and lose your concentration.

The key fact is that you shouldn’t work too hard, but at the same time you shouldn’t  work too easily either. If you exercise too lightly there will be a much more limited training effect (overload). You can, however, get exhausted even if you train too easily; you just have to go on for hours.

Being “exhausted” is when you empty your water and carbohydrate storage; you get dehydrated and sugar empty. Our experience is that this condition is not good for endurance growth, we see many marathon runners commit this blunder in their training. Remember that adaptation is specific; you improve in what you are doing. So, when you run hours after hours, you get good in slow running.

It is not possible to train the body to become independent of water. It is, however, possible to train up the body to save carbohydrates because long runs will train your fat burning capacity (metabolism) There will be a trade off between these factors, but our recommendation is to limit the very long runs, those of more than two hours. (It is better in other sports like cycling and cross country skiing simply because you can eat and drink much more while training)

The other expression we us is “getting tired”. By “tired” we mean that we are working hard in and around the anaerobic threshold with plenty of carbohydrates and water onboard. This is a state with very good endurance growth potentials; you train to run fast and not slow. If you train correctly, this is how you do effective interval, fartlek training and fast long runs (say up to 30 min).

Aerobic work load with fat acids as dominant fuel (main engine, alactic)

This is the engine that normally is on duty when you rest. All of us, even very slim people, have large amounts of fatty acids stored in our bodies at all time. Most of us have enough fat fuel onboard for days and even weeks of activity. The word “fat” itself is in some parts of the world a very negative word, simply because a large percentage of the population have too much of it.

Some quantities of fat, however, is a must and is totally normal thing for healthy people, but this is again dependant on the right type of fat. There are different kinds of fatty acids since fat is a large family of acids. The disadvantage of fat from a training and exercise point of view is that it is a bit slow; it needs more oxygen to burn relative to carbohydrates.

The energy content of fat per weight is two times that of carbohydrates. The bottleneck with fat acids, however, is their need of oxygen for combustion. As we have learned, is it normally the oxygen supply that limits your work and sport performance, not the lack of fuel. To give the same amount of energy as carbohydrates, fat acids, on the average, require approximately 16% more oxygen.

The question of how much fat acids this requires is not interesting simply because we have days and weeks of them stored in a normal body. It is only in sports lasting more than 90 minutes that it is important to develop the fat burning capacity because of the limited storage capacity of carbohydrates. People with good endurance normally have a well-developed and effective fat metabolism.

These athletes start with dominant fat burning just after a few minutes of relative hard work like in a marathon, a long bike race or in 50 km. of cross country skiing. Athletes not as well trained will burn a larger fraction of carbohydrates at the same work level. The result is that they often meet the well-known wall before they reach the finish line.

It takes a long time to build up your fat metabolism capacity; normally several years of training. The type of training we think is most effective are long easy runs. It is important that this training is easy and not too hard (because then the carbohydrate dominance will take over). At the same time this type of training should not be too easy either.

Our experience is that you do not have to do training for hours and hours to develop fat burning. Ingrid very seldom ran for over 2 hours, and then only infrequently in the last months before a marathon.

The interesting thing with these long easy runs is that the central system (lungs and heart) is working harder, at the same pace, than the carbohydrate dominance metabolism. The reason for this is the higher oxygen demand for fat burning relative to carbohydrates. This therefore, leads to better training of the bottleneck.

As a rule of thumb, an untrained person will burn a mix of 50% fat and 50% carbohydrates at a workload that is not necessary very high since the person is untrained. A well trained endurance athlete will burn up to 80% fat and 20% carbohydrates at a workload that is relatively high; much higher than the workload the untrained is able to achieve.

If the workload gets too high, then even the well-trained endurance athlete will also tip over to carbohydrate dominance. With an even higher load, the work will become more and more anaerobic as the threshold is passed.

The creatine-phosphate system or engine (anaerobic and alactic)

This engine is normally resting. We call this energy system the “emergency engine”, since it wakes up in typical emergency situations such as getting scared, angry or when fighting for your life.

This engine is run by high energetic phosphate compounds (CP = creatine-phosphate and ATP = adenosine triphosphate), and does not use oxygen. Even if this is an anaerobic system, it does not produce lactic acid. Such a system is also called an alactic system, i.e. anaerobic without lactic acid.

We could also call this system the battery, the lifesaver or the explosion. This is the energy system for explosive, short and intense reaction sports and is also important in ball games. This energy system, however, has little or no importance for typical endurance sports (long distance running, cross country skiing, cycling etc.).

The main reason for this is that this system has fuel for only 5-8 seconds of workload at full speed. To start or “ignite” this energy system you have to activate large muscle groups, and there is no intensity scale here: you either to give all or nothing.

You may have felt this engine when getting scared or frightened. Its reaction time is very short; just a fraction of a second, and your instincts are ready to “fight or flight”. This was the energy system that allowed our ancestors to escape wild animals.

The unique thing with this engine is its immediate response. It has the greatest power of all energy systems, and it is anaerobic with no lactic acid (i.e. alactic) as a side effect. After an such an “explosion” you will experience heavy breathing because your body immediately starts to recharge the “batteries”, or the energy used, and to do this your body needs a lot of air (oxygen) and energy.

As you can see, the aerobic energy systems are the “battery chargers”, and the better and stronger these are, the faster the charging will take place. After a “blow-out” you will need about 2-3 minutes with rest or easy exercise until you are fully charged again. This is the reason this system is very important in ball games where the duration and intensities of rushes vary from total rest and easy jogs to full speed.

Maximum power can be up to 4,000W (Watts) or 4 kW (approx. 5.4 Hp) for well trained male athletes, while for women the power can be up to 2,400W or 3.3 Hp. These peak power is possible for very brief moments lasting for only fractions of a second in such events as the long, high jump or the discus throw.

This effect is about 15 times the maximum aerobic power you can produce. A 100 m. dash sprint performed by a good sprinter produces about 3,300 W where all energy systems are working. About 85% of the energy is anaerobic.

Other sources indicate the maximum effect from the creatine-phosphate system can reach 7-8,000 W.

When are you ready again after a full speed rush lasting 5-8 seconds?

If you are able to rest after a rush, it takes about 22 seconds to load 50% of your tank; after 44 seconds 75% of the tank is filled up. (Another source has shown 50% recovery after 30 seconds and full recovery after 2 minutes.)

Your physical condition is of course an important factor of how fast you recover. The better your aerobic fitness, the faster the recovery since the key factor in recovery being how much oxygen is available in the cardiovascular system.

This engine is very important in sports with many intervals of rushes and rest periods like in ball games. In our opinion, the value of aerobic base training is underestimated in these sports. The “battery” charger of the creatine-phosphate energy is your aerobic capacity; the stronger it is, the faster it recharges and you are ready for a new rush.

The lactic acid system or engine (anaerobic and lactic)

This system or engine is normally resting. We call this system the “help engine” since it helps us when the aerobic systems are not able to provide the necessary support. The engine starts at different situations:

  1. If you change too fast from rest situation to a demanding physical situation. An example of this is when you are walking easily and suddenly start to run. The aerobic systems are too slow to take this sudden change so they get help from this engine. After a number of seconds the aerobic systems wake up and take over the workload. The transition time lasts from a few seconds to 1-2 minutes. This is a type of anaerobic work that people experience daily. Some lactic acid is produced, but you hardly feel anything either in your pulse or in your breathing.

  2. If you are in a full speed rush powered by your emergency engine (creatine-phosphate), and if you have to go for more than 5-8 seconds, the help engine takes over when the emergency engine is out of fuel. The help engine will run as long as it can if you are pushing hard, but the harder you push, the shorter time it will power you.

  3. One of the aerobic main engines is running. If you exert yourself, the system using carbohydrate fuel will become more and more dominant. At a certain stage it will not be able to push more and the aerobic engine will need help; you have passed your anaerobic threshold. The lactic acid system is the help engine that starts now and so you are able to exert yourself more. The aerobic and anaerobic engines are now working together. Both your pulse and your breathing frequency increase while at the same time your feeling of pain also increases.

The help engine, or lactic acid system, is not very important for endurance sports. Together the two anaerobic energy systems actually only represent a quantity of energy equal to approximately 1 minute of aerobic energy. This minute of energy is important for a 400 m. or 800 m. runner, but is not important for an athlete with a competition lasting 140-200 minutes such as a marathon.

The anaerobic lactic acid system, or help engine, is not very fuel efficient; it uses 13 times (1300%) more fuel than the aerobic engine.

This engine has a large effect. A well-trained male athlete can produce up to 2000 Watts at peak power, but if this engine is run more than a relatively short time, the effect will fall very fast. After 6 min the power produced is down to about 350 Watts.

It is important to know that the anaerobic energy systems are unstable systems. This means they are only able to run for a very limited time (but with large capacity). The lactic acid system also has the disadvantage of producing the by-product of lactic acid. This lactic will accumulate if you are “pushing” this system, with the result that you will become stiff, will feel more and more pain, and after a while will be forced to stop.

In a way, you are strangling all of your energy systems when you get stiff (accumulate lactic acid in large concentrations); it is like a fire in your “engine room”. We will now repeat what higher concentrations of lactic acid do to you:

  • A feeling of thick legs and arms

  • Painful muscles

  • Heavy breathing – hyperventilation

  • Negative effects on coordination; you feel clumsy, and you lose your motor capacity

The environment in the working muscles become more acidic which means a lower pH.

  • This acidic environment can disturb, limit or destroy the aerobic enzymes with the result that the aerobic capacity can be reduced. In other words, training too hard and too often reduce your fitness level.

  • An acidic environment in the muscles can also damage the muscle cell walls and also reduces the fat metabolic capacity of the muscle.

  • The more acidic environment in your muscles, the longer restitution or Rest time is needed.

  • The recharging of the creatine-phosphate is delayed and reduced in an acidic or stiff muscle.

  • The risk of getting injured is much greater in stiff muscles.

Training program

Together, the topics we have covered under physical training create the base for building a training program. The building blocks of physical training are Load, Rest and Progression (LRP). If our Load has been hard, then we also should make sure to compensate it with a good, long rest. That makes sense. Persons in good shape normally have a well-adapted system to take care of their recovery.

For some athletes rest does not mean they do no training; easy training or recovery training is also one type of active rest. One rule of thumb is one hard and two easy workouts. You are probably familiar with the saying “No pain, no gain”. This probably has its foundation in the idea of adaptation, or the overload principle, which we covered earlier.

But, you shouldn’t take such types of sayings literally, you don’t have to be masochistic to improve your level of fitness. Typical patterns for training workouts over a week look like this:
hard – easy – easy – hard – easy – easy – total rest or:
hard – easy – easy – hard – easy – long – easy

If we take a look at longer time frames like weeks or months, we also find typical patterns in the training (periodization): hard – harder -easier is a typical weekly and/or monthly pattern. In this time perspective we use progression to benefit from the overload and overcompensation principles.

To make sure the body is able to recover, you have to reduce both training intensity and volume after several periods of progression. Progression is very important for a top athlete, but it is not so important for the recreational jogger who just wants to be in good, healthy shape.

The fundamental basis for physical exercise is as explained in the section about adaptation, but remember that there will always be the individual factor involved. A training program should only be used as a rough guide; you should always make your own personal and individual adjustments. Remember, you are the only person on earth able to do this for yourself. A training program is not intelligent; hopefully you are!

>The physical Load can be achieved in 3 ways:

  • Even, steady state Load; aerobic long work/run

  • Aerobic Load with variation and Rest periods; interval and fartlek

  • Anaerobic tempo training; hard and short workout with short Rests

Have you ever reflected over why we use these different methods? The simple answer to this is found in our energy systems. Most people are not aware of this, but you should now be more able to understand why.

At even, aerobic Load we are working on a comfortable level without any troublesome feeling of pain, and our aerobic energy systems are working in a steady state mode. A typical training session would be a long easy run

When we work at aerobic Load with variation, we push our aerobic energy systems to their limit, (i.e. the anaerobic threshold), and sometimes we even go a bit over. We are now pushing so much that the feeling of some uncomfortable pain is a part of the game, but then we interrupt the Load phase and take a short Rest.

After the resting, we repeat the same workload, and then interrupt the Load for a new Rest. By varying the Load this way between Load and Rest, we are able to work within the threshold zone for a much longer period of time as compared to only one, long repetition without Rest. If you worked within the same Load using only one long repetition, you would be totally worn out in just a small fraction of the time as compared to the accumulated time with many repetitions, and you would accumulate much more lactic acid in your cardiovascular system.

This type of workload would actually be like competing in a race, with both anaerobic and aerobic elements. This is how it should be in a competition, but not in daily training. The key message is that the interval or fartlek should not be too hard (but not too easy either)

We do not recommend anaerobic tempo training for endurance athletes simply because this type of quality is not needed, and it also involves a very high risk since it can easily reduce your aerobic capacity.

Work and training have specific effects: I you want to become good in running, then you run, if you want to be good in swimming, then you swim. As we have mentioned, we are not only training muscles, tendons and organs, we are also training the teamwork between all these elements (functional adaptation)

There are numerous trainable qualities in the human body, such as strength, speed, flexibility, elasticity, co-ordination, and the quality we are most focused on, endurance. Clearly, it is not possible to train all these qualities at the same time. You must evaluate the needs and priorities in your activity or sport and, based on these, you design and develop your training program.

Authors: Ingrid and Arve Kristiansen

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