0800 040 7526
As discussed in the last blog, we are a bit like a clever hybrid car, and combine 3 different types of energy systems to make energy for movement, growth and all the other things that keep us alive and breathing. Understanding energy systems underpins the study of exercise and the effect it has on the human body. Whether it’s during a 26-mile marathon run or one explosive movement like a tennis serve, skeletal muscle is powered by one and only one compound… adenosine triphosphate (ATP) . However, the body stores only a small quantity of this ‘energy currency’ within the cells and it’s enough to power just a few seconds of all-out exercise . So the body must replace or resynthesize ATP on an ongoing basis. Understanding how it does this is the key to understanding energy systems. An ATP molecule consists of adenosine and three (tri) inorganic phosphate groups. When a molecule of ATP is combined with water (a process called hydrolysis), the last phosphate group splits away and releases energy. The molecule of adenosine triphosphate now becomes adenosine diphosphate or ADP .
The most powerful of these systems that re-synthesises this ATP is the creatine phosphate or CP system. It is also the one that gets exhausted the most rapidly.This is the system that would be used in a golf swing or a shot putt. This system does not need oxygen, fat or carbohydrate but uses chemical energy, and so it’s called anaerobic. We use this energy system for activity at 95-100% of our maximum exertion, and it lasts only for 10 to 15 seconds. Remember that we use all these systems together, always as a combination, but one system is dominant. A good example of this is blinking. While you are sitting at the computer at work you will be using the oxygen system (more on this later) but every time you blink you are using this powerful CP system.
Having looked last time at the creatine phosphate system, which we use for short maximal bursts, today we will look at the second energy system down, the lactate system. Like the creatine system this energy system makes energy without oxygen:if the intensity during aerobic exercise becomes greater that the aerobic system can provide for it will take over. Similarly when near maximal exercise lasts longer that the CP system can provide for it will take over.
The conversion of glucose to lactic acid is occurring constantly in the body and only becomes a problem when lactic acid starts to to accumulate. If the lactic acid production and removal are equal then there is no problem, but if the production of lactic acid exceeds the muscles and cardiovascular system’s ability to disperse it there will be a build up of this lactic acid which will eventually cause the cessation of the activity. This is known as the onset of blood lactate accumulation (OBLA). It is associated with sensations of laboured breathing, heavy limbs, pain and aches in the muscles which together will cause the exercise to stop. These sensations are in fact a result of increased hydrogen ions that are a result of this excess lactic acid.
Targeted interval training will improve the body’s ability to withstand the build up of lactic acid (known as lactic tolerance) and/or to remove it more quickly thus preventing this accumulation. This anaerobic training (the dreaded anaerobic intervals!!) quickly uses up the glycogen stored in the muscles and liver (our fuel tank) and requires short periods (1-3 minutes) of strenuous activity followed by periods of recovery. Ideally this recovery should be active (for example walking or slow jogging between faster running or rowing gently between harder intervals to aid return of blood back to the liver. By contracting muscles in this recovery mode you are helping to squeeze blood back up the arteries through clever one way valves, so your heart does not have to do it all on it’s own! This is why after a brutal interval your personal trainer should force you to walk or move about even if you really only feel like flumping down.
This second energy system is one of the most important in many sports, from squash, rowing, rugby, tennis and boxing. These are the activities where we need up to 95% of maximal energy but also for a sustained periods of a few minutes. So a rally at tennis followed by a break for serve, a passage of play in rugby followed by a penalty and so on. The short duration of the lactate system is particularly challenged by rowing, where a typical race is 2000m or 6 to 7 minutes. The energy system used is the lactate one, but it is asked to go beyond the time at which it runs out. So the first 3 minutes is fine, it’s the next 3 in which your body will be screaming to stop but your mind must make it carry on. This also explains why of all the Olympic sports the rowers are the ones that collapse after a race. I too have too adopt the foetal position after a good 2k time. this is why interval training is so important for fitness gains.
My 2 previous blogs have looked at the CP (rocket fuel) and Lactate (petrol) energy systems, today we’ll have a look at the third and final one, the aerobic or oxygen system, which in our car fuel comparison is more like diesel.. Aerobic simply means “with oxygen” and refers to the energy system that produces ATP (the source of all our energy, see the blog on CP energy systems) from the complete breakdown of carbohydrate and fat in the presence of O2. The aerobic energy system is dominant when there is sufficient O2 in the cells to meet the energy production requirements. This is especially true if the body is at rest, and the oxygen system is the dominant one up to about 60% of maximum exertion.. The fuel sources for this energy system are fatty acids (fat!) and carbohydrate, stored in their blood as glucose, and they supply the body with ATP during aerobic metabolism. Whether the body is at rest or exercising aerobically, both carbohydrate and fat are required, just in varying proportions. Fat is commonly said to burn in a carbohydrate flame, meaning that fat cannot be broken down without the presence of carbohydrate. The production of energy from the oxygen system produces only ATP (where the energy actually comes from), CO2, water and heat, so there is no nasty waste product like in the lactate system (lactic acid), and thus the oxygen system is only limited by time taken to refuel during exercise. The complete breakdown of 1 glucose molecule will regenerate 36 moles of ATP or 263Kcals. 1 molecule of fat will yield 460 moles of ATP, making it a far more concentrated energy supply; however carbohydrate remains the preferred source of energy since it will realse it’s energy a lot faster, even though it has less of it per molecule to release.
Now that we have looked at the three diferent energy systems we can begin to see why understanding them is important, not just from a scientific view but for anyone who wants to begin training these energy systems to improve-an athlete, fitness enthusiast and of course a personal trainer. In the next blog we will look at the impact these energy systems have on training and how the energy systems are the key not only in getting fitter but also in personal training for weight loss. Remember that all these systems operate simultaneousle, but one of them will be dominant at a given time depending on the level of exertion. The CP system takes us from 95-100%, the lactate system from 60-95%, and the oxygen system from 0-60%.
We now have an overview from the last three blogs on how the energy systems work, and what intensity and duration they are used for. But where is this energy actually made? All three systems produce energy at the cellular level, but in different places within the actual cell. Aerobic energy production occurs in organelles (small cell structures) called mitochondria. The larger the mitochondria within a cell, the greater potential energy that cell has from ATP. This could mean that an athlete could run, swim or cycle for a sustained period of time without fatigue. The CP and lactate systems also produce energy in the cells, but outside the mitochondria in the cell cytoplasm.
Remember that there is a summary of energy systems on our the knowledge page, with pretty diagrams. Have a look. In the next blog we will put all of this science together and look at how understanding energy systems is vitally important if you want to get fitter or better at a particular activity. By understanding which activity uses which energy system we can pinpoint that system and train it to be better. This is not just important for a personal trainer but for anyone who wants to improve, get fitter, lose weight tone up, build lean muscle etc.
Now that we have been through the energy systems it gives us an insight into what type of activity uses which energy system, and also how long the different energy systems last for, the fuel they use and any waste product that they produce. This is extremely useful if we want to train someone for a particular type of sport, want to make someone lose weight, or just make a personal training client fitter and slimmer.
We can, for instance, see that the only energy system that uses fat as a fuel is the O2 system, which is dominant from 0-60% of maximum exertion. Therefore this is the energy system that we use the most when at work, sitting watching telly, shopping and so on.Therefore if we can increase the amount of energy we use at rest it will have an important bearing on fat loss. Metabolic rate at rest happens to increase lots the more lean muscle thet you have, so by resistance training we will increase lean muscle, so we will increase metabolic rate at rest, so we begin to target the O2 system more for most of the day every day, and will burn more fat!
Similarly, if I have a personal trainer client in Windsor who is a member of a rowing club, I can improve his rowing by targeting the energy systems used in rowing. A 2000m row uses the aerobic and anaerobic systems in about a 60-40 split, so our training should be a combination of longer endurance work (O2 system) coupled with anaerobic intervals of higher intensity (60-90%) for 1-3 minutes. If I have a personal trainer client in Maidenhead who wants to be better at sprinting as she wants to win the parents race at the school sportsday, then we need to work mainly on the CP system, so shorter maximal bursts, as this is the energy system almost exclusively used in the 100m sprint. On the other side of the scale I recently trained Wendy in Egham for the Benidorm Marathon, as this is a distance race the energy system dominant in the O2 system, so the training is mainly focused on longer endurance types of training.
For a broader overview have a look at the energy continuum diagram, where various sports are ranked by their aerobic and anaerobic demands..
As we have seen in the previous few blogs, oxygen is vital for survival as we need it to make energy to keep all our systems functioning, and to keep the oxygen energy system going. The use of O2 in the cells of the body is known as O2 uptake or consumption. When the body is at rest oxygen uptake (VO2) is approximately 3.5 millilitres per kilogramme of body weight per minute (ml/kg/min). This value of oxygen uptake at rest is also known as 1 metabolic equivalent or 1 MET. Exercise can therefore be categorised into light, medium or heavy depending on the amount of O2 uptake required or the METs. The maximum amount that a person can take in (respiratory) transport (cardiovascular) and use (muscular) will therefore provide an indication of their fitness. The more O2 that they can take in, transport and use, the higher intensity they can work at and the fitter they will be. This maximal oxygen uptake is called VO2max and is generally accepted to be the best guide to assessing someones fitness levels, and can be directly measured using various aerobic tests. Accurately measuring VO2max involves a physical effort sufficient in duration and intensity to fully tax the aerobic energy system. In general clinical and athletic testing, this usually involves a graded exercise test (either on a treadmill or on a cycle ergometer) in which exercise intensity is progressively increased while measuring ventilation and oxygen and carbon dioxide concentration of the inhaled and exhaled air. VO2max is reached when oxygen consumption remains at steady state despite an increase in workload. We could do the bleep test (a 20m shuttle run, timed by a recording over 23 minutes, with a faster pace each minute), the slightly less harsh Rockport walking test, or an expensive session on a bike with a BUPA team. If you really want to know how fit you are your Diets Don’t Work personal trainer can do one of these tests with you.
The important thing to recognise is that we can improve VO2 max through cardiovascular training, and that your body will adapt and change to stresses and overload placed upon it. At the correct intensity of cardiovascular training there are a number of adaptations that happen, which we will go through in the next blog. In the meanwhile even just a short burst of activity a few times daily will be enough to start these adaptations, making you fitter, lighter and even healthier!!
We are pleased to write that our personal trainer Stephen Hitchcock will be extending his area coverage. Based in Egham, Stephen will now be our personal trainer for the additional areas of Richmond, Twickenham and Sunbury, as they are only a short hop down the A30 for him. Stephen is another Premier qualified personal trainer, and has the additional benefits of massive running experience, boxing/sparring qualifications, and of course a witty repartee to keep you amused when well into your 4th minute of the plank. You can read his full personal trainer qualifications and profile on our “meet the trainers” page, but if you are thinking of making some positive changes to your life, and need to get fitter or lose some weight or both, then Stephen and Diets Don’t Work can give you the best possible chance of success.
So, by now you should have no need for a personal trainer, as you are so educated by these Diets Don’t Work blogs. Coming up the next time we will start to make sense of the energy systems and see how we can use them to our advantage to get fitter and lose weight. But today it’s a brief visual table of how it all works: