Understanding Energy Systems in the Human Body

When we talk about fitness, we often think about respiratory capacity and cardiovascular endurance (cardio). In this series of articles, I want to introduce to readers another extremely important element, that is: the energy systems in the human body.

A good example: the 100m track and the 42km marathon use two completely different energy systems. You can't develop a marathon energy system expecting to improve your 100m!

The same can be applied to other sports like football, rugby, weightlifting, etc. In team sports, even different positions on the field, the development of systems The energy system is also quite different. Understanding the physiological needs of each sport, competition position, as well as how the body provides energy for each different type of activity will help you get the most appropriate and optimal physical preparation plan.

I. First, what is energy?

Food provides energy for the human body. After digestion, the body will store that energy in the form of carbohydrates (starch), fat (fat) or protein (protein). However, cells cannot directly derive energy from these substances. And that's when the body's energy systems have to work, processing nutrients, turning them into usable energy units (ATPs), supplying cells to serve. for all body activities, including movement.

In other words, the body cannot directly use food for energy. All must be converted into units of ATP and the body uses ATP to maintain life. If your body is a car, then gasoline is the nutrient. And engines are the energy-generating systems in the body. Depending on how fast or slow you go, the engine will have to work differently. A car designed for long-distance running will have a different engine than a racing car. The same can be applied to the human body in motion. A 100m athlete must develop a different energy system than a long-distance runner, as well as athletes in team sports (basketball, football, etc.).

II. 3 Energy Systems in the Body

For exercise, depending on the intensity and duration of the activity, one of the three ATP-PC, Glycolysis or Oxidative systems will play a key role in providing energy for that activity. .

I use the word mainstream because of the fact that, once exercise begins, all three systems are activated together, just different in the rate and amount of ATP produced. So depending on the demand, each system will contribute more/less to the energy supply. For example, when you sprint at full speed for 10 seconds, your body now needs a large source of energy, available immediately so that you can complete the goal at the highest intensity. According to the diagram illustrated below, it can be said that in these 10 seconds, all 3 energy systems are working, but the main contribution is from APC-PC with 95%, then Glycolysis with 3% and finally is Oxidative 2%.Running 100m, extremely intense (extreme) but short duration Team sports, running at medium-high intensity and interval

1. Phosphagen system (ATP-PC)

This is a system that can provide immediate energy to the body through the direct use of a small amount of ATP stored in the muscles. This system will play a key role in providing energy for activities of extreme intensity (maximum-effort), for short periods of time (under 10 seconds).

The ATP-PC system works without oxygen, so it is always ready to provide the body with energy in the event of an "emergency", when other systems are not able to generate the required amount of ATP. immediately to meet the demands from the movement.

While providing a fast, pure and powerful source of energy for intense activities, the Phosphagen system can only operate for about 6-10 seconds. The reason is because the source of ATP in the muscle has a certain limit. Once this available ATP is depleted, other energy systems will take the lead.

However, the intensity of your activity will not be as it was in the beginning. And in order for the body to accumulate this source of ATP, you must rest for 3-5 minutes to be able to work at the same intensity. This is why after sprinting or lifting heavy weights, you have to rest for a while before you can do it again.

An easy-to-understand illustration: for example, the activity you perform requires 10 units of ATP energy immediately. As a beginner, you can finish at full intensity thanks to the Phosphagen system. But when the available ATP is depleted, you won't be able to operate at the same intensity as other systems can only provide 4-6 ATP units in that amount of time. So you have to reduce the intensity or rest to allow the body to re-assemble its ATP reserves.

There is a scientific ratio of “exercise:rest” when using the Phosphagen system, which is 1:10/12. That is, for every second of using this system, you need 10 to 12 seconds of rest for the body to re-integrate the ATP source in the muscles. For example, if you do a 10-second sprint, you need to rest for at least 100 seconds so you can do it again with the same effect. This doesn't mean that if you don't rest enough you won't be able to run again, it's just that if you don't rest enough, the effect won't be as good as it was at the beginning (instead of the first 10 seconds you run 100m, not enough rest). , 10 seconds you can only run 80m).

Sportsmen/athletes that rely on this system will demonstrate extremely fast, powerful, and explosive movement. These can be mentioned as powerful punches in boxing, 100m runs, Olympic weightlifting, extremely intense activities in football/basketball such as running fast, pressing disputes, jumping, kicking the ball. …

Training to develop the Phosphagen system will help improve explosiveness, strength, and speed of application. However, it cannot prolong the amount of time that this system fuels the body!

Therefore, developing strength, explosiveness and speed of force application will be the goals of the development of the Phosphagen (ATP-PC) system. Specifically, please refer to part 2 - developing energy systems in the body!

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2. Glycolytic system (anaerobic)

After ATP-PC stops working, the Glycolytic system will come into play, playing a key role in providing energy for the body to maintain moderate-high intensity activity for the next 2-3 minutes. The Glycolytic system also works without oxygen, using the nutrients carbohydrates (starches) stored in the muscles (glycogen) and in the blood (glucose) for energy. Because it takes several steps to convert Glucose to ATP, the Glycolytic system provides energy more slowly than the Phosphagen (ATP-PC) system.

If the typical operation for using an ATP-PC system is a 100m run, the typical operation for a glycolytic system is a 300-400m run. The main sports using this system include: team sports such as football, basketball, rugby; badminton, swimming or martial arts…

The most interesting thing about this system is the fact that it produces lactic acid during the conversion from glucose to ATP. People still think that lactic acid is what causes "pain," a feeling like "burning" muscles when exercising at high intensity. This is absolutely not true!

Scientists have found the real cause behind this pain. This is because in the process of using ATP, a certain amount of Hydrogen atom (H+ ion) is produced as a by-product. When the body is working at high intensity continuously, a large amount of ATP is used and a large amount of H+ ions are also secreted. H+ ions will lower the pH in the muscles, making the environment inside the muscles more acidic; and this is really the cause behind the pain / burning sensation when exercising.

Meanwhile, the conversion from Glucose to ATP produces a by-product called Pyruvate. Pyruvate will combine with Hydrogen atom and produce Lactate. Thus, lactate is actually a beneficial compound, not as harmful as people think. The generated lactate means that Pyruvate has taken away H+ ions to help the environment in the muscle become less acidic. After being created, Lactate will follow the circulation and be pushed out, to other parts and processed by the 3rd system, Oxidative, and reused to create energy.

The larger the amount of H+ ions, the more lactate will be accumulated (Pyruvate collects Hydrogen atoms). When the rate of H+ ion production is faster than lactate accumulation and the rate of lactate expulsion, muscles become more acidic and begin to lose performance. This phenomenon is known as Lactate Threshold, which roughly translates to Lactate Threshold.

According to the illustrative diagram, you can see that from a speed of 5-8 mph, the body can still integrate lactate (Pyruvate collects H + ions to reduce the acidity of the muscles). Milestone 8 is the Lactate Threshold. Immediately after, the amount of H+ ions becomes too large => the formation of lactate and the ejection rate cannot keep up => accumulation of a large amount of lactate (representing a large amount of H +) => acidified muscles The phenomenon of muscle pain begins to appear.

What do all these theories have to do with practice?

Dotted line: before exercise

Dotted line: after exercise develops the Glycolysis system, the lactate threshold will be widened.

When it comes to developing the Glycolysis system, the biggest goal will be training to "widen" the Lactate Threshold for the body. When the lactate threshold is widened, it means that the body's ability to push out lactate is improved (remember lactate carries H+ ions) => less lactate accumulation => less H+ ions => reduced acidity = > works longer.

To expand the lactate threshold, you must determine and practice a little above the lactate threshold, repeat many times to let your body adapt and get better at "collecting" H+ ions, forming lactate and then pushing it out so that muscles do not hurt too quickly and then reduce mobility. Specifically, please refer to part 2 - developing energy systems in the body!!

3. Oxidative system (aerobic)

The oxidative system is the main energy supply system for the body at rest or during low-intensity activity. This is the only system in the human body that uses oxygen, for the purpose of processing carbohydrates (starch), protein (protein) and fat (fat) for energy.

The first "burned" nutrients will be carbs (starch), then will come fat (fat) and if you work long enough, it will "burn" also protein (protein) to make ATP. . That's why sports that require a lot of endurance (based on the oxidative system), often produce athletes with a "shrink" body.

Because it has to go through many complex metabolic processes in converting nutrients to energy, the rate of ATP generation of the Oxidative system is the slowest. Although slow, but the total amount of energy generated is much larger than the other 2 systems. In other words, an Oxidative system is a system that releases energy slowly, "smoldering" but extremely persistent.

After ATP-PC and Glycolytic are no longer active, Oxidative comes into play and is the main source of energy for the body from 3 minutes onwards, and can last up to several hours. The typical sport, which relies entirely on the Oxidative system, is marathon running, or long-distance cycling.

Although not as prominent and powerful as other systems, it can be said that Oxidative is the fundamental energy system of movement. In addition to its ability to generate energy for low-intensity endurance activities on its own, it contributes to other systems as follows:

• As for the Phosphagen system, after the energy is depleted, the Oxidative system will play a role in re-supplying the ATP reserves in the muscles when you stop/reduce the intensity of the activity. This is why athletes with better Oxidative systems tend to recover faster than others. For example, you lift heavy weights and use up all the energy from the Phosphagen system. While resting, the Oxidative system will help you re-integrate your ATP source. The more productive you are, the faster your recovery time.

• As for the Glycolytic system, the Oxidative system will help process the accumulated lactate to generate more energy. The accumulated lactate will be processed in the mitochondria cytoskeleton (where the Oxidative system works). The faster the oxidative system works, the better, the faster the lactate is processed => more energy is generated and the lactate in the muscles can be pushed to the Mitochondria at a faster rate => less lactate in the muscle = > less H+ ions => less acidic => works longer. Simply put, Mitochondria is like a room where the Oxidative system generates energy, and it has a certain capacity. Once it's full, lactate from the muscles can't get in. If we can help it improve its ability to operate at higher performance, then it can process lactate faster and create more space for lactate in the muscles to be taken in. If it works too slowly, does not process lactate in time, the amount of lactate remaining outside the muscle will increase more and more => more H+ ions => increased acidity.

In summary, if Phosphagen and Glycolycitc provide energy for "key" activities when moving (high intensity activities), then the Oxidative system is the fulcrum to help athletes continue to compete and recovery.

It is possible to imagine a specific case in football. A striker quickly rushes to the position of the ball, struggles to get the ball and then shoots hard. Can he maintain such an intensity of activity continuously? Of course not. He slows down, goes for a light jog or even walks to restore his strength and prepare for another rush.

In physiology, what does this mean? He has drained the ATP reserves in his muscles and can no longer work at high intensity (if the situation forces him to continue to be active, the Glycolytic system will step in). The ATP-PC system is exhausted. At this point, he will walk or run “slurry”, light intensity forms, using the Oxidative system, so that this system slowly regenerates energy for later activities.

If the Phosphagen and Glycolytic systems are well developed, the striker will be extremely powerful and effective every time he decides to "speed up". If the Oxidative system is well developed, his total distance traveled per game will be higher (tactically beneficial), and his recovery from each boost phase will be faster (maintain intensity). high activity longer).