The creatine phosphate system (ATP-CP)
When you exercise, your body needs energy to keep going. The creatine phosphate system is one way that your body gets that energy. It works really quickly, but it only lasts for about 10 seconds. After that, your body has to switch to a different system to keep getting energy.
Think of it like driving a car. The creatine phosphate system is like using first gear. It gets you going really quickly, but if you only used first gear, you would use a lot of gas and not get very far. Your body needs to switch to a different system, like shifting into second gear, to keep going.
The creatine phosphate system doesn't produce any waste, but it's not very efficient. It only makes one molecule of energy for every molecule of creatine phosphate used. So even though it's helpful, your body can't rely on it alone to keep going during exercise.
Overall, the creatine phosphate system is an important part of how your body gets energy, but it's just one piece of the puzzle. Together with other systems, your body can keep going during exercise and other physical activities.
The anaerobic or lactic acid system is another way that your body gets energy when you exercise. It uses glucose, which is a type of sugar found in foods like potatoes, rice, and bread. Your body stores glucose as glycogen, and then breaks it down to release energy without using oxygen.
This system works really quickly, but it can only work for about two to three minutes at a time before it starts producing a waste product called lactic acid. If your body produces too much lactic acid, it can stop your muscles from contracting, so you can't keep exercising.
Think of it like driving a car. The anaerobic system is like using second gear - it's helpful for a short burst of speed, but you can't use it for the whole journey. It's not very efficient, either. Your body only gets two molecules of energy for every molecule of glucose used.
That's why your body needs to switch to another system, like shifting into a higher gear, to keep getting energy during exercise. The anaerobic system is an important part of how your body gets energy, but it can't do it alone. Together with other systems, your body can keep going and stay healthy and strong.
The aerobic system is how your body gets energy when you exercise for a longer amount of time. After a few minutes of exercise, your body starts using glucose with oxygen to make energy in a process called aerobic glycolysis. This system is more efficient because it produces more energy, and doesn't produce lactic acid like the anaerobic system does. Instead, it produces carbon dioxide and water as waste products.
The downside to this system is that your body can only store enough glycogen (a form of glucose) for about two hours of medium-intensity exercise. If you're doing higher intensity exercise or if you've used up your glycogen stores in previous exercise, you won't be able to exercise for as long using this system.
It's like driving a car with a half-empty tank - you can't go as far before you need to refuel. To keep your body going during long workouts, you can drink carbohydrate drinks to supply glucose to your muscles. After exercise, it's important to eat a carbohydrate snack to replace the glucose that you used up.
Ultimately, your body has a more efficient system that uses fat and other fuels as energy. However, the aerobic system is an important part of how your body gets energy during exercise, especially for longer workouts.
Fat (with oxygen)
After a few minutes of exercise, your body can start using fat as a source of energy. This system uses small amounts of glucose and oxygen to release energy by breaking down fat, carbohydrates, and oxygen in a part of your muscle called the mitochondria. Unlike the anaerobic system, there is no build-up of lactic acid, but your body produces carbon dioxide, water, and heat as waste products.
This system works best for low-to-moderate intensity activities like walking or jogging at a comfortable pace. It can only be maintained for about two hours because it needs glucose to work. If you start exercising with low glucose stores in your body, you won't be able to keep going for as long without eating carbohydrates during your workout.
Different types of fat from food can produce more than 200 ATP molecules for every molecule of fat, glucose, and oxygen used, making this system very efficient for muscle energy. However, if your body runs out of glucose stores, it can be harder for your body to use fat, which is why eating carbohydrates is important when exercising.
If you exercise regularly, your body becomes more efficient at moving through the different energy systems, like shifting gears in a car, and can start using fat as an energy source more quickly than someone who is not used to exercising.
Your body actually uses all of the energy systems we talked about in the last few posts at the same time when you're exercising. Each system provides energy at different times, depending on how intense your exercise is.
For example, when you start exercising, your body needs a lot of energy right away, but the aerobic system can't keep up. So the anaerobic system starts providing more energy to keep your muscles going. As you keep warming up, the aerobic system starts to provide more and more energy because your body can use oxygen more efficiently.
After about 30 minutes of low-to-medium intensity exercise, your body mostly uses the fat system for energy, with the other systems providing a small amount. But if you suddenly increase the intensity of your exercise, your body needs more energy right away. It gets that energy from extra stores of glucose in your body.
The problem with this is that you need a lot of glucose to sustain high-intensity exercise for a long time. When your body breaks down glucose really quickly, it produces a lot of lactic acid, which can stop your muscles from contracting. That's why high-intensity exercise that produces a lot of lactic acid usually only lasts for about two minutes, and less if you're not very fit.
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