Three Energy Systems Part 1 By: Scott Canipe
Knowledge of the three energy systems of the body will certainly help those that are concerned with being physically fit. This includes achieving muscle strength, muscle endurance, flexibility, high cardiovascular capacity, good balance, improving body composition, and increase reflex stability.
Anytime there are muscle contractions or even cellular activity in the body, energy is being acquired from some sort of a supply. This includes rigorous exercise, growth and repair of cells, thinking deeply, or simply blinking the eye.
Our bodies are made up of cells, tissues, and organs. Groups ofcells make up tissues such as bones, muscles, blood, etc. Groups of tissues form organs such as the brain, heart, lungs, etc. Cells, tissues, and organs function in one synergistic conglomeration to form bodily systems such as the cardiovascular, respiratory, lymphatic, etc.
The three energy systems are used to fuel all of these different mechanisms. Training and exercise stimulates and conditions each one of these necessary bodily mechanisms to achieve overall fitness and health. This is called "homeostasis."
Before I get into the three energy systems a question must be asked, "What is energy?" A simple definition of energy is the ability to do work or make change.
Ultimately, all energy that the body uses comes from sunlight. Sunlight affects vegetation through a process called photosynthesis. Photosynthesis is a chemical process that transforms carbon dioxide into sugars and other compounds using the sun’s energy. Human beings either eat the vegetation or animals that consume the vegetation. Therefore, the energy is transferred from the sun to vegetation to animals to people or from the sun to vegetation to people.
Once energy is consumed in the human body, it is stored and subsequently used in three different ways. Specific chemical reactions affect three energy systems that supply fuel to make the muscles and other bodily functions achieve their work.
For any truly serious student of fitness, it is important to know where this energy is stored and how it is released to the three metabolic pathways.
ATP, known as adenosine triphosphate, is a complex molecule that is made of three parts:
ATP is formed from the energy that has been released from the breakdown of food. It is produced in the mitochondria of the cells. The mitochondria are typically referred to as the “power plants” of the cells. ATP functions as the “reservoir” or “currency” of energy for the cells. It is not energy within itself however; it stores and releases energy much like a battery does.
ATP releases its energy whenever it is broken down into ADP. At this point, energy is transferred to specific functions that are needed in the body. This is how it happens:
An ATP molecule consists of three phosphate groups. Hence, the “T” in ATP means “tri” or "three" phosphate groups. Whenever ATP is combined with water (called hydrolysis) the last of the three phosphate groups break away and energy is released to wherever it is needed. The three phosphate groups are already electron charged. In chemistry, molecules that are charged the same naturally repel one another, so when the third group breaks away it does so rather forcefully. The ATP molecule now becomes anADP (adenosine diphosphate) molecule. The "D" in ADP stands for “di” or double meaning “two” phosphate groups.
Chemical reactions must replace the third phosphate group back to the ADP so that it can be converted into ATP again. There is a continual cycle of the third phosphate group breaking away from ATP, releasing energy, forming ADP, and then another phosphate group being added back to ADP to make ATP again. The adding back of this phosphate group is called “phosphorylation.”
Phosphorylation is what produces ATP. Since muscle cells constantly need ATP and ATP storage is very limited, the muscle cells must reproduce ATP, which can be accomplished via three energy systems:
If phosphorylation (adding the third phosphate group back to the ADP making it ATP) takes place in the presence of oxygen it is called the aerobic energy system also known as oxidative phosphorylation. If it occurs without the presence of oxygen it is called the anaerobic energy system which has two parts referred to as anaerobic ATP-CP and anaerobic lactic.
These are the three energy systems. These systems are interconnected. They overlap each other in a phase like manner to provide a smooth transition from one energy system to another as exercise is being done. This allows the body to perform at its best through all levels of exercise intensity.
In the above-mentioned information the three energy systems are only simply explained. However, for a more detailed explanation of how these three energy systems work and affect exercise click here for part II.
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