Energy Systems and Training
Your body requires energy to do anything and everything, including sustaining life. There are 3 different systems that create energy in our body and understanding these systems are extremely important when designing training programs and workouts.
First off, What is energy systems training? Energy systems training teaching the body how to create adequate supplies of energy. The right training elicits the amount of ATP needed and this ATP provides the fuel for higher levels of physical activity.
What is ATP? Adenosine triphosphate, or ATP, is the main source of energy in the human body. ATP is a molecule that consists of adenine, ribose (sugar), and three phosphates. When the bond between the three phosphates breaks, energy is released. The ATP molecule must be re-formed, if they are not then our energy stores would be depleted. Maximizing this cycle ensures that the body has enough fuel to live and exercise.
There are 3 different energy systems and the one used the most at any given time depends on the intensity and duration of the activity. The 3 systems are: the Phosphagen System, the Anaerobic Glycolysis System, and Aerobic Metabolism. Understanding how each one of these works and their role during exercise is essential in designing exercise programs.
The Phosphagen System
The main source of fuel during this system is phosphocreatine. Phosphocreatine is one molecule of creatine and one molecule of phosphate. When phosphocreatine releases its phosphate molecule, it helps replenish the body's ATP. The phosphocreatine releases its phosphate when a specific enzyme is releases, this provides the energy the body needs. The one thing to know with this system is the energy it provides is short term, meaning it is beneficial for those engaging in short bursts of exercise.
The Anaerobic Glycolysis System
This system does not rely on oxygen for its process, so it releases stored glucose in the absence of oxygen. This process is also more effective at producing ATP than during phosphagen. In the early stages of anaerobic glycolysis lactate increases. This lactic acid build up creates a burning with in the muscles. It is at this point athletes can feel the switch to the glycolytic system being the primary energy system. This lactic acid has a bad rep among exercisers, yet lactate does have a few benefits. One is that is can be converted into glucose, which can supply the body with more energy. A second benefit if that the heart uses lactate to support a healthy heart rate. The problem with this system is when lactate accumulates faster than the body can get rid of it. This is called the lactate threshold and once you reach this point physical performance begins to decline and muscle soreness increases. More conditioned athletes generally have a higher lactate threshold.
The Aerobic Metabolism System
This system gives the body the fuel it needs to sustain longer duration exercise and relies on oxygen to create ATP. The first stage of the aerobic system is the Krebs Cycle, which is a very intricate and involved process using oxygen to produce ATP. Aerobic glycolysis occurs in the mitochondria, which means the more mitochondria you have the greater access to energy you have and the greater your ability to exercise for longer periods of time. Aerobic training increases the mitochondria in muscle tissue, this enables the body to create more ATP.
How do these systems function together?
While all systems are technically providing energy at once, there is an order as far as which system is providing the most energy. Once exercise begins that main system in play is the Phosphagen system and this remains for the first ~7-10 seconds after which the Anaerobic Glycolysis system begins to be the main source of energy. This remains the same for up to ~2 minutes in which the Aerobic system takes over and supplies energy for long durations.
How do we use this to help create exercise plans?
Once you understand the energy systems and how they interact together, you can begin to apply this knowledge to designing exercise programs. Higher intensity exercises are going to utilize energy stores quickly and will create a build up of lactic acid. Lower intensity, longer duration exercises will utilize the aerobic system more so and will maintain a manageable level of lactic acid. We also know how long it takes to restore these systems and "restock" the ATP stores. Since we know how long it takes to "restock" ATP, we use these time frames to build the rest periods we put in our workouts. Teaching the body to better use each energy system gives it access to them all. This will supply maximal energy and power and a more well rounded exercise program.