"Metabolic Marvels: The 4 Energy Systems”

"Energy is the currency of life, and its production fuels our existence." - Unknown

In this blog, we'll explore the fascinating world of ATP production, the powerhouse of our cells. Whether you're a performance athlete or simply curious about how your body works, this article has something for everyone. So let's dive into the four energy systems responsible for fuelling our bodies, and unlock the science behind ATP generation.

Briefly, we have 4 energy systems that work together all the time. These are the ATP-CP, Anaerobic (Glycolytic), Aerobic (Glycolytic), and the Fatty Acid Oxidation systems. Like mentioned before the 4 of them are used at the same time, but depending on the activity and intensity of exercise, there is usually a dominant one. We’ll break down each of these energy systems so you can understand them, and learn how to improve your cardiovascular endurance.

ATP - CP

This system is the fastest way to synthesize ATP. It is used for brief explosive activity, however, it only lasts up to 10 seconds. Creatine phosphate, a high energy molecule, is broken down and used to create ATP, and then fuel exercise.

🚨 Limit: It only lasts up to 10 seconds since creatine phosphate stores deplete quickly.

Creatine is stored in your muscles and it can also be enhanced through creatine supplementation. To find more about creatine and its benefits, you can read our blog: “Creatine: The Game-Changing Supplement”

Anaerobic (glycolytic) system

This system is used for short duration intense exercise. It uses glycogen (derived from carbohydrates) and glucose (sugar) to metabolize reactions. However, because it is an incomplete reaction (there’s not sufficient oxygen supply), your body will start producing lactic acid after glucose and glycogen stores are depleted.

🚨 Limit: Because this system produces lactic acid, and the accumulation of lactic acid in your body creates muscle fatigue and lower energy levels, this system is limited to 2 minutes.

Aerobic (glycolytic) system

This system works just as the anaerobic (glycolytic) system, but because enough oxygen is present, the body enters further reactions: Krebs cycle and electron transport chain. With oxygen available, one reaction of this system produces up to 38 ATP per reaction.

🚨 Limit: This system is usually limited by the ability of an athlete to sustain long duration exercise and the ability of his cardiovascular system to deliver oxygen.

Fatty acid oxidation system

Fat is high energy fuel and produces a lot of ATP. It is by far the strongest energy system. Through fatty acid oxidation 1 unit of fatty acid equals more than a 100 ATP.

This energy system provides high energy fuel, but it is hard to metabolize (to process the reaction) since large amounts of oxygen are required for each reaction to occur.

🚨 Limit: Rarely limited by the supply of fatty acids. Its main limitation is the duration of exercise at a low-steady intensity. As intensity increases from low to high, it is difficult to maintain the required oxygen levels. Therefore, your body will switch to another energy system.

How to Train Your Energy Systems

Training the ATP - CP System

The ATP - CP system provides immediate energy for short bursts of intense activity, such as sprinting, jumping, and weightlifting.

It can be trained with explosive power training exercises that involve quick and powerful movements, such as short sprints, Olympic lifts, and jump training. Make sure to include sufficient rest intervals between efforts allowing ATP and creatine phosphate stores to recover. This improves the system's ability to generate energy quickly. Additionally, rest relief (no movement when resting) is required to replenish ATP stores between sets.

Training the Glycolytic System (Anaerobic System)

The anaerobic (glycolytic) system provides energy for high-intensity activities lasting from 30 seconds to several minutes.

It can be trained by performing intense exercises (e.g., sprints, burpees) for 30 seconds to 2 minutes, followed by rest periods to allow for lactic acid clearance and partial ATP restoration. However since lactic acid creates fatigue, how can endurance athletes best delay muscle fatigue during training? The answer is through work relief. Movement when resting such as walking or jogging slowly clears lactic acid and prevents ATP-CP re-storage, since you don’t want the previous energy system to recover.

Training the Aerobic System

The aerobic system provides energy for activities lasting longer than a few minutes. The training approach for this system is long-distance steady-state cardio: activities like long-distance running, cycling, or swimming at a steady pace for an extended period. This stimulates the aerobic system and enhances oxygen utilization.

If you’re running a marathon for example, you should emphasize training the aerobic (glycolytic) system since it is an activity that requires steady-state cardio at an average pace.

Other sports use a combination of systems. E.g. Boxing uses the and ATP-CP system for explosive bursts of energy, and the anaerobic (glycolytic) system for series of punches at low oxygen and high intensity that can last up to 30 seconds. This means that including exercises that target both of these systems during your training would be beneficial to optimize performance.

In conclusion, your body is always producing ATP, whether at rest or exercising. There are 4 energy systems and depending on the duration and intensity of the activity, your body will switch within systems, and choose a dominant one that best suits the needs of the present.

Remember that an athlete's training program should be tailored to their specific sport, goals, and fitness level. Proper periodization and recovery strategies are essential to achieve optimal athletic performance.