College Essay Examples

The Three Energy Systems Defined

The Three Energy Systems Defined

Before starting any activity, our body requires the right amount of energy to power us on. Our diet plays a big role in sustaining us as we go through our daily activities and workout regimens. The nutrients in the food we eat get metabolized into adenosine triphosphate (ATP) to power our cells. But in order to understand this better, here is a brief look at how energy pathways work.

The Phosphagenic System

Our body primarily uses three metabolic energy pathways/systems. The phosphagenic system uses up creatine phosphate readily available in our muscles for rapid ATP production. It is power-packed but short-lived hence effective for high-intensity activities such us long jumps and discus throws where sudden bursts of energy is needed. The other two involve the breakdown of sugar called glycolysis. The anaerobic form of glycolysis uses up carbohydrates as its fuel. This supplies energy that is of slightly longer duration and perfect for activities of moderate intensity such as 1-3 mile leisure jogs or a 3-minute freestyle swim of medium effort. Of the three systems, aerobic glycolysis is the only process that burns fat as fuel. This form of metabolism is slower and requires oxygen but produces more sustained energy that is perfect for low-intensity activities of prolonged duration such as a 6-mile run or circuit training.

Therefore, if I were to effectively train for a marathon, it would be best to train mainly with the aerobic energy system, while utilizing the other two in conditioning the body. Understanding this dynamics allows me to incorporate specific activities into a training plan that maximizes our energy production and consumption.


Gagliardi, C. (2019). The Three Primary Energy Pathways Explained. American Council on

Exercise. Retrieved from The Three Primary Energy Pathways Explained

Heffernan, A. (2019). All About Your Metabolic Energy Systems. Experience Life. Retrieved

from All About Your Metabolic Energy Systems

Kelso, T. Understanding Energy Systems: ATP-PC, Glycotic and Oxidative – Oh My!

Retrieved from

Winn, Y. (2019). How to Train for a Marathon. REI Co-Op Expert Advice. Retrieved

from How to Train for a Marathon

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By Hanna Robinson

Hanna has won numerous writing awards. She specializes in academic writing, copywriting, business plans and resumes. After graduating from the Comosun College's journalism program, she went on to work at community newspapers throughout Atlantic Canada, before embarking on her freelancing journey.

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