The Three Energy Systems

Learn the basics of the body's three energy systems and the role they play in a balanced training program.
Gabriel Rusher
December 27, 2021
The Three Energy Systems

As was briefly mentioned in last week’s blog, the human body is equipped with three different systems for producing the energy (in the form of ATP) it needs; the phosphagen, glycolytic, and oxidative energy systems. Understanding how these systems function will make it easier to understand the important role that a general fitness program plays in one’s health and performance.

Phosphagen: This energy system takes advantage of the ATP (adenosine triphosphate) that is already stored within the body, which can be utilized immediately. This makes it ideal for high intensity, short duration tasks such as an echo bike sprint or a heavy clean and jerk. However, the body’s storage of ATP is limited and will run out within about ten to thirty seconds.

Glycolytic: Once stored ATP is depleted, more will need to be made. This system converts carbohydrates into energy anaerobically and is predominantly active during moderate intensity exercise that lasts between thirty seconds to three minutes. For activity lasting longer, the body will begin to rely on the oxidative system. 

Oxidative: This system is aerobic, meaning it relies on oxygen to break down carbohydrates and fats into energy, and is most active during rest and low intensity exercise that exceeds three minutes. Higher intensity activity will bias the use of carbohydrates, while lower intensity activity will rely primarily on fats.

Keep in mind, too, that these systems are all active during exercise; certain forms of exercise will simply bias one of the three. That is why it is important for a fitness program to be well-rounded and thought out; if varying stimuli are not introduced, one system will excel to the detriment of the other two. So, keep nailing the intended stimulus. It’s good for your health!  

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