All About Your Metabolic Energy Systems

Three different metabolic energy systems power your workouts — and your day. Here’s how each one works, and how to make the most of them all.

illustration with shadow figures

Most of us understand our bodies about as well as we understand our cars. We know we’re supposed to take them out for a spin once in a while, and keep them well fueled. But when it comes to grasping precisely how that fuel gets converted into motion — well, we’re not entirely sure.

So let’s take a look under the hood, shall we?

Like a hybrid engine, your body has several ways of turning the stuff you eat into the stuff you do. All of these metabolic energy systems are switched on during physical activity, but each plays a different role depending on available energy and the specific demands of the task. Each burns a particular type of fuel at a particular rate — thereby affecting fat loss and muscle gain in a particular way.

These are the three systems:

  1. The adenosine triphosphate–creatine phosphate (ATP-CP) system, or phosphagen system, supports very brief, high-intensity activities like a single-effort vertical jump.
  2. The glycolytic system provides energy for activities of slightly longer duration and lower intensity like strength training.
  3. The oxidative system supports long-duration, lower-intensity activities like walking or distance running.

In recent years, exercise physiologists have learned how to target each system with specialized training to better prepare individuals for a specific event or sport.

Discover how your body’s energy systems interact — how to challenge each one so you can reach your fitness goals faster and more efficiently.

CSCS, is a contributing editor at Experience Life.

Illustration by: Nanette Hoogslag

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