General Physical Preparedness

Test Your Energy System Capacity

These three workouts will give you a better idea of which energy system you need to improve on.

When looking at broad strokes, the human body has three main energy systems to accomplish work. The first is the phosphagen system, which allows athletes to access 90 to 100 percent of energy output. This system can only be sustained for up to 15 seconds.


Second, there’s the glycolytic system that lies somewhere in the middle, in which athletes can sustain up to about 85 percent of potential output from 15 seconds up to several minutes. 

The last system is the oxidative system. Unlike the previous two anaerobic systems, this energy system is aerobic. The oxidative system amounts to up to about 60 percent of output and can last almost indefinitely.

If you want to zero in on how your fitness measures up when it comes to energy systems, try these three as tests:

CrossFit Total

This CrossFit version of a powerlifting meet includes a one-rep max back squat, deadlift and shoulder press. It’s not the only way to measure your capacity in the phosphagen system, but it will give you some balanced insight.


You didn’t think you’d get through this list without seeing “Fran,” did you? When scaled correctly, Fran feels like a blistering 800-meter footrace (with weights), which makes it a bit more robust than a running test. Choose weights that will give you a chance to finish largely unbroken. Anything longer than five minutes is a different test.


The old-school CrossFit Endurance shirts that read, “You don’t know cardio until you’ve done Helen” are my favorite. “Helen” is three rounds that include a 400-meter run, 21 kettlebell swings and 12 pull-ups. If you scale it right, it feels like a 1-mile footrace. The kettlebell swings and pull-ups should be fast and allow you to transition without stopping from movement to movement.

If you perform well in some but not others, you may be able to recognize “gears” that need some attention in your engine. Good luck!