How do we know CrossFit improves fitness? There isn’t one definition of fitness, but we have some models that we use to define it and guide us in our quest to become more fit!

Let’s get science-y with the Three Metabolic Pathways.

There are three metabolic pathways that provide our muscles with energy: the phosphagen pathway, the glycolytic pathway, and the oxidative pathway.

The phosphagen pathway dominates high power, short duration efforts: things that take less than 10 seconds but require a huge power output. Think a few reps of a heavy lift, or an 100-yard dash.

The glycolytic pathway acts in the 30 second to 2 minute range, and powers high power efforts that last a little bit longer than 10 seconds! Think Tabata squats, or short, intense workouts like “Fran”, “Grace” etc.

The oxidative pathway provides energy for all longer, lower-powered aerobic activities. Think longer, less intense workouts like “Murph”.

Total fitness requires training each of these pathways. Our programming attempts to balance the effects of the three.

Food For Thought

Which pathway dominates today’s WOD?

Learn More

The Three Metabolic Energy Systems by Jason Karp, PhD
The Quest to Measure Fitness by Tony Budding

Have Questions?

Ask them in the comments!

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Bite-Sized CrossFit Concepts is our series of quick primers on some of the fundamental principles of CrossFit, as well as common misconceptions and frequently asked questions. We hope that they will help you understand why we do things the way we do, and train smarter!