EPOC is the acronym for Excess Post-exercise Oxygen Consumption. Many refer to it as the “afterburn.” To better understand how EPOC works, let’s review the basics of energy systems.
Note: If you wanting to eventually transition into a career as a sports performance professional, weight loss specialist, or a personal trainer, EPOC is an important concept to familiarize yourself with.
ENERGY SYSTEMS 101
There are three energy systems:
1. Phosphagen (ATP-PC)
2. Glycolytic
3. Oxidative
All three energy systems work during physical activity with varying involvement, depending on the action’s duration and intensity.
PHOSPHAGEN (ATP-PC) SYSTEM
The phosphagen (ATP-PC) system harnesses ATP for highly intense activities lasting 10 to 30 seconds, e.g., jumping, sprints, and plyometric exercises.
THE GLYCOLYTIC SYSTEM
The glycolytic system uses carbohydrates to produce ATP for activities lasting 30 seconds to 3 minutes, e.g., boxing rounds.
Both the phosphagen (ATP-PC) and glycolytic systems occur in the cell’s cytosol and are anaerobic. The end product of glycolysis is pyruvic acid. When oxygen is present (aerobic respiration), pyruvate enters the mitochondria for oxidative metabolism.
In the absence of oxygen, it ferments to produce lactic acid. Lactic acid produced in muscle cells is transported through the bloodstream to the liver, where it is converted back to pyruvate.
