What is EPOC?

I am sure many of you, if not all, have been told or heard that increased physical activity burns more calories at rest; I want to assure you that this is correct! But if I may, I’d like to go into a little more detail and explain just exactly how and WHY this is.

Lets get right to it…

Following exercise, physiological processes do not immediately return to baseline. In fact, studies have shown metabolism to remain elevated for HOURS following resistance exercise (Schuenk et al., 2002)! However, the extent of the physiological effects post exercise doesn’t just depend on duration; but even more so, on INTENSITY.

One of the ways to measure post-exercise activity within the body is something called, excess post-exercise oxygen consumption or EPOC.

By definition, it is the difference between the total oxygen consumed in recovery and the total oxygen theoretically consumed at rest during the recovery period. For example, if a total of 5.5 L of oxygen were consumed during recovery until your resting value of .310 L/min was achieved within 10 minutes, your EPOC would equal 5.5 L – 3.1 L (.310 L x 10 min) or 2.4 L. Now, I know right now you’re probably thinking “WHAT THE?!”. In English? This simply means that the combined physiological effects elicited from the previous exercise session AND during recovery required an ADDITIONAL 2.4 L of oxygen to return back down to your resting rate of .310 L/min (Exercise Physiology, 7th Ed.).

How Does EPOC Reflect Post-Exercise Metabolic Activity

Allow me to provide a graphical representation (EP, 7th Ed.):

The FAST component (straight red line) is a single exponential curve that corresponds to the decline of oxygen consumption and represents the first phase of recovery immediately following cessation of exercise. The SLOW component (straight orange line) corresponds to the decline of oxygen as well but as you can see, at a much slower rate! Also, pay attention to how long in time the slow component is present following very high intensity exercise!

As you can see, as the intensity of exercise increases, so does the amount of recovery needed. This increases the total amount of post-exercise oxygen consumption (the yellow part)!

How Does Post-Exercise Metabolic Activity Contribute to Calorie Burning

As you know, there are three main macronutrients that encompass sources of calories in food: carbohydrates, fats and proteins. Fats, btw, have the highest concentration of calories per gram – 9 Cal/g! However, when you participate in high intensity or maximal exercise, you deplete much of these nutrients as well as substrates that combined with circulating enzymes, are required for normal physiological function. So to replenish these missing components of biological work during recovery, the body must “oxidize” or burn ADDITIONAL fatty acids to synthesize the energy needed to recover what was lost and to return all physiological function back to normal levels.

Thus, the higher the intensity of exercise – the longer the EPOC recovery duration – the larger the rate increase of fat metabolism at rest! Which means…more calories burned at rest!

I’d rather not fry your brain (and mine) any further so in a future post, ill go over resistance training as a means to encourage an extended EPOC!

Take care everyone,

PJ