What is EPOC and Why is it Your Fat Burning Friend?

Yuri Elkaim, BPHE, CK, RHN
myTreadmillTrainer.com

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Exercise after-burn, also referred to as excess post-exercise oxygen consumption (EPOC), is the number of calories expended (above resting values) after an exercise bout.

EPOC represents the oxygen consumption the body uses to return to its pre-exercise state.

The physiological mechanisms responsible for increased metabolism following exercise include oxygen replenishment, phosphagen (ATP-PC) resynthesis, lactic acid removal, increased ventilation, and increased blood circulation and body temperature.

Your body can take anywhere from 15 minutes to 48 hours to fully recover to a resting state. Studies have found that the magnitude and duration of EPOC depend on the intensity and duration of exercise.

The Effect of Intensity

Research demonstrates that the intensity of your cardio workout bout has the greatest impact on EPOC.

As exercise intensity increases, the magnitude and duration of EPOC increase.

In a study by Bahr and Sejersted (1991), subjects completed exercise bouts at intensities of 29%, 50% and 75% of their VO2max for a period of 80 minutes. The greatest EPOC was reported following the highest exercise intensity (75% VO2max) with 30 liters of oxygen consumed or 150 calories burned.

(Note: it is well understood in all exercise physiology and nutrition texts that for every liter of oxygen consumed, approximately 5 calories are burned.)

Additionally, the duration of EPOC following the highest intensity exercise was significantly longer when compared to the lower-intensity bouts (10.5 hours versus 0.3 and 3.3 hours). That’s an astounding difference!

These results are very powerful and demonstrate once again that intensity is king when it comes to burning calories. So even if the calorie count on your cardio machine isn’t what you want it to be don’t worry – the real fat burning benefit is taking place for several hours after your session!

One of the reasons for this occurrence is that after exercise your body is restoring its depleted glycogen (carbohyrate) reserves, therefore, it turns to fat for its primary fuel source!

In a more recent study, Phelain and his colleagues also investigated the effects of low-intensity (50% VO2max) and high-intensity (75% VO2max) exercise on the EPOC response.

Although the energy expended during both exercise bouts was the same 500 calories, the higher intensity bout caused a significantly higher EPOC than the lower intensity bout – 9 liters of oxygen (or 45 calories) versus 4.8 liters (or 24 calories).

I wrote an article some time ago entitled “Why Sprinters Are So Lean” which talked about the training methods that sprinters utilize to achieve their goals and, as a by-product, a fit and toned muscular body.
And guess what?

Do you think that sprinters partake in long, slow runs?

Absolutely not!

If you’ve ever seen a sprinter’s training session the one thing you would have noticed is the intensity at which they train. They perform near maximal efforts for short periods of time. This includes their resistance and cardio training. And the results speak for themselves. How many sprinters do you know of that are fat and flabby?

Let’s have a look have at some more studies...

A 1993 study by Smith and McNaughton investigating both male and female subjects, reported significant increases in EPOC following the highest exercise intensity. (What a surprise!)

The subjects in this study exercised at 40%, 50% and 70% of VO2max for 30 minutes. At the highest intensity EPOC was 28.1 L (140.5 calories) for men and 24.3 L (121.5 calories) for women...

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