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

Yuri Elkaim, BPHE, CK, RHN
myTreadmillTrainer.com

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The Effect of Duration

Research consistently reports that a direct relationship also exists between the duration of exercise and EPOC. One study investigated the effects on EPOC of exercise duration (30, 45 and 60 minutes) at 70% VOmax.

They reported EPOC values of 6.6 liters of oxygen (33 calories over 2 hours), 14.9 liters of oxygen (74.5 calories over 3.4 hours) and 33 liters of oxygen (165 calories over 7.6 hours) for durations of 30, 45 and 60 minutes, respectively. The researchers concluded that increasing exercise duration significantly increased total EPOC.

In another study, women were asked to walk on a treadmill at 70% VO2max for 20, 40 and 60 minutes. The authors reported a significantly higher and longer EPOC following the 60-minute duration treadmill workout. The values were 8.6 liters of oxygen (43 calories), 9.8 liters of oxygen (49 calories) and 15.2 liters of oxygen (76 calories) for 20-, 40- and 60-minute durations, respectively.

In a similar study, subjects exercised for 20, 40 and 80 minutes at 70% VO2max and had EPOC values of 11.1 L (55.5 calories), 14.7 L (73.5 calories) and 31.9 L (159.5 calories) for each duration, respectively.

These studies suggest that given sufficient aerobic exercise intensity, exercise duration is also an important factor influencing EPOC and hence the amount of calories you will burn after an exercise bout.

Several studies have investigated the effects of combining high intensity with even longer duration. Maehlum and colleagues reported an EPOC of 26 L (130 calories) following 80 minutes of cycling at 70% VO2max in eight men and women. In addition, the subjects’ VO2 was still elevated by an average of 5% for 24 hours post-exercise!8 Several other studies have also confirmed these findings.

In studies investigating EPOC following shorter-duration exercise, the results are quite different. But do keep in mind that the following 2 studies used very moderate exercise intensities. In one of these studies, a very low EPOC average of 3.1 L (15.5 calories) was observed following 30 minutes of cycling at just 60%–65% VO2max.9 And, in another study, Sedlock and colleagues found that the average EPOC following 20 minutes of exercise at 75% VO2max was only 6.2 L (31 calories).

So I’m pretty sure that you can now see that an overwhelming number of studies conclude that EPOC can contribute significantly to overall caloric expenditure. However, it is important to keep in mind that EPOC results will vary depending on several variables including gender, the exercise modality employed, and most notably the intensity and duration undertaken.

I will elaborate much further on the variable “exercise modality” in much more detail in answering the second part to our initial question “What type of cardio is best for weight loss?” For now, just sit tight and keep reading, we will get to that in a few minutes.

Interval Training vs. Continuous Exercise

Here is another very important fact to remember – the majority of studies have concluded that intermittent aerobic exercise bouts (known as interval training) elicits a greater EPOC response when compared to continuous exercise bouts!

But before getting into the science, just so you understand, let me explain the difference between these two methods of training.

Continuous training is fairly straightforward. It involves exercising at the same intensity for a given amount of time. Pretty boring, eh? Well, your body certainly thinks so!

On the other hand, Interval training is highly invigorating as it involves repeating bouts of high-intensity and low-intensity efforts. For instance, if you are running this could mean sprinting for 20 seconds followed by jogging for 40 seconds. This sequence would then be repeated several times for a given amount time.

Interval training has a special place in my heart. It has been an integral part of all of my clients programs, including the men’s soccer program at the University of Toronto.

This method of cardio training also plays a fundamental role in my critically acclaimed iPod workout programs - Treadmill Trainer and Fitter U.

References:

1 Børsheim,E.,& Bahr,R.2003.Effect of exercise intensity, duration and mode on post- exercise oxygen consumption. Sports Medicine,33(14),1037–60.

2 Bahr,R.,& Sejersted,O.M.1991.Effect of intensity of exercise on excess post-exercise oxygen consumption. Metabolism,40(8),836–41.

3 Phelain,J.F.,et al.1997. Post-exercise energy expenditure and substrate oxidation in young women resulting from exercise bouts of different intensity. Journal of the American College ofNutrition,16(2),140–6.

4 Smith,J.,& McNaughton,L.1993.The effects ofintensity ofexercise on excess post- exercise oxygen consumption and energy expenditure in moderately trained men and women. European Journal ofApplied Physiology,67,420–5.

5 Chad,K.E.,& Wenger,H.A.1988.The effect of exercise duration on the exercise and post-exercise oxygen consumption. Canadian Journal of Sport Science,13(4),204–7.

6 Quinn,T.J.,Vroman,N.B.,& Kertzer,R.1994. Post-exercise oxygen consumption in trained females: Effect of exercise duration. Medicine & Science in Sports & Exercise, 26(7), 908–13.

7 Bahr,R.,et al.1987.Effect of duration of exercise on excess post-exercise oxygen consumption. Journal ofApplied Physiology,62(2), 485–90.

8 Maehlum,S.,et al.1986. Magnitude and duration of excess post-exercise oxygen consumption in healthy young subjects.Metabolism, 35(5),425–9.

9 Sedlock,D.A.1992. Post-exercise energy expenditure after cycle ergometer and treadmill exercise. Journal ofApplied Sport Science Research,6(1),19–23.

10 Sedlock,D.A.,Fissinger,J.A.,& Melby,C.L.1989. Effect of exercise intensity and duration on post-exercise energy expenditure. Medicine & Sciencein Sports & Exercise, 21(6),662–6.

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