Hi! I am new to this blog and have enjoyed reading the posts. A question regarding EPOC. It's a follow-up question to the thread that was posted regarding the guy promoting 4-min abs on the Today show. He stated that resistance training does something that aerobic exercise does not and that is provide a higher/longer EPOC. Can someone explain the physiological rationale behind this statement? Why and how? Thanks!
Excess post-exercise oxygen consumption (EPOC) is a measurably increased rate of oxygen intake following strenuous activity. The extra oxygen is used in the processes that restore the body to a resting state and adapt it to the exercise just performed. These include: hormone balancing, replenishment of fuel stores, cellular repair, innervation, and anabolism.
EPOC is accompanied by an elevated consumption of fuel, some studies found that included fat, but others did not find a similar effect. None of the studies set up to investigate the effect used very large sample sizes, possibly due to the cost of conducting the experiments.
The EPOC effect is greatest soon after the exercise is completed and decays to a lesser level over time. One Experiment found EPOC increasing metabolic rate to an excess level that decays to 13% 3 hours after exercise, and 4% after 16 hours. Another study, specifically designed to test if the effect existed for more than 16 hours, conducted tests for 48 hours after the conclusion of the exercise and found measurable effect existed up to the 38 hour post-exercise measurement. (Schuenke 2002)[1]
Studies show that the EPOC effect exists after both anaerobic exercise and aerobic exercise, but all studies comparing the two show that anaerobic exercise increases EPOC more than aerobic exercise does. For exercise regimens of comparable duration and intensity, aerobic exercise burns more calories during the exercise itself [1], but the difference is partly offset by the higher increase in caloric expenditure that occurs during the EPOC phase after anaerobic exercise. Anaerobic exercise in the form of high-intensity interval training was also found in one study to result in greater loss of subcutaneous fat, even though the subjects expended fewer than half as many calories during exercise.[2] Whether this result was caused by the EPOC effect has not been established, and the caloric content of the participants' diet was not controlled during this particular study period.
In their 2004 survey of the relevant literature, Meirelles and Gomes found: "In summary, EPOC resulting from a single resistance exercise session does not represent a great impact on energy balance; however, its cumulative effect may be relevant.".[2] This is echoed by Reynolds and Kravitz in their survey of the literature where they remarked: "However, it should be emphasized that the overall weight-control benefits of EPOC, for men and women, from participation in resistance exercise occur over a significant time period, since kilocalories are expended at a low rate in the individual postexercise sessions."[3]
What is clear is that the EPOC effect is greater the greater the intensity of the exercise and the greater the time spent during the exercise phase. Most studies found a linear relationship with time of exercise and the effect. One found a curvilinear relationship between the intensity and the EPOC effect, though others found a linear relationship.
Thanks for the reponse! I guess my frustration in the field is that fitness professionals may say correct information, but use it in the wrong context. Often times that leaves lay-people, and even us on the field confused. You (you in general terms) can say that there is SOME research that supports that EPOC is higher after resistance training versus aerobic training. But, then you need to define what type of resistance training the research supports. HIIT is definitely different than 4 minutes of slow ab exercises, just as it's different than 30 minutes of high intensity aerobic exercise. Sorry, just a rant. Thanks for the post. It was great reading!
I had to write a hefty term paper for Comparative Physio of Exercise class a couple of years ago - and my assigned topic area was "does EPOC vary with fiber type" - I'm sure I have the various references/citations at home somewhere if you want to read at least the abstracts to see what they were comparing. If I can find them and then find links for them, I'll try to put them here for you to review. (I'll try to include only the human studies - but since it was a Comparative course, I had to include studies with rats, fish, lizards, etc. as well)
Lisa will no doubt come back with some details for you, but I think the greater point you'll find is that the greater the intensity (over a given period of time) the greater the EPOC. No one is saying running doesn't create EPOC it's just a matter of intensity. You'll certainly get a higher EPOC sprinting intervals for 4 minutes then you would from 4 minutes of crunches. However you'll probably get a greater EPOC from 4 minutes of deadlifts then the sprinting (more total weight moved, therefore more power generated/required = greater EPOC).
On a personal level I try my best to balance my desire to run far and fast with an equal desire lifting heavy things. I find that when I favor the running I get fatter but also drop weight. When I favor the lifting I gain muscle and lose fat.
Edit: Here is a nice little article on measuring intensity with a link at the end to a calculator that will measure your power output.
Quote:
What is intensity? Intensity is defined as the work performed in a certain amount of time. Intensity equals power output, or watts produced. This power output can be measured based upon your body weight, height, the amount of weight you're using, and the amount of time it takes you to move that weight a certain distance. Intensity is relative to one's own psychological and physical tolerance and is the reason that all ages and abilities can workout together in a single CrossFit class using different weights and achieving different times. This relative power output is why you shouldn't get upset if there's someone who finishes a workout two minutes ahead of you, but performed 25 lb. deadlifts instead of the 95 lb. deadlifts you did. Additionally, if you feel like you've reached your max potential for a named workout like "Fran", then add ten pounds the next time it comes up and go hard and fast. You might end up with a slower time, but your power output may go up. From now on, look at your workouts from the perspective of power output instead of simply how fast you can go. If you want to improve your performance, measure your power output for various exercises and workouts and strive to improve your intensity level.
Here's an example of power output for men and women. Take an average 6' tall man weighing 200 pounds who performs 20 pullups in 30 seconds. That amount of work produces about 320 watts of power. Likewise, an average woman who is 5'4" tall, weighs 120 pounds, and performs the same number of pullups in 30 seconds produces 169 watts of power. In order for the 120 pound woman to produce the same amount of watts as the 200 pound man, she would have to perform her 20 pullups in 15 seconds, or add 80 pounds of weight and perform the pullups in the same amount of time as the man. Should the two even be compared? Probably not. So what good is this measure of intensity, or power output?
Power output is the essence of CrossFit and the reason why CrossFit creates such an incredible neuroendocrine response in the body, or the reason why so many of our CrossFitters see such dramatic changes in their body composition, strength, and overall fitness level. If power output is such a key ingredient to CrossFit, then it should be measured. To make this easy, play with your calculations by using the power output calculator from the Performance Menu. Click HERE.
of course, with these studies, they compare what they want to compare and control what they want to control - and we are stuck making sense of those results even if it isn't our specific question. That's why you have to see 10s of studies and their results and basically form your own option as a mini-review of the literature.
For example see this study where they designed two exercise protocols and controlled for same O2 consumption during the exercise period - and compared EPOC for the next 60 mins (not the next 24hrs, probably not the WT protocol we'd like, since they matched on O2 consumption we assume the circuit was as aerobic as the treadmill rather than anaerobic, etc). SpringerLink - Journal Article
I had to write a hefty term paper for Comparative Physio of Exercise class a couple of years ago - and my assigned topic area was "does EPOC vary with fiber type"
And what was your conclusion? Please edumacate us. But only with the executive summary.
hmm - I'll have to find my paper and read the conclusion section and get back to you - something about probable differences in fiber type recruitment in training being responsible for the differing magnitude of EPOC effect but during the EPOC period different fiber types being responsible for the actual post-exercise O2 consumption. As I recall, there was research showing red muscle fibers consuming the O2 (as one would expect) and then how substrates were moving locally between cells and in the bloodstream in order for the rebuilding/recovery of the white muscle fibers to take place. So - it depends on what question you are actually asking - causing higher EPOC or what is actually doing stuff during EPOC and what are those things that are consuming the excess O2 during the EPOC period - and why.
[ I remember one study you might appreciate where they were doing hard cycling - either sprints or just high intensity and the subjects had one arm in a sling (inactive) - and they measured increased uptake in the deltoid of lactate (which was then reconverted to pyruvate and oxidized) - so the inactive red muscle was helping the lactate threshold / exercise level by clearing that metabolite - so arms can be important in cycling) ]
Hmm. that is very interesting about the cycling, inactive muscles and Krebs.
The question I was asking was just more out of intellectual curiousity on what is actually 'doing stuff' during the process, not for anything practical. Since I teach, my mind works that way. Thanks for the reply.
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