When I looked at EPOC, I threw out a lot of data regarding the actual impact of exercise on the post-exercise calorie burn. Since that piece was on the long side to begin with, I decided to save some more concrete examples for today’s follow-up blog.
Semi-recapping from yesterday, the paper conclude that high intensity training can generate larger EPOC’s at least in terms of the percentage contribution. The paper suggested that values of a 7% EPOC for steady state work but 14% for interval work were approximately correct values so that’s what I’m going to use.
As I mentioned yesterday, and want to look at in more detail today, although 14% sounds impressively larger than 7%, this can be terribly misleading. 7% of a large number can still be more than 14% of a much smaller number even if the percentage contribution is higher in the second case. And no matter how you cut it, the majority of calories burned come during the workout, not afterwards. As you’ll see, the EPOC doesn’t amount to jack for any realistic amount of activity. Even for large amounts of high-intensity activity, the majority contribution of calories still comes from the exercise itself.
What I want to look at today is how those values might apply in the real world in terms of determining how different types of exercise affect energy balance. This is going to be a lead in to next week’s series of articles where I make some slightly more concrete statements about the role of either intervals or steady state exercise for fat loss. Which of course leads into comments on how to practically implement either one.
Now, in the illustrations below, I’m going to be using some values that may seem pulled out of thin air; they are not and I want to describe briefly where they are coming from.
I have a Power Meter based bike. That is, a bike that has special cranks to measure how much mechanical power I am putting out.
In addition to measuring my power output on the bike, it tells me how much total work I’ve done at the end of the ride in kilojoules; this can be converted to calories by multiplying roughly by 1. So 450 kJ expenditure is about 450 calories. Before I continue, let me explain this since anybody who knows math/physiology will realize that it’s not right.
Converting Power to Calories
To accurately calculate calories from kilojoules, you actually divide by 4.2 (so 420 kJ = 100 calories). Obviously it’s not one to one unless you’re one of the trainers on the Biggest Loser (bit of an in-joke there, you’d have to watch the show).
However, exercise efficiency while cycling varies from 20-25%, meaning that only that much of the actual caloric expenditure goes into power output. The rest is lost as heat.
So to figure total calories burned you re-divide by anywhere from 4 to 5 (depending on efficiency). If you assume 25% efficiency, you re-divide by 4. Essentially you divide kJ by 4 and then multiply back by 4. So you end up being able to roughly estimate calorie burn by simply taking kJ as the calorie burn at a 1:1 ratio. Ok, back to the article.
As well, I’ve checked the value on the powerbike using the Bodybugg (the little armband thingie that estimates energy expenditure based on body heat, movement and a couple of other things).
I’ve also recently checked the bike against the caloric expenditure from my new Polar RS800 watch and it is basically identical to the powerbike’s kJ reading with the Bugg being in close shooting distance of both (the value isn’t identical). My point being that the values I’m going to use, I consider accurate. I’m not making them up so that my math will support what I’m trying to argue.
Now, semi-tangentially, a lot of people on my forum have been using the Bugg and one thing that keeps coming up (so I might as well address it) is disappointment that an interval workout invariably ends up burning either about the same or less total calories than a similar amount of moderate steady state.
That is to say that 30 minutes of intervals may burn roughly 300 calories. But so does 30 minutes of moderate intensity cardio (for trained folks). And the intervals are a hell of a lot tougher.
How Does that Even Make Sense?
The reason of course is that the interval workout is alternating between very high caloric expenditures and very low expenditures such that the average expenditure still ends up coming out about the same. That is, say I do 1 minute intervals with 1 minute rest, alternating between 15 cal/min during the hard bit and 5 cal/min during the recovery. That’s an average of 10 cal/min. I can achieve that same 10 cal/min consistently with moderate intensity cardio. The second workout will be far easier to complete.
So if there’s a huge benefit to intervals, one place it might come is from the EPOC (note: there are other potential benefits of intervals that I’ll be addressing in future blog posts).
So I’m going to be focusing ONLY on EPOC here. Again, I’m going to assume a 7% EPOC for steady state cardio and a 14% EPOC for intervals and put those into some real world perspective.
Say I do 20 minutes of intervals and burn 200 calories. I get a 14% EPOC which is 28 whole calories. Total calorie burn = 228 calories.
Let’s say I do 20 minutes of steady state cardio and burn the same 200 calories. 7% EPOC which is 14 calories = 214 calories.
So, for an equivalent duration workout, the interval workout comes out a whopping 14 calories ahead due to the impact of EPOC. That will net me an extra pound of fat loss every 250 days (3500 calories / 14 calories per day = 250 days). Hooray. Clearly, for any equivalent length workout the interval training will always come out slightly ahead.
Except that you wouldn’t expect someone to do longer and and longer and longer interval workouts; the whole point of intervals (or one point) is that they are more time efficient, that you get all you need in somewhere between 4 and 20-30 minutes (depending on which expert you’re listening to and what they’re selling).
So it’s more useful to compare that 20 minute interval workout to longer steady state workouts which is what most would do in the real world.
Here are calculations for different length steady state workouts based on an average burn of 10 cal/min and a 7% EPOC.
30 minutes = 300 calories + 7% EPOC = 21 calories = 321 calories.
40 minutes = 400 calories + 7% EPOC = 28 calories = 428 calories.
50 minutes = 500 calories + 7% EPOC = 35 calories = 535 calories.
60 minutes = 600 calories + 7% EPOC = 42 calories = 642 calories.
Now lemme be generous and assume I’m doing 30 minutes of intervals with a 14% EPOC
30 minute interval session = 300 calories + 14% EPOC = 42 calories = 342 calories.
While this is certainly a few more (21) calories than the 30 minute steady state session, it pales in comparison to the longer sessions. Sixty minutes of steady state cardio burns 642 calories, compared to 342 from the interval training. Looking purely at energy balance (and, again, there are other issues to consider) and fat loss, which will get me lean faster?
But you say, I don’t have time to do an hour of cardio, I get bored doing cardio, etc, etc. Those are practical considerations (which are, of course, important), not physiological ones and I’ll be coming back to those in next week’s continuation of the series. Purely physiologically speaking, the EPOC argument just doesn’t hold up. Not only is the EPOC from any realistic amount of intervals or steady state cardio irrelevant, short interval sessions still burn far LESS calories than longer steady state sessions.
The intervals only come out a TINY bit ahead if you compare workouts of identical length and even there the difference is absolutely insignificant.
But between now and Monday, here’s a question for my readers (or the pro-interval crowd) to ponder:
Let’s say I want or need to train daily for fat loss (most athletes train every day, as do most dieters).
Which am I more likely to do on a day-in day-out basis? Which is more likely to lean me out faster? Which am I more likely to BE ABLE to do daily (from a recovery standpoint)?
- 30 minutes of intervals: burning 342 calories including EPOC.
- 60 minutes of moderate teady state cardio: burning 642 calories including EPOC.
Note: Yes, I’m making it sound like it’s an either/or choice here which it’s clearly not. But just consider that one issue in isolation for now.
Note again: I’d note again that this series of articles is absolutely NOT meant to be against interval training as one tool in the fat loss arsenal. My issue is simply with the uncritical claim being made that intervals are always superior to steady state (or that steady state is somehow detrimental to fat loss) as well as some of the arguments being made to support the contention that interval training is any of these things.
Next up in the series, Steady State vs. Intervals: Explaining the Disconnect
Similar Posts:
- Steady State vs. HIIT: Explaining The Disconnect
- Explaining Exercise Efficiency
- EPOC: Excess Post-Exercise Oxygen Consumption After Exercise
- A 45-Minute Vigorous Exercise Bout Increases Metabolic Rate for 14 Hours
- Steady State and HIIT
Obviously b
This is a really good series.
As I can recall in the general fitness / bodybuilding world, all this intervals stuff really got going when Clarence Bass discovered Tabata / Tremblay’s work and promoted it in one of his books and on his site. (well that is where I first came across it anyway). It was only after that that the whole world started doing tabata this and tabata that. However from what I recall the Tabata study at least was primarily concerned with increasing VO2 max rather than thinking about fat burning. There was a study somewhere as well that saw intervals improving endurance performance. I suppose what I’m rambling is that the original thing was about improving fitness rather than fat burn.
By the way have you looked at Gail Trap’s work on intervals that got a bit of exposure on the internet last year: e.g
https://ajpregu.physiology.org/cgi/content/abstract/293/6/R2370
or
https://www.nature.com/ijo/journal/vaop/ncurrent/abs/0803781a.html
Cheers
Chris
“this can be converted to calories by multiplying roughly by 1. So 450 kJ expenditure is about 450 calories.”
??
chris
the first interval fat loss stdy I recall wa the Tremblay study which I reported in my first book back in 1996. Then Shawn Phillips wrote about intervals for fat loss in MM2k.
I’ve read the work you cite, yes. And this is why I’m trying to make it clear in this series that I am not ANTI-interval. Clearly it has benefits under certain conditions (note that it’s usually being tested in isolation with no resistance training or diet control which is a far different thing than doing it while lifting or watching diet).
Artie, I left out the conversion b/c I thought it would confuse people.
To convert kj to kcal, you divide by 4.2 (420 kJ = 100 calories). So roughly by 4. However, only ~25% of the total calories burned during cycling goes to producing work (this is the average efficiency for a cyclist). So you multiply back by 4 for total calorie burn. Hence it’s roughly a 1:1 conversion.
Lyle
Personally, I am much more likely to do B every day.
That is one thing that the BodyBugg did for me– realizing that certain high intensity cardio type activities don’t burn nearly as many calories as they FELT they should has made me drop them in favor of more pleasant/”easier” ones. (I don’t enjoy busting ass for very little reward.)
People are much more likely to keep doing something when they don’t come to dread it. :p
I think both have their place, but– I do longer duration steady state for caloric/fat burn and higher intensity interval type stuff for cardio fitness. Two separate goals in my mind.
Hey, I liked this blog. It was moderate intensity, long duration cardio that contributed to my own weight loss. But, once I hit a certain weight, moderate cardio seemed to no longer work for me for weight loss, though certainly did help me maintain.
However, about a month ago, I started much shorter but much more intense cardio, and I started losing again. During that month, I dropped 2% in body fat, from 11%. Stopped for now, because it was burning me out, and I did achieve the results I was after. For the next six months, I’ll work on gaining mass.
Then this kills the myth about gerilja cardio?
Your math is seriously flawed, and it ruins your calculations. In particular, EPOC is excess oxygen consumption OVER the resting (or baseline) metabolic process, after exercise.
Let’s compare. Your baseline metabolic rate is, say, 80 kcal an hour. Now, go ahead and do an hour of moderate intensity steady state aerobic exercise. Your EPOC is now about 7%, which means that in the hour after you are done, you will burn 80 kcal + 7% of 80 kcal (about 85 kcal) by doing nothing but resting and recuperating.
Now try a high intensity interval training regimen, like Tabatas, which raise EPOC to 14%. In the hour after exercising, you will have burned 91 or so kcal by doing nothing but resting and recuperating. Now, the thing about High Intensity Interval training is that it elevates your EPOC for up to 36 hours. Granted, it declines linearly (more or less), so it’s not like it will be 14% for 36 hours. It will start off at 14%, and decline by about .4% every hour. So, during the second hour, you will have used 80kcal + 13.6% of 80kcal (about 91 kcal), just by resting and recuperating. In the third hour, you will use 80kcal + 13.2% of 80kcal (about 90 kcal). Do the math, and you will see that if you do HIIT, and reach a peak EPOC of 14%, you are raising your resting metabolic rate by an average of 7%, for 36 hours. (Again, it’s a big triangle, with 14% right after exercise, and 0% at about 36 hours after exercise. If you cut the peak off, and fill in the valley, you will get a 36 hour wide, 7% tall rectangle)
If we assume that EPOC declines at the same rate (.4% oxygen consumption per hour), then we see that steady state aerobics will raise your oxygen consumption by about 3.5% for 17 hours. Again, this 3.5% figure is an average, based on doing 7% in the first hour, 6.6% in the second, 6.2% in the third, and so on. But even this assumption is not borne out by research. The fact of the matter is that EPOC declines more quickly after moderate intensity aerobics than after HIIT. Even if we don’t take this into account (the quicker decline), you use less than a quarter of what you would have done with HIIT.
So if you do 64 reps, at an estimated kcal each, and your RMR is 80kcal an hour, Tabatas will be responsible for a little over 265 calories over 36 hours. For four minutes of effort.
Even better, HIIT improves anaerobic fitness as well, which has the effect of raising your RMR even after EPOC is over. Moderate intensity steady state hardly improves your anaerobic fitness, and so does not raise your RMR, excluding EPOC.
In “absolute” terms, MISS is better. But HIIT hits the sweet spot between time and effort put in and gain put out. You reach a point of diminishing returns. You will still get more benefit if you do more, but less benefit for each additional minute.
On the other hand, the most important factor for “fat loss” is diet, followed closely by anaerobic strength. Eat about 200 calories less than your maintenance diet would demand, do Tabatas and mixed weight training, and you will lose a pound every 7-8 days. That rate will increase some as you gain lean muscle mass (it will eventually decline again).
Please read the research review by Laforgia on the site, the math is not wrong. The EPOC percentages are related to the energy cost of the exercise bout, it does NOT represent an increase above baseline metabolic rate. As well all of your assumptions about the rate of decrease of EPOC are completely incorrect. No way does metabolic stay elevated for 24 hours following training so your math based on those assumptions are totaly incorrect; that’s an old myth. Seriously, read the research review. It’s the first link in the article.
The other things you discuss in terms of increasing fitness are also discussed in other articles in this series.
Sorry, the “myth” has been proven in multiple papers. Your math is wrong, and it is wrong because you don’t even understand the basic definition.
“The EPOC effect is greatest soon after the exercise is completed and decays to a lower level over time. One experiment found EPOC increasing metabolic rate to an excess level that decays to 13% three hours after exercise, and 4% after 16 hours. Another study, specifically designed to test whether the effect existed for more than 16 hours, conducted tests for 48 hours after the conclusion of the exercise and found measurable effects existed up to the 38 hour post-exercise measurement.”
(https://www.springerlink.com/content/g9w8mhl6yjc1r9yh/)
“Excess postexercise oxygen consumption (EPOC). Oxygen uptake above resting
values used to restore the body to the pre-exercise condition.”
https://www.marshall.edu/etd/masters/Asano-Shinichi-2005-ma.pdf
Did you read the LaForgia paper linked at the top of this article? It reviews all of the pertinent research. Because you managed to cherry pick one of the SINGULAR papers showing a massive prolonged increase in EPOC following resistance training while ignoring the rest that showed no such thing. Please read the LaForgia research review for a complete look at the topic.
Quoting from the conclusion from the LaForgia paper I have now recommended you read my review of twice:
“Notwithstanding the underestimation of the EPOC associated with high-intensity intermittent work, it appears that such an EPOC only comprises a small proportion (*14%), albeit larger than for equated submaximal work (*7%), of the net total oxygen cost of exercise. The EPOC therefore does not pose a significant additional acute energy balance problem for athletes performing high-intensity intermittent work. How- ever, the cumulative effect of the EPOC over a 12- month period with regular training (three times a week) could impact significantly on energy balance and produce an expenditure equivalent to the energy stored in *1.5 kg of adipose tissue. The utility of supramaximal interval training for weight loss is nevertheless limited because this type of training is beyond the capabilities of non-athletes.”
Note that even if the EPOC can be mechanistically related to an increase over resting metabolic rate (I stand corrected here), the total EPOC is still related to the energy cost of the activity itself.
That is the total EPOC is related to the energy cost of activity and my math is correct in this article.
EPOC can only be 1% for highly trained people. If you do HIIT style workouts 3 times a week then you would start to fall into this category. Doing 4 minutes of HIIT described above will not provide an EPOC response unless you were doing the entire 4 minutes flat out.
The other problem with HIIT is that you will be subject to overtraining very quickly.
Dave if you do tabatas it will provide an EPOC response, if you do them properly like burpies, you’ll still be trying to catch your breath 10minutes later.
And that EPOC amounts to jack squat
https://www.bodyrecomposition.com/research-review/research-review-effects-of-exercise-intensity-and-duration-on-the-excess-post-exercise-oxygen-consumption.html
@ajs, your are correct. I just finsihed a HIIT workout for about twenty minute, got my heart rate past 190, I’m 31 btw, and now about 40 minutes after my body is still trying to recover. I also do steady state cardio for about one hour or so regularly and I can tell you that I have never felt like this….ever…including running a half marathon. To lose those last few pounds and really lean up, HIIT with EPOC is where its at!
When it comes to fat loss, if something sounds too good to be true, it usually is. That’s why I was always skeptical of the claims made about HIIT. For just 30 minutes a day 3 times a week, you too can have six-pack abs! Sounds like one of those infomercials you see on TV. Now I’m not saying HIIT is a waste of time. I just think its supporters are exaggerating its effectiveness in order to appeal to folks looking for shortcuts. People are also looking for something new. For years, we were told that steady state cardio was the best way to burn fat, but people got tired of hearing that. So along came HIIT(which really isn’t that new) promising people that they didn’t have to do hours of boring cardio or risk looking like a marathoner. And as we’ve seen above, the anti-cardio crowd will happily cherry pick the studies that support their argument or even try to scare people by telling them that cardio will eat up all their muscle. Thanks Lyle for yet another great article.
You will be at least a little be more focussed in the workout intensity regarding to get as much you can the more accurate kcal expenditure. I realize that your paper is aimed mainly to the EPOC impact -in fact no objection about your conclusions- but I don´t understand where you basis on for HIIT kcal expenditures.
Gentlemen-
Why not combine the two? Do your 3 sets of 4 minute tabatas with Kettlebells, bringing your HR to 170, (rest in between sets), then enjoy your long, slow burn run or bike. The slow burn , ala moderate speed jog/run for 30 mins, will be a refreshing break from the all out effort of the V02max Tabata.
I don’t see why everyone thinks they have to be right. I noticed the only person who is stating personal experience for both sides has good things to say about both. if you ask me, people should do whatever works. long winded moderate cardio was more straining for me because I have thick bones a naturally bulky upper-body and so jogging a mile was heavy on my legs and meant not being able to walk normal the next day.
With that being said, along with interval strength training, I did laps around the soccer field, mixing jogging and sprints. In about a month and a half I lost 11 pounds (despite building muscle weight) without any diet modification and work out times being only 10 to 15 minutes long. More importantly my resting heart rate dropped from a dangerous ninety something to an impressive 60 beats per minute since the time I started interval training. So whatever numbers and studies you want to throw out there, your not gonna tell me its not effective.
Don’t get me wrong, Im not knocking moderate cardio, plenty of people have lost a life altering amount of weight through that method, but that fitted their body type. I’m just saying, let people try for themselves before you scare them away from potential exercise methods they might enjoy.