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TOPIC: Fit vs unfit: calories burned doing identical exercise?

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May 19, 2010 7:45 AM
Does someone who is more physically fit burn more, less, or the same amount of calories doing the identical exercise at the identical rate with weight of the two individuals being the same? Basically if two people, one fit and the other not as fit, run 5K in the same time and both have equal weight, are the calories burned equal? Sure the fitter person's heart rate and perceived effort will be much lower but are the calories consumed the same?

I have been trying to find an answer out on the net and have been unable to find any study that actually measures this. Most just show that an athlete exercising at 80% burns more calories per minute than a non-athlete exercising at 80%.

I can see all three possibilities.
1. Fitter burns less: A fitter person's muscles are more efficient in use of energy and can produce more mechanical work per calorie. But are their muscles really more efficient at creating work per calorie or more efficient at producing work per gram of muscle?
2. Fitter burns the same: Work is work and it takes about the same total energy to move the same mass through the 5K. Muscles do not become more efficient per calorie, simply more efficient per gram.
3. Fitter burns more: Assuming the fitter person has more muscle mass for the same total weight, that mass burns more calories doing the identical exercise but has the ability to burn many times that rate if pushed. Like a small cylinder engine getting better mileage than the V8 in the same car driving at 60 mph.

The reason I am asking is my HRM (Polar F11) is showing lower calories burned because as I get fitter, I am able to bike longer and faster but my heart rate is going down. Using it as a guide for exercise calories I may not be eating enough to cover the actual calories burned. The HRM has OwnIndex (a VO2Max calculation) but its limitation is it cannot determine VO2Max in a vacuum. A sedentary person and a top athlete or anyone in between can generate identical HR patterns so the HRM can only compute an accurate VO2Max if it knows which person is the top athlete and which is the couch potato. Therefore it doesn't really work for someone like myself who has been exercising heavily for the last 5 weeks and clearly notice an improvement in fitness unless I change my activity level for the last 3 months and that seems specious at best.

Does anyone have a references to studies that answer this question?
May 19, 2010 7:56 AM
Yes in theory, as you become fit doing the same exercise you will burn less calories and have a lower heart rate. This is one of the main reasons to switch up your exercise routine every 4-6 weeks to shock your system. That being said, the more muscle mass you have the more calories you burn as muscle burns more calories than fat. So you would have to assume that the 2 people have the same body fat %, as, from my understanding, if you weighed the same with different % body fat the one with more muscle would burn more calories at the same intensity, or in your example the gap would be smaller between the 2 with the amount of calories burned.
Edited by erickirb On May 19, 2010 7:58 AM
May 19, 2010 8:04 AM
For such a great post I'm afraid that I don't know the answer.

I would say that my heart rate monitor is a god send because it is a Polar so syncs up to the treadmill and Elliptical. When I first started to be in the fat burning all I had to do was WALK at level 3. Now I barely break a sweat before level 8.

My fat burning zone is somewhere between 120 and 135 so I use the heart rate monitor to constantly push me to keep it in this range. I run between level 10 and 12 which is double what I used to be able to. I am guessing that because I am pushing myself ever harder to maintain the fat burning zone I am still burning around the same amount.

I would say that if it was unfit vs fir then the fit would have to really ramp up the effort to match.
  773631
May 19, 2010 8:04 AM
Great question, I am only giving my opinion, no studies to back it up. But as you increase your capacity for work per minute(fitness level), your intensity will go up enough to allow for the amount that your heart rate will decrease. I think the amount of calories lost would be about the same because of that.
May 19, 2010 8:07 AM
Muscle cells build more mitochondria in response to the demands placed upon them by exercise. Cells themselves become more efficient. The type of muscle used during exercise will drive which cells develop.

Ultimately, if you can get your heart rate to the same point (same weight and age and other conditions the same), you should ideally burn the same amount of calories. But, as you train your body, and your cells become more efficient at waste exchange, it gets harder to raise your heart rate to that same max (for that same exercise).

Typically, as you get healthier and more conditioned, both resting heart rate and max heart rate for identical exertion will drop. That's why you can push harder longer-because identical workouts will require less and less perceived exertion as you get more fit.
May 19, 2010 8:10 AM
QUOTE:

Yes in theory, as you become fit doing the same exercise you will burn less calories and have a lower heart rate. This is one of the main reasons to switch up your exercise routine every 4-6 weeks to shock your system.


But where is the data that shows you actually burn less calories as an exercise is perceived to be easier? Sure the routine becomes easier as your body improves its fitness but perceived effort and calories burned at not the same thing. Switching up routines is necessary to improve fitness to the next level but it doesn't directly have to do with burning calories as in you don't change routines just so you can increase calories burned and that increases fitness.
May 19, 2010 8:16 AM
QUOTE:


But where is the data that shows you actually burn less calories as an exercise is perceived to be easier? Sure the routine becomes easier as your body improves its fitness but perceived effort and calories burned at not the same thing. Switching up routines is necessary to improve fitness to the next level but it doesn't directly have to do with burning calories as in you don't change routines just so you can increase calories burned and that increases fitness.


Honestly, If I were you and really needed to see the hard data, I would go to my local university library and use their search engines to search for journal articles related to this topic. Use www.pubmed.gov and start there.
  817637
May 19, 2010 8:21 AM
I've always heard you burn less and I believe it. Here's why:

When I first started on the elliptical, I put my weight in at 170. I could easily burn 300 calories in 30 minutes. Yesterday, at 160, I was on for a total of 25 minutes (including cool down, which I only cooled down for about a minute just for efficiency purposes) and only burned 268 while consistently burning 10.5-11 calories per minute. I had to work harder to get up to 10.5 than I used to even 5 lbs ago!!! I have to now be to the point where I think my legs will fall off AND KEEP GOING to even get 10x the time I'm on. I planned for 270 because I honestly felt I could make it but I just couldn't do it. Not because I was fatigued...it just didn't happen.

Hope that makes sense, it did in my brain, haha! Also, when I take walks...I used to be able to burn over 300 calories walking for 30 minutes (obviously slower than than on the elliptical) and now I'm lucky if I hit 150 going for 25 minutes.
  746692
May 19, 2010 8:37 AM
QUOTE:

Does someone who is more physically fit burn more, less, or the same amount of calories doing the identical exercise at the identical rate with weight of the two individuals being the same? Basically if two people, one fit and the other not as fit, run 5K in the same time and both have equal weight, are the calories burned equal? Sure the fitter person's heart rate and perceived effort will be much lower but are the calories consumed the same?

I have been trying to find an answer out on the net and have been unable to find any study that actually measures this. Most just show that an athlete exercising at 80% burns more calories per minute than a non-athlete exercising at 80%.



I think you answered your own question and the study you found is the key:
More fit person (MF) burns less than Less Fit person (LF) doing exact same thing. (we are only talking calories above and beyond BMR associated with the exercise).

The study you found used a percent of max., or an 'intensity' if you will. 80% for MF is going to be an exercise that is harder/longer/faster/etc than 80% for LF. IE MF may be able to run 5 miles in 30 minutes at 80% and LF may only be able to run 3 miles in the same time at 80%.

So when they both do EXACTLY the same exercise MF is going to be using a smaller %, therefore less calories (in all but some mathematical exceptions as MF and LF approach being about the same).

However, 80% for MF versus 80% for LF represents MF doing more total work after the same period of time, and also burning more calories.
May 19, 2010 10:05 AM
QUOTE:


I think you answered your own question and the study you found is the key:
More fit person (MF) burns less than Less Fit person (LF) doing exact same thing. (we are only talking calories above and beyond BMR associated with the exercise).

The study you found used a percent of max., or an 'intensity' if you will. 80% for MF is going to be an exercise that is harder/longer/faster/etc than 80% for LF. IE MF may be able to run 5 miles in 30 minutes at 80% and LF may only be able to run 3 miles in the same time at 80%.

So when they both do EXACTLY the same exercise MF is going to be using a smaller %, therefore less calories (in all but some mathematical exceptions as MF and LF approach being about the same).

However, 80% for MF versus 80% for LF represents MF doing more total work after the same period of time, and also burning more calories.

I'm not following your logic. We agree that:
1. A more fit person at 80% effort burns more calories per minute than a less fit person at 80% effort.
2. A more fit person uses less percentage of maximum effort than less fit person doing the identical work.

However I don't see how you can make the leap that in case #2, the more fit person uses less calories. We already agree that in case #1, the more fit person burns more calories per minute when effort is equal and work is unequal. Therefore the effort must be unequal when the calorie burn rate is equal between the two. The question is "How unequal?"

I looked on the www.pubmed.gov website and could not find anything on the subject. Maybe researchers think the answer is so obvious that it doesn't need a study.

Given that most cardio machines and internet calculators only use weight * time * rate of work to estimate calories so that a 6'2" 200lb very fit man will show the same number of calories burned as a 5'1" 200lb woman that hasn't exercised in forever for the same workout and that HRMs use weight * time * some formula using fitness, max heart rate, resting heart rate, and % of max heart rate effort to compute calories, it seems like mechanical work is mechanical work when it comes to calories burned. There is likely to be a small percentage difference but not that much for most people.

So HRMs like my Polar F11 that only uses weight, time, HR, and fitness level to calculate calories and does not include actual work like distance and exercise type, it may not be very accurate when fitness is changing relatively rapidly during the initial 3 months from couch potato to very active.
May 19, 2010 10:05 AM
this is an interesting topic.

I think both are important to do.
May 19, 2010 10:15 AM
QUOTE:



So HRMs like my Polar F11 that only uses weight, time, HR, and fitness level to calculate calories and does not include actual work like distance and exercise type, it may not be very accurate when fitness is changing relatively rapidly during the initial 3 months from couch potato to very active.


Yup - also, on top of that your polar came up with its algorithm (and coefficients) by being based on observable/measurable activity across large samples (such as running and bicycling).

and to clarify case # 2, you are right overall, but the way i am bounding it is like this: lets only focus on calories used to do the exercise (not all the other calories needed to maintain muscle/BMR etc.). Then when I do that, I can think of the calorie burn rates. All else equal, the two rates are different and MF is burning less than LF. Of course there are lots of other factors that aren't usually equal, such as body weight, but at least you can get to the heart of the matter, which is you know they are unequal, and you know which one is greater/less than the other....the question of 'how unequal' then becomes a whole other matter! :)
May 19, 2010 1:30 PM
You might want to look at this:

http://www.myfitnesspal.com/blog/Azdak/view/calories-burned-during-exercise-it-s-the-intensity-not-the-heart-rate-that-counts-26524

Because of the wide spread use of HRMs, people have gotten the whole "calories burned during exercise" thing completely ass-backwards.

The fact that heart rate decreases over time for the same exercise intensity does NOT mean you are burning fewer calories for that effort (assuming that weight has not changed). It means that your VO2 Max has INCREASED, so that now the workload represents a smaller percentage of your maximum than it did before.

If all you do is look at your HRM, you will come to the conclusion that you are burning fewer calories. Once again, I have to empahsize--HRMs do NOT measure calories. They do not measure anything except heart rate.Heart rate is NOT directly associated with calories expended. Heart rate is ONLY an jndicator of percent of VO2 max--and even then, only during steady state aerobic exercise--not strength training, not during HIIT, not during daily activities, etc.

If your VO2 max is 10 METs and you are working a 7 METs, you are working at a 70% effort. At 7 METs, an 80Kg person will burn ~ 560 Kcal/hr. If your VO2 max increases through training to 14 METs, that 7 MET effort is now 50% effort. Your heart rate will be noticeably lower. However, that 7 MET effort will STILL burn approx 560 Kcal/hour for an 80Kg person. It's just that now. the person can work at a 70% effort of 9.8 METs and burn ~780 Kcal/hour.

If your HRM still thinks your VO2 max is 10 METs, yeah, it will show a reduced caloric burn (because HR is now lower). Answer: UPDATE THE SETUP INFORMATION IN YOUR HRM. Again, the HRM is not some sort of ominisicent self-thinking, self-conscious being. It is a machine that needs to be programmed properly to do its job.
May 19, 2010 1:48 PM
Azdak - I heart you.

Thank you for the clarity, as always.
  81265
May 19, 2010 2:07 PM
QUOTE:

If your VO2 max is 10 METs and you are working a 7 METs, you are working at a 70% effort. At 7 METs, an 80Kg person will burn ~ 560 Kcal/hr. If your VO2 max increases through training to 14 METs, that 7 MET effort is now 50% effort. Your heart rate will be noticeably lower. However, that 7 MET effort will STILL burn approx 560 Kcal/hour for an 80Kg person. It's just that now. the person can work at a 70% effort of 9.8 METs and burn ~780 Kcal/hour.


So to actually clarify this and make sure we read you right, you are saying that 2 80 Kg people doing the exact same activity will burn the same amount of calories in an hour regardless of their VO2 Max's being different and regardless of their bodies' composition (eg 1 of them is 40% body fat and has very little lean muscle mass and say the other one is 6% body fat with lots of lean muscle mass)?
Edited by mworld On May 19, 2010 2:14 PM
May 19, 2010 2:28 PM
Bumping so I can keep track of this one. :)

Interesting discussion!
  201872
May 19, 2010 2:40 PM
I don't know the scientific explanation to your question..but I can say from experience that the longer I worked out and got more "in shape" the harder it has been to get my heart rate up and keep it up... and in simplified terms - harder to see that same "calorie burn"

That's all I got.
Edited by Laceylala On May 19, 2010 2:43 PM
May 19, 2010 5:02 PM
QUOTE:

QUOTE:

If your VO2 max is 10 METs and you are working a 7 METs, you are working at a 70% effort. At 7 METs, an 80Kg person will burn ~ 560 Kcal/hr. If your VO2 max increases through training to 14 METs, that 7 MET effort is now 50% effort. Your heart rate will be noticeably lower. However, that 7 MET effort will STILL burn approx 560 Kcal/hour for an 80Kg person. It's just that now. the person can work at a 70% effort of 9.8 METs and burn ~780 Kcal/hour.


So to actually clarify this and make sure we read you right, you are saying that 2 80 Kg people doing the exact same activity will burn the same amount of calories in an hour regardless of their VO2 Max's being different and regardless of their bodies' composition (eg 1 of them is 40% body fat and has very little lean muscle mass and say the other one is 6% body fat with lots of lean muscle mass)?


More or less, yes. Any differences will be relatively insignificant given all other factors involved--e.g. the fact that anything we do related to calories--from estimating BMR to estimating activity calories, to estimating exercise calories, to estimating food intake calories, is all, well.....an estimate. So those differences you cite are going to fall within the general "error of estimate".

We tend to focus WAY too much on these trivial differences--that was the whole point of the blog. There are hundreds of comments a day on subjects like this that might amount to a difference of less than 5 percent, when most people could increase their workout intensity a tad, follow a more structured focused program, and with a combination of the improved quality of work and the improved fitness level that would come with it, increase their caloric burn by a substantially greater margin.

The main point I want to repeat over and over again is that using HRM data as "proof" of decreased caloric burn (in the absence of weight loss) is just 100%, no, 1000% wrong.
May 19, 2010 5:24 PM
I have 2 of the exact same HRM's. So for fun one day I used them both. One was set to the weight I am and one was set to my goal weight. I turned them on at almost the same time and and walked on the treadmill until the one set to my goal weight read 300 calories burned. Turned them both off at almost the same time. There is a 30 pound difference between my goal weight and the weight I am now. The watch set to my current weight read 327 burned and the other 300. That is about a 10% change! That is just my experience!
  160056
May 19, 2010 5:29 PM
QUOTE:

I don't know the scientific explanation to your question..but I can say from experience that the longer I worked out and got more "in shape" the harder it has been to get my heart rate up and keep it up... and in simplified terms - harder to see that same "calorie burn"

That's all I got.

The more in shape you got, the more mechanical work was required to get to 75% effort but you were also burning more calories at 75% effort as you improved your fitness. If you had to run 5 miles instead of 3 miles to get the same calorie count then your calorie counter needs to be adjusted unless it was simply due to significant weight loss between the 3 mile runs and the 5 mile runs.
May 19, 2010 5:33 PM
QUOTE:

If your HRM still thinks your VO2 max is 10 METs, yeah, it will show a reduced caloric burn (because HR is now lower). Answer: UPDATE THE SETUP INFORMATION IN YOUR HRM. Again, the HRM is not some sort of ominisicent self-thinking, self-conscious being. It is a machine that needs to be programmed properly to do its job.


I agree my HRM needs to be updated but without spending money and time to get an actual VO2Max analysis, I have to rely on the HRM to determine it. I have no basis to change it to some arbitrary value other than I know it is higher than when I did it the first time. The problem with the HRM is that it is only accurate if my fitness level hasn't really changed that much in the last 3 months and right now it is changing for the better almost weekly. The HRM test results actually went down a point during this last week.
Edited by canstey On May 19, 2010 5:43 PM
May 20, 2010 6:49 AM
QUOTE:

QUOTE:

QUOTE:

If your VO2 max is 10 METs and you are working a 7 METs, you are working at a 70% effort. At 7 METs, an 80Kg person will burn ~ 560 Kcal/hr. If your VO2 max increases through training to 14 METs, that 7 MET effort is now 50% effort. Your heart rate will be noticeably lower. However, that 7 MET effort will STILL burn approx 560 Kcal/hour for an 80Kg person. It's just that now. the person can work at a 70% effort of 9.8 METs and burn ~780 Kcal/hour.


So to actually clarify this and make sure we read you right, you are saying that 2 80 Kg people doing the exact same activity will burn the same amount of calories in an hour regardless of their VO2 Max's being different and regardless of their bodies' composition (eg 1 of them is 40% body fat and has very little lean muscle mass and say the other one is 6% body fat with lots of lean muscle mass)?


More or less, yes. Any differences will be relatively insignificant given all other factors involved--e.g. the fact that anything we do related to calories--from estimating BMR to estimating activity calories, to estimating exercise calories, to estimating food intake calories, is all, well.....an estimate. So those differences you cite are going to fall within the general "error of estimate".

We tend to focus WAY too much on these trivial differences--that was the whole point of the blog. There are hundreds of comments a day on subjects like this that might amount to a difference of less than 5 percent, when most people could increase their workout intensity a tad, follow a more structured focused program, and with a combination of the improved quality of work and the improved fitness level that would come with it, increase their caloric burn by a substantially greater margin.

The main point I want to repeat over and over again is that using HRM data as "proof" of decreased caloric burn (in the absence of weight loss) is just 100%, no, 1000% wrong.


thanks for the explanation - always knew they were different, but knowing that the margin is igsignificant from a practical stand point is good.
May 21, 2010 3:33 AM
if only more people would read this thread! it might cut down the number of people obsessed with listening to their heart rate monitor to determine an "accurate" reading for calorie burn.
  651441
May 21, 2010 7:35 AM
QUOTE:

if only more people would read this thread! it might cut down the number of people obsessed with listening to their heart rate monitor to determine an "accurate" reading for calorie burn.


I agree. I listen to my HRM for calories burned and adjust my intake accordingly until my body says otherwise. If I am sluggish and/or weak during my routine or my body is screaming for food (not cravings) then I eat additional healthy calories regardless of what MFP and the HRM say and it has worked well so far. Now that I know that my HRM is reading a little low I can compensate for it a head of time.
May 23, 2010 6:54 PM
Please don't let what azdak is telling you lead you to up your calories in any way!!! He's just always making the point that the HRM is a tool, and not accurate for a lot of things.

If you are using this site to figure out your before exercise calories and then adding in ALL the calories your HRM is telling you, then you are most likely already double dipping on some of the calories anyhow.

Example: HRM says 500 for your 1 hr, but you would have burned 100 calories doing nothing for that 1hr anyway and you chose a lifestyle that takes that 1hr of doing nothing already into account on your daily calorie needs.

So you were most likely already overestimating anyhow...so if the HRM is slightly low due to all the above, it may just get you closer to the reality if you are using the calories this site is giving you anyhow.

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