Fit vs unfit: calories burned doing identical exercise?

I would think differences in BMR would make a difference as well as differences in fitness. Two people of same height, sex, age, weight, and BF% are not going to necessarily burn calorlies at the same rate for any activity. There are so many other variables that could figure in.

Bump for the incredibly interesting discussion. I didn't see much on a quick google search but a couple of the responses have been very informed and made a lot of sense.

I would think differences in BMR would make a difference as well as differences in fitness. Two people of same height, sex, age, weight, and BF% are not going to necessarily burn calorlies at the same rate for any activity. There are so many other variables that could figure in.

There are variables, but they are not enough to make a realistic difference. You will always have interpersonal variability--which is why research studies need a certain number of subjects and the variances have to fit within certain confidence levels in order to be considered significant. However, that variability is just in the normal human population.

For the most part, however, calories burned depends on intensity and mass--the nature of the mass is not that important.

I don't think you're ever going to find an exact answer. If everything was based solely on heartrate, then yes, the more fit person would burn less calories

but, like you said, the more fit person may have a greater muscle mass, so they continue to burn more calories for longer after the exercise than the less fit person, etc.

I know that if my husband and I ran together, it would certainly seem like I was burning a lot more calories.

Running an 8 min mile for 2 or 3 miles would be near max effort, where he can run sub 5:30 at his max effort.. so if he was running the 8min miles with me, he'd barely be working.. my HR prob 170s and his 120s or 130s.. but he's larger, and has a larger percent muscle mass than I do (he's 10-11% body fat at 5'10 and 152lbs where I'm 22% BF at 5'7" and 138ish) so his metabolism is probably higher, so maybe it equals out in the end? hmmm. not sure how you could ever get a definite answer on this.

The answer is pretty definite. It's natural for people to speculate in discussion groups, but the actual science behind this question is simple and settled and it has been for decades.

If you are both running at a steady-state pace, then the oxygen cost of the activity is the same. Thus, the only difference in calories burned would be the difference in body weight. You are correct in saying it will "feel" easier for the more fit person to run at that speed, but that is because they have a higher maximum aerobic fitness level---but the fact that it feels easier does not mean the person is burning fewer calories.

Ok, I did not read all the posts, so forgive me if someone has mentioned this before:
But it's hard to find an "identical exercise" for any two people. Running, especially would not be it.
There is so much more to energy expenditure in running than simply body weight/muscle mass. For example, the other day, I saw a guy running: he sort of leapt forward into a deep lunge, pulled himself up and threw his other leg forward. He was sweating buckets and near to tears, but made very slow progress. An experienced runner runs very differently from that, minimizing loss of energy through proper technique and therefore using much fewer calories.
Cycling might be more standrdizable (forgive me, cyclists), since once you have clip pedals, the motion cannot vary as much as with running. Of course, you can still engage different muscle groups etc...

Ok, I did not read all the posts, so forgive me if someone has mentioned this before:
But it's hard to find an "identical exercise" for any two people. Running, especially would not be it.
There is so much more to energy expenditure in running than simply body weight/muscle mass. For example, the other day, I saw a guy running: he sort of leapt forward into a deep lunge, pulled himself up and threw his other leg forward. He was sweating buckets and near to tears, but made very slow progress. An experienced runner runs very differently from that, minimizing loss of energy through proper technique and therefore using much fewer calories.
Cycling might be more standrdizable (forgive me, cyclists), since once you have clip pedals, the motion cannot vary as much as with running. Of course, you can still engage different muscle groups etc...

No, running energy expenditure is pretty standard. Like any statistical analysis, there is a standard of error around every measurement but when it comes to estimating energy expenditure for running, the error is small enough that the standard equations for estimating energy expenditure can be applied to most runners running at speeds above 5.0 mph. Taking a single anecdotal outlier doesn't change established science.

In the beginning though, the body does become more efficient DURING the activity you practice, but I re-read and realized thats not really your question. I first answered this in a general way thinking it was another beginner question starting into shape, but it looks like I was wrong and you are actually asking about an athlete level? As the other doggie said above (I'm a dog picture too at this point ), its not going to significantly change if the bodyweight is the same, and the activity is the same at all as you increase fitness for the same practiced activity, and HRM will show reduced calories burnt, and in a way lie to you, because all it measures is HR vs weight....but only *IF* you are in very good shape for the activity. They usually over-estimate some for beginners, and for top athletes they can under-estimate. But, unless you are losing weight when you dont want to or having trouble with gains or going lots of miles on your bike, it probably isn't very significant.

The analogy I like to use is two automobiles, one that badly needs a tune up and one that is operating in top condition. The car that needs a tune up will need to work harder to drive down the road than the properly tuned vehicle. As a result it will have worse gas mileage (higher calorie expenditure) than a properly tuned car.

That's a bad analogy, and doesn't fit the actual biology.

If you want a car analogy, it's more like two identical cars, one with restricted air and fuel flow, one without. Both will use the same amount of fuel to go the same distance, but one will be able to get there much faster.

I am about 180 pound and 5'8. I calculate my bodymass, and estimate how I burn kcal for each individual excercise. I have logged them all, under cardio in MFP personal library. As time progress, excercise will become more and more strenious, so a total change will happen to my routine. I am looking forward to this, as I am getting bored with the indoor gym, and I hope to do some skiing in the new year.

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?

If they have the same body weight and are working at the same intensity over the same duration then the calorie expenditure will be the same.

The problem in your question is you have no concrete way of gauging intensity and whether it is equivalent although you have kept weight and duration constant. Speed, recorded heart rate, sweat etc doesn't tell us that.

The analogy I like to use is two automobiles, one that badly needs a tune up and one that is operating in top condition. The car that needs a tune up will need to work harder to drive down the road than the properly tuned vehicle. As a result it will have worse gas mileage (higher calorie expenditure) than a properly tuned car.

That's a bad analogy, and doesn't fit the actual biology.

If you want a car analogy, it's more like two identical cars, one with restricted air and fuel flow, one without. Both will use the same amount of fuel to go the same distance, but one will be able to get there much faster.

Actually I think your analogy is worse. That'd be like wearing a mask while running vs not wearing a mask while running. That's not analogous to being fitter vs not fitter.

Let's try this a different way. Think about riding a bicycle with normally inflated tires, vs riding a bicycle with underinflated tires. You'll have to work much harder to ride the same distance on the bike with underinflated tires. That's the analogy to someone who is less fit doing the same workout as someone who is more fit. They may travel the same distance but one will have to work much harder to get there.

They may travel the same distance but one will have to work much harder to get there.

Except they don't. They both do exactly the same amount of work, which is why they both burn the same number of calories.

One may *feel* like they are working harder - but (s)he isn't.