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Heart Rate, Activity Type and Calories Burned

eebee's picture

Hey can any of you answer a question for me? Is it true that I would burn more calories in one hour of running than, say, one hour of cycling, if my heart rate is the same for both? If so, can you explain why?

Whilst fixing up a heart-rate monitor that tells me how many calories I burned, I had to attribute a particular code to my activity type (inline skating). This particular hrm didn't have that listed in the manual so I picked a code that was halfway between the highest possible code for cycling, and mid-point for running. I have no idea how close to correct this is. During this process I asked myself 'Well if my heart rate is the same, what does it matter what activity I'm doing? Surely a heart rate of 150 is a heart rate of 150 no matter what I'm doing?'. I started to research this partly because I wanted to be sure I was in the ball park regarding my calories burned, but mostly because the issue of different activities burning more calories at the same heart rate was driving me bonkers. Obviously I understand that within the same exercise category (i.e. skating) and at the same heart-rate (i.e. 150 bpm), I would burn a different amount of calories compared to myself if my weight or body composition changes. But that's not part of my question.

After countless Google searches for a snowballing list of key terms and phrases, I landed upon many a forum site, rife with opinionated arguments and ensuing tangents about the accuracy of Polar's calorie counter system, elliptical machines vs stationary bikes and their calorie counters, and other points. Alarmingly enough, several on-line 'fitness' coaches either couldn't explain the answer to my question, or contradicted themselves in the process:

http://www.usatoday.com/community/chat/2001-04-30-fenton.htm

"Mark Fenton: You're right on target to consider heart rate, as that's the gold standard. The best way to make a comparable workout would be to maintain the same heart rate for the same amount of time. That ASSURES that it's a physiologically equal effort"

According to Polar, and University of South Carolina's Compendium of Physical Activities study, that's a load of poppycock.

I started to get a hint of a clue from a UK protein forum:

Just wondering if I jog at a heart rate of 170bpm will I burn the same number of calories as if I bike ride at 170bpm??? I know jogging burns more calories than biking but does that take into account the same heart rate or is it based on the fact you don't need to be working as hard to bike as to run???

Not at all. Calories is a measure of energy. Energy = Force x distance =>Energy = mass x acceleration x distance

So u see its the weight u must support and the distance u do that decide total calorie burn, HR is pretty redundant. U dont have to support ur own weight on a bike so u burn a hell of a lot less cals.

Thank u! U have no idea how glad I was to find something remotely relevant after 6 different searches yielding hundreds of mostly futile results, and arguments about weight, body mass and online calorie-expenditure calculators! 

Along the way, oxygen intake and expenditure seemed to lurk around the edges of the big answer I'm looking for. At one point I came to believe it had to do with how the body effectively uses oxygen whilst working out. But then linear things (.pdf) came into it in this article: Does Heart Rate Predict Energy Expenditure? Yes, But…..  by J Farringdon & D Wolf. BodyMedia Inc. Autumn 2006.

Ok! This is as far as I could get, and I'm sick and dizzy from the whole thing. Does anybody out there know why running, skating, cycling, digging the weeds, etc., all have different 'codes' by which calorie expenditure is calculated, and that 150 bpm cycling means a different caloric-output than 150 bpm skating?

Comments

dreeves's picture

Heartrate is Only a Rough Proxy for Calories

I earned Best Answer on Yahoo Answers a while ago for a similar question, so clearly I'm an expert on this! :)

There's actually a simple answer:  as you train at a sport you get more fuel efficient (can go farther with the same calorie expenditure) but also your engine, so to speak, gets bigger (you can turn more calories into motion in a given amount of time).  So if you train skating and not running you'll be able to burn more calories in an hour of skating than running.  I'm pretty sure that that's a much bigger effect than how many muscles are used in skating vs running.

Now cross-country skiing (or inline skating with poles -- it's pretty cool; need to have carbide tips though so they grip the pavement) is another story because far more muscles are involved.

Oh, and don't forget that you can skate for much longer than you can run because it doesn't beat the crap out of you with every step!

Heartrate is only a rough proxy for calories, by the way.  I don't believe it works well for comparing between sports.  It is possible to measure calorie expenditure directly in the lab but it takes a lot of equipment.

Skateylove,

Danny

eebee's picture

Polar doesn't care how long I've been training!

The statement "Heart rate is only a rough proxy for calories" gave me an ahah moment, and that helps me understand the bigger picture on this. I can see that heart rate is only a portion of the equation. But my original bafflement was caused by Polar or the Uni of SC having to come up with a different code or multiple (not sure of the proper math term) to be used in conjuction with a person's heart rate to calculate calories burned at a certain activity. It is not the same for running as it is for skating, for example. And Polar cares not how long I've been skate-training, or whether I just can't possibly run for 5 hours straight. They just flat say that if I run at 150bpm, I will burn more calories than if I cycle at 150bpm. Why?!

 

And for further muddying of the issue, I read in several places that exercise that involves both the arms and the legs at the same time actually burns less calories at the same heart-rate, compared with those that either only use arms, or legs, but not both. This seemed counter-intuitive to me until another ahah moment where I read that a person is more efficient when using arms and legs, therefore exerting less energy (but wouldn't their heart-rate be lower, too?!).

 

I really don't care how accurate my calories-burned comes to, because an hour of skating is good either way. And I understand that if I had a lab work with me I could get a better idea for me personally. I just would like to know why there needs to be a different multiple for different activities, and why puffed-outness in one activity burns more (or less) calories than the same level of puffed-outness in another activity. It only bothers me because I don't understand it :-)

roadskater's picture

Puffed-Outness as a Proxy for Volume of Oxygen Max VO2Max

By puffed-outness, are you meaning heart rate beats per minute, or do you mean "out of breathness" or "breaths per minute" or "volume of oxygen taken up"? I know sometimes I take many shallow breaths and sometimes I take perhaps fewer deep ones. I think you meant heart rate beats per minute, but maybe not.

[As an aside, I think I sometimes breathe in rhythm with the strokes or strides, and I think I read somewhere in a running book or magazine that this may not be such a great idea, but I don't remember why, and I do it anyway.]

As I recall the question, and certainly as I find the question interesting to me, I agree it is hard to find an answer from anyone if you keep saying, "no, I mean at the same heartrate for a particular person, on a given day, so that means easier skating or moderate cycling or whatever for that person to reach that specific heartrate."

It is not hard for me to see that it is easier to get my heartrate up to 170 skating than it would be riding a bike...but that's not the point.

I'm still not clear why 150 bpm should represent a different calorie burning rate for different sports for a given person on a given day.

Perhaps the answer is that puffed-outness is different that heartrate. If there's a more direct relationship between oxygen uptake and calories burned than there is between heartrate and calories burned, that would describe it. Perhaps that's the point of getting those values based on type of exercise...maybe those tables are predicting how much oxygen uptake is likely on average for a particular activity at the same heartrate. That might be the explanation we seek?

roadskater's picture

Heart Rate, Oxygen Uptake, Calories Burned, Yikes

Thanks, eebee, for lots of work hashing this out. I hope we find the answers and know it when we find it.

 

I'll be happier if I can get my HRM strap to read for an entire workout, but that's another issue.

 

I hope the new Polar RS200 heart rate monitor is up to all the button-pushing and analysis. If not, at least it's RED! I'm jealous, as my 725i is boring black and silver with only a red button...and it's huge!

 

Anyway...I like the idea that weight bearing exercise burns more calories at the same heartrate. I like it but am still not sure.

 

The linear relationship between heartrate and oxygen uptake makes sense to me (not that my understanding or believing changes it) since I perceive the function of the heart beating to be oxygen delivery rather than calorie burning. However, I don't know if that's right, ha!

 

But for the same heartrate for the same duration it is still hard to grasp why the activity matters. Hmm. But these dudes (y dudettes) seem to be saying that the same heartrate and time on skates will burn a different amount of calories than on a bike.

 

No matter what I like seeing that big calorie number after a several hour roadskate! Even if it's bogus I love it!

timv's picture

Scientific exercise physiology: don't expect too much imho

Interesting discussion here, and I'll add my thanks to EB for doing all that work to dig up references and parse through those muddled and contradictory online threads.

 

Blake has heard many versions of this rant from me, but I read through a huge amount of literature on this stuff in the 90s, from popular marathon training guides to Dr. Timothy Noakes's massive The Lore of Running to thick university-level textbooks. I think I'm pretty good at knowing when a theory holds together well and when it just doesn't, and I came away thinking that what we're being told about training and human performance just doesn't hold together.

 

My empirical argument for this is that, guided by the best scientific training theories, English-speaking and western European distance runners have gone from being the best in the world (Roger Bannister, Peter Snell, Jim Ryun, John Walker, Sebastian Coe, etc) to being barely able to beg their way into a top-flight international race. And it's not just that Africans and South Americans and other runners have improved faster than them. "Our guys" are actually slower in absolute times than their compatriots from 30 or 40 years ago, despite huge improvements in support and training conditions--not the least of which being a very lucrative European professional track circuit which lets top runners live very comfortable lives as full-time athletes in place of the humiliating "shamateur" world of the 60s and 70s.

 

So if you feel like that what you're being told about exercise and oxygen consumption and calories burned doesn't add up in any consistent way, I'd say that you have reached the correct answer and you should feel ok to stop there, unless you feel like starting a physiology lab and doing a lot of basic work on your own.

 

skart's picture

Not sure how true this is,

Not sure how true this is, but I always thought that since running involves more muscles than cycling or skating it burns more calories. Just a thought.

kjg's picture

My first (uneducated)

My first (uneducated) thought, was that I think I would have a hard time keeping my HR at the same level skating as I can running - especially since running you don't get any rests on the downhills.

Then, I came across this runners world article (referencing a paper) on the relative calorie burns of running and walking the same distance.

http://www.runnersworld.com/article/0,7120,s6-242-304-311-8402-0,00.html

 "When you walk, you keep your legs mostly straight, and your center of gravity rides along fairly smoothly on top of your legs. In running, we actually jump from one foot to the other. Each jump raises our center of gravity when we take off, and lowers it when we land, since we bend the knee to absorb the shock. This continual rise and fall of our weight requires a tremendous amount of Newtonian force (fighting gravity) on both takeoff and landing."

So maybe skating is more like midway between walking and running, depending on your knee bend ;-)

Interestingly the article goes on to say "Now that you understand why running burns 50 percent more calories per mile than walking, I hate to tell you that it's a mostly useless number. Sorry. We mislead ourselves when we talk about the total calorie burn (TCB) of exercise rather than the net calorie burn (NCB). To figure the NCB of any activity, you must subtract the resting metabolic calories your body would have burned, during the time of the workout, even if you had never gotten off the sofa." This is something I have often thought about at the end of a long skate when my HRM has a large number of calories burnt. 

eebee's picture

Oxygen Use & Muscle Exertion

Yes, Skart, what you said makes sense with some of the things I read (which I also now can't find), to the effect that when you use more muscles, or use muscles more intensely, the use of oxygen (or whatever the proper terminology is) to exert those muscles affects calorie usage. But I may be completely wrong :-)

 

From insidetri.com:

"When heart rate monitor is used to measure energy expenditure, it is based on a linear relationship between heart rate and oxygen consumption that exists for each person. However, the same heart rate may not correspond to the same level of oxygen consumption in each person, and there is individual variability, so it is only estimation"


 

What trips me up on this is that I had assumed that if you use more muscles & oxygen, that your heart-rate would automatically go up, much like when making a concerted effort to skate down lower, it shoots my heart-rate up proportionately with the quad burn!  Or like Blake says when doing the double-push, he goes faster, but that makes his heart-rate higher and not sustainable during a multi-hour event. But apparently from the studied PALs (physical activity level), what I had always believed is not true: that the more puffed-out you get, the more calories you burn. What a revelation!

And KJG, I used to believe that exertion-wise, skating was indeed about halfway between running and cycling, but I was confusing exertion with speed! According to those Energy Expenditure charts, skating burns typically more calories than fast cycling but less than flat-out running, if heart rates are equal. It would be fun to climb a mountain road, pure uphill, on skates (and get a ride down again). You could probably sustain similar heart rates to a fast run that way.

 

Some answers and articles did actually attack this issue from a gravitational or weight-bearing perspective.

 

I'm not hung up on the calories though - I'm hardly one to micromanage food quantities, and whether I'm burning 300 calories per hour skating, or 700 calories per hour skating, that's fine with me. I just was fiddling about with my heart rate monitor and decided on a whim to play with the calorie function. Then I got annoyed with myself for not understanding why different activites produced different calorie expenditure at the same heart-rate, and now I'm possessed. So I'm gonna flog this one like a dead horse until somebody can give me the answer :-)

eebee's picture

So what I'm Getting out of this is...

 ...I just confused myself again. Going back to an article I linked to in my first post: "Does Heart Rate Predict Energy Expenditure? Yes, but...", by J Farringdon & D Wolf, Body Media, Inc., Autumn 2006... I keep going back to this one statement...

"HR is linearly related to oxygen uptake for dynamic activities involving large muscle groups".

 (Do they mean 'large muscle groups', or 'large muscle groups'?!) :-)

So assuming that using larger muscle groups, or more muscles means higher oxygen uptake, I still have it set in my head that at the same Heart Rate I'd be using the same calories. It still seems to me that the more muscles I use, the more my body is working, the more calories I'd be using, and that my heart-rate would reflect that. How can I burn more calories at less exertion in one activity than in another? It's deja vu all over again and still doesn't make sense to me. There must be something hugely, embarrassingly obvious that I'm not seeing here (other than nobody else gives a hoot) :-)

 

Another wacky point I found out along the way, is that exercise involving both arms and legs at the same time, burns less calories at the same heart rate than a legs-only exercise. I only saw this once, though. Now that really sounds crazy.

 

This kind of reminds me of the counter-intuitiveness of relative humidity, and how the rel hum gets lower when the temperature rises. It feels so humid outside when it's hot, but it's really only, say, 20% relative humidity. I finally got that one after about 3 days of head-scratching.

 

 

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