Calories Burnt Heart rate Montor reading

Gazzaputt

I have just invested in a Polar heart rate monitor.

I have set it with resting and max heart rates (60 and 171) and from this it gives a 'zone' to ride in between 117 and 147. I'm 36 and weigh 185lbs.

This I do find the zone a little hard to maintain as I have had a break of about 5 weeks and I'm just starting to ride regular again. I averaged 151bpm on my ride yesterday morning and then 146bpm on the way home.

The calories burnt for the morning ride were 1320 and in the evening 1200 odd.

My total ride time for both was about 2hrs 20 mins and 37.4 miles were covered average speed 16mph.

Does the calories burnt seem right?

Pagem

it will only be an educated guess as there is no way to accurately know the calories your body burns in any given exericse other than via a lab test.

also, heart rate monitors are great for training but again i would only use them as a guide and not the rule as there are many inaccuracies with using such a device, such as: defining and calculating max hr, failure to recognise level of starting/improving fitness etc.

i tend to use mine with a level of conscious 'percieved effort' to help me train in certain 'zones'

ut_och_cykla

At a guess 1000+ kcal per hour would seem a bit high. If its a running HRMonitor the calculations for cycling come out a bit high. As Pagem says its only a guide. USeful for comparing your own performance over various times/terrains but not an absolute figure.

No doubt Ric will be along soon to sing the virtues of power measurements

Ric_Stern/RST

ut_och_cykla wrote:

At a guess 1000+ kcal per hour would seem a bit high. If its a running HRMonitor the calculations for cycling come out a bit high. As Pagem says its only a guide. USeful for comparing your own performance over various times/terrains but not an absolute figure.

No doubt Ric will be along soon to sing the virtues of power measurements

We don't know the exact time the OP rode for on each leg of the ride. If we guesstimate it was 70 mins each way; then on the way out he expended (according to the Polar) 1320 Kcal. This would approximately equate to ~ 315 W average power.

Given that the OP is 84 kg; this would be a power to mass ratio of 3.75 W/kg. On a flat, slow (Chelford for those who know it in the UK) 25-m TT course on a bog standard bike, with no aero anything, i can average 40 km/hr (25mph) at that power to mass ratio.

So, if the OP was going at that sort of velocity or could do on a flat slow TT course, it's possibly correctish. On the other hand i suspect, given that the poster was averaging 16 mph that the energy expenditure is way off.

There are essentially only two ways to know how much energy you expended:
1) go to a lab and find out (but be aware that efficiency changes under different conditions, so, while the lab figure will be accurate in an accredited lab; the actual figures will change out on the road; trail; track etc

2) get a power meter (SRM; Power Tap; Ergomo); you can track mechanical work done; which nicely correlates with energy expenditure and will get you an excellent ball-park figure

Ric

Gazzaputt

Cheers guys. I thought 1000 calories an hour is pretty high but then thought at an average heart rate of between 146 and 151 it could be near.

Gazzaputt

Oh yea my average cadence was 67 peak was 84.

Jeff Jones

Calories burned relates to work done, not your heart rate. Work done is dependent on distance travelled, weight, hills, aerodynamics, wind, rolling resistance etc. Also, work = power x time.

If everything is equal, save for fitness, a fit rider will burn the same amount of calories as an unfit rider if they ride next to each other, but at a lower heart rate. Or if you look at it another way, the fit rider can burn more calories per hour than an unfit rider, because they can go further.

Gazzaputt

So does anyone know how Polar monitors calculate calories burned?

ut_och_cykla

According to the very helpful staff at heartratemonitors.co.uk each monitor brand/type has its own 'algorhythm' - which I take to mean a mathematical kind of sliding scale calculation of calories used based on factors as listed by 'jjones' weight, time etc. It gives repeatable results but not necessarily accurate ones and of course it doesn't know why your heart rate is elevated or what the rest of your body is doing - sitting in sauna, running downhill, or cycling up.
You don't have to bin your HRM (tho' Ric would prefer you used power meters ) but use it in conjunction with a bike computer (distance, speed etc) & common sense. You can also get a better picture by looking at sites like Kreutzotter. If you think you've burned x calories on a ride fill in the stats and see if you really did average 40km/h!

Ric_Stern/RST

ut_och_cykla wrote:

According to the very helpful staff at heartratemonitors.co.uk each monitor brand/type has its own 'algorhythm' - which I take to mean a mathematical kind of sliding scale calculation of calories used based on factors as listed by 'jjones' weight, time etc. It gives repeatable results but not necessarily accurate ones and of course it doesn't know why your heart rate is elevated or what the rest of your body is doing - sitting in sauna, running downhill, or cycling up.

They don't give repeatable results, because your HR varies significantly at a given power depending on various conditions

You don't have to bin your HRM (tho' Ric would prefer you used power meters ) but use it in conjunction with a bike computer (distance, speed etc) & common sense. You can also get a better picture by looking at sites like Kreutzotter. If you think you've burned x calories on a ride fill in the stats and see if you really did average 40km/h!

It's not that i want everyone to purchase a power meter (although undoubtedly that would be nice), it's that i don't think people should use a HR monitor for things it's not truly calculating if you need to rely on them (e.g. the original poster would likely end up increasing his fat mass, if he relied on the energy expended figure to calculate his daily diet). If you just want to use it for a number to record in your training then you could probably get a better answer by guessing, making your own scale up, or going to analyticcycling.com and working it out.

Ric

SteveR_100Milers

I think the conclusion is that the calories burnt function of an HRM is often wildly inaccurate. Ric is right in that if you want an accurate measurement of specific energy expenditure, then a power meter is the only way. The convert all of the food you eat from calorific values into joules (easily anough done just hunt for the coversion formula on the web bound to be there somewhere) and there you go. So long as your power meter also has a total energy expended measure, which again would be in joules you're away! Question is, do you really want to spend £100's of pounds on a device which although accurate, is probably of no real additional benefit to a weight loss programme than conventional calory counting and using your HRM guide. You can after a period of time calibrate your HRM calory readings to your weight loss. (which is probbaly better measured as fat loss or how smaller your waistline is getting rather than weight, as increased muscle mass will offset the loss of fat)

Gazzaputt

This is the link to Polar 'Owncal'

http://support.polar.fi/PKBSupport.nsf/ ... enDocument

Johnpsanderson

It's not that i want everyone to purchase a power meter (although undoubtedly that would be nice),

Is Ric on commission from PowerTap or something? Power seems to come up in every post?!?!

Ric_Stern/RST

i mention SRM and Ergomo in the same posts as well (actually, i just tend to say "power meter"; but sometimes qualify that with PT, Ergomo or SRM; simply because these are the only meters that measure power well).

And, yes, i sell all 3 of those power meters. The reason i mention power meters frequently is that they lend themself to answering certain questions that people bring up.

Lastly, i don't mention them in every post. However, if someone is talking/asking about energy expenditure, training, data analysis, aerodynamics, then power meters are, imo, very important aspects of those and many other issues.

Ric

Zero Sum

It is becoming increasingly clear that power combined with HR is the best way to get the most out of your training, there is no doubt about this...

HR can only go so far, there are too many varying factors....far too many, start training with power and you will see the difference...

Yep they are expensive, but worth it, you want more out your cycling then power measrurement is the way to go...

ut_och_cykla

Johnpsanderson wrote:

It's not that i want everyone to purchase a power meter (although undoubtedly that would be nice),

Is Ric on commission from PowerTap or something? Power seems to come up in every post?!?!

:shock:

Johnpsanderson

Yep they are expensive, but worth it, you want more out your cycling then power measrurement is the way to go...

OT really but I was thinking about this last night as I was training on the quiet country lanes of Suffolk in the fading light.

Obviously I only have so much money to spend on cycling and at the moment something like a quality set of lights (say £150) are much more important, simply so I can continue training rides through the winter.

Next on the list would probably be better clothing to make the whole experience more comfortable - rather than getting by with cheapo base layers in the winter and ending up cold and sore. I'm sure a full Assos wardrobe would make time on the bike more enjoyable (and more likely) all year round.

After that a house with a garage where I can turbo train would be a bonus. At the moment I am restricted to turbo training outside on the driveway - not much good if it rains - which sort of negates the point.

Once all that was sorted I could probably start considering coaching. Which looks pricey - although I am sure worth it.

And then I suppose I have no excuse not to make my next purchase a power meter.

Of course this means i'll have sacrificed all the bits we want to buy - like new wheels and whizzy carbon bikes and will be scratching around for the cash for essentials like tyres, tubes, cassettes, GO!, etc. Not to mention holidays, new car, etc...

How does everyone else manage it? (Given that we are too busy cycling to develop careers with massive salaries!)

Ric_Stern/RST

Johnpsanderson wrote:

OT really but I was thinking about this last night as I was training on the quiet country lanes of Suffolk in the fading light.

Obviously I only have so much money to spend on cycling and at the moment something like a quality set of lights (say £150) are much more important, simply so I can continue training rides through the winter.

Next on the list would probably be better clothing to make the whole experience more comfortable - rather than getting by with cheapo base layers in the winter and ending up cold and sore. I'm sure a full Assos wardrobe would make time on the bike more enjoyable (and more likely) all year round.

prior to running my own business, when i had to keep more 'normal' hours, i used to train on the turbo/rollers monday to friday once daylight saving had finished; and the roads at the weekend.

After that a house with a garage where I can turbo train would be a bonus. At the moment I am restricted to turbo training outside on the driveway - not much good if it rains - which sort of negates the point.

i turbo in the house (lounge or kitchen). If you have carpet down try not to get oil on it ;-) :shock:

Of course this means i'll have sacrificed all the bits we want to buy - like new wheels and whizzy carbon bikes and will be scratching around for the cash for essentials like tyres, tubes, cassettes, GO!, etc. Not to mention holidays, new car, etc...

How does everyone else manage it? (Given that we are too busy cycling to develop careers with massive salaries!)

I'm not going to tell anyone how to spend their money (and if i did there would be likely bias in my reporting). However, what you (possibly) have to do is decide where the greatest returns will be? Would it be on carbon frames? aero wheels? training? buying a present for your better half so that they allow you to do more cycling? etc.

This paper gives some answers; but doesn't mention anything about presents for your better half
http://www.ncbi.nlm.nih.gov/sites/entre ... d_RVDocSum

Ric

DaveyL

Ric, can I ask about your original post on this thread. How did you get from calories burned to a wattage figure? It looks like there is an assumption of 25% efficiency (for want of a better term) in terms of calories out converted into power - is that right? And if so, how good is this 25% estimate?

Ric_Stern/RST

DaveyL wrote:

Ric, can I ask about your original post on this thread. How did you get from calories burned to a wattage figure? It looks like there is an assumption of 25% efficiency (for want of a better term) in terms of calories out converted into power - is that right? And if so, how good is this 25% estimate?

You're correct. In trained cyclists of (virtually) any ability [thermodynamic] efficiency varies between about 20 and 26%

Then, because 1 Kcal = 4.18 Kj and efficiency is ~ 25% these basically cancel with each other. So, when you have a power meter (which all measure in Kj) you can pretty much say that whatever ride you did in Kj was the same in Kcal, i.e., if the mechanical work done was 1000 Kj, then an excellent ball-park figure is to say that you expended ~1000 Kcal.

Of course, in a lab, you can measure your efficiency with expired respiratory gases. However, it's important to note that efficiency varies with cadence, power output (intensity), topographical conditions, etc. So, even though you may know that at (e.g.) 200 W your efficiency is 22.5% it'll vary out on the road (and thus just changing the Kj to Kcal suffices).

Ric

DaveyL

Thanks for the reply Ric. This leads me to something that has been eating at me for a while.

Does it imply that powermeters might not be as accurate as we think? They are accurate at telling you how much power is driving the bike along, but because of this variance in the engine's (i.e the body's) efficiency, is this information reliable? It's like saying that when you are having a bad day, are ill, or tired, your HR will not correlate as normal with your power output - i.e the illness/tiredness has affected your engines efficiency. The same surely applies to power measurements - your power output may still be your usual 250 W, but if you are tired/ill your efficiency will drop, and that will mean the body is not performing at its normal level in putting out that 250 W, so at the fundamental physioplogical level, the measure of power on the bike is not completely accurate (or is it?)

I'm not sure I've made this point particularly well, but it's not something I see mentioned much when it comes to power meters. Is this really an issue or is it something power meter users don't need to worry about?

Ric_Stern/RST

DaveyL wrote:

Thanks for the reply Ric. This leads me to something that has been eating at me for a while.

Does it imply that powermeters might not be as accurate as we think? They are accurate at telling you how much power is driving the bike along, but because of this variance in the engine's (i.e the body's) efficiency, is this information reliable? It's like saying that when you are having a bad day, are ill, or tired, your HR will not correlate as normal with your power output - i.e the illness/tiredness has affected your engines efficiency. The same surely applies to power measurements - your power output may still be your usual 250 W, but if you are tired/ill your efficiency will drop, and that will mean the body is not performing at its normal level in putting out that 250 W, so at the fundamental physioplogical level, the measure of power on the bike is not completely accurate (or is it?)

I'm not sure I've made this point particularly well, but it's not something I see mentioned much when it comes to power meters. Is this really an issue or is it something power meter users don't need to worry about?

I'm not entirely sure i understand what you're trying to say (but i have just got in from intervals...).

If i think i understand you, i'd say that efficiency and HR are immaterial. That is you may have to do a session, lets says, 90-mins at 230 - 270 W. It doesn't matter whether your HR is an avg of 150 b/min for this or a 160 b/min (if it's often 150). This is because, contrary to popular opinion, a HR monitor doesn't tell you anything other than how fast your heart is beating. In terms of endurance exercise, what's important is cardiac output, which is HR x stroke volume. In other words stroke volume at a given power can alter to maintain cardiac output (as could e.g., arteriovenous O2 difference -- the difference in arterial and venous blood oxygen content).

Likewise, efficiency varies all the time (e.g. ride along at 200 W at 75 revs versus 100 revs and it'll increase, as it would if you rode at 300 W versus 200 W).

At the end of the day you either do the session, or you don't (because you're fatigued, ill, glycogen depleted, whatever). HR is just a dependent variable (mine varies tremendously depending on various factors)

Ric

DaveyL

Yes, I don't think I expressed myself very well before. My point is not so much about HR, but continuing the analogy - on two separate days you do your one hour session at 250 W. One the second day, you are feeling a little tired, or ill, so although you have completed both sessions at 250 W, your internal engine's energy output has been quite different (depending on the efficiency of the body's engine on those two days).

My point was, does this matter or not in terms of power training? And as a secondary, power may be a much more accurate measure of performance than HR, but it is measuring the more fundamental variable of the body's energy output. Now, this may be a moot point as it is, at the moment, not something which I guess is easily measured. I am just curious as to whether all this makes a difference or not, as it is not something I have seen discussed very much when power meters are mentioned.

Ric_Stern/RST

DaveyL wrote:

Yes, I don't think I expressed myself very well before. My point is not so much about HR, but continuing the analogy - on two separate days you do your one hour session at 250 W. One the second day, you are feeling a little tired, or ill, so although you have completed both sessions at 250 W, your internal engine's energy output has been quite different (depending on the efficiency of the body's engine on those two days).

My point was, does this matter or not in terms of power training? And as a secondary, power may be a much more accurate measure of performance than HR, but it is measuring the more fundamental variable of the body's energy output. Now, this may be a moot point as it is, at the moment, not something which I guess is easily measured. I am just curious as to whether all this makes a difference or not, as it is not something I have seen discussed very much when power meters are mentioned.

It doesn't matter. If you're supposed to be doing your one hour at 250 W or whatever, you either do it, or you don't. If it felt horrendous because you were tired or ill, you'd stop. That said, you can use the power meter (and Performance Manager chart in WKO software) to ascertain when you're going to be feeling tired, and schedule training accordingly.

ric

DaveyL

But you might be somewhere inbetween feeling 100% and feeling so ill/tired that you won't complete the session. I guess my point is that, say your efficiency drops a few % because you are a *bit* tired but not enough to really notice a big difference (after all you can still do the hour at 250 W) - is the physiological adaptation going to differ because your body's efficiency has dropped a little? Is it going to matter if it differs? I suppose you will still get some benefit from your workout even though at a more fundamental level than bike power it hasn't been as consistent as power has told you it is (from session to session).

Sorry if this is irrelevant, it's just that I haven't seen much about correlation between the body's energy output and power, or the effect of "internal efficiency" and was curious as to whether it mattered or not. From what you've said, it doesn't seem like it does.

jonny8055

Johnpsanderson wrote:

a house with a garage where I can turbo train would be a bonus. At the moment I am restricted to turbo training outside on the driveway - not much good if it rains - which sort of negates the point.

Get yourself down to B&Q for a mini gazebo - plastic tent with no sides on it. Cost £12 early in the summer, probably on sale now. Outdoor turbo training without the rain, and packs down to nothing when not in use.

Gazzaputt

can I ask did anyone read what Polar had to say about their calorie counting program on their monitors and any comments?

Ric_Stern/RST

Gazzaputt wrote:

can I ask did anyone read what Polar had to say about their calorie counting program on their monitors and any comments?

Briefly, iirc, they seem to be vaguely okay if you're a sedentary woman doing some moderate exercise (walking i think). When tested with trained athletes, they're not too good.

ric