Squint

The best comparison would be to use the HRM on an outdoor ride with a powermeter. HR is likely to be elevated indoors not to mention the problems comparing HR between two different rides.

I constantly see ridiculous calorie expenditure numbers on the web forums, the result of Polar OwnCal and online calculators and other charts.

Ric Stern has said they're basically random number generators and he's right.

cyclezen

What params are used to set your HRM to get Kcals? I did basically the same kinda ride on Sat morning, up Gibraltar Rd around here. It's avg 8% grade with some longer pitches up to 12%, 3800 ft from the SB Mission to top. At ride start it was 36F in town, 32F on the hill, gusting headwind coming down the hillside on the upper 1/4, overall loop was 41.8 miles covered in 3 hrs 9 min, bike weighs about 23 lbs as was equipped, I'm at 164 lbs currently. We took it easy as the group was varied, and also rolled easy on the return leg. My HRM came back with 2942 Kcals for the ride... I was at mid-140s most of the way up, which is 75% of my MaxHR, best I can figure is I start going anerobic once I'm in the mid 160s.

Quite a bit less than your 4200 Kcal, even with consideration for the 20 lbs diff. I know we aren't 'comparable', but would think we'd be closer.

Breaking down the ride into 'climbing' and 'flat' (not really flat but 'handgrenade close' anyways) sections and pluggin into the https://www.kreuzotter.de/english/espeed.htm the total time ridden and Kcals came pretty close to my actual ride time and HRM Kcal number...
I think I like that online calculator...

berts

Thanks for the input.
From the above could I say that a very inefficient rider produces less wattage (=power?) at a higher cal/hr rate than his efficient counterpart? In other words must wattage also take into account the inefficiency of the machine (human body)?
If so how is this factored in the calculations?

bmike

I have a CicloSport HRM. I set my sex, weight and age?, it calcs the calories based on HR and time. My route was 3800' of climbing in a loop -2 decent climbs on each side, and the balance doing the New England Hills thing. Not much chance to cruise along. My HR was elevated most of the day. In the second half I really focused on keeping it below LT... but I knew I blew by that on a few good climbs. My average HR was 159.

I put the ride with estimated grade into the kreuzotter site and got numbers similar to the CycliStats results.

supcom

Ah, you have hit upon the HRM vs. power meter issue. Before power meters became available for bikes, all the 'experts' claimed that you need an HRM to know how hard you are working. But now that power meters are available, the 'experts' say that you need a power meter to know how hard you are working because your heart rate lags your exertion level and because your output power vs. heart rate may vary from day to day.

In the end, you have two tools that make different measurements. But neither measurement tells us the efficiency of the human body. To measure the efficiency, we would need to do something like measure the total heat produced by the body in generating various power levels. This could be done in a lab, but not on the road. So we are left with the tools that are available and apply some average loss factor to the data.

HRMs estimate calorie burn based on prior research to correlate heart rate to energy consumption. It is, of course, an estimate that may, or may not apply to a given individual. A good HRM that takes into account weight will probably be close enough for 99% of us. In my case, I use a Polar S720 and get pretty repeatable results for similar exertion levels. The data also correlates fairly well to overall estimates of calorie burn vs average speed I have seen for cycling.

Obviously, any simple table of calorie burn vs speed is going to be valid only for average terrain and weather conditions. Cycling up Mt. Washington is going to require much higher calorie burn than the tables would estimate based on your average speed!

CdCf

The efficiency of the human body for cycling is pretty much fixed at between 20 and 21%, for virtually every rider proficiency level.

Therefore, a simple power meter, provided it's accurate, will very precisely tell you the energy spent by a rider on any given ride. Just take the energy output recorded by the power meter and multiply by five.

cyclezen

same params on my HRM - nashbar 1200 - which is a relabeled Reebok, I think.

big difference might be that my climb was one continous section and the descent was consistently long with pedaling only to pass each other as we played 'speed razor'... That long downhill makes quite a difference on heartrate. Don't believe I topped high 80's on any of the downhill sections - 10 miles of non-stop, no-sideroad-access descent is awesome fun! Then another 2 miles of limited access before easy rolling again.
The rest of the ride was mostly 2 up small ring 17ish mph with just a few small hill sections.
I checked the HRM at the descent base and was around 2,400 Kcals, which left about 500 Kcals to cover for the final 14 miles at 17avg - I guess thats about right.
I'll have to take note and compare what my Kcals are when I do shorter hills but keep them coming throughout the whole ride - be interesting to see if there's a diff.

bmike

Sounds like a fun time.
Most of my rides here average 800 - 1000' of climbing per 10 miles. Up / Down / Up / Down depending on route. HR 80 on a downhill? Wow. If I even think about cycling my heart rate is around 100 - 110. I'll have to start tracking my RHR. (I usually do twice a week in the summer...)

berts

You probably mean the power (not energy) output recorded by the power meter - right?

Thus the equation would be:

4.3 kcal/hr = 1 watt
instead of
.86 kcal/hr = 1 watt

therefore
850 kcal/hr = 197 watts which is a bit less than what terrymorse indicated.


It is interesting if indeed my body efficiency for cycling is the same as Lance Armstrong's (he just is capable of burning that much more energy). This brings up some intriguing physiological questions.

terrymorse 

You left out one important item: the efficiency of the human body, or its ability to turn food into useful work. Estimates for efficiency range from 20% to 24%, so the 986 watts number above converted to account for effficiency is 197-236 watts.

CdCf

I don't know exactly how existing power meters work, but I know how they could/should work.

I assume they record instantaneous power at frequent intervals, say several times every second. It's a simple matter then to find the area of the power vs time curve, which is the total "mechanical" energy for the ride.
(The body's energy expenditure would then be about five times that.)

So, I did mean energy, not power. Believe me, I know the difference!

Regarding the 20% efficiency figure...
Of course, I'm only repeating stuff I've read, but I suppose almost everyone else here is as well, so it's up to you to decide whom to trust...

Doggus

What HRM do you use? I'm looking for one.

Byk42

What tandem club are you on? From your profile, it looks like you're in the area of the Double DATES club. From what I remember, they have several fast teams. They had at least a half dozen teams that regularly do centuries at well over 20 mph average. I know a couple teams that even ride sub 4-hour centuries. But, maybe that's not your club.

Craig

Doggus

Yep, that's the club. We've only ridden with them once, they don't seem to do many rides. Maybe it was a concentrated 'no drop' ride although the pack did split up into two groups. There were only 7 or 8 teams that day and they claim membership of around 100 (I think). So I'm sure there are others out there that are faster. We rode with one team that rides a Calfee carbon fiber tandem...they were fast. No way we could keep up with them. But here's another question...I've always read that tandems are faster. The day we rode with them (Calfee team) we were on a group ride with the local PACC racers. They couldn't keep up with the PACC racers and we couldn't keep up with them. What gives? They are supposedly racers too.

DannoXYZ 

I got about 3100 Calories for a 60-mile ride I did last weekend using the kreuzotter site. Using the online calculators I get anywhere from 2700-3600 Calories. The thing I can't figure out is how to account for elevation gain on the ride. Since it's a loop, you end up at the same point for a zero change in elevation and all the hills in between aren't included in the calculations. I guess I need a computer that logs total elevation gain, then average that out over the ride distance to get an average for "slope of road".

Then there's also wind to deal with and changes in drag based upon the attack-angle of the wind. A full-on headwind actually isn't the worse since you have a small frontal area while a wind from 30-50 degrees is the worse. Not sure how to incorporate that data into the calculators as well. I think I need to get a Powertap or SRM...

TomM

Somewhere I read where 100 feet of climbing is equal to 1 flat mile.

vbclown

+1 for fitday. Website is free or even better, buy their stand alone software.

NomadVW 

I love your posts. Mostly because I'm reminded that I don't think about most of these things while riding, but I know that people do if I want to find something out. I'm comforted with the notion that people think about these things while I'm thinking about how poorly some guy painted the solid white line on the road.

VW

TomM

How much drag is generated by the wind flowing around the body?

bmike

above a certain speed, it plays more into energy consumption than weight... hence the drafting and team tactics of road racing. (and the decline of fuel economy in autos)

bmike

sigh... yes.

darn cool technology on the bike.
i've looked at em. wish i could spend the $$... but can't see it in the near future.

pacemaker

Sorry to take so long to reply to your question. Out on business. I use the Polar F11. I've only had it since Xmas but I know the feedback I get from it is good for me and as long as you input the correct info it will be very accurate for anyone. Seems several post on this thread have tried to complicate a pretty simple concept as energy exp. Refering to efficiency; Lance is no more efficient than some out of shape couch potato when it concerns energy exp. Take Lance and a guy the same Ht, Wt, Age and body comp as Lance but in less shape: to go 5 mile on a bike they will each use the same number of kcals.

bmike

Not informed enough on the body science to take this on... but it doesn't seem right. More in shape would seem to mean better tuned to burn energy where it counts. As you develop muscle and aerobic capacity I would imagine the tools the body uses has to crack open energy and turn it into motion get better at it.

DannoXYZ 

Just pedaling form will make a big difference. If the couch-potatoe pedals in squares and pushes down when the pedal is at the very bottom, there's a lot of force that goes into rocking the bike laterally and bounces the rider up and down without creating any forward movement at all. So in the 5-mile example, it may be possible for the couch-potatoe to have to burn off 20-30% more energy than a smoother more efficient rider that pedals in circles.

The converse is also true in that if Lance rides that 5-miles at 35mph, he's gonna burn off more energy than someone who rode that same distance at 15mph.

CdCf

If we assume they're absolutely identical in weight, size and shape, use the same position on the bike, and pedal at the same cadence, on identical bikes, then they will have to expend the same minimum amount of energy to travel any given distance.
BUT, the "non-Lance" driver will use up more energy in the process of travelling the distance.

I doubt the difference is great, though. I think it would amount to 5-10% or so. That's just a guess, however...