Calorie expenditure calculations?

[OakLeaf]

Not that I count calories in :rolleyes: but you know I'm a data geek, and I need to know how accurate my Garmin Forerunner's calorie counts are. 1700 calories for a 2-hour ride seems like an awful lot, especially when the claimed expenditure for a 1-hour run is only around 500. I know the software takes into account HR and speed, not sure what else (if anything). Anybody have any idea if these are really in the ballpark?


ETA: maybe I'm wrong and it doesn't take HR into account, in which case it's probably totally off.

[maillotpois]

I haven't been using the HR strap on my Garmin and it still gives me calories, so I don't think it requires HR data. I think it factors elevation gain, weight, speed, etc. in to the equation. I think the Garmin data may run a bit high. I know there've been discussions about the Polars running high on calories. I will say the Garmin data I get is lower than plugging the info into some calorie counting sites.

[Veronica]

With the Polar you can do a fit test and it essentially makes an estimate of your VO2 max. I think the higher your VO2 max, the more calories you burn.

I use the calories burned number as way to show how much effort I put out. I figure as long as I'm getting the data from the same place, it will be consistent in its flaws. It's interesting to do a Spinervals in the morning and then do the same one in the afternoon. My calories burned is usually higher in the afternoon. Not by a huge amount, but there is a difference.

V.

[jayjay]

I have a similar aching question about how many calories burned does one hour of riding amount to.

I ride steep hills mostly , as I live on top of a peak along a ridge of lesser peaks. If I were to hop on my bike from my front door, and coast until I stopped, I'd be about 6 miles down the road, from 2000elevation to probably about 60 ft over sea level. So all my local little rides involve a lot of climbing. So, just today, I rode 12 miles, but coasted half of it. Riding uphill for only 6, as for every incline there's a decline. Does it all factor in? If I ride 2 hours on any given ride, be it flat or hills, the average might be the same, so, I'm just wondering.

[echidna]

If the Garmin uses the same GPS base maps as most popular mapping software (and I don't know this for certain but do believe it to be so), it is overestimating the amount of climbing you're doing by 20-25%. The issue is this: following roads on a landform reduces the amount of climbing you do because when we build roads we cut and fill to even things out, but the terrain to the sides of the roads remains the same (and that's what's measured on the base maps that a GPS system uses).
For most of us, we can count on using between 200 and 300 calories per 1000' climbed (lower amounts for lightweights, higher amounts for Athenas). So if you go on a 2-hour ride and your Garmin says that you climbed 5000', it is inherently overestimating your energy expenditure by around 250 kcal.

[OakLeaf]

I don't think it uses the base maps at all in the calorie calculation, I think it just looks at the GPS triangulation, which is wildly inaccurate. I'll come back from my usual 37-miler in Florida and it'll say I've climbed 900 feet :p. No, it isn't dead flat, but there sure isn't 900 feet of climbing - 60 feet or so over the bridge each way and four or five 10 foot humps.

When I recalculate the calories in SportTracks, that usually takes it down by about 25%. But it still apparently doesn't consider the HR. So I get basically the same values if I'm doing the ride in a paceline, solo in still weather, or in a 25 mph wind. So I guess I've answered my own question ;)

[tulip]

Depending on your size, weight, the terrain, etc., a good rule of thumb for cycling is that we burn between 13 and 17 calories per minute. Chris Carmichael says so, and so I would bet that he knows.

[maillotpois]

If the Garmin uses the same GPS base maps as most popular mapping software (and I don't know this for certain but do believe it to be so), it is overestimating the amount of climbing you're doing by 20-25%.

Many of the Garmins (such as my Edge) also have a barometric altimeter that makes the climbing data much more reliable. (Until you run it through something like Motion based, which I don't, but which does bump the climbing about 20 - 25%.)

[VeloVT]

I use a super low-tech, unsophisticated, non-nuanced formula to calculate calories burned for dieting purposes. It as follows:
100 cal/mile running
40 cal/mile cycling

Doesn't take into account speed, wind, hills, weight... but for basic dieting purposes (and quickly calculating whether a given snack is justified on a long ride), it has served me pretty well. If I were trying to plan nutrition for a serious event, I might want something a little more accurate...

Out of curiosity, let's see how that stacks up too:
For a 2 hour ride:
Chris Carmichael's calculation -- between 1,560 and 2,040
My calculation, assuming average of 20mph while riding (that is, not the actual average speed on your computer, but the speed you see most often) -- 1,600
Oakleaf's Garmin -- 1,700

There's some calculator online somewhere that lets you plug in your weight, the bike's weight, the wind speed, elevation gain, power output, whether you've shaved (just kidding)... and it makes an estimate for you... this might not be much less accurate than a GPS/hrm, given how many variables and fudge factors it seems there are...

[kfergos]

There's some calculator online somewhere that lets you plug in your weight, the bike's weight, the wind speed, elevation gain, power output, whether you've shaved (just kidding)... and it makes an estimate for you... this might not be much less accurate than a GPS/hrm, given how many variables and fudge factors it seems there are...Anybody know where this online calculator might be?

I find lots of vague ones that ask for your weight, how long, and generally what activity. They're not really very helpful because it doesn't take into account your amount of effort and so forth.

[martinkap]

Bicycle ride calorie calculator ... no affiliation:
http://www.geocities.com/SiliconValley/Vista/6434/CalCalcApplet.html

[SadieKate]

If the Garmin uses the same GPS base maps as most popular mapping software (and I don't know this for certain but do believe it to be so), it is overestimating the amount of climbing you're doing by 20-25%. The issue is this: following roads on a landform reduces the amount of climbing you do because when we build roads we cut and fill to even things out, but the terrain to the sides of the roads remains the same (and that's what's measured on the base maps that a GPS system uses).
For most of us, we can count on using between 200 and 300 calories per 1000' climbed (lower amounts for lightweights, higher amounts for Athenas). So if you go on a 2-hour ride and your Garmin says that you climbed 5000', it is inherently overestimating your energy expenditure by around 250 kcal.
As MP says, it depends on which Garmin you use and whether it has a barometric altimeter. See here for more discussion on elevation correction.

http://forums.teamestrogen.com/showthread.php?t=27852&highlight=garmin

It would be interesting to know if Wolfgang of SportTracks does after-import correction of calorie count. I dunnoh. I don't care. I probably should, but my pea brain only has space for so much.

[SadieKate]

The Kreuzotter site appears to be down but still accessible from the archive. It's way cool.

http://web.archive.org/web/20050408065837/www.kreuzotter.de/english/espeed.htm

[michelem]

SadieKate posted this link a couple years ago: http://www.active.com/story.cfm?STORY_ID=12851&CHECKSSO=0&SIDEBAR=569&CATEGORY=century%5Fchallenge

I find I do well with approximately 100 calories per hour, running or cycling. More than that and I get digestive troubles.

Everyone is different, but for me, when running I don't take anything in (calories or water) for anything less than an hour, or 8 miles. I take in a Hammer Gel and approx. 10-12 oz. of water for every hour over an hour, in approximately 20 minute feeds. I like to carry the gel and water separately so that I can quit taking in calories if my tummy starts feeling upset.

For cycing, I use Perpetuem (for some reason, I do really well with it cycling, but it give me the runs when running!). For a 4-5 hour hilly ride I'll mix two 24 oz. bottles with 1-2 scoops Perpetuem in each. If it's really hot I'll refill one of the bottles with plain water and drink some or all of that as well.

Like others have said, experiment and see what works for you. :)