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What's the best way to guestimate calories burned on the bike?(21 posts)

What's the best way to guestimate calories burned on the bike?Ken of Fresno
Feb 17, 2003 3:05 PM
I'm sure there must be some formulae for calculating calories expended during exercise. I would think they would include variables such as weight, age, time spent exercising, heart rate (or maybe % or LT to be more accurate?) etc. I've seen various sites like http://www.caloriesperhour.com that use a description of the activity such as "vigorous cycling (14-16mph)" to give a very rough estimate, but it seems that this is a little too rough for obvious reasons. Any of you nutrition buffs out there know of a formula that will allow me to determine approximately how many calories I burn while riding?

Thanks in advance,
Ken
Not Macas again?deHonc
Feb 17, 2003 3:11 PM
Ken mate,

I hope you havn't been tucking into the McValue Meals again!!! Its a good question - I don't really have an answer other than the calories burnt are probably less than you might imagine - my solution - be careful what you eat and ride lots!

Best Regards,

Dan
LOL! Nope. Just trying to count calories as close as I can. (nm)Ken of Fresno
Feb 17, 2003 3:14 PM
more importantly...how many calories do you burn afterColnagoFE
Feb 17, 2003 3:36 PM
you burn calories all day long and after a workout your metabolism continues to burn at an increased rate--for an hour or more.
I've studied the heck out of thisDougSloan
Feb 17, 2003 3:52 PM
Since calorie intake is critical in 500 mile (and longer) races, I've really tried to find good guidelines. Best I could find is roughly 500-700 calories per hour, about half of which is stored fat, and the other half glycogen and replaced (injested) glucose. Best your digestive tract can handle is about 300 carbohydrate calories per hour.

Doug
Here's the formulaKerry
Feb 17, 2003 4:31 PM
calories/hr = [V*W(.0053 + %G/100) + .0083(V^3)]*7.2

where V is speed in mph, W is bike + rider weight in lbs., and %G is grade in per cent. The factors listed here (0.0053 for friction + rolling resistance and 0.0083 for aerodynamic drag) are obviously not absolute. They will vary with efficiency of the tires and drive train, and with the aerodynamics of the bike + rider combination. Both of these assume a racing position on a racing bike. A clunker bike or a more efficient riding position will change these numbers, which are averages anyway. Power to overcome friction and gravity is proportional only to rider weight and ground speed. Power to overcome wind drag is proportional to the cube of the air speed. For reference, 1 hp = 2700 calories (because of human metabolic efficiency of 24%); 1 calorie = 0.276 watts; 1 hp = 746 watts. Here, calories are kg-calories, or "food calories." I suppose that the human efficiency could be a function of age or duration of exercise, but I have never seen any corellations there. HR and caloric expenditure are related, but not in a way that can be calculated, as they are individual.
Thanks! Does V^3 = V to the third power? (nm)Ken of Fresno
Feb 17, 2003 5:27 PM
yes the thirdcyclopathic
Feb 18, 2003 4:35 AM
aerodynamic resistance is a square of speed and work is speed by distance. Since power=work/time and distance/time, power = V*V* S/time or V*V*V

BTW if you're too lazy to multiply you can use analyticcycling to estimate power output. Since overall efficiency is 20-25%, and there's 4.18wt to cal your consumption will be cal = pwr * 5 / 4.18 or roughly cal=pwr.

there's a little twitch nutrition Cal is indeed 1000cal, and consumption above is calculated per second. To get consumption in Cal per hour you'd need to multiply by 3.6.

At 250wt consumption will be 900Cal/hr and at 150 540Cal/hr.
Pros climbing Mont Ventoux burn ~1500Cal/hr very impressive
Here's the formulaSnyder
Feb 17, 2003 7:15 PM
I would love to know where you got that formula, or if you developed it yourself.

If I put in 20 mph as speed and I am riding into a 5 mph head wind, would I use 25 as the V representing air speed, that gets cubed?

Thanks
Several referencesKerry
Feb 18, 2003 4:41 PM
The first time I saw the formula was in "Bicycling Science: Ergonomics and Mechanics" by Whitt & Wilson (MIT press, 1974). The formula they presented did not have the coefficients defined, but they present data from which you can calculate the components if you are so motivated. Subsequently, the coefficients have been published in Bicycle Guide and Adventure Cycling (plus many scientific papers). Until recently, Bicycling was using this equation with a bad set of coefficients (applicable to beach cruisers and unfit riders), but I notice that as of the November issue, they are posting more reasonable numbers. Again, a more/less aero postion will affect the aero coefficient, and a more/less efficient bike will determine the friction coefficient. I've seen a lot of data from several labs and cycling magazines that support the accuracy of the formula (e.g. measured power outputs for TdF time trials).
That sounds about right. After doing the math I get...Ken of Fresno
Feb 18, 2003 10:52 AM
about 350 cal/hr @ 15mph, 675 cal/hr @ 20mph and 1100 cal/hr @ 25mph. That is in the range of what Doug mentioned and about what I would expect. Thanks! This really helps determine about how much I need to consume in order to keep a slight calorie deficit for the day to reach my goal weight. Although, as ColnagoFE mentioned, there is the whole problem of figuring out the extra calories burned due to increased metabolism after exercise. I doubt that's as easily calculated.

Thanks again,
Ken
Wow, I burn 100cal/hr...noveread
Feb 18, 2003 12:18 PM
Or did I do this wrong? With 157lb combined weight at 17mph I get 100 cal an hour (assuming no wind and level terrain)!

Bummer...

Good thing Mickey Ds announced removal of the "Big-N-Tasty" from the $1 menu today...

Noveread
Or should it be 395cal/hr? nmnoveread
Feb 18, 2003 12:25 PM
395 is what I get.Ken of Fresno
Feb 18, 2003 1:20 PM
Whis is exactly 75% of the calories in a Big N Tasty (no cheese).

Ride to eat :)
Ken
problem with formulasDougSloan
Feb 18, 2003 1:38 PM
Problem with the formulas is the huge fudge factors or unaccounted for variables, like your body efficiency (internal and drag), temperature, cadence, etc. You might as well just estimate if you have precision of plus or minus about 25%.

Doug
Check out the dataKerry
Feb 18, 2003 5:07 PM
If you compare the results of this formula with the numbers reported from people with SRMs and Power Taps, you'll find it to be much more accurate than +/- 25%. It's more like +/- 5%. Your calorie burn is not going to be signficantly affected by reasonable temperatures (you sweat to keep cool and wear clothes to keep warm) or cadence within a reasonable range. For fit individuals, the body efficiency doesn't vary much either. From this formula, you get a lot more accuracy than other available methods.
New training tool idea...noveread
Feb 18, 2003 2:13 PM
Perhaps some sort of new training tool could be developed that included in it's display not calories burned per hour, but amount of tasty item earned? Using above example I could earn a Big-N-Tasty (no cheese) if I ride for 1hr20min at 17mph. Perhaps the display could be graphic oriented and as I ride along, I nice big 'ol Big-N-Tasty (no cheese) burger gradually materializes on the display. And if I do a 20min TT effort during that workout a piece of cheese gets put on the burger!

Noveread
I'd buy one. Sprint for that pizza! nmKen of Fresno
Feb 18, 2003 3:10 PM
re: What's the best way to guestimate calories burned on the bike?moving up
Feb 18, 2003 11:14 AM
One other option - some heart monitors such as made by Polar allow you to program your height, weight, age, sex, and activity level (based on a test result the monitor will perform for you) and then it calculates your actual calories as they are expended. I use the Polar brand and strap it to the handlebar to watch my heartrate and check the calories when I am done. You can check it during a ride if you like without effecting the timing or heartrate functions. Price was about $150 w/tax.

What is very interesting is the variance in calories expended, which does not always correlate with perceived exertion. Typically, I ride in a hilly area (west side of Austin) and average 15 - 18 mph. Calories run 700/hour at the 15 mph pace and are up to 1000 - 1100/hour at the 18 mph pace (I'm not in Lance A's shape so I'm working hard on the hills). Days when you fill strong may actually result in lower calorie output and days when you feel tired may result in more caloric output.

Good riding.
Your experience tells why an HRM doesn't work for this.Kerry
Feb 18, 2003 4:16 PM
HR is way to variable to correlate with calories burned, and calories burned vary widely based on factors that are not directly tied to HR. Yes, your HRM gives you calories burned, but it's a poor estimate, as you have learned.
Easier WAY - WEIGHT WATCHERS cardboard calculatormazobob
Feb 18, 2003 3:06 PM