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Ok. Here's my question. Assume 2 identical riders. Cyclist # 1 rides 10 miles at 10 mph, # 2 rode 10 miles at 20 mph. Would each cyclist burn/use the same number of calories? Since work is measured in foot pounds, it would seem to me they would expend the same amount of energy, since they moved the same amount weight over the same distance.

I know that cyclist # 2 benefitted from more aerobic exercise, etc., etc. That's not the question. Did they both expend the same amount of energy, requiring the same amount of fuel?

I honestly don't know the answer, but I hope someone can enlighten me. :confused:
 

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Mr. Versatile said:
Ok. Here's my question. Assume 2 identical riders. Cyclist # 1 rides 10 miles at 10 mph, # 2 rode 10 miles at 20 mph. Would each cyclist burn/use the same number of calories? Since work is measured in foot pounds, it would seem to me they would expend the same amount of energy, since they moved the same amount weight over the same distance.

I know that cyclist # 2 benefitted from more aerobic exercise, etc., etc. That's not the question. Did they both expend the same amount of energy, requiring the same amount of fuel?

I honestly don't know the answer, but I hope someone can enlighten me. :confused:
It would be very close, but there would be small differences.

There is probably more heat generated by rider #2, and energy would be used to dissipate that heat.

They would do the same amount of work, yes, but the human body has ineffeciencies depending upon multitudes of factors.

If you had a power measuring device, and could measure the total work, they would both use the same amount of kilojoules to do the same route, regardless of whether it took one second or one year.

Silas
 

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Work (energy) equals the integral of force wrt distance. So if the rider is going up a steep hill and the only significant force acting is gravity (which is indpendent of speed), the 2 riders will do the same amount of work. On the other hand, if the rider is riding into a strong headwind so the only significant force is wind drag, then the force goes as the square of the velocity and the faster rider does 4 times the work of the slower one. In real world conditions, the force will be the sum of aero drag (force goes as velocity squared), gravity (force independent of velocity), and rolling resistance and other losses (also independent of velocity) so the actual relation between the work for the faster and slower rider will be between equal and 4 times as great.
 

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Pretty much wrong

SilasCL said:
It would be very close, but there would be small differences.
Yeah, small differences like it takes roughly 12 calories per mile to go 10 mph and 30 calories per mile to go 20 mph. Total calories at 10 mph = 120. Total calories at 20 mph = 300. Within an order of magnitude, I guess those are the same number, but looked at a different way, it takes 2.5 times as much energy per mile at 20 mph as at 10. Power to overcome aerodynamic drag increases with the cube of velocity.
 

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What more can you say? Nicely worded.

The simple answer is "No, because of wind resistance's exponential increase compared to speed."
 

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Kerry Irons said:
Yeah, small differences like it takes roughly 12 calories per mile to go 10 mph and 30 calories per mile to go 20 mph. Total calories at 10 mph = 120. Total calories at 20 mph = 300. Within an order of magnitude, I guess those are the same number, but looked at a different way, it takes 2.5 times as much energy per mile at 20 mph as at 10. Power to overcome aerodynamic drag increases with the cube of velocity.
As usual Kerry is correct. My brain was evidently shut off during my last post.

Silas
 

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According to fitday.com which I use to track food intake also has a section where to input the amount of calories burn during activites. According to the website you burn 1322 at 20mph for 10 miles and 881 calories at 10 mph for 10 miles. So that is 441 calories difference.
 

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Clark said:
According to fitday.com which I use to track food intake also has a section where to input the amount of calories burn during activites. According to the website you burn 1322 at 20mph for 10 miles and 881 calories at 10 mph for 10 miles. So that is 441 calories difference.
Those numbers seem unrealistic. Since we have power meters it is pretty easy to calculate the approximate calories burned from cycling. FWIW, I think when I've figured this out in the past a top level cyclist capable of putting out like 450 watts for an hour burns something less than 1500 calories. Of course, most of us can't work at nearly that rate. At 10mph for an hour I'd be surprised if you would burn more than 300-400 calories max unless you were dragging a parachute behind you :)
 

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Dwayne Barry said:
Those numbers seem unrealistic. Since we have power meters it is pretty easy to calculate the approximate calories burned from cycling. FWIW, I think when I've figured this out in the past a top level cyclist capable of putting out like 450 watts for an hour burns something less than 1500 calories. Of course, most of us can't work at nearly that rate. At 10mph for an hour I'd be surprised if you would burn more than 300-400 calories max unless you were dragging a parachute behind you :)

Well you know its going to vary with each person. It also depends on your Heart reate and weight also. In general these number are not that far off. Those numbers are based on someone weighing 200lbs. Here is a web site that will support it.

http://www.nutristrategy.com/fitness/cycling.htm

Take your powermeter and go figure out how many calories you would burn then, since that is the most accurate way to calulate verus a heart rate monitor.
 

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I tracked what I ate and my exercise amounts (cycling and fast walking) for a week once. I didn't change what I ate or how I exercised from my normal routine. On most days the alleged calories that I burnt during exercise (not couting BMR) exceed the calories that I ate and the calories that I ate were at or below my calculated BMR. I should have been so calorie deficient that I would be very weak and losing weight like crazy. My weight kept stable and I felt fine.

I believe that most of the published calorie burnt during exercise numbers are very optimistic. I'm not sure that the various BMR equations are realistic either.
 

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I believe that most of the published calorie burnt during exercise numbers are very optimistic. I'm not sure that the various BMR equations are realistic either.[/QUOTE]


I think the published are for normal person at a certain with a melboic rate and ect. But each person different and the only real accurate way I beleive to know how moany calories that you burn is using a powermeter because that is actually mearsue how much power you are putting out. With that you can figure out how many calories you burned.
 

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Clark said:
Well you know its going to vary with each person. It also depends on your Heart reate and weight also. In general these number are not that far off. Those numbers are based on someone weighing 200lbs. Here is a web site that will support it.

http://www.nutristrategy.com/fitness/cycling.htm

Take your powermeter and go figure out how many calories you would burn then, since that is the most accurate way to calulate verus a heart rate monitor.
It doesn't matter what someone weighs, etc if you can measure power. Because if you can measure power you can figure out how much work was done and from that how many calories burned. The reason Lance is faster than you or I is because he can do more work per unit time (i.e. put out more power) thus he can burn more calories per unit time (and sets a realistic upper limit of what is humanly possible). In cycling I don't believe it has been shown that there is any great differences in efficiency between individuals that might allow one to accomplish more work with less calories burned.

So, we know the fastest cyclists in the world can do about 450 watts/hour which equals 397 calories burned, we also know that muscle is only about 25% efficient, and the rest is loss at heat. So 4 x 397 = 1588 cal (I remembered incorrectly before, so its slightly more than not less than 1500 calories) being what is humanly possible. To burn off 1322 calories in 30 minutes (i.e. 10 miles at 20mph) one would need to put out 769 watts over that 30 minutes, this is not humanely possible! To burn up 881 cal in 1 hour (i.e. 10 miles @ 10 mph) one would need to put out 256 watts. Which while possible for most reasonably fit people, would require you to either be going up hill or dragging a parachute to only be going 10mph at that power output on a bike!
 

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so, should i believe my HRM when it said i burned around 2200 calories in 2.5 hours on a hard group ride yesterday? the whole idea of it taking the same amount of calories to go the same distance regardless of effort or intensity kind of confuses me.
 

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Clark said:
Well you know its going to vary with each person. It also depends on your Heart reate and weight also. In general these number are not that far off. Those numbers are based on someone weighing 200lbs. Here is a web site that will support it.

http://www.nutristrategy.com/fitness/cycling.htm

Take your powermeter and go figure out how many calories you would burn then, since that is the most accurate way to calulate verus a heart rate monitor.
My spreadsheet (using the Kerry equation), which has done a good job of matching my weight loss over the last 3 1/2 months, would give you 389 Cal for 10 miles at 20mph. 1322 is way too high. That seems even higher than Bicycling mag. - TF
 

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Calories burned.

TurboTurtle said:
My spreadsheet (using the Kerry equation), which has done a good job of matching my weight loss over the last 3 1/2 months, would give you 389 Cal for 10 miles at 20mph. 1322 is way too high. That seems even higher than Bicycling mag. - TF
What about calories burned while climbing at a moderate to brisk effort, half of the time sitting and half of the time standing, with calm winds, at an average grade of 5.5%, for X10 miles in 71 minutes? (bike wt= 18.5 lbs with half full water bottle. My weight= 175 lbs.)
 

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TBomb said:
so, should i believe my HRM when it said i burned around 2200 calories in 2.5 hours on a hard group ride yesterday? the whole idea of it taking the same amount of calories to go the same distance regardless of effort or intensity kind of confuses me.
Assuming you're reasonably fit and it was a pretty fast group (i.e you're riding hard the whole time) that seems like the right range (880 cal/hour = ~250 watts/hour).

It's a physics thing; to move X weight, Y distance takes a certain constant amount of work, however long it takes to do it. However, as others have pointed out on a bike this isn't in reality true most of the time because the main impediment to movement is drag and drag doesn't increase linearly with speed. Consequently someone putting out twice as much power will not go twice as fast unless climbing such a steep hill that drag becomes meaningless.
 

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ru1-2cycle said:
What about calories burned while climbing at a moderate to brisk effort, half of the time sitting and half of the time standing, with calm winds, at an average grade of 5.5%, for X10 miles in 71 minutes? (bike wt= 18.5 lbs with half full water bottle. My weight= 175 lbs.)
Is that with an Italian or English threaded bottom bracket? Shimano or Campy?
 

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ru1-2cycle said:
What about calories burned while climbing at a moderate to brisk effort, half of the time sitting and half of the time standing, with calm winds, at an average grade of 5.5%, for X10 miles in 71 minutes? (bike wt= 18.5 lbs with half full water bottle. My weight= 175 lbs.)
873 :) TF
 

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Discussion Starter · #20 ·
Thanks everybody, for the excellent responses. My question arose from a lunch-time conversation with some fellow faculty members.

There were certainly some variables that I didn't consider, or hadn't thought about. Despite the fact that I've been adult riding since the mid-60's, and am a former cat 2 racer, I never thought to figure in wind resistance. DUH! :rolleyes:
 
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