This question is from a comment I got on my Calories Burned in Running vs Cycling post.
Question: If you double the speed you cycle will you burn more than twice the calories since air resistance increases exponentially with speed?
Answer: According to Dr. Edward Coyle of The University of Texas in Austin who did a study to determined the average values of oxygen consumption by cyclists at difference speeds, your position that if you “double the speed you cycle at, you will burn MORE than twice the calories” is incorrect. Here are the numbers Dr. Coyle’s tests came up with.
mph | calories/mile
10: 26
15: 31
20: 38
25: 47
30: 59
Here they are in metric.
km/h | calories/km
16: 16
24: 19
32: 24
40: 29
48: 37
You can see from these numbers that while at 10mph you burn 26 calories per mile but you don’t burn 54 calories per mile at 20mph but only 38 .
In metric at 16kmph you burn 16 calories per kilometer but at 32kmph you don’t burn 32 calories but only 24 calories per kilometer.
My typical average speed is 25kmph (15.5mph) so I am burning 19 calories per kilometer (31 calories per mile). Yesterday I managed to do 12.4km in 25:01 which is an average speed of 20kmph (18.6mph) which is close to my max.
While air resistance is an issue according to Dr. Coyle’s the effect is not doubled when you double your speed from 10mph to 20mph (16kmph to 32kmph).
When it comes to bicycle we are not dealing with the same speeds we are dealing with when it comes to cars. Wind resistance increases exponentially in higher speeds but not in lower speeds.
Biking on a non-professional level we are dealing with speeds below 30mph (48kmph) which are covered in Dr. Coyle’s numbers.
In cat 4 races, riders maintain an average speed of 18mph to 20mph (29kmph/32kmph), in cat 3 riders 24mph to 28mph (39kmph/45kmph), and in the US or EU pro circuit riders maintain 30mph to 35mph (48kmph/56kmph).
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July 6th, 2009 at 4:22 am
The question is not well-posed. The numbers clearly show that you do not double the number of calories/mile if you double your speed. However, you do more than double the number of calories/hour, which is the rate of burning calories, which is what most people want to know.
According to your numbers. 1 hour at 10 m.p.h. burns 260 calories (sounds low to me….) 1 hour at 20 m.p.h. burns 760 calories, which is much more than twice 260.
July 8th, 2009 at 5:37 pm
Hi John Yelton,
I thought the question was clear. The person wanted to know if you double your speed do you double your calorie burn per mile or km. In most cases the answer is no. While I don’t have numbers that go past 30mph or 48kmph it appears the way the graph is going in higher speeds this would be the case. How ever when you get into 30mph or 48kmph average we are then into the pro circuit. I can hardly do 32kmph average over 25km.
I would agree that calories/hour is the rate people want to know but calories per distance for a certain speed can be changed to calories per hour very easily. Again when you get above 30mph or 48kmph you are into the pro circuit and far above what a normal person can do.
I see you point about 1hr at 20mph would burn 760 calories. I think I will review my numbers as there seems to be something off in them. That’s for pointing this out!
July 16th, 2009 at 12:18 pm
It also depends how much you and your bike weigh. Moving 120lbs over 10 miles requires a good deal less caloric expenditure than 200 pounds.
Here’s an interesting link comparing calories per hour and rider’s weight.
http://www.nutristrategy.com/fitness/cycling.htm
Hope this helps.
February 1st, 2010 at 5:57 am
Wind resistance does not increase exponentially at all. The drag felt by an object is proportional to the square of the velocity at virtually ALL speeds relevant to a cyclist (only if you were cycling through treacle would viscous effects dominate and the relationship would be more linear). I suspect what Dr Coyle has done is measure some performance metric indoors ie. out of the wind (however see the qualification below).
The power required to overcome the drag increases proportionally to the velocity times the drag – ie. the cube of the velocity – and since energy is power times time the answer is YES you will burn more than twice the calories (actually 8 times the calories).
Now for the caveats: 1) it doesn’t really scale perfectly since you will only burn more than twice the calories you would have burned on top what you would have burned had you not been cycling thus there is an offset, 2) transmission losses and friction between the tires and road surface also scale with velocity, 3) in the results there is a cubic scaling present but given the sparsity of the data points it is hard to justify a particular fit, 4) it may be worth considering that cycling at lower speeds may be fairly inefficient and thus the lower speed data points could be mis-representative and 5) technically, for this to be true the rate of energy consumption must be constant.
So cycling at double the speed will theoretically use at least 8 times the calories – this is the minimum according to the laws of physics and to suggest otherwise one must present more than out of context data.
February 4th, 2010 at 8:13 am
Hi Tom,
Thanks for you good information.
I think we also have to take into consideration that there is a maximum speed a cyclist can maintain. For it is between 32 and 33kmph on a 12.5 distance that has a couple of nice hills and some other up and down grades.
So when it comes to running a person may be able to burn more calories when they try to run themselves out than if they try to cycle themselves out. Also depending on the fitness level a person is at it may be more possible to sustain running longer than cycling and hence do better in burning calories running than cycling.
Cycling has a lot to do with the fitness level of your legs where running seems to have more to do with cardio.
Thanks!
Bob.