Calories expended per hour!

SMIKEY said:

Do these numbers sound correct?
Weight 198
Duration of exercise 60 minutes
Bicycling: 12-13.9 mph, leisure, moderate effort950

Calories expended 950

Doesnt that seem a tad bit high for such a moderate amount of energy?

It does sound a bit high, and my guess is that it's closer to 600-700 calories.

There really isn't an accurate way to measure caloric output with equations or those online calculators. They just give VERY general estimates, which is usually enough for most people to track for weight loss. But so much more depends on your caloric expenditure than weight, duration, and speed of your ride. The only way to tell exactly how many calories you expended is to go to a lab and have your oxygen consumption measured during the ride. Then you can tell exactly how much you burned. 🙂

SMIKEY said:

Do these numbers sound correct?
Weight 198
Duration of exercise 60 minutes
Bicycling: 12-13.9 mph, leisure, moderate effort950

Calories expended 950

Doesnt that seem a tad bit high for such a moderate amount of energy?

Sounds way high to me. Using the assumption that kjoules= kcals burned, I just multiply power in watts (ie, joules/sec) x 3600 seconds/hour to get an estimate of calories burned/hour.

At 13 mph on a level, a velo calculator indicates you're putting out around 60 watts; that's only 216 kcals for your 1 hour effort.

Lot's of variables in the real world, like winds, terrain, road surface, position on the bike. But I'd say 200-300 kcals/hr is in the ballpark for an estimate.

dhk said:

Sounds way high to me. Using the assumption that kjoules= kcals burned, I just multiply power in watts (ie, joules/sec) x 3600 seconds/hour to get an estimate of calories burned/hour.

At 13 mph on a level, a velo calculator indicates you're putting out around 60 watts; that's only 216 kcals for your 1 hour effort.

Lot's of variables in the real world, like winds, terrain, road surface, position on the bike. But I'd say 200-300 kcals/hr is in the ballpark for an estimate.

WOW!! Now thats getting down and dirty with those numbers. Is this formula something you learned through the years or is it simple math? Can you utilize the formula for other activities??

Well, I can't take credit for the formula. Ric put out the estimate that kjoules of work done are roughly equal to kcals burned....that's the key assumption.

Since kwatts are the same as kjoules/sec, all you have to know is your power output (in kwatts), and multiply by the number of seconds you're working. EG, for riding at a good pace, say 0.200 kwatts of power output (maybe 18-20 mph), you're burning 0.200 kcals per second. For an hour, that's 0.2 x 3600 seconds, or 720 kcals.

The tough part of course is estimating your power output on the bike. Unless you have a power meter, hard to know with any precision. You can use a velo calculator, but you still have to guess at all the variables like wind, elevation, surface, aero position on the bike. As you know, these change constantly in the real world.

dhk said:

Well, I can't take credit for the formula. Ric put out the estimate that kjoules of work done are roughly equal to kcals burned....that's the key assumption.

Since kwatts are the same as kjoules/sec, all you have to know is your power output (in kwatts), and multiply by the number of seconds you're working. EG, for riding at a good pace, say 0.200 kwatts of power output (maybe 18-20 mph), you're burning 0.200 kcals per second. For an hour, that's 0.2 x 3600 seconds, or 720 kcals.

The tough part of course is estimating your power output on the bike. Unless you have a power meter, hard to know with any precision. You can use a velo calculator, but you still have to guess at all the variables like wind, elevation, surface, aero position on the bike. As you know, these change constantly in the real world.

The big problem with this calculation is that it would produce zero cals at zero power which of course is wrong. There has to be a fixed component (the cals burned just being alive and this varies significantly between different sized people) and a variable component dependant on the power output. I don't think Ric's formula was ever intended for use on such low power output levels. It certainly couldn't be used for other activities as it is based on power output riding a bike and powermeters are not available for most other activities.

pod said:

The big problem with this calculation is that it would produce zero cals at zero power which of course is wrong. There has to be a fixed component (the cals burned just being alive and this varies significantly between different sized people) and a variable component dependant on the power output. I don't think Ric's formula was ever intended for use on such low power output levels. It certainly couldn't be used for other activities as it is based on power output riding a bike and powermeters are not available for most other activities.

it's to work out the energy expended from the actual cycling, not anything else.

my polar says I burn 400-500 calories an hour on a training ride, and 700-800 calories an hour in a crit.

spacefuzz said:

my polar says I burn 400-500 calories an hour on a training ride, and 700-800 calories an hour in a crit.

You need to take the polar data with a pinch of salt. When caculating the amount of KCal expended based on heart rate, etc even polar say's that it could be up to +/- 10%. If I remember right Rick from RST said something similar in a past post as well.

That all being said I still use the readout on my polar to give me an idea of when to take on gels during a hard ride.

Back to the original question depending on the terrain I have been on rides that suggest that I am consuming upwards of 1100 KCal and hour and felt like it to.

jcjordan said:

You need to take the polar data with a pinch of salt. When caculating the amount of KCal expended based on heart rate, etc even polar say's that it could be up to +/- 10%. If I remember right Rick from RST said something similar in a past post as well.

The Polar is an excellent indicator of energy expended. +/-10% is relatively speaking a very accurate measurement. Besides if you are comparing various ride routes, speeds etc from ride to ride using the same watch then you are getting a direct comparison of values. This is more important than the definitive accuracy of the number itself im my opinion. 😎

I also get 400-500 calories/hour for training rides on both my Polar and Computrainer.

ALL: I'm 130lbs so keep this in mind when making comparisons.

spacefuzz said:

my polar says I burn 400-500 calories an hour on a training ride, and 700-800 calories an hour in a crit.