Total work (KJ) versus caloric expenditure (Kcal)

[CycleFast]

When I do a ride with my PowerTap I can easily find the total number of joules for the ride. Since 4.2KJ is approximately equal to 1Kcal, and the metabolic efficiency when cycling is usually 20-25%, you get a 1:1 relationship between KJ and expended Kcal, e.g. a 1500KJ ride means that my caloric expenditure is roughly 1500Kcal.

My question is, does this "equation" include my resting metabolic rate as well? Let's say my resting metabolic rate is 100Kcal/hour. I do a 4 hour ride, and my PT shows that I have done 1500KJ of work. Is my total energy expenditure for this ride 1500Kcal + 4 hours x 100Kcal/hour = 1900Kcal?
Or is my resting metabolic rate included in the estimated 1500Kcal?

Any thoughts on this?

_________
CycleFast

 

[gvanwagner]

IIRC your metabolic rate factors into the 20-25% effeciency part of the equation. IOW the higher your metabolic rate is compared with the energy cost of unloaded pedaling the lower your efficiency will be. Don't quote me on that though. That being said the 1:1 ratio that most use implies really good efficiency.

According to Allen Lim
%- Kcal per KJ
Novice
18-1.33
19-1.26
Amatuer
20-1.19
21-1.14
Us Pro
22-1.09
23-1.04
Grand tour pro
24-1.00
25-.96
26-.92


Of course taking into account that there are wide variations in each group of riders.

 

[gvanwagner]

Also, there are wide variations in a single person efficiency because of terrain, weather, shoulder rocking and intensity etc.

 

[PaulMD]

When I do a ride with my PowerTap I can easily find the total number of joules for the ride. Since 4.2KJ is approximately equal to 1Kcal, and the metabolic efficiency when cycling is usually 20-25%, you get a 1:1 relationship between KJ and expended Kcal, e.g. a 1500KJ ride means that my caloric expenditure is roughly 1500Kcal.

My question is, does this "equation" include my resting metabolic rate as well? Let's say my resting metabolic rate is 100Kcal/hour. I do a 4 hour ride, and my PT shows that I have done 1500KJ of work. Is my total energy expenditure for this ride 1500Kcal + 4 hours x 100Kcal/hour = 1900Kcal?
Or is my resting metabolic rate included in the estimated 1500Kcal?

Any thoughts on this?

_________
CycleFast

Yes, you are pretty close with this assumption.

 

[fascat]

IIRC your metabolic rate factors into the 20-25% effeciency part of the equation. IOW the higher your metabolic rate is compared with the energy cost of unloaded pedaling the lower your efficiency will be. Don't quote me on that though. That being said the 1:1 ratio that most use implies really good efficiency.

According to Allen Lim
%- Kcal per KJ
Novice
18-1.33
19-1.26
Amatuer
20-1.19
21-1.14
Us Pro
22-1.09
23-1.04
Grand tour pro
24-1.00
25-.96
26-.92


Of course taking into account that there are wide variations in each group of riders.

Also check this article out:
http://www.pezcyclingnews.com/default.asp?pg=fullstory&id=3570

RMR, as I understand it, speaks more to the amount of calories you burn each day, walking around, breathing, sitting, etc..

SO RMR + Energy Expenditure (kJ's, 1:1) = Total Daily Caloric Requirements

 

[CycleFast]

Thanks a lot guys, this was very useful!

_________
CycleFast