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Posted
13 minutes ago, MongooseMan said:

Happy to have my math proven wrong :)

You still have to multiply your kJ of work performed by your metabolic efficiency, and then you have to convert kJ to kcal (Cal). Luckily those two cancel out for most people, so while your math was not perfect, your answer is ballpark correct. 😉

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Posted
3 minutes ago, bleedToWin said:

You still have to multiply your kJ of work performed by your metabolic efficiency, and then you have to convert kJ to kcal (Cal). Luckily those two cancel out for most people, so while your math was not perfect, your answer is ballpark correct. 😉

Yup, the linked article says that almost word for word :)

image.png.e93b0d2c55cbdd0ce9025d9f0c7202d2.png

Posted (edited)
1 hour ago, MongooseMan said:

For anyone, 

Energy (joules) = power (watts) x time (seconds)

To get kcal

Energy (kcal) = Power (watts) * Time (hours) * 3.6

 

So, if your zone 2 is 200W, then every hour is 200 x1x3.6=720kcal

To convert to grams of carbs, divide by 4=180g (which you're unlikely to eat but gives you an idea)

 

Happy to have my math proven wrong :)

 

Sources:
https://www.welovecycling.com/wide/2020/05/14/how-to-convert-watts-into-calories-burned-on-the-bike/

https://www.omnicalculator.com/conversion/grams-to-calories

The math is wrong 

1 joule is 0,239006 gcal not kcal

1joule is 0,000239006 kcal

or 1 kcal = 4184 J

 

i would simply convert kcal to watt hours 

1kcal = 1.16222 W.hr

 

Edited by DieselnDust
Posted
On 5/14/2024 at 2:51 PM, DieselnDust said:

1 kcal = 4184 J

But to perform 4184 J of work on a bike most people need to metabolise 4.184 kcal of glucose. 1 kcal for the work as you calculated, and the rest for heat and noise and for some bobbing their heads up and down aimlessly for some reason...

Posted
1 hour ago, bleedToWin said:

But to perform 4184 J of work on a bike most people need to metabolise 4.184 kcal of glucose. 1 kcal for the work as you calculated, and the rest for heat and noise and for some bobbing their heads up and down aimlessly for some reason...

I don’t make the conversion factors up, I read them from a table of conversion factors that is written by a standards body like ASTM and ISO

Posted
15 minutes ago, DieselnDust said:

I don’t make the conversion factors up, I read them from a table of conversion factors that is written by a standards body like ASTM and ISO

Yes, but you are not done.
You did it all perfectly, but if you are doing conversion to kcal it's because you are looking at energy derived from glucose and relating it to work performed on a bike.

Posted
On 5/14/2024 at 1:19 PM, cadenceblur said:

The zone 2 calorie statement, is that for everyone?

It depends where the crossover point is for “everyone” what which point the burning of carbs that fats is a 50/50 split. The bottom of zone 2 is certainly majority fats for Matt Beers, but not so much for the lesser trained person.

Posted
2 hours ago, bleedToWin said:

But to perform 4184 J of work on a bike most people need to metabolise 4.184 kcal of glucose. 1 kcal for the work as you calculated, and the rest for heat and noise and for some bobbing their heads up and down aimlessly for some reason...

Aah you’re talking about efficiency?

that’s going to vary from person to person

so using the baseline conversion at 100% efficiency and measure actual kcal burned you get an idea of their efficiency, then apply that to determine how many kcals they need to consume 

what I am confused about is why the articles numbers are off by 1000? What underlying assumptions and calcs have they made in the background to fudge the numbers by that factor

Posted
On 5/17/2024 at 12:37 PM, DieselnDust said:

Aah you’re talking about efficiency?

that’s going to vary from person to person

so using the baseline conversion at 100% efficiency and measure actual kcal burned you get an idea of their efficiency, then apply that to determine how many kcals they need to consume 

what I am confused about is why the articles numbers are off by 1000? What underlying assumptions and calcs have they made in the background to fudge the numbers by that factor

Most people have a very similar cycling efficiency, hence all of us using the same value that makes calculations easier. Won't be off by much.

"off by 1000" remember food Calorie (Cal) is 1000 physics calories (cal). Stupid yes, but just the way it is...

 

Posted
43 minutes ago, bleedToWin said:

Most people have a very similar cycling efficiency, hence all of us using the same value that makes calculations easier. Won't be off by much.

"off by 1000" remember food Calorie (Cal) is 1000 physics calories (cal). Stupid yes, but just the way it is...

 

Aah yeah that’s the missing link , I’m using cal cal as in physics cal.

 

👍🏼

Posted
10 minutes ago, Dexter-morgan said:

Here a thread about an insanely strong South African cyclist changes into a debate over KJ, Cal, conversion factors and such, got to love the BH scientists - My head hurts just thinking about this.

Swing it back!

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