Cal and kJ

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theller
Posts: 7
Joined: Fri Jun 05, 2015 11:15 am

Cal and kJ

Post by theller »

I'm wondering what these units mean on the newton.

Example: This morning I rode 20.9 k with an average power of 149W, it took 54 minutes 48 seconds.
The newton displayed 468 cal and 489 kJ.

54:48 is 3288 seconds, 3288 s * 149 W = 489921 Ws = 489921 J = 489.921 kJ. This is also what the
Newton displays.

But what does the 468 cal value mean? 1 kcal is approx 4.18 kJ, so 489,921 kJ = 117 kcal
brookside
Posts: 48
Joined: Tue May 05, 2015 7:03 am

Re: Cal and kJ

Post by brookside »

There's a difference between the total energy your body burns and the energy used as motive force. Only about 25% of the total energy your body uses during a ride is available for propulsion, the rest is dissipated as heat. To put it another way, if you want to burn 500 kcal (calories as we normally mean them) during a ride you'll need to use about 125 kcal as energy to move the bike. The Newton shows the total energy your body burned during the ride in calories (kcal) and the energy used to (just) move the bike in kjoules.
Velocomp
Velocomp CEO
Posts: 7793
Joined: Fri Jan 11, 2008 8:43 am

Re: Cal and kJ

Post by Velocomp »

brookside wrote:There's a difference between the total energy your body burns and the energy used as motive force. Only about 25% of the total energy your body uses during a ride is available for propulsion, the rest is dissipated as heat. To put it another way, if you want to burn 500 kcal (calories as we normally mean them) during a ride you'll need to use about 125 kcal as energy to move the bike. The Newton shows the total energy your body burned during the ride in calories (kcal) and the energy used to (just) move the bike in kjoules.
Correct!
John Hamann
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