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Cal and kJ
Posted: Fri May 26, 2017 3:22 am
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
Re: Cal and kJ
Posted: Wed Jul 19, 2017 2:03 pm
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.
Re: Cal and kJ
Posted: Wed Jul 19, 2017 3:12 pm
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!