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Suunto Ambit2 S, Suunto Ambit2, Suunto Ambit3 Peak, Suunto Ambit3 Sport, Suunto Ambit3 Run, Suunto Traverse, Suunto Ambit3 Vertical, Suunto Traverse Alpha
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WARNING: This app introduced an error to the power calculation that will result in overestimation. This app updated danielp27's existing running power app (FEB2016) by adding a more accurate slope estimate for walking speeds. That was a nice update. However, the final power calculation was rewritten using the distributive property of multiplication, but with an error. It incorrectly reads "power = (cKin*SUUNTO_USER_WEIGHT) ..." It should read "power = (cKin*speed) ..."
No, the power is calculated each second, then the units are J/s that is in watts. The body weight in kg is needed to obtain joule units, that is (cKin*SUUNTO_USER_WEIGHT) is in joule each second (in watts). If you multiply cKin*speed the units wouldn't have any sense.
My cKin hasn't the same equation that in GOVS.cpp. Neither the cAero. I have been talking about these topics with Ale Martínez some time ago. In any case, the results are independent of this fact when each cKin definition is used.
I took a look at GOVSS.cpp. That, in turn, references (Arsac 2001), which came from Skiba's govss.pdf. However, when you look at Skiba's paper, his one reference for Arasac is actually in 2002: "Modeling the energetics of 100m running by using speed curves of world champions." The full text is available for free online. Basically, that's the primary reference we should all be basing our cAero and cKin on.
You're right that cKin and cAero are expressed in J/kg (along with cSlope). So *all three* should be multiplied by SUUNTO_USER_WEIGHT. I've only seen that done in GOVSS.cpp. You'll want to fix that. You're right that cKin (as calculated here) doesn't need to be multiplied by speed. However, Arsac also recommends multiplying cKin and cAero by efficiency (n^-1), which no one is doing. There are a few other things as well.
If you look at cAero definition in line 46 of GOVSS.ccp at Github site you will see that weight appears as denominator and then it is necessary to multiply cAero by weight to obtain the power contribution of this term in line 57 of GOVSS.cpp. In my app it isn't necessary because my cAero definition doesn't include the weight as denominator. And as I told you I knew that cKin (as calculated here) doesn't need to be multiplied by speed.
And with respect to efficiency of converting external work to its metabolic energy equivalent, it is not clear when to use it if you look at page 1783 of Arsac paper (bottom at left column).
Keep in mind that these app needs an accurate measurement of vertical height, I mean, it will only work properly in devices with barometric sensor. In all case, it is good to have a reference of the power to serve as a training guide and to compare between days. Thanks a lot for your interest and comments.
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