Power calculation: what is is based on and how precise?

[OddStuff]

I'm very interested in the power calculation. From a bike exercise test I know at which HR and power my lactate threshold currently is. But my main sport is running. I am not totally sure where exactly my LTh is for running, but I think it's quite a bit lower, and I was wondering if I can somehow use the power data to get a better comparison. But then I see that my power data is completely above the cycling LTh power apart from a few negative spikes. Which might be possible as I have a suspected muscle disease. Or the data is completely useless, which might also be very possible.

Btw, would a moving average be possible here as well? My data is very spiky due to lots of pace variations.

[laufhannes]

From Garmin: Running power is expected to be higher than bike power because metabolic efficiency is much higher for running than for cycling. This means athletes can convert the same amount of oxygen into more power when running than we can do when cycling.

So you can't compare raw cycling and running power values.