Originally Posted by
DrIsotope
If you could somehow magically eliminate a huge chunk of variables affecting HR, you would still have only a ballpark guess of the raw/weighted power. HR is affected by everything, power is power. A recurring trend in my data is that as the ride length increases, power output dips as HR climbs, due to fatigue/dehydration... usually. So I can assume that past hour 5 or 6, HR will be slightly elevated at a similar level of effort versus hour 1 or 2-- but looking at the HR graph I have no idea whatsoever of what the power output would be.
And that's if you're trying to predict for one person-- forget it if you're looking at multiple people. The variables are almost infinite. On the same ride on the same course over the same time at the same moving speed, my wife's avg. HR might be 30bpm higher than mine-- I'm 8 inches taller, 30% heavier, make more power, my bike is 10lbs heavier, etc. Her not having a PM, I could make absolutely no guess at all as to her power output based on her HR (any online power calculator would give a better ballpark guess.) Her resting HR is ~15bpm lower than mine. But she also gets wicked nervous before rides and in heavy traffic-- I can see the HR spikes on the ride analysis.
TL;DR: power and HR are unrelated because you cannot determine one from the other.
I think you are missing the forest for the trees here, if for no other reason than Powercal does exactly that (i.e. calculate power from HR). Well, that and the fact that HR responds to activity effort level because of human physiology. That’s just how we work.
Probably what’s trpping you up is that you’re thinking X HR = Y watts, which is not the case, and subsequently, neither the basis for how PowerCal works. Rather, it’s the rate of change of HR that drives the Powercal algorithm. This makes short duration efforts difficult for PowerCal to handle, but from about 40 secs out, it does better, and total ride averages have proven to be pretty similar to direct force meters.
In fact, Powercal doesn’t even have a calibration requirement because it doesn’t predictably improve accuracy, which gets to my point to the OP, namely that it takes heaps of power and HR data to overcome the intrinsic inaccuracy of deriving power from HR. It has been done, by Cycleops, the top power meter company in the world, but it seems far fetched that your small company could get anywhere near the level and quality of analysis they have done.
So yeah, it’s just observably absurd to claim that HR is not related to power, and there is at least one commercial product from the preeminent power meter company in the world to prove it.