Not sure I understand what you are trying to say, do you find the prediction to be helpful? 150-190 BPM is such a huge range, what useful information can be derived from it?

It provides perspective and a target training effort.

I've done a good session if I push to 155 bpm. I don't need to worry about finger-sticks for lactate accuracy, because there's no-risk I'll do twice-a-day twice-a-week threshold sessions.

If I'm not even in the low-end of that huge bpm range, I quit and take a recovery day.

Those error bars are too wide for the formula to be useful for training based on heart rate percentages.

I've already said that I have found it to be useful:

https://news.ycombinator.com/item?id=43083815

:so please explain why I haven't :-)

You are doing nothing that requires the formula to be precise. A 10bpm standard error, meaning the max is very possibly 20bm off where you think it is, means that you can't reliably distinguish between efforts that someone doing serious training would want to be distinguished.

> You are doing nothing that requires the formula to be precise.

Exactly.

My guess is that neither are most other readers and commenters here. (Any evidence to the contrary?)

Meanwhile, what do those error bars tell use about "training based on heart rate percentages." :-)

> someone doing serious training

Care to say what you mean?