I found the heart rate sensors to be wildly innacurate and was a bit shocked that they only check every five to ten minutes or so. I’m not sure what the point of including them is when that’s the case.
I bought one and was keen enough to purchase the very expensive variety ($1,400) but I returned it…
Mr. Grey
1

How did you determine this?! Have compared three different models to full-on hospital equipment, exercise and Plain Ol’ counting…

You may have received a faulty one, the every 10 minute check is intended to save battery – though if you want more granular management of course it constantly updates during exercise and workouts.

The first watch I bought had a sensor issue, it read pulse rates fine but couldn’t determine altitude or whatever makes the stand sensor work (the blue ring if you actually owned an Apple Watch.) and thanks to apples brilliant customer service this was not an ordeal, and they threw in a free band for “my troubles.”