Discussion: heart rate skeptic

Of course I am in no position to know what's going on with your heart. But that doesn't stop me from having an opinion, opinions are cheap: The early high rate is baloney.

At least, that's my experience with my own watch. Different watch than you (Polar Vantage M) and I just use its wrist sensor (one of the selling points of the Polar was that their wrist sensor is supposed to be better), but I very often (not always) get the same thing as you're seeing: heart rate significantly high for the first few minutes of a workout, then drops down to a more sensible-seeming reading that continues for the rest of the run. I know the high rate is baloney because when I have noticed it before (or just as) I take the first step, I sometimes have done a quick manual pulse check before getting going. The watch reads, say, 85, and I know that doesn't make sense for me (might make sense for Betsy), so I check it, and sure enough, it's, say, low 50s. (My pulse is quite slow, some combination of genetics and fifty years of running.)

Yes I know the chest strap is supposedly more accurate, but I still don't believe it. My hypothesis is that the issue is not in the data from the strap or the wrist sensor, but in the algorithm the device uses to process the raw data into a pattern. Though it's interesting that Garmin and Polar, presumably developed independently, do the same thing.

Same thing here. Using Suunto Ambit 3 with chest strap.

I haven't had a chance to do a manual check yet, but it's a pretty strange effect if it's artificial. When I first had a watch with a wrist HR sensor, I could easily tell when it was double-counting (the measured rate was double what it should have been). And there was an abrupt shift when it sync'd correctly: a cliff more than a slope. But this effect, which it sounds like you both have too, is different. When I first turn it on getting ready to run, it tracks correctly. Then as my HR gradually rises at the onset of exercise, it starts reading high, by around 30 bpm. Later, when I've leveled off, it gradually returns back to zero offset. It seems like the HR detection and filtering algorithm is pretty sophisticated, more like a predictive AI than a simple thresholding.

I did several stop-and-check HR measurements today. The chest strap reading for the first mile or so is bogus. It's especially bogus that it decreases during the biggest climb on this route.

Could Suunto, Polar, and Garmin all be using the same silicon/firmware inside that processes the raw HR data? Wouldn't have thought so, but maybe so if they are all making the same "error".

I too thought at first that the watch was simply doubling my pulse at the beginning, especially since mine can easily be down in the 40s when I start, but it doesn't seem like when I look at more data--more like the 30 bpm too high that you mention.

A quick search finds some threads like this and this. The first one assumes the HR spike is real and tells you to warm up first. The second one assumes the HR spike is not real, and also tells you to warm up first. But it alludes to an averaging process in the HR filtering algorithm, which I believe to be the case, but I'm pretty sure it's just a few seconds' moving average. What we're seeing is many seconds long, and it's an overrun, not an average.