@abnv @running I had a similar experience and read up on it a bit. Wrist based (optical) sensors can give spurious readings sometimes and Garmin apply a lot of signal processing to separate out the heart rate signal from other signals like your arms swinging, and sunlight pulsing under the watch as you move, etc. Sometimes these methods fail. Be especially suspicious if your HR reading matches your cadence.

Otoh, the '220 - age' formula is what's known as a linear regression. It predicts the average - but there's considerable variation around the average. Iirc the standard deviation was around 10, which means 95% of people would expect a max HR within +/-20bpm of the formula, and 99% within +/-30bpm. So 202 for a 40 year-old is plausible.

I'm a similar age and I've seen 202bpm on a Polar optical sensor and 198 on a Garmin electrical chest strap, both running hard uphill.

@abnv @running If you’re using a chest strap with it, the values are likely correct. If you’re using the built-in wrist sensor, you’re probably experiencing cadence lock. It’s a phenomenon of optical HR sensors that pick up on your cadence instead of your HR. Compare your cadence values to your HR. If they are similar, that’s what’s happening.

In any case, best go see a doctor and perform an ECG and lactate threshold test under stress. It’s what I did, to make sure.

No. I have a mk2i and when I run on the treadmill it almost doubles my real heart rate. I had to buy a chest strap to get accurate data.

@abnv @running I've been using Garmin watches for about 5 years now and what I can say is that it's quite consistent with the results from my annual sports medical checkup.

Every now and then my Garmin tells me that the max HR goes slightly up or slightly down.

But would I use it as medical advise? Never ever, at best it is an indicator. Close enough to medical reality for me™, but if you really want to know, consult your MD.