I'd say, as others have said in this post, that the high HR could be legit. I also agree that your wrist HR is not always accurate. I used a 735XT which is wrist-based HR and I've had my HR be steady at 125 for the first half of an easy run and jump to 150 and stay steady there for the rest of the run (treadmill, same pace, same % grade). I would say use a chest HRM if you use HR during training.

With that being said, one of the guys I train with (same age as me) has an easy run HR limit of 165 and runs 180-185 during a 70.3 run, while my easy run HR limit is 140, and I average 165 during a marathon. HR changes from person-to person, age, training load, etc as others have said.

take your HR manually. Don't rely on gadgets to do everything for you. They are just tools to help and you have to understand their limitations.

That being said, can't you tell without actually counting what your HR is within a small margin of error? I can usually estimate my HR based on exertion level for a variety of activities within 10 beats, usually less. Certainly the difference between 190 and whatever it would be while on an easy run.

Since you first posted this question I have had my 735 lock onto my cadence while running 2 long runs in a row. Both time it was after a stop at a stoplight where my pulse dropped. When I restarted my pulse was showing 190 and I wasn't even breathing hard yet. I could make it vary by changing my stride, so it was definitely locked to cadence.

I think it has something to do with pulse and cadence crossing the same number and the watch picking the wrong one to follow. I haven't figured out how to get the watch back to reading my pulse once that happens yet, but it is pretty annoying.

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"...the street finds its own uses for things"

Im 31 and I do most of my runs in the 175 ish range (7-8) miles.
Been to the doc - had EKGs - etc and all normal. Resting HR is upper 50s.

Most I have had it sustained is about 183 but I can maintain that for maybe 3 miles before I just get winded.

Whaaaaaat. Holy cow. What was his resting heart rate.??

How painful was it when you did half? I'm asking you because when I hit my max which is about 170, I feel like I'm going to die. I can hold that only for 1 min, 1:30 if I'm lucky. How can you tolerate such pain? It's mind boggling.

To OP, if that's close to your maximum HR and your watch and monitor are not out of order, switch that sends pain to your brain is turned off so good for you!!

It’s been a while but from what I remember I went out comfortably hard. At about 3-4 miles was when my body wanted to stop but I kept pushing. Maybe started at 7/10 in legs burning and was at 9/10 at mile 4. Aerobically it was a 7/10 the entire race. Ultimately it was my legs that gave out and was the limiting factor somewhere between 1 and 2 miles left. The last mile which was a 10/10 with every step a mental battle to keep going. Different than an IM as i didn’t feel like my muscles were going to cramp just that they were burning with every step being a battle. Felt like my muscles were about to give out at the end. - this was followed by the sorest I have ever been for a week after this race. Worse than the 2 IMs I have completed.