HR since v5.0 update

• I replaced a 645 where a strap mounting post disintegrated with a 245 as a quick replacement and on connecting it updated to V5.00 before I had a chance to run with it. I have found the HR to be laughably high during a run and only get sensible values by reluctantly wearing a chest strap. The training effect has been 5 and the VO2 max estimates plummeting using the optical. I ran really hard with the chest strap last night and got believable values that were 20bpm lower than with the optical. I never had issues with the 645s optical HRM.

I couldn't compare with my phone because my hands were too sweaty. But, I did take a manual pulse for 30 seconds immediately at the end of my run. My findings for that 30-second interval were:

• Watch HR at start: 169
• Watch HR at end: 120
• Manual heartbeats counted: 62 (effective HR 124)

It's apples and oranges. Still, even assuming an exponential drop in heart rate over the the interval while I was sitting still, the watch seems to be measuring high compared to my actual heart beats.

Note also that this was my first trail run since getting the watch; my other runs have all been on packed surfaces. For reasons I don't understand, Garmin differentiates between "run" and "trail run" activities (even going so far as to exclude the latter from VO2 Max measurements). Just FYI, in case this has any bearing on HR measurements.

Lastly, that's interesting about the strap. I'll tighten it before my next run and see if there's a difference. Thanks for the suggestion.

I've made my second training with tighter strap and again data looks good, so I think this is it (at least for me).

I did my first run last night with the strap tighter, and wouldn't say that the HR stats were any better. They were lower than previous runs, but I was putting in less effort - mainly because the watch / app keep telling me that I'm over-training and need to rest. (I know that's a chicken-and-egg issue if the watch is wrong in the first place.)

Anyway, I'd say that the watch is still measuring too high, when my HR is high, even when snugged tightly to my wrist.

My primary evidence for this is comparing with my manual measurements while swimming. When I'm swimming my hardest, my arms/lungs are burning, and I'm gasping for breath at the wall. 15-second manual measurements put my HR at high 150s, maybe low 160s if I'm going all-out. While running yesterday, I was breathing steadily and evenly for an hour, had energy to spare, and the watch reported an average of 157, with a max of 173. That can't possibly be true, given how relatively easily I was exercising.

Has anyone else noticed a change (or not) by tightening the strap?

Another vote for having the strap as tight as possible seems to bring the HR values down to reasonable numbers. I am nervous about this because I have an unusable 645 where a strap mounting post came apart and my superglue repair doesn't look that great.

For me the HR is still the same

I have the same problem, both with my HRM Run and the 245M sensors. My easy runs are usually around 125 bpm but for a week it's been around 145. I have no idea how they keep messing perfectly working things up with every update.

I have just done my next run with LOOSEN strap and stats gone through the roof (heart rate, training effect etc.). Looks like another confirmation of strap hypothesis:)