I recently purchased a Forerunner 235 which has an optical, wrist HR sensor. I’m careful to make sure it’s actually aligned to my HR before I start running. Today was weird though. It seemed to sync up properly when I put the watch on and start up correctly. But then it did this weird stair step thing you can see in the data. It started in the low 130s and would stick at a value and then increment by one beat at regular intervals until I finished the run. I’m positive my HR was in the 160-180 range for a large chunk of the run (I ran an 18 minute tempo in the middle of the run). It dropped when I stopped my watch at traffic lights and stopped to walked when the tempo interval was done, but it was clearly not measuring my HR properly.
So any ideas what happened? I’ve seen it lock to cadence if it’s not on on tight enough - that was pretty easy to spot based on the numbers and can’t explain numbers around 140. No idea what it was measuring this time though. I’m sure if I’d powered it off and on it would have been ok, but I wasn’t sure it was wrong until I’d started tempo and I didn’t want to restart watch so I just ran by feel.
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