I have the same question as Monty. i wouldn't put ANY stock in a 2s reading from a consumer HRM...including any chest straps. that goes double while indoors. Even my Polar H10 strap (paired with Garmin F6) looses its mind indoors every once in a while. I don't know if its from 2.4 GHz interference or something else. But, it does fine outside....indoors at least once a week it goes haywire (100 or 190 indicated instead of 150 true) for 30s or more....long enough for me to take a manual pulse reading and go "nope, that ain't right".

You say that you "felt it"...what does that mean, exactly? That's like 4 heart beats.