Anyone experienced low heart rate during first ftp block? I had a chest monitor on and wrist monitor and the were within 5 beats of each other saying my heart rate was 110 while riding at ftp. Just did a ramp test also so I know the ftp is accurate. I typically don’t notice my heart rate until it gets above 160 so not sure if this artifact. But this is the second time it’s done this.
I had this happen consistently while wearing a Wahoo Tickr. I contacted support and they sent me a new one, which resolved the issue.
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Couple of things to check - is the strap clean and has it been moistened first? Either might affect the connection until you start to properly sweat.
ETA: Just noticed you had a wrist strap too. Is your ftp set correctly and what level of fitness are you coming from?
How long have you been using TR workouts?
I’ll put money on faulty HR data.
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Ditto, new battery time for the chest hrm.
The optical wrist hrm will be garbage, especially for these intervals.
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I wouldn’t go quite that far. My wrist HRM is bang on the money. Well, I say bang on, I mean its within a few beats. Certainly not like the above.
that would be fantastic if someone has nailed optical wrist hrm accuracy - which one have you got?
I can sense a tone in your voice 
Its a Garmin, yes I know of previous issues, I’ve had previous models and issues before, etc etc etc. This one is pretty damn close, tracks changes well and is more than good enough for me.
Certainly not “garbage”.
haha no tone, I would genuinely like to see it done! I’m also wearing a garmin and anything above z3 reads c.20 bpm low and for intervals like in the OP it may as well flatline 
From what I’ve read that seems to be what you have to accept for optical sensors on your wrist.
Thanks for the thoughts. It is a wahoo ticker and I’ve been using it with trainer road since January when I started. I’ll try cleaning it and replacing the battery and if that doesn’t work I’ll give them a call. For my wrist it is a garmin and it tends to be accurate at steady efforts but it def lags on intervals, I was just surprised that it would wrong for five mins that’s pretty unusual. Here is my ramp test.
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My vivioactive wrist/ optical based hr is sh1t and often reads 10-30bpm low on the maximum during intervals compared to the chest strap but you had both 
Ive had a failing HR strap read low until I think it reaches the correct level of sweat conductivity. A new battery, reversing/ resetting the polarity are the things perhaps to try before replacing.
A further musing as it looks to have read better in the preceding warm up, perhaps there was a source of interference during the intervals
Is your cadence throwing your HR off?
This is a good point! Its a known issue with a few HRMs.
The cadence stands out as unusual to my eyes.
I can imagine how that might throw out a HRM if the contacts aren’t making a good connection.
Is it possible that the lower cadence is keeping the actual HR lower during the first set? As in the legs taking the load.
Being shorter intervals I can also imagine a low ramp test result allowing someone to get away with a low HR in the first set of that workout.
This was the best example I could quickly find that shows what I mean. Stuff knows what I was doing but my HR drops off with my cadence when I’m comfortably below threshold.
Another one I’ll add from today where I deliberately made my HR jump around.
I also compared my Fenix optical HR along side part of this. With the band on tight it was within a couple of bpm.
(Sorry about some of the text being hard to read).