Heart rate still inaccurate

[t.parker]

Since moderators encourage users to post new threads about the issue then this is what I'm gonna do.

As usual, another analysis. Exercise - indoor spinning. Progression training (each stage gets heart into the next zone and keeps it there for a while). I use 5 zones (one Anaerobic, I don't break it down into A1, A2 and A3). Fitbit zones are too simplified to be used for training.

Orange - Fitbit Sense, Red - PolarOH1 (optical), Blue - PolarH10 (strap)

Just a short explanation of the showcased exercise and chart:

Each horizontal black line is an HR zone separator. Each vertical blue line separates training stages.

Threshold and Anaerobic zones are very narrow, hence zigzagged line (I elevate my HR and let it go down by either stopping pedalling or just lowering gear - in other words, I can pretty much control my heart response, feels almost like a video game ;)). Anaerobic section drops a lot more because it requires more rest.

.

Used devices:

• PolarH10 (chest strap, most accurate) paired with Garmin watch
• PolarOH1- optical sensor, unsupervised (recording offline, extracting the data after exercise)
• Fitbit Sense - no explanation needed

PolarOH1 and PolarH10 are so close that both lines are pretty much overlapped. PolarOH1 has a few small hiccups but it could be used with no problem for HR-based training.

Fitbit Sense again disappoints. 

There is a huge difference during warmup and the first part of low-aerobic sections. I'm not sure why because it looks like Sense was going to kick start with other devices and suddenly it just dropped to <100 and started elevating from there. It took over 4 minutes to get back to more accurate readings. It's ~10% of the time of the whole activity.

The low-Aerobic stage, when Sense finally gained some accuracy is still quite messed up but let's say, acceptable. Nothing to be used for HR training but if somebody focuses on calories, that should be good enough.

Tempo/Endurance seems to be also more or less ok although there is one unexplained dip in HR. At least the device recovered quickly.

The Threshold seems to be problematic. The 3/4 of Threshold are probably alright on average. The HR is noticeably lower than H10 and the zigzag pattern doesn't exist. There are some dips, too. In the last quarter, however, all hell breaks lose! The Sense's readings are rubbish and this pretty much stays like that through the Anaerobic stage. It's the last 10 minutes of the activity (and higher intensity). This makes for 27% of the total time which is rubbish.

As for cardio and spinning (where cyclist doesn't experience any bumps on road, doesn't need to turn etc. so there is no extra noise), the result disappoints.

Link to Analysis #2 

[SunsetRunner]

@t.parker I want just to thank you for your impressive activity to analyze the HR issue of Sense. I hope Fitbit can extract valuable data to fix the sensor in a near future. Thanks again.

[deiG]

Fitbit said they are not fixing it "in the immediate future". The original post is here:

https://community.fitbit.com/t5/Sense/Heart-rate-inaccurate-on-Fitbit-Sense/m-p/5029213#M39300

[SunsetRunner]

Hello @deiG, 

Actually @LizzyFitbit wrote "but may not be able to provide a fix in the immediate future". The way I read is that they are at work but facing some problems and therefore they don't want to give false hopes that the issue will be solve soon. But I'm confident they are doing their best.

[LizzyFitbit · Accepted solution]

Hi everyone,

Thanks for the details provided and every step tried on your own. As you may know, this issue experienced with the Sense has been reported to our team and our response can be found here. Your feedback and patience are truly appreciated, please know we'll keep our team informed of this situation.

I'm going to close this thread from further comments. However, if you have a different question about our Fitbit products, you can create a new thread to receive help from the Community members.