Armband heart rate monitor lag?

I coach a 26 years old girl that is quite new to cycling. She is cycling since 2020. She has a lot of volume (17000km in 2021, 11 500 already this year).
She follows structured training and works with a power meter since the end of 2021. It’s been a successful year so far (finished 10th in her road race nationals championships) .
The girl is struggling with steady state Z5 workout. So we changed it to tabata 30/30 40/20 format, and it’s working better.

The thing is that her heart rate is either turning on or turning off even on tempo, sweetspot intervals. Her heart rate takes sometimes 5minutes to turn on.

On the internet, the reviews are all saying it is accurate.

So do you think that this lag in her heart rate is down to aerobic system that should be developed or down to a inaccurate armband heart rate monitor ?
See the graphs below for exemple, they really shows that massive lag.
What can I improve ? Get her a Classic heart rate monitor or doing anything special in her training for erasing that ?

Since you are questioning the heart rate monitor data, checking with another one (likely a quality chest strap version) is a good idea. Test with both monitors in place at the very same time and see what they show during the workout and after. This requires tracking and recording on two devices as well.

  • If they match up reasonably well, it might be a training related issue.
  • If they differ notably, you have an equipment and/or use issue.

Here’s my heart rate as recorded by my Polar Verity Sense on my left bicep as I was doing some sweetspot intervals. I think these look pretty ‘normal’.

The first two intervals for your athlete look like equipment malfunction to me.

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What Chad said. But they way you ask about getting a different monitor makes me think this is someone remote so can’t just have them easily wear a different monitor for a quick test.

Maybe another thing to check is add cadence to the chart. Is HR very close to cadence? Not as much a problem for cycling (I think) but easy to check if the data is there. A better explanation:

That sudden increase in HR seems like equipment failure most likely. If HR really does jump that quickly a cardiologist may be good to see

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Thanks for your fast replies.
She is using polar verity sense. The thing is that I have that problem on a lot of intervals. It is someone remote but gonna check that with her in 2weeks time with my chest strap, records on differents devices and do the comparaison.

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I use a Scosche Rythem armband. rock-solid. FWIW.


So is the polar in general. But if there is an issue with the person two different optical sensors may get the same results. How its worn may be an issue (hence the link I posted before)

make sure the firmware is up to date:
as there have been updates:

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Where does she wear the armband? I also have a Scosche and it works very well. However, if it is too tight then muscle flexes will affect accuracy. Similarly if too loose. What brand does she use and how old is it?

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+1. Inside bicep for me works better than any other location I’ve tried.


Polar verity sense. Around biceps. We are going to get her a chest monitor. Because most of her heart rate datas are like that when she does intervals and if it’s inaccurate, I really hate that (missing a way to mesure improvements).

The Polar Verity is well regarded.

There are some easy things to try like tightness and position. It can be better in different places. Also, she could cover it to eliminate outside light.

Finally, check the connection and whether there are any interference issues.

My scosche rhythm 24 started dropping signal and getting less reliable right on cue as the 1 year warranty was up. I’m back to using a chest strap.

Chest straps also react to changes faster than optical IIRC.

Get a good HR strap (polar h9/10 which is slightly better or a current gen Garmin strap) and you’ll have accurate hrv data during exercise to do alpha 1 so could improve your data collection even more

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Same. I could not get a Wahoo TICKR to work consistently, despite getting a free replacement. The last time I used one was to wear it to sense check the Verity Sense. Once I saw they were within ± 2bpm, the TICKRs went into a drawer and remain there.

The Verity Sense has been flawless.