Hello; a couple of my indoor rides recently have exhibited a sudden and sustained jump in my HR that isn’t accompanied by an obvious jump in power or cadence. I have an H10 Polar HRM; could it be faulty? Or could there be a physiological explanation?
Yesterday’s example led Intervals concluding that my LTHR had increased by 6 having been pretty staic for some years. See screenshot of the timeline.
I don’t know much about Polar watches. I’ve seen some Reddit posts about Garmin watches doing something similar though!
If your power zones are correct, I’d assume the second part of your ride to have the correct HR. Z4 at 140bpm would be pretty good, although not impossible depending on age I guess.
But the line of the first part just looks to have too many flat sections with sudden spikes, whilst the second part looks like I’d expect it to look.
So not much I can say really expect try your watch a little tighter when cycling and go through the forums 
Do you track your HR elsewhere? Are you seeing any other changes in your HR when not exercising?
Thanks. The H10 is a chest strap HRM and generally reckoned to be one of the best. The zone chart, based on my regular LTHR looks pretty unlikely (I’m 74 years old).
Polar H10 is a chest strap HR monitor, not a watch. In my experience it’s the most reliable HR sensor I’ve used, better than Garmin and Wahoo. The only time I’ve seen odd data has been when the battery is getting low. Perhaps the chest strap itself wasn’t tight enough, or the electrodes needed a bit of moisture.
I had some troubles with the strap (not the sensor).
It showed differently though. In my case there was a ´sticky´ HR value and then a sudden drop/raise.
I put the sensor on the strap of my Garmin Dual and everything was fine again.
Thanks. It’s pretty new (mid-August) so battery shouldn’t need changing yet and the strap appears to be in excellent condition. And I’ve not seen anything “funny” about my HR elsewhere.
I gave the strap a decent lick so it started out damp, and then I got sweaty! I can try tightening it next time.
The whole graph looks suspicious to me. Heart rate goes up or down without corresponding to power. How long have you been using this strap?
5 months - since mid August.
5 months isn’t a long time, but I have found the straps don’t last as long as the transmitter units. Sometimes you can see the electrode pads showing signs of damage. How often do you clean the strap, and how do you do it?
I usually just put the strap in the wash with the clothing. I use a laundry bag for the strap and mild non-bio detergent. But I don’t rub it down first or prep it in any way - just “bung it in the wash”!
It could be either a device issue (HRM or recording device) or physiological. The only way to find out is to start troubleshooting. Try using other HRM devices and recording devices. Change one thing at a time. Start with the low hanging fruit by changing the HRM battery, then start swapping hardware in an attempt to track down the source of the jump. You can also confirm the HRM is recording the correct HR by manually checking, both prior to a sudden jump and then again afterwards. Also, as @Matthew_Burton asked, watch for any physiological similarities elsewhere in life.
It is a rather distinct increase that leads me to suspect the issue is hardware related. Still, stay open to any explanation in order to mitigate myopic vision.
As far as I recall, Polar give the impression that you need to wash ocasionally in the washer with mild detergent and at low temperature (usually rinsing with water after use). I never put mine in the washer. Do the electrode pads look OK?
I take mine under the shower (without sensor off course…) and gently rub with soft soap, then rince and dry. First I roll it in a towel to get the most water out and then let it hang for a couple of hours to completely dry.
I second this method and/or hand wash it with some soft soap under the tap. Furthermore, I run mine under the tap and put it on almost dripping wet. Whenever I have experienced HR data that I thought was inaccurate, it was when I would put it on without getting it wet.
Happy to report that things were back to normal yesterday on my next ride. I’d moved the strap to a different position (above rather than below the pecs) and all seemed fine. As before it was a flat course with a large field so cadence and power were pretty flat until I tired in Q4.
Thanks for everyones input - much appreciated.
To echo something mentioned already, but getting the sensor areas quite wet has resolved all issues I’ve had with my chest straps. I’ve often seen the same jump from wrist-based HR from my Garmin Instinct, an example of which is included from a full-gas hill-climb I did in 2023. On the first climb (see elevation) my HR was showing as being around 100bpm, when I was actually redlining a bit and had to back off because I was probably getting close to what was at the time, my max of ~185.
You are now wearing the strap “above rather than below the pecs”? I have never seen anyone wear it above the pecs / sternum / nipples. Polar and Garmin both recommend to wear it below.
Other option to getting the electrodes wet, and ensuring a good contact with skin, is to use electrode gel like Spectra 360. I never had any issues since I started using that.
Yeah Spectra is good stuff!
