For some time now I have the impression my heart rate seems off.
I’m using a Polar H9 for over a year now and cross tested with a Wahoo tickr.
On my todays FTP test it seems to be wrong again.
My 20 minute effort had such a stable HR - 180 for 3 minutes straight. No way this is correct. Especially when compared to the movement of the HR before that 20 minutes.
Also the last 5 minutes my HR jumped and fell from 130 to 160, back down and up again even tho I had layed on the floor for a few minutes after the effort and was just noodling at 100-70 Watts for recovery.
I had exactly the same symptoms with my H10. Polars tend to ´stick´ to the last measured value. The strap was faulty.
Now using the strap from Garmin dual with the H10 on it.
I had a similar issue recently with Polar H10. In August 2021 I had a minor heart attack - so I’m sensitive to anomalous heart rate behaviour. The H10 worked fine for a year, then it started playing up (after 30-45 mins in a Zwift race, the indicated HR would slowly decline, despite me climbing a hill or sprinting to the finish). Replacing the battery did not fix it. The definitive test was when I wore a Halter Monitor for 24 hours (a 5-wire portable ECG recorder), and compared the output… my heart was behaving normally. It was the Polar H10 that was faulty. (Thanks cardiologist.) I was reimbursed for the HRM and went back to buying Garmin.
I’ve been using the Polar H10 primarily for cycling, and when it works, it’s one of the most accurate heart rate monitors I’ve used. It pairs well with training apps and devices, providing reliable data for general riding.
However, in recent months, I’ve experienced frequent dropouts, particularly during long efforts, bike racing, and high-intensity intervals. On a 30-minute hill climb, my heart rate starts off accurately at 155–174 BPM, but after 10–15 minutes, it suddenly drops to 66–96 BPM, regardless of effort. The same happens during longer interval training, making it difficult to gauge intensity correctly.
What makes this even more frustrating is that while my heart rate readings drop, my power output and RPE (perceived effort) remain high. This makes it impossible to rely on HR-based training, especially when aiming for 90–95% of max HR. I suspect heavy sweating is the culprit, as the issue arises once I start sweating heavily. While I understand that wear and tear is expected over time, I would have hoped for better durability from a premium HR monitor.
If you rely on steady, accurate HR tracking for intense efforts, be aware that this monitor may become unreliable over time, especially in sweaty conditions.
I also have the H10. I think this is a symptom on a worn out strap, I had similar issues with my old strap. The H10 is a fantastic sensor when it works, but the strap wears out fast. Just get a new one for € 30 or so and the problem will go away.
Also, when you wash it, don’t stretch it in the longitudinal direction, just wash it with soap and don’t stretch it. For me a strap lasts between 1-2 years.
