When we reviewed the Polar M430 recently we raised one pretty big issue with the running watch - the heart rate sensor didn't provide readings on dark skin. In fact, I was not able to measure my heart rate with this device even once despite multiple attempts.
We raised the problem with Polar while a reader also got in touch with us to say they had experienced something similar with Polar's A370 fitness tracker. The company has been investigating the issue and has now responded admitting that it has "identified a small firmware issue with the M430 and A370", which has caused its heart rate monitor to struggle providing readings on dark skin. Oh dear.
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It added that this has affected "a very limited amount of users" and that the issue will be addressed in a firmware update that will be due out in early September. We'll re-test the feature after the update.
This isn't the first time we've heard about wrist-based heart rate monitors struggle to produce readings on darker skin. The Apple Watch and the Xiaomi Mi Band 2 are just two devices that have come under scrutiny from some users in the past.
So why does it happen? Well, part of it is down to the green light-based optical sensors that these wearables rely on to provide heart rate data. As we've discussed in great detail before, skin tone and even tattoos have been known to affect the ability that these sensors have to generate the signal inside of the body it needs to provide HR data.
Is it acceptable that this happens? We're not so sure. While it's certainly good to see Polar is addressing the problem, it does raise more questions about whether the testing of these optical heart rate sensors is carried out on a wider range of people and skin tones before they are available to buy.
Here's hoping it doesn't happen again, but we have a feeling this won't be the last time we're talking about heart rate sensor issues.
Have you had problems with Polar's heart rate sensors? Let us know in the comments.