Polar M430 and A370 heart rate sensors have a problem with dark skin

The company is addressing the issue with a firmware fix
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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.

Read this: Why Fitbit's sensor shake-up is a huge deal

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.

Polar M430 and A370 heart rate sensors have a problem with dark skin

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Michael Sawh


Michael Sawh has been covering the wearable tech industry since the very first Fitbit landed back in 2011. Previously the resident wearable tech expert at Trusted Reviews, he also marshaled the features section of T3.com.

He also regularly contributed to T3 magazine when they needed someone to talk about fitness trackers, running watches, headphones, tablets, and phones.

Michael writes for GQ, Wired, Coach Mag, Metro, MSN, BBC Focus, Stuff, TechRadar and has made several appearances on the BBC Travel Show to talk all things tech. 

Michael is a lover of all things sports and fitness-tech related, clocking up over 15 marathons and has put in serious hours in the pool all in the name of testing every fitness wearable going. Expect to see him with a minimum of two wearables at any given time.

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