After many years my old Polar S625X started with geriatric problems. For example IrDA drivers bugs on Windows 10, buttons on the watch, chest strap, Polar’s announcement that PolarPersonalTrainer will be discontinued…
It was time to find a new HR monitor. My wife uses M400 and she is satisfied with it. Polar M430 GPS Running Watch is its successor with optical heart rate measuring and some improvements. I read many reviews and M430 really looked promising. My wishes were: not expensive, GPS, Android and cloud support, optical HR measurement (I have enough problems with chest straps)…
M430 has everything I want and it wasn’t expensive in January (189 EUR was my price in a local store). The only reservation was an awareness that optical HR measurement isn’t very accurate. Having that in mind, I have read this part very carefully on all reviews. The conclusion was that it isn’t perfect, but is usable and that M430 has one of the best results in a field trial.

All features are well described on many websites (includes Polar’s) and I won’t repeat what other reviewers have already said. Only my disappointments follow.

1. Software
The Android software works as it should. From my perspective, its main task is to synchronize data from M430 to the Polar Flow. Otherwise, Android PolarFlow is simple to use, user interface is nice and works fast.
With S625X I have used PolarPersonalTrainer. PolarPersonalTrainer will be closed down so all users must move to Polar Flow. Polar Flow looks modern, but PolarPersonalTrainer has more advanced functions and Polar could simply upgrade it with modern design and support for newer devices.
When I tried to transfer training data (10 years!) to Flow, I found out that this can’t be done! WTF!
 I have asked Polar and get a classic corporative answer: “Thank you for contacting Polar customer care. Unfortunately, you can only transfer data from PPT to Flow when using one of the following Polar products: RCX3, RCX5, RC3 GPS, CS500, CS500+, RS300X, RS800CX, CS600X, FT80, FT60, FT40, and FT7. I apologize for the inconvenience.”
Crazily. I’m sure that all records (regardless of watch model) are stored in the same way in their database. They simply don’t allow users of S625X to export their own records.

I have tried many tricks and I can at least export data from PolarPersonalTrainer (but only 25 records at once!!!) in XML. And don’t expect that XML can be imported in Flow. It has to be a “political” decision, there simply isn’t any technical reason.

Then I found the second clumsiness in Flow. You can’t compare two (or more) training like you can in PolarPersonaTrainer. Isn’t that one of the most interest things you can do with your sports data?

2. Charging 
Polar M400 uses the standard (waterproof) micro USB cable that is available almost everywhere. With M430 Polar has introduced a custom made port. If you have cable at home, you can’t charge your watch in a car or in the office. Forget it. If you run out of battery, your M430 will be useless until you get your cable. You can buy a Polar M430 Charging Cable for about 20 EUR (usury of course).
Not only that, the connector on cable doesn’t clip in very firmly.
As far as I know, Polar has problems with USB port corroding and charging on M400, so they had a reason to do that.

3. Battery
Many reviews glorify battery life on M430, but I’m not on their side. To be honest, the battery is not bad and it shows good results if I compare it to the competition. But for sure it can last longer. I expect to charge it every second (or third) day. If you have longer training, then expect to charge after every training. My friend also comments that he isn’t sure if his M430 has enough battery juice for longer activity (6-8 hours – like mountain day).
Luckily, M430 has some settings where you can lower energy consumption.

4. Optical Heart Rate
Now we came to the main problem on M430. Its main function is HR measuring, but here it fails as deep as it can. What is wrong? First 10 or 15 minutes (or even half an hour) it shows wrong HR.
I now that watch should be positioned as described in user manual. I tried with tightening more, tightening less, move watch higher or lower on the wrist, cover watch and skin (cold factor), wearing watch hours before training… But it simply doesn’t work ok at the beginning of training.
First minutes readings are far from real. It is winter in Slovenia, temperatures are near freezing point. It is understandable that on cold weather condition, the sensor performance (heart rate accuracy) could be effected as the blood flow is slower.
It is interesting that HR readings are real when I preparing for training. But after I start, numbers fall down to approximately 95-105 bpm. And stays in that zone for 10-15 minutes. It looks like my blood flow to hand almost stops when I start with training.

I asked Polar Support and here is their answer: “This is a common problem with OHR sensors. They need some time to adjust to your skin and you did everything right: moving the watch, covering it, etc. We recommend to put on the watch some time before your training. This allows your skin to get accustomed to the watch. When putting on the watch the blood flow will be hindered at first, but then the skin gets used to it and the blood flow will improve. But nonetheless it can happen, that the watch needs several minutes to calibrate itself to your pulse. This is not a bug, but an expected behaviour.

And as you described, it differs from person to person.”

I accept that M430 reacts a little slower, this is usual behavior for optical sensors. I checked the datasheet of the manufacturer of sensor and they say that sensor’s response time is 8 seconds. It is understandable and doesn’t lose HRs because it simply writes them a little later.

I prepared a simple video to show the problem:

Note: Old S625X was with me some months ago when I was on medical heart test. And it was very accurate.
Cold is definitely an important factor here. I tried with ski gloves on my hands and although problem still exists, M430 readings were at least a little better.
It is interesting that M430 has problems if my heart rate is high (or increasing). On the other hand, when my heart rate decreasing (for example when I turn downhill after ascent), it starts working ok. I even noticed that if my track on the ascent comes to gentle part, the HR readings on M430 starts to increase (opposite from real where HR starts to decrease).

Things are even worse. HR readings can be inaccurate from time to time even when the device is in “good area”.

5. Other annoyances 
There are some minor annoyances. For example, buttons are a little soft and user don’t get good feedback. Another annoyance is three seconds long press for finish training. If I add a little delay from a soft button, then this long press is way too long for me.

What can I say? Polar M430 isn’t usable if you want to follow your HR with optical HR.
What will I do? I don’t know yet. Maybe buying a chest strap is the cheapest solution. You can believe that I’m not very keen to buy an expensive strap because I already feel (at least partly) cheated from Polar. And then give them more money – hm, is this smart?
All in all, I am disappointed with M430, but otherwise (except upper issues), M430 can be a very interesting device. I’m also waiting for the higher temperature to see if readings will be more accurate.
UPDATE (24th February 2018): I have tried with borrowed Polar H7 (chest strap) and M430 works like a charm.
UPDATE (9th October 2018): Don’t miss to read part 2 of this topic. Did service help?
Also don’t miss a final article with useful tips: How to get more accurate heart rate readings?.