Polar A370 Review | Smart Fitness Band

Polar A370 Review

In this Polar A370 Review we take a look at Polar’s latest fitness band with optical HR.

Polar A370 Review Buy Price Sale

Polar make devices that I like to wear. I love the aesthetics.

This Polar A370 review looks at the new band in a little more detail.

They might not have 1000 features to go wrong on their devices but they seem to have the key features that most people regularly need.

If I was not wearing a sports watch and instead wearing an activity tracker, this would be it.

Updated & refreshed from an earlier A360 review


We will look some more at the A370 features:

  • Optical Heart Rate on the wrist – no chest strap required.
  • Quality, high-resolution colour Touchscreen
  • Activity-tracker, sports tracking and inactivity/sleep tracking
  • You can wear it in the pool for swimming
  • Good aesthetics and wearability
  • Awesomely detailed online/smartphone app.
  • Re-broadcastable bluetooth HR (Q2.2016) – nice but not necessary
  • More detailed on-device exercise stats to complement those on the app.
  • Indeed, a great quality item. Far superior to much of the deceptively photoshopped tat that we seem to be persuaded to buy from competing companies.


  • GPS – GPS is tied to your smartphone. But including it inside the band itself would reduce battery life to one day as Apple found to their cost. There is NO magic battery technology due anytime soon.
  • Like all other optical HR solutions for the wrist, HR readings are inaccurate to varying degrees – as Fitbit may have found to their cost with this lawsuit. The A370 is better than some in this respect and OK for fitness purposes.

It is a good, useful and usable product.

Certainly a sign of even better things to come.

Who should buy this?

Happy Polar A370 users might include at least the following:

  • People who want a modern looking activity tracker that also tracks sleep
  • People who also want to do sporty activities – such as gym, classes and steady state exercise
  • People who want detailed web/smartphone app-based metrics
  • People interested in one of the most accurate calorie estimation companies (Polar)

Who should not buy this?

  • People who want absolutely every feature on a small wrist based device, including a large screen and 2 week battery life 🙂 Reality check! That product doesn’t exist and no-one, including, Apple are anywhere close.
  • People who want to undertake high intensity and/or high precision exercise where high heart rates will be involved.
  • People who want super detailed metrics on the wrist. You need a dedicated sports watch.

The Review

You get the A370 (available in 3 sizes) and a micro USB cable. You also get POLAR FLOW which comprises the following components (all free):

  • Polar Flow web service – online analytical platform (this is not the legacy polarpersonaltrainer.com)
  • Polar Flow app – smartphone version of the online web service.
  • Polar FlowSync – gets the data from your PC to the web service (this is NOT the legacy WebSync software)
  • You can use your smart phone’s Bluetooth or a cable to synchronise data.

<Here’s> the Polar A360 manual if you need specific step-by-step walkthroughs of the menus.

A Closer Look At The Polar A370 Review Details

As I’ve said, it looks good with clean looks. It has a great colour, touchscreen screen with one-button control.

The A370 has a reasonably sized screen balancing readability and 247 comfort.

With the inclusion of a metal strip at the side of the screen both ooze MUCH more quality than the majority of the cheaper-looking, plastic competition.

The A370, however, is more of a modular design. ie you can change the strap! As you can see the nice-feeling rubber strap simply pops off. Earlier models of the previous A360 iteration had straps that came off too easily. This has been improved with a white plastic retaining ridge that is part of the new strap design, which you can just see below.

Polar A370 Review Buy Price Sale
Not the prettiest of photos…warts and all!!


You can also see the micro-USB port’s cover which comes off too. This IS a little fiddly. The risk of losing the cover is much-minimised by the addition of a retaining strap that you can just see in the images.

I have been swimming with the A370 (and the A370 still works!) so supporting the claim that it’s ‘waterproof’ to 30m depth. My gut feeling is that it will be Ok as an occasional swimming device rather than a daily one. NEVER Dive in a pool with the A370 and you might be OK.

It’s great that the A360 only needs a standard micro USB cable. The downside of this is the nature of the USB port and cover that is required. Many other vendors are choosing to go down the proprietary charging cradle route; this adds cost but perhaps is technically better.

Rain/Water: I have just come back from swimming with the A370 – the touchscreen worked fine when I was at the end of lengths. I don’t understand why some people say the touchscreen doesn’t work in the rain. It works for me in the pool. The pool is wetter than rain, right? Sorry.

Sensitivity of screen – again I would say this is fine. The screen perhaps turns off a little too quickly for my liking (but it’s fine). I turn my wrist to see the time and the time magically appears (most of the time!).

Comments on Functions And usability

There are 4 areas in the interface: My Day, Training, My Heart Rate and Time

  • Time – shows the time/date
  • My Heart Rate – Measures your Heart Rate
  • My Day – shows what you accomplished today and what is left to be done. There is more detail behind completed activities.
  • Training – is the place to choose to start recording your activity/sport. you will have already created the activity profile online with Polar Flow. you choose the activity, the HRs and you are ready to go.
  • Settings – do not disturb, broadcast HR, continuous HR tracking.

You can choose to follow a relatively simple interval/phase workout that you create online in Polar Flow


The A360, in use, is a standalone sports device that does not require anything more. But in this evermore connected world there is, of course, more.

The A370 has links to update the device and to share your activity; using either your smartphone or a USB cable you can synchronise your A370 with the Polar Flow web service. This is where you view your activity in detail and where you send back exercise updates to your A370.

You will periodically want to link to your computer with a USB cable to charge the device and to update the A370s internal software (firmware) as this will have many updates and features added throughout 2017/8 and beyond.

The Bluetooth link to your phone will support smart notifications on the A370.


When combing 24×7 HR with an accelerometer Polar can have a good go at analysing sleep quality and sleep stages. Their press release, below, indicates that they compare the A370’s performance to PSG (That’s polysomnography rather than Paris St. Germain for my Paris-based readers). But even PSG is not perfect….analysing sleep is HARD. We’ll hopefully see how Polar do later when I get my hands on one. Either way you should expect BETTER results from any company, like Polar, who includes a half-decent 24×7 optical HR sensor in the algorithm rather than just basing their sleep analysis and recommendations on movement.


Optical HR Unit

The optical unit remains unchanged from the earlier A360. I’ll re-use some old images.

We’ll come on to the accuracy of the optical HR later but for now here is a visual comparison to the MIO Velo/Link and Epson Pulsense – both different but competent devices in their own right. Each use subtly different optical technology.

Polar A360 Review
Polar A360 vs MIO Link/Velo vs Epson Pulsense


Here is Polar’s range of watches/bands. The M200 and A360/A370 share the same sensor. Whereas the M430 and M600. The 6-LED sensor of the more expensive Polar watches is better but the sports format of those watches may not be what you are looking for.

Polar M430 Detailed Review optical lineup

Finally we come to the clasp/strap retaining mechanism. No doubt this is the bit you all came here to read ;-). Please feel free to retweet this clasp pictures to all your followers, they’ll be interested too 🙂 But seriously the A370’s strap is slightly improved over the A360, shown on the left. It doesn’t come apart off so easily and the new clasp means it will not come off by accident.

Polar A370 Review Buy Price SaleI did find that after charging it was REALLY important to ensure that the main unit was properly inside the rubber strap. If you don’t do that you risk the main unit popping and potentially losing/breaking it.

Steps, Beats, Holisticity and Activity Tracking

A weird sub title. Bear with me. It’s fairly important.

If you’re buying one of these activity trackers you might want to think about what you are measuring and why you are measuring it. There IS a right answer, IMO, about what should be measured but that needs to be tempered with the kind of person you are and the use to which you are going to put your device.

  • Low-level/low-intensity tracking – if you are ‘just’ measuring 5000 or 12000 steps a day and ‘only’ want to know how much restful sleep you got then you only need a simple device. The A370 is NOT simple but CAN do this job well. And look pretty whilst doing it.
  • Low- and medium-intensity tracking – if you are doing ‘sporty’ stuff that is going to raise your HR then 1000 walking-steps are NOT the same as 1000 running steps. The INTENSITY of the activity will have a DIFFERENT IMPACT on your fitness. You could measure and infer the impact of speed but this won’t work (uphill/downhill/wind) and requires a battery-hungry GPS. So heart rate is actually quite a good way to gauge INTENSITY; it’s not perfect, just good. So if you do 6000 steps plus a step class plus a 30 minute steady state/easy run then the cheaper activity trackers will NOT reflect well your holistic/overall efforts. The Polar A370 WILL DO THAT. Garmin and others do similar things. Whether your heart rate is 145bpm for 30 minutes or 148 for 27 minutes – it doesn’t really matter as the kind of person doing this level of activity doesn’t NEED to know their exact heart rate/durations. They might WANT TO but they don’t NEED TO (IMO).
  • Higher intensity activity tracking – you people are athletes of some form or other. You need a sports watch. Actually you need something like a pretty Polar A370 for most of your stuff AND a functional sports watch for your intense stuff where the precision of execution/analysis is important. Perhaps to you people a high degree of accuracy is important and, in any case, you will most likely also need power/speed/pace so the A370 ON ITS OWN is clearly not for you.

Continual heart rate monitoring: Why? The A370 can do this but I just don’t see the benefit. Tracking resting HR overnight does have a purpose in, sort of, tracking your recovery from exercise/stress

If you need continual HR for medical reasons then you need to buy a medical-grade device. That will NEVER be an optical device on the wrist. NEVER.

So, IMO, with all this in mind you need to approach your choice of lifestyle with a dose of pragmatism around the choice of lifestyle monitoring device(s) you make.

With this in mind we move on to…

Heart Rate Accuracy

Resting heart rate and one-off readings are fine (below). You can just see the Samsung at 70bpm.

Polar A360 Review
Polar A360 64bpm HR vs 920XT 65bpm vs Samsung Gear Fit 70bpm

Heart Rate Accuracy – Overall Effect

If we look at a fairly intense VO2max swim session. 14 minutes of swimming in a 25 minute session. The TRIMP score shows 32 (Garmin HRM-TRI) vs 37 (Polar A360). For a wrist optical HR device this is probably on par with other similar devices in a relatively intense and hostile environment that it wasn’t really designed for. If you were using this to track your overall intensities and durations then it would be OK.

Swim HR Data,

Heart Rate Accuracy – In Sports

Comparing the same track to the HRM-TRI we can see that, in the warmup, the two did not match. This Garmin HRM-TRI typically reports a 1% to 4% error rate in Firstbeat so although we are initially inclined to place the fault with the A360/A370, maybe it’s not so clear-cut? As the interval starts the Polar DOES lag for over a minute and then tracks well enough through to the end of the warmdown.


Turning to running, I was pleasantly surprised with the running accuracy as these 3 different runs show, below. Polar’s A360/A370 compared very well to the Garmin HRM-RUN. In some uses this Garmin HRM-RUN reports over 50% errors in Firstbeat…..(just so you know! but usually 1%-7%) – yet I would treat it as ‘accurate’. hmmm.

Clearly the A360/A370 does not quite track the Garmin and there seems to be some small drop-outs and also some delayed lags. On the whole it’s pretty good.

With the same HRM-RUN (reporting 4% error) the A360/A370 again did well until 35 minutes into the session when it lost the plot. On reflection the drops in the A360’s reading seemed to be when I was on aerobars (minute on, minute off, ish) and this exposed the watch to more airflow from my fan. Might this change in position disrupt bloodflow to my wrists – possibly. Of course that is where the A360/A370 is measuring it. It can’t measure what isn’t there to be measured.

Blue Polar, Red HRM-RUN

The accuracy seems competently useful for non-athletic levels of activity tracking and lower level exercise tracking.

Notes: Although I did NOT formally re-test optical HR with the A370 it seems to give a consistent level of performance to the A360. It’s possibly slightly improved but it’s not a step change improvement. Nevertheless the accuracy is good enough for this type of device, in my opinion.


The power behind the Polar A370 comes from the FLOW app and the online Polar FLOW website. You can add new types of sports/exercises. There is relatively limited scope available for the options you can set but at least it is good to categorise and track your committment to individual activity types across time.



You get some nice summaries at the end of your exercise on the app. As an aside many oHR devices (eg Garmin) do not show ANY heart rate for swimming.

Polar Flow M200



The A370’s beautiful screen eats the battery juice. Hence you will only get about 4 days. That’s not bad compared to the day and a bit for the Apple Watch 😉  But 4 days is less than other bands.

I am satisfied with 4 days battery for the A370.


  • Waterproof (WR30)
  • Wide-viewing angle full colour TFT display with capacitive touchscreen
  • Screen resolution 80 x 160 pixels (RGB)
  • Screen size 13mm x 27mm
  • Vibration alerts (not audio alerts)
  • Polar proprietary optical heart rate module (2 green LEDs, 1 photodiode, analog front-end)
  • Battery life up to 3 days with 24/7 activity tracking, including 1 hour of training per day (without smart notifications in use) with continuous HR


I like the A370.

I gave my old A360 to my partner. They like it and use it as their preferred tracker in conjunction with the OTHER Ring

The A370/A360 is SO much better than some of the ugly, inaccurate tat that is out there pretending to do a similar job well.

If you are an athlete and quite like the idea of re-broadcasting the HR. Don’t do it! Wrist-based HR will never reliably give precise and accurate HR.

Polar’s overall wellness/activity offering is highly competent. They know what they are doing.

Some of you will like the connected-GPS. It will be as accurate as the GPS on your smartphone – which can be awesome…or not. Depends entirely on your phone.

The 247 heart rate, in my opinion, has somewhat limited true value. Yet I know that LOTS of people are really interested in that level of introspection. For lower levels of HR, the A370 is going to be pretty accurate much of the time (good).

Firmware v1.0.25 used


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