- Comfortable to wear
- Good battery life
- Multiple wearing options
- Not as accurate as chest strap
- Confusing LED modes
- Easy to lose
Chest straps and wrist-worn optical sensors are the mainstay of heart rate tracking for sport and fitness, but neither of these designs cope particularly well in the water. That's where Polar wants to change things with the OH1+.
The update to the original OH1 heart rate monitor armband now adds the ability to monitor your heart rate from your temple by clipping the sensor onto your swimming goggles. You can still wear it on your arm, but it now opens up the ability to measure effort levels when you next jump in the pool.
The heart rate monitor also offers both ANT+ and Bluetooth connectivity, so you can pair it with a wider range of compatible gym equipment, cycling computers and your other Polar devices.
You can also stream your heart rate insights to multiple devices simultaneously, including the Polar Beat fitness training app on your smartphone.
But the real test of any heart rate tracker is in the accuracy once you start to work up a sweat. We put the OH1+ to the test on runs in the pool and on the gym floor to find out how it stacks up in the reliability stakes. Here's our full verdict.
Polar OH1+: Design
The OH1+ is identical to the OH1. The sensor with its six LED optical heart rate monitor is roughly the size of two £1 coins or a handful of quarters stacked together, and very lightweight at just 5g. It’s smaller than the Wahoo TICKR Fit and Scosche RHYTHM 24 heart rate monitor armbands, which makes a big difference considering where you’re supposed to wear it. It also means you can attach it to your goggles.
It’s worth noting that the OH1+ doesn’t carry the very latest Polar heart rate Precision Prime sensor tech that you can find packed into the Polar Vantage V, Vantage M and Ignite watches.
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For training on dry land, the sensor clips easily into a cradle on the strap and the armband is easy to fit and adjust for your forearm and biceps, though we preferred the slightly wider band on the TICKR Fit for overall comfort. It’s worth noting that our forearm to gun-size ratio is pretty equal and those with bigger biceps might find it more fiddly having to adjust the strap to move between the two locations.
There are three different colour armbands to choose from: black, grey or orange
The OH1+ is controlled by a small metallic button on one side of the sensor, used for powering the OH1+ on and off and starting a session when you want to use the monitor as an independent training device – storing the data locally for sync later. The button is a little fiddly to press, particularly if you have it in one of the clips and you’ve got wet fingers. Thankfully, you only need to do this at the start and finish of a session, rather than on the move.
On the opposite side of the sensor there’s one single LED light that flashes to indicate different states such as when you’re in pairing mode. The multitude of combinations of colours and flash rates are somewhat confusing and we found we had to regularly refer to the user guide to commit these to memory. You will learn them over time but you can’t just fire this up and workout.
Pairing the OH1+ with a watch or an app works just like a regular chest strap, and once you’ve linked your watch should automatically pick up the OH1+ for subsequent training sessions. This will vary depending on the device you’re linking it to though.
Other than the two sizes of goggle clips, the only other element in the box is a USB cradle that you use to charge the OH1+ or sync it over the web using the Power Flow Sync software, if you choose to do this rather than using Bluetooth and the Beat app or your watch.
You clip the sensor into the dock which can then plug into a USB plug or socket on your laptop. While this does mean you have to carry the extra cradle to charge it, it’s neat and simple. A full charge takes roughly 90 minutes. The cradle seems robust enough but like the OH1+ itself is eminently losable thanks to its size, so you need to keep an eye on where you stash it.
Polar OH1+: Features and syncing
Because the Polar OH1+ is primarily a companion device, there aren’t many ‘features’ to speak about. However, its ability to unlock the training tools in the free partner Polar Beat app is definitely a bonus.
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You can connect the OH1+ and use the app-and-strap combo to set benefit targets for your training sessions, choosing from six different goals including recovery, tempo and maximum training. You can also do a simple five-minute fitness test to benchmark your progress and see it in real time with audio guidance, whether your current intensity level is burning fat or improving fitness.
As with other traditional chest straps, you can also pair the OH1+ with third party training apps like Strava and other Bluetooth Smart and ANT+ devices. We tried this with both Strava and Suunto and it worked instantly.
Data you record using the Beat app also syncs to Polar Flow, the company’s much more extensive suite of training tools and data insights.
There are a number of ways to get your data into Polar Flow. You can pair and sync with the Flow or Beat app on a smartphone over Bluetooth or plug the sensor into the USB port of a laptop using the dongle and fire up the Flow Sync tool. We found you needed to switch the OH1+ off and on again and then open the Flow app to ensure it synced.
In the pool: The swim test
Seeing as the swim-enabling goggle-clip is the major news with the OH1+ we’re going to start there.
Fitting the OH1+ to your goggles is initially a fiddly process, but once you’ve worked out which of the two goggle clips fits best, you’re good to go. Polar claims the clips cover most goggle straps on the market and we tried it on three different brands. Getting the clips onto the straps and positioning the sensor on your temple is a bit more of a faff than sticking on a chest strap, but once you get the knack it’s okay.
Essential reading: Swimming wearable metrics explained
You’re advised to wear the sensor on your left temple if you breathe in from your left side when swimming freestyle, and vice-versa if you breathe in from your right side. For anyone who breathes both sides it’s not really clear what’s best.
You need good skin contact with the LED sensors at all times and we found maintaining contact was easy enough; the sensor stayed in place no matter how much we jostled about in the water.
However, in our tests with one pair of goggles we found that regardless of which clip we used and how we adjusted the goggles, the sensor lifted them slightly on the sensor side, letting water leak in. This was alleviated somewhat with a swimming cap, but you’re supposed to be able to wear the OH1+ without one and this has made it uncomfortable to do so.
On swims over an hour the OH1+ dug in a little, though it definitely stayed put better than a chest strap – there was none of that drag you get on a chest-worn sensor on the turns. In the comfort stakes, from a male perspective, there’s not much to choose between the two in the pool.
The other major problem we experienced with the OH1+ in the pool was knowing when it was tracking. If you’re using the sensor without pairing it to a watch or the Polar Beat phone app, there’s a specific combination of button presses to make it track as a standalone device.
The first problem here is that the combination of button presses detailed in the manual isn’t very clear, and even when we followed the instructions exactly we regularly finished our swim to find no data recorded.
The second problem is that once the sensor is clipped in place and on your temple, you can’t see the small flashing LED, so you can’t tell if it’s flashing the correct colour and pattern to be recording.
Finally, the only way to see if you’ve got it in tracking mode correctly is to sync the OH1+ to an app, but that means ending your session, at which point you have to go through the same process and the same problems occur. It feels like Polar needs to make this whole process much simpler and perhaps have a LED colour just for standalone tracking.
After multiple workouts in the pool and in the gym where at the end we found no data had been recorded, eventually we decided the only way to really reliably track data was to bring our phone and pair the OH1+ with the Polar Beat app. But that’s far from ideal in the pool.
When it comes to the swim stats, we tested the OH1+ on the temple for a 1,000m swim against the H10 chest strap. This was a 30 lap swim alternating front crawl with breaststroke and the only stops being at the wall to turn.
The H10 strap clocked 131 bpm average and a 168 bpm max heart rate against the OH1+ at 128 bpm average and 140 bpm max. That’s a significant difference. In fact, while Polar Flow was able to give us a training benefit readout at the end of the session based on heart rate, the Beat app simply told us we needed to train for at least 10 minutes at 50% of our HR max to get that readout. So the discrepancy in heart rate readings was enough to make Polar’s own apps offer different assessments of our workout session.
You can also see from the chart above that the OH1+ plummets back to zero between laps, whereas the H10 shows our heart rate holding fairly steady throughout. From the experience in the pool – where we didn’t rest – the latter is clearly more accurate. Those OH1+ plummets would also account for the lower average heart rate reading.
What’s also a little peculiar about how the setup works is that although Polar Beat data syncs into the Polar Flow app as well, the summary screen doesn’t show all the same details. So if you’re a Flow user that’s a little frustrating. The naming conventions of the workouts also don’t match up which is a little confusing.
On the road: The run test
The OH1+ can be worn on the upper or lower arm for running and cycling depending on your preferences, and both are relatively comfortable once you get the tightness right. We found the OH1+ stayed firmly in place and contact between the skin and the sensor was good, though you will get impressions left on the skin and some interesting tan lines if you run in the sun.
Was it more comfortable than a chest strap? As a man, the difference was marginal, but again this might be a different story for women.
The fact the strap is a machine washable is great because ours very quickly picked up some serious sweaty odours. You’d think it’d be less prone to that than a chest strap but apparently not.
When it comes to the heart rate tracking accuracy, we tested the OH1+ optical sensor on a range of runs up against the Polar H10, and here are two examples from one forearm and one upper arm run.
For this test we ran a route that included a rolling section of ups and downs. Pace and intensity fluctuated and there were pauses where we decided on which route to take.
The OH1+ matched the H10 well for the opening section of this run but what stands out here is that it seems to register more deep drops in heart rate than the H10. That’s not dissimilar to what we saw with the swimming data. There are approximately 16 occasions where the reading drops down significantly that aren’t there for the H10.
It was the H10 that more closely matched our experience on the run. Though there were stops and starts and periods where the effort dropped, these weren’t long enough to see our heart rate return to a near-resting rate, particularly in the final miles here where we ran largely uninterrupted.
For this test we ran a slightly longer route that also included a rolling section of ups and downs, with some miles that took in steeper hills and a few stops and starts where pace and intensity fluctuated.
What’s really interesting here is that the OH1+ matches the H10 very closely, much more closely than when we wore it on the forearm, suggesting you get better results wearing it in this position than on the forearm.
The H10 also registered a slightly higher intensity at the lower end of the scale than the OH1+, but interestingly they were almost identical at picking up the effort in the tempo zone.
When you put these two sets of data together it does raise the question that the OH1+ might have a tendency to read lower than the H10, particularly during periods where movement is slower or ceased.
In the gym: High intensity intervals
Our final test took us to the gym to see how the OH1+ coped with the more rigorous demands of high intensity intervals, where there are big changes in the amount of arm movement, rapid shifts from rest to higher intensity and different equipment to factor in. Again we put it up against the Polar H10 chest strap and wore the OH1+ on the upper arm.
OH1+ clocked a max heart rate at 167bpm, the minimum at 83bpm and the average at 144bpm. Meanwhile the Polar H10 had 167bpm, 83bpm and 146 average. That’s a very close match.
You can see from the heart rate data above that the OH1+ performs well, matching the H10 closely for the majority of the session. However, once again you can clearly see instances where the the OH1+ readings plummet and at least one occasion around 20 minutes in, where it shows our heart rate has dropped, where the H10 doesn’t show this much recovery, presumably between a set.
Polar OH1+: Battery life
Polar claims you’ll get up to 12 hours of training time with the OH1+ and we found that to be accurate. That’s not as long as the 30-hours you get from the Wahoo TICKR Fit or what you can expect to get from a chest strap, but it’s enough to see you through an average week of workouts before you need to juice up.
Spotting when your battery is low can be tricky. The small LED flashes green five times for OK and red five times when the battery is low. You won’t know that unless you read the user manual and it’s easy to miss when you power up. It’d be great if the Polar Flow or Beat app showed you the battery status of connected devices as a percentage to make this more reliable.
When you do need to recharge, a full power up takes approximately 90 minutes.
How we test