Heart rate sensors typically come in one of two forms. The chest strap style and the wrist band style. The problem with chest straps is that they are not the most comfortable of devices. Its also a lot of hassle putting one on. The problem with the wrist band style is accuracy when it comes to high intensity activities.
Essential reading: Heart rate zone training with wearables
This is where the Polar OH1 comes in. A middle of the road solution, the lightweight gadget is an optical heart rate monitor that’s not meant to go around your chest or your wrist. Instead you wear it around your upper or lower arm. Polar says their little gadget makes heart rate tracking simpler than ever.
I strapped one on to find out just how precise and convenient it really is.
In the box, the OH1 arrives with a soft textile machine-washable armband, the circular optical heart rate sensor and proprietary charger. The main unit slips easily and stays securely in place in the plastic holder that is attached to the velcro strap.
This is not a bulky device. About the size of a coin, the core roughly measures just under 30mm in diameter and weighs only 5 grams. The strap adds an additional 12 grams.
The OH1 straps onto your arm and reads your heart rate through the 6-LED optical green sensors on the underside of the main unit. Similar technology can be found on the Polar M430. The lights bombard your skin using a high rate, hence the accuracy. Most other optical heart rate monitors use up to 3 LED lights.
Similar to its main competitor, Scosche Rhythm+, all you need to do is slip the armband on your upper or lower arm and you are set to go. The sensor needs to be on the underside of the armband in firm skin contact. To ensure accuracy from the outset, it is advisable to wear your OH1 for a few minutes prior to starting a training session.
I have used the little gadget in both locations with no problems whatsoever. Once adjusted, the armband is comfortable and stays in place. If you wear it on your upper arm you can completely cover the tracker with your shirt sleeve. You shouldn’t see the green LED’s when you’re wearing it which adds to the discretion. All in all, the strap is very comfortable, a huge improvement over bulky chest straps.
Out of the box, Polar OH1 a works with all compatible Polar sports watches, trackers and cycling computers. Because it transmits your heart rate via Bluetooth Smart, it also works with third-party devices and connects to smartphones. A much anticipated firmware update in April 2019 also brought ANT+ connectivity.
Those that prefer training without a watch or a phone will be happy to know the OH1 has 4 GB of internal memory. This is good enough for storing up to 200 hours of training data.
In terms of battery life, you can expect to receive up to 12 hours of continuous use, which is enough for even the longest of training sessions. The charging cradle that comes with it resembles a little USB stick. Just pop the little sensor in, stick the charger into a computer port or USB power adapter, and the 45 mAh lithium polymer battery will recharge in a couple of hours. Polar says you can charge and discharge the battery over 300 times before a notable decrease in its capacity.
Polar’s OH1 has a water resistance rating of 3 ATM (down to 30 meters), so you can use it in both dry and wet conditions. Which means you can go for a jog in the rain, worry-free. And yes, its even suitable for swimming! You can use Polar OH1 in the water to store a swim session into the sensor’s internal memory. When using it with a Bluetooth wrist unit, you won’t be able to view your heart rate in real-time as Bluetooth transmission does not work under water.
The main thing to know is that this is only a heart rate monitor, so don’t expect a step or calorie count or anything of that nature. Its not there, so don’t look for it. But do expect a device that will provide you with accurate heart rate measurements.
To switch it on, simply press the single physical button on the side of the sensor. This is confirmed by one flash. To enter standalone training mode, press the button twice. This will be confirmed by 2 flashes. To switch off, just press and hold the button. A white light indicates that no heart rate is detected, green signifies success. Red flashing indicates that its time to charge the battery and blue that its syncing.
During the initial setup you’ll be asked to set where you wear your product and fill in your physical settings. I’m not really sure why this is necessary as the algorithms and processing of data is the same regardless of the position. Perhaps so that Polar can better understand their customer base.
In broadcast mode heart rate data is sent via Bluetooth to compatible devices in real-time. The OH1 works with Polar Beat and a wide variety other third-party fitness apps such as Strava, Endomondo, MapMyRun, etc. In standalone mode heart rate training data is stored internally for syncing later on.
Essential reading: Heart rate zone training with wearables
At the end of the training session all the data is wirelessly uploaded to the Polar Flow app installed on your smartphone for convenient review. In the Polar Flow web service you can also plan your training, track your achievements, get guidance and see detailed analysis of your training results.
You’ll find that the OH1 is wonderfully accurate, much better than a wrist based heart rate monitor and pretty close to what you would get if you were to wear a chest strap. In my test sessions, I found that if there was a discrepancy, it was only by 2 or 3 beats per minute. And only with very high intensity activities or at the beginning of a session.
Here are results from a 3 kilometer run that show how the OH1 compares to a Garmin Forerunner 935 paired with the Scosche Rhythm+. The first pic is the OH1 reading. As you can see the two are nearly identical.
As with most optical systems, there may be a bit of trial and error on the part of the user as to where the best location is to get the best results.
Polar also sells the H10 chest strap. Apart from the form-factor, there are a few differences between the two devices.
Like other optical heart rate sensors, the OH1 shines LED lights to detect your heart rate. The H10, on the other hand, uses the electrical activity of your heart (ECG). This means, the H10 will probably produce more accurate measurements, particularly when it comes to hard interval training sessions. Also, if you’re into swimming or triathlon, you are better off with the H10 as it uses 5kHz frequency to transmit your heart rate under water. Another difference is that the H10 can run up to 6 months on a coin cell battery, whereas you will need to recharge the OH1 from time to time.
The OH1 has much better memory, though, whereas the H10 can only store one training session so you need to sync each time. Oh, and lets not forget the convenience of not having to strap the OH1 around your chest.
Polar’s middle of the road solution features a great design with a few options in term of where you can wear it. There is actually very little not to like. What impresses most, though, is the accuracy of readings. Its close to what you would get with a heart rate chest strap and much better than a wrist based heart rate device.
As mentioned, its main competitor is the Scosche Rhythm+. Identical in price, both dish out data of similar quality. In OH1’s favor is that its smaller and more discreet as all lights are on the underside of the unit. Also, the Scosche has no internal memory and does not have as good waterproofing or battery life.
The OH1 is light, comfortable and accurate. If you are planning to ditch the old chest strap you won’t go wrong with Polar’s latest heart rate monitor.
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