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Monday, June 24, 2019

Review: Polar OH1+ Optical HRM

This year's Spanish tour highlighted that I really liked using the Garmin Fenix 5X as a head unit, but when it gets mounted on the bars, the unit makes up HR data. I supposed I could just ignore it, but the engineer in me hates collecting bad data. During the tour, I used the Garmin chest strap, but it had a few major problems, chiefest of which was that I simply didn't like wearing it. I browsed various reviews of optical HRM straps that can be worn on the upper arm, and the Polar OH1+ seemed the most useful for my situation, coming with a swim goggle adapter for swimming.

Out of the box for cycling, the device seems much more accurate than the chest strap or the built in Fenix 5X optical HR sensor, lending credence to DCRainmaker's claim that the most important factor in optical HRM accuracy is where you wear it. The better accuracy can be attributed to 2 things: (1) is that the strap is worn under a sleeve, which not only hides it in photos, but also shields it from sunlight, which helps accuracy. It also doesn't bounce like the Fenix would, which given its weight unsurprisingly gives inaccurate results. (Not that the much lighter Vivoactive HR was any better --- Arturo and I liked to call its HRM science fiction data generator)

The better performance over the chest strap is because at the start of a ride, I don't always remember to put liquid on the monitor for better electrical contact, so the HRM would spaz out at the start of a ride.

The sensor itself is a small disc that weighs 5g. The band is 14g, and the charger (which is also tiny and easy to lose) is 8g. This compares very favorably with the Garmin chest strap's 73g. The charger doubles as a usb sync device if you record your HR during a swim session.

I tried it twice while swimming. The first time, I saw blips in the HRM output that puzzled me.
I saw the dropouts and were puzzled. I thought it might have been user error (which happened the first time because I didn't realize how to verify that I had truly started a recording on the device --- look to see that the led blinks twice every 2s). The second time, I tried it again and with better monitoring, figured out what happened:
Every time I did a flip turn, I ran the chance of flipping the unit so that it faced away from my temple instead of monitoring it. At one point, the unit even fell off the goggles onto the floor of the pool, and luckily I saw it! What this means is that for swimming, the unit is strictly useful only for pool use where you have a chance to spot the missing unit and retrieve it. Don't try to snorkel or open water swim with it.

I tried a third time and shifted the unit forward on the goggle strap, and lo and behold, I finally got a clean run of data.


While the unit does pair with the Fenix 5X for swimming and will show you your heartbeat during rest periods between intervals, the Fenix does not maintain a connection with the unit during the workout proper and will not record HR. You have to use the polar app for that! This is disappointing but the swimming is a bit of a bonus anyway, as compared to using the unit for cycling, where it is lighter than its competitors and also a little cheaper.

All in all, I'm keeping the unit. It's useful enough when touring, and despite the glitches it is somewhat interesting to see how hard I'm working during my swim workouts, and is much more accurate than either of the devices it replicates the functionality of. Recommended.

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