Matthew Miller/

For daily heart rate tracking,including during sleep, a watch with an optical heart rate monitor is perfectly fine. But if you run intervals or train with heart rate zones as your primary metric, then nothing beats a chest strap.

Chest straps have improved over the years, but I still have scars from the early straps that gouged into my skin below my chest muscles. I've been wearing Polar and Garmin chest straps and, overall, they work fairly well, although I have to wear them tightly or they tend to slide down my body when I sweat too much.

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For the past week, I've been running, rowing, walking, and biking with the newCoros Heart Rate Monitor , which comes in the form of an armband that you mount on your bicep or forearm. It is extremely comfortable thanks to the spandex and nylon materials and low profile, 9.7-gram sensor block. 

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COROS Heart Rate Monitor

Thenew arm-mounted Coros Heart Rate Monitor provides a comfortable and accurate source of heart rate data.

View at Coros

There are five LED lights with 4 photodetectors on the bottom of the monitor, and at its thickest point, it is only 9.9mm deep. It is secured to the strap with a couple of clear brackets so you can easily slide it off to clean the band over time. 

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Coros says the Heart Rate Monitor can record your data for up to 38 hours with 80 days of standby. It charges via a USB cable and proprietary charger that connects to the contacts on the back of the monitor, with two hours needed to fully charge it up.

Matthew Miller/

The monitor is rated for 3 ATM, so you can safely wear it in inclement weather and while sweating during your workout. The included strap fits arms from 7.09 to 12.6 inches. I have it extended nearly to the full length, but it is still very comfortable and secure.

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If you run intervals, participate in activities outside with bright light, or perform activities where you have lots of wrist and arm movement, then you have likely experienced consistently poor heart rate tracking with a traditional smartwatch. There is a lack of deep tissue on the wrist, which is why a chest or arm-mounted heart rate strap provides a more accurate experience.

The Coros Heart Rate Monitor can connect to virtually all Bluetooth devices, including gym equipment, bike computers, and more. I tested it with theCoros Apex Pro 2 , Vertix 2 , Garmin watches, and a Hydrow rowing machine. The COROS setup, through the smartphone application, was seamless. And after pairing to the app, your connected watches can detect the strap nearly instantly.

Matthew Miller/

My results showed the best performance with a connected Coros watch. When I connected it to Garmin watches, I saw fewer data points on the plot. It turns out that the Garmin Forerunner 965 was set to record data in 'smart' mode rather than the more traditional 1 second interval. I changed the setting on the watch and I am now seeing the exact same heart rate results with multiple devices connected to the Coros Heart Rate Monitor.

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I also tested the Coros Heart Rate Monitor to theGarmin HRM-Pro chest strap with a resulting plot that showed almost the exact same results. With this level of performance, I am moving to the Coros monitor since it is much more comfortable than the chest strap and has an internal battery that can easily be charged via USB.

Comparing the Coros tracking (blue) to Garmin's (purple). It's nearly the same.

Matthew Miller/

In addition to a standard run over hills, I ran intervals to check out the responsiveness of the monitor and was very pleased with the results. It quickly picked up the variance between walking and running with changes in heart rate tracked perfectly.

While I enjoy running, I've come to row on the Hydrow as my primary overall body workout. It was easy to connect the Coros Heart Rate Monitor to the Hydrow and, again, it is a much more comfortable experience to have the monitor secured to my upper arm rather than around my chest.

Matthew Miller/

I also started an activity on the watch with the strap connected and then left the watch behind to see if the strap would continue to measure my heart rate in an offline manner, but the result showed that any heart rate tracking was stored on the monitor without a connected watch.

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Coros states that swimming support will be provided with a future update. 

The Coros Heart Rate Monitor is available now for$79. You can also purchase additional straps in Orange, Lime, and Grey for$15 each. Compared to competing arm-mounted heart rate monitors from Polar, Wahoo, and Rhythm, which are all more expensive and have shorter activity tracking periods, Coros' latest option is looking to bring the best value. 

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