Are you sick of your wrist based heart rate monitor giving you farfetched numbers? Well it might be time to consider a dedicated heart rate monitor. I used to rely on my watch to tell me my heart rate, then I upgraded to a chest strap, these days I use the COROS Heart Rate Monitor. In this post I am going to discuss this relatively new device, it’s features and why it is now my preferred heart rate monitor.

The Quest for Accurate Heart Rate Data

For trail running, I prefer using rate of perceived exertion (RPE) as a guide for intensity over heart rate. This is due to the many shortcomings of heart rate which I won’t go into here but will refer you to this article (link) by Jason Koop.

I still like knowing my heart rate at any given time as an additional guidepost for intensity. It can help knowing when to slow down on recovery runs or to speed up during running intervals. And it can be used to calculate various internal load metrics. I recently had lab testing done to determine my aerobic (LT1) and anaerobic (LT2) threshold heart rates (link to article). Using these numbers I can use heart rate to monitor my time in certain training zones.

There are two different types of heart rate monitors that are commonly available:

• Electrode type monitors (chest straps)
• Optical heart rate monitors (wrist based or arm band)

Wrist Based Monitors

Most people’s first experience with heart rate is through the wrist based optical heart rate monitors that come in most popular GPS watches. An optical heart rate monitor uses LED light to penetrate the skin and detect blood flow changes in capillaries, then it calculates the heart rate based on the light absorption patterns.

Wrist-based heart rate monitors are renowned for their inaccuracy, these are some of the causes:

1. Arm Movement – Excessive swinging or technical terrain disrupts optical sensor contact.
2. Cadence Lock – Occurs when an optical wrist-based heart rate monitor mistakenly tracks your cadence (steps per minute) instead of your actual pulse.
3. Poor Blood Flow Detection – Optical sensors rely on detecting subtle blood flow changes under the skin, but the wrist has less vascular tissue compared to areas like the chest or upper arm. Bones and tendons reduce the sensor’s ability to “see” blood flow clearly.
4. Cold Weather – Reduced blood flow to extremities can cause false low readings.

Chest Straps

Chest straps are the gold standard for accuracy. They directly measure heart rate via electrodes that measure the heart’s electrical impulses. I own a Garmin HRM-Pro and have been using it for many years.

It is a great sensor that provides highly accurate heart rate readings. But there are many downsides to these devices. Firstly they can be quite uncomfortable to wear, especially for long periods and with a running vest pack on. In my case the strap is constantly sweaty or wet. After each run I need to rinse it thoroughly in the shower, but it never fully dried before the next run which leads to the deterioration of the elastic and a kind of disgusting strap.

My main issue with the Garmin device is that the strap cannot be replaced, so when the elastic inevitably deteriorates you will need to buy a whole new device, which seems like such a waste. It is planned obsolescence. My strap was being held together by glue and it was less than 2 years old.

Arm Bands

Arm band heart rate monitors are a good compromise between accuracy and comfort. They use an optical sensor that is positioned higher up on the arm in a more favourable location typically on the bicep. This allows the sensor to glean significantly more accurate readings than wrist based due less motion, a tighter fit and a better blood flow through the muscle.

This is where the COROS strap comes in. I became fed up with the discomfort of wearing a chest strap and was looking for alternatives. The COROS seemed to tick all of the boxes for me, so I bought one and ditched the chest strap. After a year of use I feel like I know the device well enough to provide a fairly decent and honest review.

First Impressions: What’s In the Box?

When you unbox the COROS Heart Rate Monitor, you’ll find a few key items, despite the box itself being quite oversized for the actual device.

Here’s what comes in the box:

• COROS Heart Rate Monitor sensor
• Adjustable strap for the monitor. This soft fabric band is resizable, allowing you to adjust it to fit your arm.
• Charging cable, specifically a magnetic USB Type-A cable. It’s a tiny charger, relatively short at about six to eight inches.
• Paper manual: This manual is important as it contains a QR code that you can scan with your smartphone to add the heart rate sensor to your COROS account, which is needed for initial activation.

Key Features and Specifications

The COROS Heart Rate Monitor is an arm-mounted optical strap weighing 19g with a soft, washable fabric band. It uses a multi-channel optical sensor with 5 LEDs and 4 photodetectors, positioned on the upper arm or bicep. The strap has up to 38 hours of battery life in use, 80 days in standby, and charges fully in under two hours with a proprietary magnetic USB cable.

It connects via Bluetooth Smart (supporting up to three devices simultaneously) but does not include ANT+ or on-board recording. It has buttonless automatic wear detection, robust water resistance (3 ATM), and broad compatibility across apps and devices.

Setting up and Day to Day Use

Initial Setup and Activation

The first thing you need to do is get the sensor onto your skin. The device features automatic wear detection and will power on when it makes skin contact. You’ll see a small green status light on the side to indicate it’s turned on.

For older straps, the crucial first step is to pair and activate it with the COROS app. The paper manual included in the box is important because it contains a QR code that you can scan with your smartphone to add the heart rate sensor to your COROS account, which is needed for initial activation.

• Note: COROS has since updated this, and newer straps may no longer require initial app activation.

Once activated in the COROS app, it will automatically pair the COROS HR sensor to any COROS watches you own, which is a convenient feature. If you own another device you will need to manually connect it. This is super easy to do and took me less than a minute to have my Garmin watch connected.

Wearing for Optimal Results

The COROS Heart Rate Monitor is designed to be worn on the outside of your bicep. This location is considered optimal for optical heart rate sensors as it provides better blood flow measurement, often resulting in accuracy comparable to a chest strap.

The band is adjustable and made of a soft fabric. You should adjust the resizable strap to ensure a snug fit against your arm. This is key to preventing movement and external light interference, which helps maintain strong signal quality for accuracy.

The design is lightweight (19g with the band) and low-profile, so it lays flat and shouldn’t snag on clothes. It is so comfortable that I often forget I am wearing it. The downside of this is that I am burning through the battery life from the extra usage when wearing it whilst not recording an activity.

Day to Day Use

The device has no on/off button. It relies entirely on its automatic wear detection. When placed on your skin, it automatically powers on and connects to paired devices; when removed, it powers off. I think it works off either a proximity sensor or a light sensor. While this is convenient, it can sometimes accidentally turn on in a bag, which might slightly affect standby battery life. I quite often see the green light flashing in my bag.

Heart rate data is exclusively transmitted over Bluetooth Smart (does not support ANT+) and can broadcast to three devices simultaneously. This means you could connect it to your watch, a treadmill, and your phone’s app all at once.

I often run to the gym recording the run on my Garmin, then pause the run and record my strength workout using the Strava app then finish the run home with Garmin. This prevents me having to make multiple run activities. The HR strap seamlessly connects to both my Garmin and my Strava phone app. Or if I run at the gym on the treadmill it can be connected to my watch and the treadmill screen simultaneously.

As well as Strava and Garmin, it works with a wide range of Bluetooth-enabled devices and apps, including COROS watches, Apple watch, Zwift, TrainerRoad, the Wahoo Fitness app, Polar, Adidas, and Nike.

To check the battery level of the monitor you need to have the COROS app installed. I have uninstalled the app and generally just charge it once a week or so. The Garmin app notifies me if there’s low battery. It seems over the top to have a large app installed on my phone just to tell me the battery level of a HRM strap.

In essence, once it’s paired and you have the fit right, you simply put the COROS Heart Rate Monitor on your arm, start your activity on your chosen device or app, and it will automatically provide your heart rate data.

Accuracy Testing Comparison

I haven’t gone deep looking into the accuracy of the device but plenty of others have. If you want a truly deep dive into testing the accuracy then have a read of DC Rainmakers review (link to review). In all of my time using it the readings have seemed reasonable. This is far better than wrist based which often gives number that are way off the mark.

The only data I have to compare is from my lab testing. During the test I was wearing a Polar chest strap and my COROS arm band. My heart rate was recorded at each interval of the test. In the table below I compare the values from both monitors. For the most part they give the same numbers with only slight variances.

Coros Arm Band	Polar Chest Strap
151	151
163	162
168	167
172	172
175	172
179	179
183	182
184	184
189	185

Pros and Cons of the COROS Heart Rate Monitor

Comparison with Competitors

This device stacks up fairly well against the competition in regards to cost and battery life. When I was looking to buy, the only other option that appealed to me was the Scosche Rythmn24 because it has the ability to record heart rate variability. But I settled on the COROS due to the better battery life and smaller form factor.

	Scosche Rhythm24	Polar Verity Sense	Wahoo TICKR FIT	COROS Heart Rate Monitor
Battery Life (Active)	24 hours	20–30 hours	Up to 30 hours	Up to 38 hours
Onboard Memory / Recording	Up to 13 h workouts	600 hours (~16 MB)	None	None
Connectivity	Bluetooth LE + ANT+, dual-mode simultaneous	Bluetooth + ANT+, dual BLE + unlimited ANT+	Bluetooth + ANT+	Bluetooth only, up to 3 concurrent devices
Water Resistance	IP68	50 m WR (swim-capable)	IPX7 (1 m), sweatproof	3 ATM (rain/sweat; avoid swimming)
Special Features	Onboard recording, HR-zone LEDs, 100 ft range, multi-mode, can measure HRV	Swim mode, clip-on (temple), long range (150 m), large memory	LED connectivity indicator, rechargeable, 50+ app compatibility	Buttonless auto on/off, washable band, lightweight (19 g)
Approx. Price (AUD)	$230	$149	$130	$139

My Honest Opinion of the Device

I’ve been using the device for nearly a year. Coming from a chest strap I love the ease of use and comfort that the arm band provides. I am willing to sacrifice a the final percentage points of accuracy for a band that is small, comfortable and easy to use.

The problem with my old chest strap is the lack of durability. The Garmin HRM-Pro does not have a replaceable strap. After less than a year of use the strap was already deteriorating and I was using glue to hold it together. Now I have changed to an arm band I have reserved my chest strap for taking morning HRV measurements using HRV4Training. With the less demanding life I expect the chest strap to last many more years. If the strap wears out of the COROS I can buy a replacement and keep the device alive for years to come.

I do have a few issues with the COROS device. The proprietary cable is kind of annoying, it’s another cable to lose. But is is small and has a nice magnetic connection. The battery life of the device is so good that you rarely need the charger. If I am going away for a few days I generally charge it up then leave the cable at home.

Sometimes I find that the strap isn’t turning on and I take it off and put it back on again. This also could be due to low battery. My friend Ziggy has had a few instances of his device locking onto a set heart rate. He gets to the end of an activity and will have a flat line heart rate. I am yet to experience this and his problem generally resolves itself. But otherwise this is a device that generally just works as it should and I usually forget I am even wearing it. Which is the ideal outcome.

Conclusion: Is the COROS Heart Rate Monitor Worth Buying?

After nearly a year of use I can say the COROS Heart Rate Monitor has become a permanent fixture on my upper arm. I don’t have to mess around with sweaty chest straps or questionable wrist readings anymore, I just put it on and it works. If you’re fed up with the hassle of chest straps but still want reliable heart rate data, this is a solid option that just makes training a little simpler.

Bottom line: the COROS Heart Rate Monitor is the comfortable, easy way to keep and eye on your ticker.