COROS Heart Rate Monitor (Optical Band) In-Depth Review

The COROS Heart Rate Monitor is a very simple product, which should make for a very simple review. After all, it doesn’t even have an on button. Instead, it has exactly one purpose in life: Transmitting your current heart rate over Bluetooth.

The main selling point? Aside from no button, it claims 38 hours of battery life. To turn it on, you simply stick it on your body. Ideally your upper arm, but the COROS Heart Rate monitor doesn’t discriminate – it’ll happily get turned on by touching any warm body part. Once that connection is established, it’ll broadcast out three concurrent Bluetooth Smart signals. ANT+ need not apply, it’s not included. Neither does it currently store any data on the sensor either, though it does have the hardware long-term for COROS to potentially add that.

With that, let’s get into it.

Oh, and as usual, this review isn’t sponsored. I’ve been using a media loaner COROS HR Monitor put through its paces, after which it goes back to COROS. Actually, COROS said they didn’t want it back due to sanitary reasons, but I think I’ll still send it back – stank and all. No company gets to preview my reviews ahead of time, nor have any say on what’s in them. As always, I’m gonna call it like it is – both the good and the bad. If you found this review useful, you can use the links at the bottom, or consider becoming a DCR Supporter, which makes the site ad-free, while also getting access to a mostly weekly video series behind the scenes of the DCR Cave. And, of course, it makes you awesome.

In The Box:

Keeping with the historical lineage of past COROS products, the unit comes in a heavily oversized box. At first glance you may be concerned about the size and weight of the device based on said box, but in reality, the actual sensor part is quite light and small. Here’s the contents:

The contents are divided up into three categories:

A) A paper thing
B) A charging thing
C) A buttonless heart rate monitor

I can’t foresee many use cases for the paper thing. I mean, there’s no buttons. You just put it on your arm. Still, I appreciate that some might not realize the app is required to initially activate it. Without that, you won’t get any broadcasting of heart rate data.

Next, there’s a tiny charger:

And lastly, the band. It includes a resizable strap that you can adjust accordingly:

Like I said at the beginning, this is not a complex product with a lot of pieces.

Day to Day Usage:

The first step, aside from any required charging, is to pair it up with the COROS app. In order to do that you’ll need to get sensor-on-skin contact, so it wakes up. If you don’t pair and activate it with the COROS app, it will not broadcast your heart rate. After this point, you don’t need the COROS app. Though, it will actually automatically pair the COROS HR Sensor to any COROS watches you have, which is a nice touch.

   

With that out of the way, you can adjust the strap as required to fit your arm. Generally speaking, the best and most accurate place for optical HR sensors is on the outside of your upper arm. You want to avoid a scenario where the sensor bumps into anything (like your chest), as that could introduce issues. Here’s a good place to wear it:

Or outside I tucked it under my jersey:

Or here, on my wife (who I also utilized for testing this go around). Note that for the two watches on her hands, those are simply collecting HR data from straps/sensors, not the optical HR sensors within then (as that’d be poor).

The key thing is ensuring that the optical sensor on the back is snug on your skin, not moving, and not being rubbed by something else that could impact accuracy. There’s a small status light on the side, so you can see whether or not it’s currently turned on.

Here’s what that sensor looks like:

Oh, and the band says “Explore Perfection” on it, which is adjustable (the band, not the wording), and has a Velcro section at one end.

Because I’m all about the details, here’s a spec sheet COROS had, for the handful of other things that I haven’t covered – including that said band is made of Nylon, Polyester Fiber, and Spandex. Also, don’t use it above 122*F. Realistically, don’t do anything above 122*F – nothing good will come of it.

Now, with the specs out of the way, let’s find the device or app that you want to pair it to. Thus far I’ve paired it to: Zwift, TrainerRoad, COROS APEX 2 Pro, a variety o Garmin watches, the Garmin Edge 840, the Wahoo Fitness app, and probably a few other things I’m forgetting. In all cases, I had no issues with pairing over Bluetooth Smart:

As noted, the unit does not have ANT+ in it, only Bluetooth Smart. Within that, it can support three concurrent connections over Bluetooth Smart. COROS says that the chipset they selected doesn’t support ANT+. While I think that’s a minor poor business decision (for reasons I’ll get to in a second), I don’t think it’s actually a huge deal. These days, virtually every app/device supports the Bluetooth Smart heart rate sensor profile. And since they’ve got three concurrent sessions, that pretty much covers any multi-device type scenarios.

The downside to this is that if one were comparing specs against their equal or lesser-priced competitors, they’d note that those competitors (including Polar and Wahoo) all support both ANT+ & Bluetooth. Which, puts them at a slight disadvantage. But again, in 2023 I don’t think it’s a huge deal.

Now, with that paired up, you’ll see your heart rate on the device/app of choice:

And that’s kinda it. I mean, there are no other functions to discuss at this point in time. COROS says that long term they’re looking to add a swim mode, which would store the data during swimming. But as of today, that mode doesn’t exist – and there’s no timelines (fuzzy or firm) on what or if that might happen. Thus, any operation of the COROS HR sensor must be with another app/device.

Finally, when it comes to battery life, COROS claims 38 hours of battery life. In my testing, this holds true. You can check the battery life in the app by connecting to the sensor. Thus I would do before/after checks to see if the burn rate matched. Further, I didn’t see any accidental battery depletion when in my backpack, so that’s good. It really does seem to require sensor-on-skin contact to wake up.

However, while the 38 hour battery claim is real (and the main thing they tout over their competitors), there’s a catch there: You’re likely to burn more battery than just the stopwatch time of your workout. For many people, there’s a period before/after the actual run/ride/gym/etc that’s going to burn battery. Let’s say (like yesterday), I got all dressed/set for my ride, then I pedaled from office to home 10 minutes away to meet my wife for her long-ride. There, she finished getting ready…and before we knew it 45 minute was spent. We rode for 90 minutes, after which we grabbed coffee/etc for another 45 minutes.

During the before/after 45 minute chunks, the HR sensor was on my skin burning battery – as there’s no off-button. Sure, I could stick it in my pocket, but I promise you it’ll fall out and get lost (done that for other band sensors before).

Is this a big deal? Of course not. And while a chest strap would effectively have the same before/after battery burn – it’s got a battery duration in the 1-2 year range. Likewise, with the Polar Verity Sense, TICKR FIT, and Scosche sensors, they all have power buttons. Thus letting you use it when you want it.  Again, not a big deal, but I’d guess that the real-world battery duration for most people is gonna end-up a wash with the Polar Verity Sense due to the pre-post burn times.

Accuracy:

Next up, let’s take a look at accuracy of the COROS Heart Rate sensor, as compared to a few different options on the market: Chest strap, wrist watches, and other optical HR sensors.

For those not familiar, the existing optical HR sensor band king (by a massive margin) is the Polar Verity Sense (previously the Polar OH-1). That band is relatively similar in concept to the COROS HR Monitor, except it has buttons, multiple sport modes, the ability to save workouts and a bunch more integration. It’s got very strong accuracy that’s well respected by every reviewer out there. So, I used that as well as the Whoop 4.0 strap as competitor options.

But I also used a COROS APEX 2 Pro watch as a comparison point, a Garmin Forerunner 955, and a chest strap (HRM-PRO Plus). In other words, plenty of competitive options here to see how things handled. And, I got my wife involved too with her running interval workouts.

Let’s first start with a slate of intervals I did on an indoor trainer, compared to COROS APEX 2 Pro built-in optical sensor, Garmin Forerunner 955 built-in optical sensor, Garmin HRM-PRO Plus chest strap, Whoop 4.0 band, and Polar Verity Sense band:

In this case, all the sensors did quite well here. Well, except Whoop 4.0. It was a bit lower/slower than everyone, but that’s kinda its thing. The COROS sensor matched the chest strap, as did the watches. But, an indoors trainer workout like this is kinda the easiest bar to pass. There’s no vibrations, no major ‘thunks’ of your footsteps, or any other environmental type issues.

So let’s head outside for a road bike ride of about 90 minutes. This includes some substantial 50KPH winds. I note the winds because with a band there could be buffeting in gusts, but the band was mostly under my jersey (albeit the watches weren’t).The comparison units are essentially the same as above:

As you can see here, again, the COROS HR sensor did quite well. Whereas the COROS APEX 2 Pro? Not so much. It struggled twice significantly (teal), and then had a few bits here and there where it struggled slightly. The Garmin Forerunner 955 (green) also had a short period early on where it struggled optically too. But the COROS HR sensor here also did fine, which again, doesn’t really surprise me.

The bicep is among the easiest places to measure something optically, and in the case of a road ride, it’s heavily cushioned from major bumps. Whereas the wrist is quite challenging on a bike, due to the strain your wrists are usually under when holding onto handlebars.

So, let’s step it up again. This time a run. In this case it was steady-state, followed by some intervals. This time the Fenix 7S Pro in place of the FR955, and then I had a COROS APEX 2 Pro in the mix, but each time it syncs it re-adds the HR strap back in there to the paired sensor list, and I didn’t remember to yank it out. Thus, it was just a duplicate of the COROS HR sensor I recorded on another watch. This time the COROS HR sensor is in purple:

And immediately you might notice what I noticed, a ton of little spikes/drops. Essentially, the COROS HR Sensor is going up/down a ton, swinging upwars of 10bpm over the steady-state line of all the other sensors. That’s a lot. Here’s what it looks like when zoomed in:

I don’t see any obvious explanation for this. It was pancake flat ground/pavement, with incredibly steady cadence. This just appears to be the unit struggling to be sure about itself. You can se it struggles a little bit after that 5th interval as well (up above).

So, let’s try another interval workout. This one a warm-up, followed by some rather hard intervals. Here you can see the COROS APEX 2 Pro (in yellow) completely loses the plot. If COROS were to be developing an ad for why you need to buy this strap, this is a good example. Albeit, a bad ad for the COROS APEX 2 Pro. The COROS HR Sensor locks on really nicely here. We see the Fenix 7S Pro struggle a bit in a few of the intervals, but nowhere near as bad as the APEX 2 Pro, which…well…just look at it:

But again, for the COROS HR Monitor, it’s fine here – and virtually identical to the other sensors.

At this point, I still want to get a few more data sets in. I’m headed out for another run shortly, plus some MTB tomorrow and a few more bits here and there. Accuracy-wise, it mostly looks good, but the wobbles on one of the runs concerns me a bit. There was no firmware update between the different workouts (it’s on the production firmware). I’ve seen optical HR sensor wobbles before on a variety of other companies products, and it can be an incredibly tricky thing to resolve. Especially if it’s triggered by only certain things/scenarios/use cases, or, if it’s transient (as seems to be the case here).

Again, it’s something that with more data over the next week or two I should be able to sort out.

(Note: All of the charts in these accuracy portions were created using the DCR Analyzer tool.  It allows you to compare power meters/trainers, heart rate, cadence, speed/pace, running power, GPS tracks and plenty more. You can use it as well for your own gadget comparisons, more details here.)

Product Comparison Table:

I’ve added the COROS Heart Rate Monitor into the product comparison table, so you can see how it compares to other options on the market. The long and the short of it is that the COROS HR Monitor has a bit better battery life (albeit with the always-on caveat I noted above), but lacks any sort of on-board recording/storage that you see with the Polar Verity Sense. It also lacks ANT+, which may or may not matter to some people.

As usual, you can use the full product comparison database to mix and match and compare to other heart rate sensors as well.

Wrap-Up:

The COROS Heart Rate Sensor seems like an interesting start for a product line from COROS. Initial accuracy seems mostly good, and I didn’t have any connectivity/integration type issues – it paired up just fine. The instant-on when attached to my body also made it easy to use. Neither my wife or I had any problems adjusting the band to find a good fit, and neither of us had any sort of slippage issues with the band design. Nor did the band every accidentally flip-over (a semi-common issue with the older Polar OH-1, which the Verity Sense resolved).

The challenge COROS has with this unit though, is primarily the launch features and current pricing. This feels a bit rushed to market, especially given its only launching in the US right now, with the rest of the world in September. With the far more full featured Polar Verity Sense just $ 10 more (and often on-sale for the same price), I’d struggle to see why I’d recommend a lesser featured and less accurate product. The Polar also has the entire ecosystem of the Polar app behind it, so you can use that to track training, zones durations, and much more. Sure, it has slightly less battery life on paper, but in practice I’d consider it a wash, because I can simply turn the sensor off. Plus, it’s compatible with more devices/apps too given it has expanded protocol support. Had COROS launched with on-device recorded included, I think the pricing would be justified.

Still, it’ll be interesting to see where COROS goes from here with it. COROS has a long record of adding new features to watches after launch, albeit a lesser/non-existent record of doing the same for their external sensors/pods. Thus it’s hard to predict exactly which camp this device will fall into long term. As usual though, more competition is good, as it encourages companies to add new features, increase performance/accuracy, and lower prices.

With that – thanks for reading!

Product Reviews – DC Rainmaker