Coospo HW807 Heart Rate Monitor Armband

The Coospo HW807 is a comfortable, accurate heart rate sensor that you wear round your arm. It's easy to live with and produces data that's comparable to the numbers you get from a chest-strap heart rate sensor.

If you don't like chest-strap heart rate sensors (and let's face it, does anyone like wearing a strap round their chest?) this is a great alternative. The data it yields tracks very closely that from a chest strap sensor.

> Buy now: Coospo HW807 from Amazon for £43.99

Here's a typical comparison of the heart rate data from the HW807 (red line), a Garmin chest-strap sensor (purple line) and, just for giggles, a Garmin Forerunner 45 that I mostly use for dog walks (blue line).

The Garmin sensor and the Coospo track each other pretty damn closely. Since I don't run (unless someone scary is after me) I don't use the Forerunner 45 as any sort of training aid, but I'm still surprised that it's a bit laggy and occasionally glitchy compared to both the Coospo and the Garmin sensors. Given the Forerunner also uses an optical sensor, you'd expect it to be very close to the Coospo, but the Coospo is clearly better.

How it works

Your typical chest-strap heart rate sensor is simple: you put it on, and it starts broadcasting your data to any ANT+ or Bluetooth device in range. Set your device to detect it, pair them and you're away. With the HW807 there's an extra step: you have to turn it on first.

The built-in lithium-ion battery is small (Coospo claims its 90mAh capacity translates to a 20-hour battery life), and while that means the unit's about two-thirds the size of a chest strap's transmitter, it also means you can't squander power waiting for action.

The HW807 measures heart rate using a technique called photoplethysmography or (mercifully) PPG for short. In the last few years PPG sensors have popped up everywhere. If you've got any sort of recent fitness tracker or smart watch, odds-on it's got LEDs on the back that shine into your skin, and photosensors that use the reflections to measure changes in volume to your blood vessels as your heart beats. Bosh – pulse measurement.

Be still, my beating heart

But PPG needs more power than passive detection of the heart's own electrical signals, which is how most chest-strap heart rate sensors work. A CR2032 coin cell (capacity about 240mAh) will power a chest strap electrocardiographic (ECG) sensor for ages, but in a PPG sensor it would need replacing every 50 hours.

To charge the HW807, you use the included magnetic charging cable. It's similar to the cables for many budget smart watches, but the pins are further apart than most – they have 10mm centres rather than the more common 4mm, 6mm and 7.62mm. That means you don't want to lose the supplied cable as you might struggle to find a replacement.

The HW807 has another trick: its flashing LED changes colour to indicate your heart rate zone. However, its zones are based on a maximum heart rate of 180bpm, and there doesn't seem to be a way of changing that. It also buzzes to let you know if your heart rate exceeds 180. I'm pretty sure if my heart rate ever hits 180 I'll know about it without being told by an electronic widget.

On the other hand I used to ride with someone whose maximum pulse was well over 200, and she'd have set this alarm off on every hill as she blasted past me.

> 15 best heart rate monitors for cycling – get useful fitness data

You're supposed to wear the HW807 round your upper arm or the thicker part of your forearm. I found the strap was too long for my wrist when I tried it watch-style, but it worked fine when pushed a little way up my forearm.

If you leave it switched on but off your wrist it turns itself off after a short while, and it vibrates and flashes its LED red to let you know it's done it. This can be quite startling when it's on a hard surface right in front of you and you're not expecting it...

Value

Fifty quid seems like a lot to pay for a single-function device. You can get an ECG-type chest-strap heart rate sensor for £20 from Halfords or £29.99 from Decathlon.

Alternatively, for not much over £100 you can find a complete Garmin Forerunner 45 GPS watch, with a metric buttload of extra fitness and health tracking features, and which – like all recent Garmin wearables – can be set to broadcast your pulse for an ANT+ computer to pick up.

However, if accurate heart rate data matters to you, then the HW807 is the better purchase as it closely tracked the data from the chest straps I used for comparison, and beat the Garmin Forerunner 45. Interestingly I found the Forerunner was slightly less accurate when I overtightened the strap looking for a better coupling between its PPG sensor and my skin.

And it's perhaps a silly reason to like a product, but I really like that I can put on the Coospo HW807 after I've pulled on the bib shorts, jersey and the rest. If you've ever had that 'Oh bollocks, forgot my heart rate strap' moment after you've dressed for a ride, you know what I'm talking about.

Who should buy the Coospo HW807?

Basically, anyone who wants accurate heart rate data from an easy-to-use sensor that doesn't feel like it's constricting your breathing. It's become my go-to not least because, as a fat biffer, I really don't find chest straps comfortable these days.

Verdict

LED-based heart rate sensor that's easy to live with