There are big differences between heart rate monitors in terms of accuracy which is never mentionned in the specifications. And there is a good reason why there is no official data about it: simply beacause it depends on which sport you are doing and there are differences between individuals. Here I make a comparison between smartwatches and armbands while cycling on a road bike, indoor and on a mountain bike. Which sensor will best suits your needs or get the best result?
A heart rate monitor is a sensor that tracks your heart rate. The heart is responsible for pumping blood throughout the body, supplying oxygen to the muscles for energy production through an aerobic chemical reaction. When you pedal harder, you require more energy, causing your heart rate to increase. Therefore, heart rate serves as an indicator of workout intensity.
There are several reasons why using a heart rate monitor while cycling is beneficial:
In each test category (road bike, indoor cycling or mountain bike), I always rode at the same pace on each part and took the same route. I used the same bike, the pressure in the tires was the same and I cleaned the heart rate monitor with water before, in order to ensure consistent readings. The smartwatches and bands should be tight enough, not too tight because optical sensors are measuring the volume of blood circulating throughout the body by measuring the light returning to the sensor. Let's have a look into the results in each category.
The Polar H10 chest strap has been used as a reference in order to measure the accuracy of each heart rate monitor. The results given here are based on my own experience and may differ between individuals, especially for optical heart rate monitors which may give different results based on the skin tone.
| Brand | Heart Rate Monitor | Accuracy (%) | Price ($) | Curve |
|---|---|---|---|---|
| Coospo | HW807 | 1.4 | 45 |  |
| Coospo | HW9 | 1.7 | 65 | |
| Apple | Watch SE 2 | 2.4 | 299 |  |
| Fitcare | HW851 | 3.8 | 45 |  |
| Coospo | H6 | 5.7 | 24 |  |
| Wahoo | TickR Fit | 7.0 | 79 |  |
| Fitcare | HW702 | 9.6 | 40 |  |
| Pixel watch | 13.4 | 379 |  |
|
| Mobvoi | Ticwatch PRO 5 | 17.8 | 359 |  |
| Montblanc | Summit 3 | 18.0 | 1260 |  |
| Samsung | Galaxy Watch 6 Classic | 20.0 | 419 |  |
| Polar | M600 | 23.6 | 230 |  |
| Xiaomi | Watch 2 PRO | 25.4 | 269 |  |
| Garmin | Fenix 5 | 30.0 | 289 |  |
| Samsung | Galaxy watch 5 | 31.0 | 279 | 
|
| Samsung | Galaxy watch 4 | 31.0 | 229 |  |
Differences on the road bike are huge between heart rate monitors, and many smart watches have trouble catching with the Polar H10 except for the Apple Watch SE 2.
Chest straps or recent arm bands seem to be the best choice.
If you have a look at some optical sensors such as the Wahoo TickR Fit or Fitcare HW702, you can see a little lag with the Polar H10. This effect is less visible on the HW807 or HW9.
| Brand | Heart Rate Monitor | Accuracy (%) | Price ($) | Curve |
|---|---|---|---|---|
| Apple | Watch SE 2 | 1.3 | 299 |  |
| Fitcare | HRM828 | 1.3 | 30 |  |
| Coospo | HW807 | 1.7 | 45 |  |
| Coospo | HW9 | 1.9 | 65 |  |
| Fitcare | HW851 | 3.9 | 45 |  |
| Pixel watch | 4.2 | 379 |  |
|
| Samsung | Galaxy Watch 6 Classic | 4.5 | 419 |  |
| Samsung | Galaxy watch 5 | 4.7 | 279 |  |
| Montblanc | Summit 3 | 14.0 | 1260 |  |
| Samsung | Galaxy watch 4 | 20.0 | 229 |  |
| Xiaomi | Watch 2 PRO | 23.2 | 269 |  |
The accuracy of smartwatches is much better on a mountain bike, I think this is due to the position on the bike with the flat handelbar (the watch is on the top of the wrist and not on the side which makes it less sensitive to vibrations) and to the lower tire pressure.
| Brand | Heart Rate Monitor | Accuracy (%) | Price ($) | Curve |
|---|---|---|---|---|
| Fitcare | HRM828 | 0.5 | 30 |  |
| Coospo | H6 | 0.5 | 24 |  |
| Mobvoi | Ticwatch PRO 5 | 0.8 | 359 |  |
| Apple | Watch SE 2 | 1.3 | 299 |  |
| Fitcare | HW851 | 1.0 | 45 |  |
| Samsung | Galaxy watch 5 | 1.5 | 279 |  |
| Wahoo | TickR Fit | 1.9 | 79 |  |
| Montblanc | Summit 3 | 2.3 | 1260 |  |
| Pixel watch | 3.3 | 379 |  |
|
| Xiaomi | Watch 2 PRO | 4.1 | 269 |  |
| Samsung | Galaxy watch 4 | 21.4 | 229 | |
| Fitcare | HW702 | 29.0 | 40 |  |
| Garmin | Fenix 5 | 39.0 | 289 |  |
If you are more focused onto indoor cycling, then you have much more choice if you want to get an accurate heart rate monitor. A recent smartwatch such as the Galaxy watch 5 or Pixel watch will be good enough for interval training.
Not all cycling head units or HRMs are compatible with Bluetooth Low Energy (BLE), so it is important to check the technical specifications before making a purchase. Some HRMs, such as the Wahoo TickR or TickR X, Polar H10, or Garmin HRM dual, can connect to multiple devices via Bluetooth Smart. This feature can be useful if you want to connect to your phone and GPS simultaneously.
If you have a smartwatch, you may need our app HR2VP to broadcast your heart rate over Bluetooth to your bike computer. However, some devices (depending on their firmware) may have trouble to connect and in this case, the solution is to connect with ANT+. Our app HR2VP Watch Bike Computer for Wear OS allows you to use your phone as a BLE into ANT+ sgnal bridge in order to connect to any bike computer. In this case, an ANT+ USB stick may be required, check compatility of your smartphone with ANT+.
Download HR2VP for Wear OS
Download HR2VP for iOS & Apple Watch
Overall, a chest strap using the ECG technology is better for tracking heart rate than wrist based optical sensors measuring blood flow, except for the Apple watch SE 2 which has an outstanding accuracy compared to other smartwatches. But chest straps may be a bit less comfortable.
Almost all chest straps have an outstanding accuracy, and measurements are often more consistent than with optical sensors. If wearing a strap is not an issue for your. It might be the best choice and also the most affordable.
There are differences depending on what kind of workout you want to do: indoor cycling, road bike or mountain bike. HRM tend to be less acurate on a road bike, especially for smartwatches. I think this is because the watch add some weight on the side when you have the hands on the hoods which amplify the vibrations. In addition, the high pression in the tires and the stifness of the carbon fork and handelbar transmits every small bump on the road integrally to the hands.
My suggestion would be to choose a HRM with an accuracy of 5% or better for serious training and around 10% for health and fitness purposes. A chest strap will give you the best results in terms of consistency and responsivness, a good arm band will be more comfortable and an Apple watch is a good all rounder but may be complicated to connect to your bike computer as a heart rate monitor.
Personally, I used the Polar H10 during years and I like it very much. It is know as the most accurate heart rate monitor on the market, which is why I choose this model. But since I got a new HRM 828 as a device to test, I must say that I take this one mostly. The reason why I like this one is that it is rechargeable, so you don't have to replace the battery and the accuracy is very close to the Polar H10. The battery life is about 50 hours so expect to charge once every 30 day or less depending on how often you use it. Both heart rate monitors have additionnal features such as on board data storage and are waterproof: IP67 only for the HRM 828, and underwater down to 30 meters for the H10 which makes it suitable for swimming as well.