How to get the best heart rate measurement from your COROS watch

Why is a chest strap more accurate than an optical sensor in a watch?

All COROS watches are equipped with an optical sensor for measuring heart rate (hereinafter referred to as pulse) from the wrist. Measuring from the wrist is very convenient, as there is no need to connect additional accessories to the watch. Using your pulse, you can determine your training zones, overall training load and plan your recovery.

Optical heart rate sensors generally only help to determine the effort expended by estimation. Athletes who undergo specialized training programs based on heart rate are recommended to use more accurate measurement methods - e.g. a chest strap. Such heart rate measurement accessories can be paired with the COROS watch via the ANT+ protocol or via Bluetooth.

Introduction

In the technological world, two factors are essential for all sensors, including optical ones: signal and noise. The signal covers everything important for collecting data from the sensor, while noise interferes with the sensor in performing the correct measurement. If the sensitivity of the sensor is increased, both factors increase - signal and noise. And it is this phenomenon that causes an inaccurate result to a certain extent. Most heart rate measurement chest straps are equipped with technologies for receiving less noise and a stronger signal, which means that chest straps have a better heart rate measurement result compared to an optical sensor, e.g. during interval training. It is also important to add that chest straps designed for measuring heart rate sense heart activity through electrical discharges that occur when the heart works. In short and simplified - this is how specialized devices in hospitals measure heart activity (electrocardiography - ECG) and such a measurement is much more accurate.

Optical sensors measure heart rate on a completely different physical principle. LEDs (often of different colors to cover different light frequencies) on the back of the watch flash and emit light through the skin. Optical sensors rely on the reflection of the remaining green light from the blood, which the watch then uses to determine the pulse rate and evaluate the heart rate values ​​that we see on the display, for example, during activity.

The COROS watch has four built-in optical heart rate sensing algorithms:

• running
• cycling
• swimming
• interval training

They are adapted to different types of training to give us the best possible accuracy. Since wrist-based heart rate sensors are more susceptible to noise interference, the COROS watch user can improve their signal while minimizing noise by taking the following steps.

What steps can you take to improve the heart rate signal?

A few practical tips and observations:

• Keep your hands warm.
  The signal in optical heart rate measurement depends on the reflection of your blood. The more blood flow you have on your wrist, the better the signal your watch will receive. The weather may not affect the accuracy of the optical measurement. If you feel cold on your hands, your blood flow has significantly decreased. The best way to solve this is to wear gloves. Another recommendation is to always warm up your body (including your hands) before starting a workout in the winter.
• Clear skin without large hairs or tattoos
  Significantly larger hairs or tattoos block the light reflection and cause problems during measurement. If you have a tattoo on one wrist, we recommend moving the watch to the other hand.
• Place your watch higher than your wrist bone.
  This is especially useful for those with thin/narrow wrists. Find an area of ​​skin on your wrist with the most blood flow.
• Wait until your watch shows a stable heart rate reading
  Just like your body, your optical sensor needs some warm-up. We recommend staying on the “Start” screen for a while and waiting for the watch to filter out some of the noise. You can also set an audio notification (alert beep) to let you know when it’s ready. If you have audio notifications turned off, a heart icon will appear to let you know.
• Choose the right training regimen
  The algorithms for running, cycling, and swimming are not specifically designed to monitor rapid changes in heart rate. If you are training intervals, select “Interval Training” in “Run” or “Cycling” mode to increase the sensitivity of heart rate measurement.

What can you do to reduce noise?

Try these tips:

• Nose strap pulled tight
  One of the key factors that causes inaccurate measurements is shock. It is best to wear your watch as tightly as possible, even if it is not entirely comfortable. This will limit the ability of the watch to move around on your wrist. During aggressive running or downhill, users often find that watches with optical sensors have higher readings, as this is when they experience the strongest shocks.
• Choose a lighter watch
  The heavier the watch, the stronger the noise in the heart rate measurement that is generated during running (shocks). Lighter watches generally maintain a stronger signal for a longer period of time.
• Place your watch higher than your wrist bone.
  This is especially useful for those with thin/narrow wrists. Find an area of ​​skin on your wrist with the most blood flow.
• Reset the optical sensor halfway through the run
  Sweat or water can increase the likelihood of your watch moving on your wrist. It is therefore not surprising if the sensor measures your heart rate accurately at first and then starts to measure inaccurately later during your workout. This could be because your hands were colder, which reduced blood flow, or because there was sweat between the watch and your wrist, which caused the watch to move. In this case, take the watch off your hand, wipe off the sweat, and try to keep a clean surface between your wrist and the sensor. Place a piece of fabric from your clothing on the sensor so that the sensor stops working (the light is deactivated). Put the watch on your wrist and continue your workout. This will reset your heart rate measurement and adjust it to the correct values.

If you want to take your preparation even further

If you are a data geek and are going to complete specialized training programs, it is generally recommended to use chest straps or other special sensors for such training. COROS watches are compatible with many third-party HR sensors with ANT+ or Bluetooth connectivity. ANT+ protocol is several times more energy efficient than Bluetooth. In other words, ANT+ accessories (e.g. chest strap) drain the battery in the watch less. If you are thinking about buying ANT+ accessories (chest strap, wattmeter, pod, powermeter, etc.), you can check the compatibility with all COROS models before buying.

ANT+ accessories compatible with COROS model:

• Pace 2
• Apex
• Apex Pro
• Vertex
• Vertex 2

Conclusion

In our e-shop you will find high-quality chest straps . And finally, we would like to remind you that training according to heart rate is just one way to monitor and improve your performance. In cycling and other sports, training has been done according to other indicators for a long time - e.g. through body power measured in watts. COROS offers a small additional device called POD for this type of training.