How Does a Heart Rate Monitor Work?

Heart rate monitors continuously measure the number of heartbeats per minute. They use either of two main methods:

• Electrical (Electrocardiography): This method uses electrodes to detect the electrical currents generated by heartbeats. This method is different from the optical sensors found in many wearables.
• Optical (Photoplethysmography): This method measures blood volume changes in the wrist or forearm using light. Infrared light is used to detect these changes, providing heart rate data.

The Most Common Types of Heart Rate Monitors

Chest Straps

Chest straps are elastic bands worn around the chest, with electrodes that detect the heart’s electrical activity. They are known for their accuracy.

Wrist or Forearm Wearables

Armbands and smartwatches measure heart rate optically. They use LEDs to shine light through the skin and sensors to detect changes in blood volume.

Which Type is More Accurate?

Chest-Band Devices

Chest straps are often the gold standard for accuracy, boasting 99.6% accuracy when used properly. They measure heart rate directly through electrical signals, making them reliable for all activities, including running and resting.

Forearm or Wrist Wearables

These wearables are accurate for low-intensity activities such as walking or resting. However, their accuracy can decrease during more intense activities due to movement affecting the optical sensors.

Why Do People Prefer Less Accurate Smartwatches Over Chest Straps?

Chest straps, although accurate, can be cumbersome. They need to stay moist to work properly, can restrict breathing, and may shift during use. Wristbands and smartwatches are more comfortable, easier to wear and remove, and have improved in accuracy over time, making them a popular choice despite being less precise.

Comparing the Accuracy of Chest Straps, Armbands, and ISSmartwatch: How Do ISSmartwatch Perform?

I tested heart rate monitors from armbands, chest straps, and wristwatches during various exercises.

Tips for Accurate Measurement

Wear your wristband with an optical monitor just above your wrist bone, about two fingers width from where your wrist meets your hand.

After a 15-minute steady run, heart rate readings from all three devices were comparable. During a 10-minute high-intensity workout, the smartwatch readings lagged slightly behind the chest strap but quickly adjusted.

Although not perfectly accurate, optical heart-rate monitors are adequate for real-time monitoring. The quality of sensors and algorithms in smartwatches like the T12 significantly affects accuracy.

Recommended Accurate Heart Rate Monitors and Armbands

Smartwatches offer convenience and comfort, while chest straps provide superior accuracy. Combining these features could fill a market gap.