The ring has an optical pulse sensor with infrared, red and green leds that allows you to record BPM and other heart metrics in real-time or for later analyses/recommendations on the Circular App. 

How is Heart Rate measured?

Each contraction of the heart results in a blood volume pulse which propagates through the bigger arteries towards the small capillaries. We can all feel this by placing a finger on top of our arteries on our neck or the palmar side of our wrist. The same happens on your finger.

The optical heart rate sensors use a methodology called photoplethysmography (PPG). PPG is a technical term for shining light into the skin and measuring the amount of light that is scattered by blood flow. That is a bit of an oversimplification, but PPG is based on the fact that light entering the body will scatter in a predictable manner as the blood flow dynamics change, such as with changes in blood pulse rates (heart rate) or with changes in blood volume (cardiac output).

In PPG recording, you don’t need electrodes, but just a device that has a proper LED and a photo receiver. That’s why it’s a common method used in wearables, such as in the Circular ring.

Infrared light and red lights travel deeper into our tissues and enable more accurate measurements than other wavelengths of light such as green or blue. However the green led will produce more robust measurements during movements.

A great benefit of having a device like the Circular ring on your finger is that it is most likely one of the most optimal places for PPG-based tracking. The reason being that it has suitable arteries and capillaries for clear blood volume pulse signals, making the optical measurement more reliable and accurate. In addition, there are no moving parts between the joints in fingers, meaning that the ring sits firmly and doesn’t move. 

How can tracking your Heart metrics help you?

Heart Rate is the main component alongside your movements and temperature variations for every Circular sleep, activity and wellness analyses.

Here is a list of the different useful metrics that are derived from your Heart Rate.

Heart Rate Variability

HRV is helpful to sleep analyses, wellness analyses, stress and recovery analyses.

To know more about HRV: Understanding Heart Rate Variability (HRV)

Rested Heart Rate

RHR is an excellent indicator of your overall wellness performance, to be correlated with your HRV.

To know more about RHR: What increases and decreases Rested Heart Rate (RHR)?

Maximum Heart Rate

MHR is helpful to your heart training zone and activity intensity analyses.

To know more about MHR: Why Max Heart Rate (MHR) is important to know

Activity intensities

Activity intensities describe the types of effort that you produce. It is helpful to quantify the intensity of your activities to calculate your active minutes.

To know more about Activity intensity: How Circular tracks your Activity intensity

Active minutes

The active minutes are basically the time you spend being active weighted with the intensity of the efforts. It helps you analyze your physical efforts in the long term and meet your performance goals.

To know more about active minutes: How Circular tracks your Active minutes, Activity Volume, and Recovery

Cardio points

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The World Health Organization (WHO) recommend staying active to maintain good heart health. They recommend that you get at least 150 minutes of moderate intensity activity or 75 minutes of high intensity activity each week. To help you apply these recommendations, Circular tracks your efforts in the form of cardio points. Circular gives you one cardio point for every minute of activity you perform in moderate activity and two cardio points for every minute of activity you perform in high activity.

VO2 Max

VO2 Max is an excellent indicator of your potential performance in endurance events.

To know more about VO2 Max: Understanding VO2 max: why is it useful?

Calories burned

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Calories burned gives you the power to make informed decisions about nutrition, weight management, and performance. Circular calculates your total calories burned including the one that you burn during your sleep and activities.

To know more about Calories burned: Circular’s calories burned

We remind you that the Circular™ ring is not a medical device and should not be used to diagnose or monitor a pathology.