Pulse measuringTracking Heart Rate: The Beginning

Before diving into heart rate trackers, it is helpful to understand the basics behind the science of normal heart rate monitoring. The most common measurement is resting heart rate – the number of times per minute your heart beats while at rest. Typically, this number should be between 60 and 100 BPM (beats per minute)1; it is not unusual for those with healthy hearts to remain below 60 BPM.2 Irregularities with heart rate, along with other symptoms, can be warning signs for severe heart conditions. Keeping track of your heart rate is a great way to ensure your heart is healthy and to achieve the results of your wellness goals.

According to the American Heart Association1, getting a rough estimate of your heart rate is very quick and simple. Take your middle and index fingers and press them against the side of your neck, your wrist, or the inside of an elbow. If you don’t feel a pulse –move your fingers slightly or try a different location. Once you can feel your pulse with your fingers, find anything that can track seconds – a watch, a phone, etc. Count the number of beats you feel over the course of fifteen seconds; multiplying this number by four will give you a rough estimate of your heart rate.

I can find out my heart rate easily – why do I need a tracker?

The simple answer to this question: the DIY method outlined above does not give the most accurate result and it isn’t very convenient.

How can I get an accurate measurement?

Holter Monitor

Holter Monitor

The most accurate heart rate measurements can be determined through a test known as an electrocardiogram, or EKG. An EKG determines your heart rate by monitoring the electric activity (electro) of your heart (cardio) as it pumps blood through your body. The EKG process involves a medical professional attaching electrodes to your body – typically on the chest, arms and legs – which then read the heart’s electrical signals. An EKG has many advantages: is it the most accurate test for determining heart rate, it is performed in a stable environment of a doctor’s office or hospital, the technology has been perfected for many years, it is non-invasive, and it can be used to determine heart rate during physical activity.

The major drawback to an EKG is in the lack of portability. A mobile EKG exists within a device known as a Holter monitor; similar to an EKG, it involves applying electrodes to the skin. While a Holter monitor is portable, it requires carrying around a camera-sized recorder at all times; they’re also strictly for medical use, so it’s nearly impossible to purchase one for daily use.

How can I track my heart rate on a daily basis?

In recent years, a process known as photoplethysmography, or PPG, is being used more and more in health and wellness.3 The PPG process passes light through an object and sees how light is reflected back to a sensor. Typical wrist and fingertip PPG sensors use an LED as the light source and position the sensor depending on where the device is located. Fingertip sensors are often found on the other side of the finger; this is commonly seen in pulse oximeters. Wrist-based sensors are often found near the LED; this is the norm for heart rate tracking.

Fitbit Surge: On (left), Off (right)

Fitbit Surge: On (left), Off (right)

In the case of heart rate tracking, the LED shines light through the skin, and some of it is reflected back due to the capillary vessels – the smallest blood vessels in your body, typically located under the surface of the skin. As your heart pumps blood into these vessels, they expand to allow for the blood to flow through them, and shrink after the blood flows out. These motions cause changes in how light is reflected back to the sensor – this allows the tracker to determine your heart rate.

While the technology behind the PPG has been nearly perfected in other applications (pulse oximeters), it still has a way to go for heart rate tracking. Activity trackers with heart rate sensors can experience issues with precise heart rate measurements, especially as your level of activity increases. They are exceptional at tracking resting heart rate, which is a great way to see how a healthier lifestyle may benefit your heart health. While they may not be as accurate as an EKG, you also don’t need to schedule an appointment. Similar to most other advancements, it’s only a matter of time until the PPG technology is on par with an EKG.

References:

1 American Heart Association

2 American Heart Association

3 U.S. National Library of Medicine