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What is heart rate variability?

This article was originally featured on The Conversation.

Your heart beats around 100,000 times every day. Heart rate is a key marker of cardiovascular activity and an important vital sign. But your pulse is not as steady as a precision clock – nor would you want it to be.

As a cardiovascular physiologist, I measure heart rate in nearly every experiment my students and I perform. Sometimes we use an electrocardiogram, such as you’d see in a medical clinic, which uses sticky electrodes to measure electrical signals between two points of your body. Other times we use a chest strap monitor, like ones you might see on someone at the gym, which also detects heartbeats based on electrical activity.

As wearable technology has grown more popular, it’s not just researchers and cardiologists who are paying attention to heart rate. You might be monitoring your own all day long via a fitness tracker you wear on your wrist. This kind of wearable device uses green light to detect blood flow beneath your skin and deduces your heart rate.

Here are what heart rate and other measurements derived from this biometric can tell you about your body’s health.

Pumping blood where it needs to go

The heart’s primary job is to contract and generate pressure that helps pump blood to the lungs to be oxygenated and then on to the rest of the body to deliver oxygen and other nutrients. Heart rate is simply how fast your heart is beating. Sometimes called a pulse rate, it’s normally presented in beats per minute. You can count your own heart rate by feeling for your pulse inside your wrist or behind your jaw.

When your body demands more oxygen, such as during exercise, heart rate will increase along with the increasing workloads.

While many people are familiar with tracking their heart rate during exertion, the heart rate at rest can also provide valuable information. The two parts of the autonomic nervous system, the sympathetic and parasympathetic, influence resting heart rate. The sympathetic branch helps coordinate your body’s stress response. The more active it is, the higher it…


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