How Heart Rate Monitors Work

How and Why You Should Track Your Heart Rate

Using a Heart Rate Monitor

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A heart rate monitor (HRM) is a device you wear to measure your heart rate continuously. There are chest strap and wrist-worn heart rate monitors. They detect each heartbeat and transmit the data to a receiver such as a watch, fitness wearable, or phone app. The data is displayed as the number of beats per minute.

Learn more about how heart rate monitors work, the benefits of using them, and how to use them for fitness.

Benefits of Heart Rate Monitors

Personal heart rate monitors measure exercise intensity so you know whether you are achieving the level of effort you are targeting. Heart rate monitors with electrodes continuously track heart rate, compared to an on-demand pulse monitor, which only shows a value at a single point. This frees you from having to stop and take your pulse.

Whether integrated into a smartwatch or a wearable like a ring, necklace, earbud, shoe, or item of clothing, many modern heart rate monitors are relatively accurate. especially during moderate-intensity activity. Wearables such as wrist-worn monitors tend to be less precise than chest-strap monitors during periods of intense exercise.

Most heart rate monitor models have indicators showing whether you are exercising in your target heart rate zone and give audible or visual alerts when you are above or below that zone.

These alerts can be integrated into the device itself or displayed on an app on a smartphone. This allows you to adjust your workout to stay at your target heart rate by slowing down, speeding up, or changing incline or resistance.

Many heart rate monitors save and display workout heart rates on a graph along with time, speed, elevation, and other aspects measured during the workout. The time in different heart rate zones may be shown at the end of the training. Simpler heart rate monitors may only show the average heart rate for the session.

How Heart Rate Monitors Work

Chest strap heart rate monitors work using electrode sensors and are considered accurate as electrocardiograms (EKG). This sets them apart from the wearable heart rate sensors found in many activity monitors and smartwatches.

Chest-Strap Heart Rate Monitors

The chest strap on a heart rate monitor has electrode sensors that can detect the heart's electrical activity as it beats. The chest strap can be made of plastic, elastic, or fabric. The sensors may be embedded in the strap or attached to the skin.

Many cardio machines in the gym have heart rate monitoring built into a handle or available wirelessly. The machine will alter the intensity of your workout automatically depending on your heart rate.

Wearables and Wrist-Worn Heart Rate Monitors

Other wearable heart rate monitors include smartwatches, wristbands, rings, and more. They use a technology called photoplethysmography (PPG). PPG is inexpensive and uses a light source to detect changes in the blood volume of micro-vascular structures near the skin's surface. The better the fit, the more accurate the result.

Other technology uses carbon nanotube threads (CNTT) integrated into clothing like vests or t-shirts to measure heart rate. The CNTT material is soft, stretches with clothing, and is washable.

If you want to use a wearable device, it may be wise to check your heart rate with an electrode strap heart rate monitor and compare it to the results you get from your wearable monitor.

How to Use a Heart Rate Monitor

If you're training for a goal-based event—attempting to achieve a target marathon finishing time, for example—a heart rate monitor may help you track your workout effectiveness.

Incorporating a monitor into your training runs can help you learn when you have reached your target heart rate zone. You'll then be able to adjust your pace or speed as needed according to the type of run you're doing.

In other words, a heart rate monitor can let you know whether you are training hard enough or too hard for your specific goal. You can use this information to adjust your training in real time. Knowing your ideal heart rate zone and the different training zones will help inform you.

Determine your maximum heart rate by subtracting your age from 220. For instance, if you are 40 years old, your MHR is 180 (220 - 40 = 180). Then you can choose to work within specific heart rate training zones.

Target Heart Rate Zones

  • Light exercise: 57% to 63% of MHR
  • Moderate exercise: 64% to 76% of MHR
  • Vigorous exercise: 77% to 95% of MHR

In choosing a heart rate monitor, look for one that has the type of display you can most efficiently use and understand during your workout. Some have pre-programmed exercise zones based on your age, while others allow you to set your zones to your individual preference.

When to Call a Healthcare Provider

It is important to note that most heart rate monitors do not detect heart irregularities or a heart attack. If you are experiencing an elevated heart rate paired with chest pain, dizziness, or shortness of breath, get immediate medical attention or call 911.

A Word From Verywell

Tracking your heart rate using a heart rate monitor during a workout can be a beneficial method of understanding your fitness efficiency. However, it's just one way to measure your workout's success.

Use the rate of perceived exertion to track your intensity without the need for a monitor. Above all, remember to listen to your body as you're working out. Take breaks or pull back on intensity to lower your heart rate.

6 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Wendy Bumgardner
Wendy Bumgardner is a freelance writer covering walking and other health and fitness topics and has competed in more than 1,000 walking events.