The Heart Rate Sensor on My Garmin Watch Is Not Accurate

Optical heart rate sensors use lights to measure slight changes in blood volume in the capillary layer just below the epidermis (outermost of the three layers that make up the skin) as blood flows through the wrist area. While Garmin’s wrist heart rate monitor technology is state-of-the art, there are inherent limitations with the technology that may cause some of the heart rate readings to be inaccurate. Suggestions to improve heart rate readings as well as factors that can affect it are listed below.

IMPORTANT: Garmin Optical Heart Rate Sensor Accuracy Disclaimer 

Proper Fit of the Watch

For the best heart rate performance from your watch, ensure the following:

• The watch should be snug, but not too tight. It is properly tight when you can move the watch and the skin underneath moves with it.

  • Too loose allows the watch can slide around, creating a gap between the optical heart rate sensor and your skin.

  • Too tight can restrict blood flow.

• The watch should be worn below your wrist bone as shown below.

  

• Wearing the watch on the outside of the wrist is recommended.

• Silicone bands are recommended for the best results with the optical heart rate sensor.

  • Leather, metal, and nylon bands are not as pliable and are more difficult to get the correct fit on your wrist.

Heart Rate Fit Video

Keep the Optical Heart Rate Sensor Clean

False Heart Rate Detection

Changes in blood volume are not always caused by changes in heart rate. Your vascular system is like a balloon, so the movement of your body or flexing of large muscle groups can affect the level of blood volume in the wrist area, which make it challenging to detect heart rate among the presence of other signals that have a much larger magnitude and that change more dynamically.

In the following example, the watch initially detected and locked onto the runner's pulse, but around 20 minutes in it locked to their running cadence, likely due to the influence of leg muscle contractions impacting the blood flow in the upper body:

Why Does This Happen?

Cold weather may cause a lack of blood in the tissue on the back of the wrist. This can occur early in a workout before your blood really starts pumping.

How Can I Prevent This From Occurring?

Warm up for around 10 minutes on cold mornings before starting your activity. In addition to this, make sure you are properly wearing the watch. Refer to the proper fit section of this FAQ above.

If heart rate accuracy is critical, we suggest using a Garmin heart rate monitor strap for the most accurate performance. Refer to your owner's manual to determine if your watch is compatible with an HRM strap.

Wrist Flexing Types of Activities Can Affect Heart Rate Tracking

Activities that flex the wrist may create an effect similar to wearing the watch too tightly and restrict blood flow. Examples include, but are not limited to:

• Burpees

• Gripping Handlebars on a Bicycle

• Push-Ups

• Racket Sports

• Rowing

• Weight Lifting

• Yoga

When this occurs, the watch may have a difficult time detecting an accurate heart rate. You can adjust the watch slightly farther up the wrist, or wear a Garmin heart rate monitor strap for these activity types. Refer to your owner's manual to determine if your watch is compatible with an HRM strap.

Additionally, heart rate is calculated differently for each activity type. Make sure your activity type matches the activity being done. For example, using the Elliptical app while running outdoors could result in incorrect heart rate being recorded.

Use the Correct Activity Profile

Each profile is designed specifically to be the most accurate during the activities that are most similar to them. Always using an activity profile on the watch that most closely matches the activity you are performing helps with heart rate accuracy during the activity and for all day tracking. 

Accuracy of Wrist Heart Rate When Swimming

When swimming, obtaining accurate heart rate readings while using the wrist heart rate sensor on a compatible product can be challenging. The large arm motions can affect the level of blood volume in the wrist area, chilly water can reduce the amount of blood in the tissue on the back of the wrist, and the water can “pull” on the watch creating a gap between the optical heart rate sensor and the skin. The same tips which apply to swimming can also apply to other activity profiles; warm up and ensure the watch is being worn correctly prior to starting the activity. Specifically:

• The optical heart rate sensor must remain in contact with your skin at all times.

• The watch must be worn snug, but not too tight.

  • If worn too loose, the watch can slide around, creating a gap between the optical heart rate sensor and your skin.

  • If the watch is worn too tight, it can actually restrict blood flow.

• The watch is properly snug when you can move the watch and the skin underneath moves with it.

Skin Tone May Affect Battery Life

Skin tone can have an effect on battery life as the melanin in the skin absorbs some of the light. Garmin® watches are designed to work on all skin tones, but as the level of melanin increases in the body, the sensor may have to work harder by increasing the optical light brightness to find a pulse. This can result in slightly more battery power being consumed.

Tattoos Can Affect Heart Rate Accuracy

The ink, pattern, and saturation of some tattoos can block light from reaching the sensor, potentially making it difficult to get a reliable heart rate reading. This can cause either inaccurate readings or a lack of readings all together. For best performance, wear your watch in an area free of tattoos.

Restart Your Watch

Update Your Watch Software

Software updates will come through the background connection of the Garmin Connect™ app. To check and install available updates immediately, use Garmin Express™ application program on a Windows or a Mac computer.