Heart Rate Monitor Introduction

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The following article is for watches with heart rate monitors, and doesn’t apply to Pebble Classic, Steel, Time, Time Steel or Time Round.

Wearing HR Watches
How HR Monitoring Works
Workout App & HR Zones
Understanding Graphs
Frequently Asked Questions


Note: if you haven’t set up Pebble Health yet, you’ll need to. Instructions can be found here.


Wearing HR Watches

Getting the best results from your heart rate monitor starts with how you wear it.

For the most accurate heart rate measurement, your watch should be worn:

  • Two finger widths (3-4 cm) above your wrist bone
  • Snug, but not too tight
  • With no clothing between your skin and the back of the watch

During exercise, try moving your watch higher up on your forearm, so wrist movement doesn’t affect accuracy.

Depending on how snugly you wear the watch normally, you may want to consider tightening it slightly during exercise so it will stay put, but not enough to cause discomfort or obstruct blood flow.


How HR Monitoring Works

Your heart rate is monitored every 10 minutes, unless you trigger constant monitoring with the Workout App, or by leaving the heart rate card open in the Health App. You may see data from longer than 10 minutes ago if Pebble Health determines a heart rate reading’s quality is poor, as it won’t include that reading.


Pebble HR-enabled devices use optical heart rate monitors, which we’ve tested for accuracy against industry-leading devices (see more on Accuracy below).  The monitor works using LED lights, which flash hundreds of times per second.


The amount of light reflected from these flashes tells the monitor how many times your heart is beating per minute.  Blood absorbs light from the flashes, so when your heart beats and pumps more blood through your wrist, less light gets reflected; between beats more light is reflected, since less blood is moving past the watch.


Using the Workout App

Pebble’s Workout app allows you to measure your heart rate continuously while working out, and view stats about your workout.  Leave it open to see real-time stats, or it will continue monitoring your workout for 60 minutes after you exit the app, as long as you don’t stop or pause it.

Using the Workout app is simple:

  • Open your watch menu and scroll down to ‘Workout’
  • Clicking ‘...’ allows you to choose a Walk, Run, or Workout (other activities)
  • Start start monitoring your workout by clicking the ‘play’ symbol (Up button)
  • Your heart rate reading may take a moment to start--this is normal
  • Scroll through your workout statistics using the Down button ‘>>’

Important note: to avoid draining the battery, the Workout app will stop monitoring 60 minutes after you close it.  If you want to work out for longer, make sure to open it periodically or keep it open.

Workout Zones measure just how hard you’re working, and are divided into the following zones:

  • Fat burn: 50-74% of your heart rate reserve; for most people this starts around 130 bpm
  • Endurance: 75-84% of your heart rate reserve; where you train for those long jogs
  • Performance: 85-100% of your heart rate reserve; when you’re giving your workout every last bit of energy you have!
Heart rate reserve is the difference between your maximum heart rate and your resting heart rate. Your intensity is determined by what percentage of your heart rate reserve you’re using.



Pebble HR watches feature an optical heart rate monitor, which we’ve tested against industry leaders, including wrist- and chest-based monitors. Please see below for specifics about our device’s accuracy, and for tips to get the best readings.

What affects accuracy? How you wear your watch is very important to accuracy (see “Wearing HR Watches” above), but other factors matter, too. For example:

  • Movement: extremely intense exercise can reduce accuracy due to excess movement
  • Watch straps: metal straps and those made of stiffer leather may not hold the monitor firmly in place, leading to poor readings.  Make sure your straps fits snugly!
  • Tattoos: dark tattoos may impair the optical monitor’s ability to read your heart rate
  • Water: while sweat or splashes of water aren’t a problem, optical heart rate monitors do not work underwater

Pebble devices with a heart rate (HR) monitor are intended to be a valuable tool that can provide an accurate estimation of the user’s heart rate. The HR monitor is designed to attempt to monitor a user’s heart rate on a periodic basis. The frequency at which heart rate is measured varies and depends on the level and activity of the user.

While the HR monitor technology is state of the art, there are inherent limitations of the technology that may cause some of the heart rate readings to be inaccurate under certain circumstances. These circumstances include the user’s physical characteristics, the fit of the device and the type and intensity of the activity. The HR monitor data is not intended to be used for medical purposes, nor is it intended to diagnose, treat, cure or prevent any disease or condition.


Understanding Graphs

Your heart rate graph is located in the Health section of your Pebble app, with the activity and sleep graphs. You’ll be able to see how your heart rate rises and falls during the day, as well as your most recent heart rate measurement.

Please note: Pebble health will disregard heart rate readings if the quality of the reading is poor.  This ensures better overall accuracy, but means you may see small delay in the most recent heart displayed.

For the most up to date measurement, open Pebble Health on your watch and click Up twice to open the heart rate card (you may need to wait 10-15 seconds while the monitor gets a good reading).



If you’re concerned your heart rate monitor has stopped operating properly there are a few things you can check very easily:

  1. Make sure Pebble Health is enabled.  Open the Pebble App and tap on the menu, then ‘Settings’, then tap ‘Pebble Health,’

  2. Make sure ‘Enable Pebble Health’ and ‘Enable Monitoring’ is toggled on under ‘Heart Rate’.

  3. Restart your watch.  Simultaneously hold the Back (left) and Select (right middle) buttons until ‘pebble’ appears on the screen.

  4. Make sure the monitor is working.  Turn on continuous monitoring by opening Pebble Health and pressing the Up button once, then look at the back of your watch.  Both sensors on the back should be green and flashing.

  5. Clean the sensor.  Using a damp cloth, rub the sensors with a circular motion.


Frequently Asked Questions

Why aren’t the lights blinking?

  • Unless you’ve turned on continuous monitoring or are exercising, your watch will only monitor your heart rate once every 10 minutes, so the sensors will be dark most of the time.  This allows monitoring with little to no battery impact.

Why doesn’t my watch (or graph) show my current heart rate?

  • Unless you have the Pebble Health heart rate card open, or are using the Workout app, your heart rate is monitored every 10 minutes, so some of your data may be outdated.  
  • Your watch will also discard a reading if its quality wasn’t within acceptable standards.  This gives you a more accurate overall reading, but may mean your watch shows that the last reading was more than 10 minutes ago.

Can I turn off the heart rate monitor and still monitor steps and sleep?

  • To do this, just open the Pebble app on your phone.  Tap the menu button in the upper right, then tap ‘Settings’.  Tap ‘Pebble Health’ and scroll down to ‘Heart Rate’ and toggle monitoring off.

Do I have to use the Workout app to monitor my heart rate continuously?

  • No. You can also click the Up button twice on your watch to open the heart rate card for Pebble Health, which will monitor your heart rate continuously until you close the card.  Some third party apps may also be used, though they may affect your battery life negatively.

Does it work/sync with other fitness devices?

  • Pebble’s heart rate monitoring doesn’t sync to other devices or services at this time.


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