Here’s why ‘sensor readings are unavailable’ show up in some Apple Watch workouts

apple watch fitness

The Apple Watch is a great tool for tracking your workouts, but perhaps not all workouts equally. Here’s what it means when sensor readings are unavailable.


If you’re an Apple Watch user, you’re probably familiar with the device’s Workout app, which lets you quickly and easily track different exercises and workouts.

However, with some workouts, you may be presented with this message. “In this type of workout, you earn the calorie equivalent of a brisk walk anytime sensor readings are unavailable.”

Here’s why that happens.

What is considered Workout activity on Apple Watch

apple watch fitness

First off, it’s important to understand that the Apple Watch estimates calories burned based on data from its built-in motion sensor and heart rate sensor. It then uses an algorithm to estimate your caloric burn.

There are likely times when you find the Workout ring on your Apple Watch closing without you actually tracking a workout. This is because Apple automatically tracks any activity above a brisk walk as a workout.

How does Apple define a brisk walk? According to one Apple Support thread, you must raise your heart rate to approximately 75% of your maximum heart rate for it to count. This, of course, is based on your own individual cardio fitness levels.

If you don’t hit these thresholds, or if you pause or slow down, the system won’t count your movement as a workout. The Apple Watch will still track your steps and calories burned, but the activity won’t close your Workout ring.

What workouts can the Apple Watch track accurately?

apple watch running

It’s important to note that Apple is relatively opaque about its health and fitness algorithms. It never explicitly states which workouts are based on in-lab testing. Also, it doesn’t explicitly state whether workouts that show the “sensor readings are unavailable” actually track your movement accurately.

However, it appears that Apple has fine-tuned its calorie prediction algorithm on a number of workouts, including walking, running, and wheelchair workouts. These are all workout types that don’t show the “sensor readings are unavailable” message when you first start them.

A full list of workouts that should produce accurate caloric burn data can be seen below.

  • Walking
  • Running
  • Cycling
  • Elliptical
  • Rower
  • Stair Stepper
  • HIIT
  • Hiking
  • Yoga
  • Functional Strength Training
  • Dance
  • Cooldown
  • Core Training
  • Pilates
  • Tai Chi
  • Swimming
  • Wheelchair
  • Multisport
  • Kickboxing

In other words, if you do any of the above workouts, there’s a good chance that your calories burned predictions are relatively accurate.

What does the “sensor readings are unavailable” mean?

sensor readings unavailable

There are some exercises, however, where the Apple Watch is not able to accurately track the movements that you make during the exercise.

Basically, this is most of the workout types you see when you scroll down and tap “Add Workout.” Apple defines these as “other workouts.”

Rock climbing is a good example. Although there’s a Climbing Workout type, the “sensor readings are unavailable” text shows up.

While the text implies that it only tracks the workout as a brisk walk when heart rate and motion data isn’t available, anecdotal user reports suggest that they are never available.

One rock climber noted in a Reddit thread that their caloric burn data was inaccurate, and more closely reflected the calories burned during a brisk walk.

Other examples of workouts where this happens include Archery, Gymnastics, and Boxing. In each of these cases, it appears that the Apple Watch isn’t able to accurately track the kind of movements used, and, instead, just tracks the activity as a walk.

Can you fix “sensor readings are unavailable” on an Apple Watch?

redpointIf you’re getting the message on your preferred workout type, there isn’t a lot you can do to fix the issue in the native Workout app.

However, the issue isn’t that Apple’s sensors aren’t advanced enough, it’s only that the company hasn’t fine-tuned its algorithms to track specific workouts.

Because of that, you can actually download third-party applications that can use the built-in motion and heart rate sensor to accurately track your workout.

For the rock climbing example we used earlier, there’s Redpoint. Built by climbers, for climbers, this app gives you accurate caloric burn information and other details about your rock climbing workouts.

There are also similar apps for workouts like rowing or gymnastics. Just run a Google search for your preferred workout type, and then see if there’s an Apple Watch app available for that specific workout.

You can also just simply use an online caloric burn calculator, like this one by WebMD. These types of tools can at least let you cross-check your Apple Watch’s data with another source.

All of this is to say that the Apple Watch tracks many different kinds of workouts with a fair degree of accuracy. For the workouts that are a bit more questionable, the device’s sensors are accurate enough for a third-party app with a more specialized algorithm.

What if my sensors aren’t working properly?

watchos workouts

There’s always the chance that you are reading this article because your Apple Watch’s sensors are actually unavailable because they’re broken or being affected by a bug.

In these cases, we recommend hard restarting your Apple Watch and ensuring that you have the latest software update available. If that doesn’t mitigate the issue, then we recommend taking your Apple Watch to your local Apple Store or otherwise contacting Apple Support.

There’s also the issue of sensor accuracy. According to Apple, there are a number of things you should do periodically to ensure that you’re getting the most accurate workout readings. They include:

  • Periodically updating your personal information. You can add data like your height, weight, and age in My Watch > Health > Health Details.
  • Make sure that Wrist Detection is enabled. Background heart rate readings won’t be taken if this is disabled, so be sure to enable it by going to My Watch > Passcode > Wrist Detection.
  • Check your fit. If your Apple Watch is too tight or too loose, you may get inaccurate readings. Make sure it’s snug but not overly tight.

You can also calibrate your Apple Watch, which helps set the baseline for a brisk walk that it uses to track many of the workouts mentioned earlier.


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