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HR not monitored at the beginning of a workout

The first 20 minutes of each workout, my apple watch is barely monitoring the heart rate. It is always trying to measure it, but in the end it's just reporting no rates or very few rates. After that time passes though, it is always working just fine and accurately.

Apple Watch Series 4, watchOS 7

Posted on Feb 10, 2021 10:52 PM

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Posted on Feb 15, 2021 10:01 AM

Hi Marion - I had exactly the same characteristics as you have described. My AW 6 on my left wrist was hopelessly inaccurate and very unreliable. It was ok on a walk most of the time but not on a run. Sometimes it would take several minutes to start recording and sometimes it would stop recording during the run. My left wrist is thinner than my right wrist and the veins on my right wrist are more prominent so I swapped the watch to my right wrist and started wearing wrist sweat bands (that I normally wear in the summer) to help hold my watch in place without having to tighten the strap too much. That worked really well but still had the occasional glitch. I then bought a braided solo loop band (non Apple) off Amazon and since changing to that my heart rate monitoring has been perfect on every run. The braided solo loop band is much more comfortable than the Nike sport loop and it holds the watch in place far more effectively without needing to be tight. It also looks a lot nicer too. I also end up without the indented marks on my wrist that the Nike strap used to leave. Feel free to discuss further - we can sort this.

6 replies
Question marked as Top-ranking reply

Feb 15, 2021 10:01 AM in response to Marion___

Hi Marion - I had exactly the same characteristics as you have described. My AW 6 on my left wrist was hopelessly inaccurate and very unreliable. It was ok on a walk most of the time but not on a run. Sometimes it would take several minutes to start recording and sometimes it would stop recording during the run. My left wrist is thinner than my right wrist and the veins on my right wrist are more prominent so I swapped the watch to my right wrist and started wearing wrist sweat bands (that I normally wear in the summer) to help hold my watch in place without having to tighten the strap too much. That worked really well but still had the occasional glitch. I then bought a braided solo loop band (non Apple) off Amazon and since changing to that my heart rate monitoring has been perfect on every run. The braided solo loop band is much more comfortable than the Nike sport loop and it holds the watch in place far more effectively without needing to be tight. It also looks a lot nicer too. I also end up without the indented marks on my wrist that the Nike strap used to leave. Feel free to discuss further - we can sort this.

Feb 13, 2021 5:56 AM in response to Marion___

Hi Marion___,


Thanks for coming to Apple Support Communities for help with your Apple Watch. As we understand, your heart rate isn't being monitored the first 20 minutes of a workout.


Have a look at this page: Get the most accurate measurements using your Apple Watch. Be sure to work through all the steps, but also see the last section:


"What else affects your heart rate reading


Many factors can affect the performance of the Apple Watch heart rate sensor. Skin perfusion (or how much blood flows through your skin) is one factor. Skin perfusion varies significantly from person to person and can also be impacted by the environment. If you’re exercising in the cold, for example, the skin perfusion in your wrist might be too low for the heart rate sensor to get a reading.


Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings.


Motion is another factor that can affect the heart rate sensor. Rhythmic movements, such as running or cycling, give better results compared to irregular movements, like tennis or boxing.


If you’re not able to get a consistent reading because of any of these factors, you can connect your Apple Watch wirelessly to external heart rate monitors such as Bluetooth chest straps. Learn how to pair Bluetooth accessories.


Heart rate is one of many factors that Apple Watch uses to measure your activity and exercise. Depending on your workout, it selects the most appropriate inputs for that activity. For example, when you’re running indoors, it also uses the accelerometer. Learn more about how your Apple Watch uses GPS and the heart rate sensor when you use the Workout app."


If the issue continues, let us know.


Have a fantastic day!


Feb 23, 2021 12:25 AM in response to Cheefy

Hi Cheefy,

thank you very much for your reply.

I read your reply and immediately bought a braided solo loop band, which arrived yesterday.

What can I say?

You are totally right:

  • yes, it is more comfortable in general;
  • yes, it even looks nicer and
  • most importantly: yes, the HR is measured far more accurately.

So thank you very much. It solved this issue.

Feb 15, 2021 7:53 AM in response to Cheefy

Hi Cheefy,

thank you so much for your reply. But I don't think that the strap could be the problem, as after that certain period of time passed, the HR is always monitored perfectly.

When I start the workout slowely (i.e. walking or yoga), meaning the HR is increasing only very slowely too, it is monitored just fine from the first moment on. But when a workout starts powerfully (i.e. running, any higher intensity workout), meaning the HR is rising quickly, it takes about 20 minutes until the watch is able to measure.

HR not monitored at the beginning of a workout

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