Too high heart rate while exercising Charge 5

[Franb1]

I work out on an elliptical trainer for 40 minutes three times per week. I check my heart rate via the trainer and check my charge 5 to see that it correlates. Mostly it does but today the heart rate in the Charge 5 went almost immediately to around 155 and stayed high the whole time. The Elliptical never went above 140 and was under 135 for the first 25 minutes. The workout was in fact fairly easy. I am 76 and don't try to press too hard.

What has caused this problem?

Moderator edit: subject updated for clarity

[DavideFitbit]

Hi, thanks for all the details about your experience with the Charge 5 heart rate feature, @Franb1. 

Before considering other options, please follow the instructions in this article to improve the accuracy of heart rate information and check the information mentioned here about other factors that could affect your heart rate reading, as this has been useful to other users who have experienced any issue related to heart rate accuracy. 

In addition, I recommend that you try restarting the device again using the three pulse restart method mentioned here below, instead of the restart option found on the Charge 5 itself: 

1. Connect your device to the charging cable. For instructions, see How do I charge my Fitbit device?
2. Press the button located on the flat end of the charger 3 times, pausing for 1 second between presses. Then wait 10 seconds or until the Fitbit logo appears.