Heart Rate monitor not accurate when sprinting

I tried to make a test when sprinting at my maximum speed to see how it behaves with the HR and it has measured that I was at 128 BPM and I am sure I was above 180. It seems that when you are sprinting it does not work correctly, I don't know why since measurement is continuous...

My confidence to this watch is near Zero, even below zero... ciq.forums.garmin.com/.../1378244.jpg

0 tmk2 over 6 years ago

This forum is full of complaints about optical HR giving unsatisfactory results in high-intensity excercise. You're not alone.

0 falconeye75 over 6 years ago

Ah ok, I didn't know about it, the vendor told me it was very reliable... If I could give it back and ask for refund...

0 tmk2 over 6 years ago

It can be reliable when you're stationary, but when you sprint the watch jumps about your wrist (this is especially pronounced on heavy watches, like the F5) and the optical sensor has a hard time getting a stable reading. Try wearing it tighter. It helps sometimes.

0 falconeye75 over 6 years ago

It can be reliable when you're stationary, but when you sprint the watch jumps about your wrist (this is especially pronounced on heavy watches, like the F5) and the optical sensor has a hard time getting a stable reading. Try wearing it tighter. It helps sometimes.

Thanks for your help, I will try it. It was already tight but I will try tighter.

0 Former Member over 6 years ago

In my testing the Fenix 5x Plus is fairly accurate for running and even interval sprints. The watch is not as accurate for activities involving the wrist such as weight training or cycling in particular.

couple of tips for improving accuracy

Have the F5 as tight as its comfortable on your wrist, the tighter the better as it restricts movement of the watch.
Give the sensor a clean every now and then, sounds crazy, but it might help