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Sudden unexplained in heart rate during runs

Former Member over 4 years ago

I've noticed that there is a very steep rise in heart rate quite early on when I run. No explanation for it, no hill, no extra intensity, feeling good, etc so what could be causing this? I'm using a Fenix5S plus. Link and photos below.

https://connect.garmin.com/modern/activity/6111903474

0 trux over 4 years ago

The optical HRM probably locked on your cadence. It happens with the OHRM. Either adjust the fit and position, or use a HRM chest belt if you need reliable data and cannot get it with the watch.

Read more on the topic here: The Heart Rate Sensor on My Watch Is Not Accurate

0 Former Member over 4 years ago in reply to trux

How do you know if it has "locked in"? My bpm and cadence are similar at the point where heart rate rises but not identical? Do these values need to be identical in order to identify a lock or just similar?

0 trux over 4 years ago in reply to Former Member

How do you know if it has "locked in"?

I do not know it, it is just a plain assumption, because there is rarely something else, that the OHRM could lock on, than either the HR or the cadence (resp. the acceleration triggering the optical signal). The resulting signal may be a combination of both of it. The OHRM will simply lock on the optical signal it detects. It does not matter whether the cadence is identical to the HR or not. If the wrist band is too loose, the optical sensor will be catching easier the light changes from the motion, than from the HR. On the other hand, if the wrist band is too tight, it may limit the blood circulation, and it may hinder so the detection as well. Read the document - all of it is explained there, as far as I remember.