This morning on my long endurance run (in zone 2, HR usually between 122 and 128), my heart rate indicator jumped sharply up several times (see image). I was running with a heart rate belt Hrm-dual. In the past, I sometimes encountered this for the first two kilometres, but after that, everything went fine. Now several more ‘upsurges’ occurred during the course of my run. I ran at about the same speed (+/- 5:40) and cadence (+/- 167) the whole time. The calculation of my average heart rate, and thus my VO2max, was obviously strongly influenced by this.
What could be the cause of this?
I already read about problems of heart rate abnormalities with the wrist heart rate, but I didn't hear about problems with a heart rate belt.
