I created a customized 10min HIIT training, without specifing any exercises, for tracking my hr during the training. The problem is, that while doing the exersises my measuered heart rate is far off. In average I get 80-90bpm fort the 10min training.
In reality my hr is somewhere between 130-140bpm (measured by the hr sensor of my phone, which is pretty accuarte). Now the interesting part is, that after the training is done (1-2 min afterwards) the watch shows my hr accurately (110-120bpm). So it goes up, after the stress.
Because of this i conclude, that there is no problem with the position of the watch on my wrist or other factors like sweat interfering with the sensor. Does anyone have an explanation for this phenomenon?