Apple Watch work incorrectly on tattooed wrists – the watch gets blocked and fails at pulse rate measurement.
The watch measures pulse rate incorrectly, and notifies on termination of training regardless of the owner’s wish.
It was found out that people with tattoos of sated black and red colour have problems more often. Faded tattoos and other colours do not result in blocking of the watch, but have a negative impact over heart rate measurement.
For example, at a normal heart rate, Apple Watch can show 80 – 90 bpm on a grey or dark blue tattoo. On a sated black or red tattoo the watch can show up to 200 (such heart rate is almost fatal).
Despite of certain inconveniences, the problem can be solved very simply – just move the watch on a place without tattoo, or disable the function of automatic wrist detection.