Heart rate accuracy issues

For me the HR detection of Instinct works pretty well in all situations, but generally it is certainly quite individual and depending on plenty of factors. Some of them are for example the skin tan and thickness, the position and the tightness of the wristband, the haemoglobin level, als also a very important factor is the peripheral vasoconstriction that can be more pronounced at some persons than at others, and also depending on external conditions like the temperature, blood oxygenagiton, medical conditions, or medication and toxins (i.e. from smoking). Garmin recommends to persons experiencing problems with proper lock up of the HRM, to warm up before starting the activity. Using a HRM belt, which is working on a different principle and is not influenced by the same factors as the Optical HRM, is certainly the best choice when you experience troubles with the accuracy of the OHR of the watch, and do not find any way to fix it byt the means I mentioned - better (tighter or looser) fit, position, other hand, inner side of the wrist, warm-up ,...