It's a lot more accurate when you set it to track an exercise. I believe it decreases polling frequency normally to save battery. I have some weird heart issue

It's a lot more accurate when you set it to track an exercise. I believe it decreases polling frequency normally to save battery. I have some weird heart issues and it can have trouble with that as well. If it's not set to track an exercise, it's frequently reading 10-15 bpm lower than my actual heart rate.