- Hi, I've had my forerunner 245 music for a week. I've noticed the heart rate changes a lot even while sitting down not moving. It will be at 65 then right after change to 65 then 67 then 65 or even go up to 70 then 68 etc etc I dont have any heart condition so I'm wondering if this is normal for the watch to do or is it a bug? I do wear the watch correctly