Hello, I tried to do some mild exercises, like going for a walk recently. Good news is that even at distances of around 6 miles I was not feeling fatigued as I used to. However, the worst symptom after exercises is a constant high heart rate. I start with a resting heart rate of around 60-80. It goes up to 120-140 while walking and stays there the entire rest of the day/night. The heart beats very hard especially at night, at I have not found a way to bring it down (magnesium etc. has only a mild effect). Is this a POTS symptom? Did anyone experience the same? P.S.: I have not yet been tested on OI, but I strongly suspect that I have it.