Different kinds of abnormalities of heart rate and blood pressure

@Jonathan Edwards, you are right, I don't think there is any evidence suggesting that strengthening leg muscles will improve muscle pump function in people with POTS enough to make a noticeable difference to lower body venous pooling and hence OI symptoms.

I was just repeating what I had heard suggested in lectures by POTS specialists and physiotherapists and didn't mean to make it sound as though it was evidence-based advice.

I suppose you could say that stronger leg muscles could be beneficial for people doing counterpressure manoeuvres, but only if their leg muscles had been previously too weak to do the manoeuvres effectively.