Thanks all for the responses and the links! I will look into light resistance training next time I see my doctor. Also will follow up on the links to Dr. Levine's site and the one of the young woman who used that method of training. Like the idea of swimming and maybe kicking in place would be a good exercise....Also like the idea of a rower.
My sons doctors want him to do water jogging. He started last week, and has not been doing too well. He is either over doing it or maybe you have to take a step backwards to go forwards. We'll have to wait and see how it goes.
Swimming is one of the best things. Anything you can do in a vertical position.
I came across this Dr Levine. He advices rowing as the best exercise for OI and POTS. He is working with the National Space Biomedical Research Institute, and he reckons that he can apply to OI and POTS what he has learned in trying to keep astronauts fit.
This is a link to an article about it
http://www.nsbri.org/NewsPublicOut/Release.epl?r=99
This is another link to a blog from a girl who has just finished a three months study with his team, and seems to be pretty happy with the results
http://www.potsrecovery.com/
On a personal note - Last year I had to stop running (not compatible with POTS), and naturally migrated to the indoor rower at the gym because on the treadmill my starting HR was 120bpm, and on the rower 90.
I guess being seated, and having your ankles close to your heart for half the movements reduces the stress caused by gravity.
I loved it so much that I bribed my husband into buying one, as I could not tolerate the walk to the gym.
I don't know what is Dr Levine's protocol, but I try to row 5000 meters most days (about 35 minutes).
It is not a magic bullet thought, as I am still unable to work and function properly, but I believe that it prevents my POTS from getting worse by avoiding deconditioning.
I also do some light resistance training for legs, calves, abs to help with blood return, and improve the skeletal muscles pump. My cardiologist recommended that.