I'm not sure who taught you isometric but it doesnt have to be pit against each other and you can breathe through it. I like pressing against a wall in various positions to strengthen joints without having them in less stable positions. I like dynamic tension ones, i think they are great. Theres a reason its part of a meditators relaxation techniques. __ xrunner, I'm getting tested for Marfans syndrome later this month, i'm tall but i'm not skinny to that degree, probably due to a healthy regime of exercise. Hyperflexibility is an indicator with that. Have you ever had your calc/magnesium levels checked? Are you tall and skinny? Could be a needle in a haystack.. just checking.