robbie i would seriously expect magnesium oxide to help anyone with constipation regardless of poor muscle function. what gwa cautions about flax and looseness certainly applies to magnesium also. if you take enough, you might as well be taking a brown pee. how can that kind of consistency NOT come out?
of course it is not good to fire things through your system that quickly in the long term. you need to keep things inside long enough to absorb the nutrition.
magnesium supplements are pretty difficult to absorb anyway, so they are less likely to get absorbed in the lower intestine where the body can put it to work on muscle function.
it is better absorbed in food. lots of things like bran, various seeds (such as flax). if you drink pop or coffee or alcohol, it could take away more minerals than dietary intake can provide, so that's when you can get into a magnesium problem. i'm not a cereal or bran muffin eater, or a nut or seed eater, by and large, so i think this is partly where my own magnesium issues came into play.
i have heard of people getting magnesium injections to circumvent the GI absorption problems, but i don't know much about that option yet.
in any case, i'm getting two issues mixed up together.
1) enough magnesium oxide in the short term, should make poo loose enough for sheer gravity to let it out.
2) getting magnesium to absorb for muscle function in the long term is better done in food. we may consume other things which make it less likely that food sources are sufficient.
i know you're having a much worse time of it than i robbie, but i can't help being optimistic when i've seen all the lesions in my brain and spine, and still the nutrients make a major improvement. probably the longer you let it slide, the more intense and broad-spectrum the therapy has to be, and i'd expect it to take it a bit longer for things to repair somewhat. personally, i love seeing the dramatic improvement when i hit on a new fix. i was basically malnourished for 15 years before i got diagnosed so i am expecting it could take as long to get back to something approaching "normal". i don't really think i'll ever get to a point where i can't tell that my spinal cord has been compromised, but i think i'll get close.
i wish i had more experience, so i could give you a more assured answer regarding level of illness and utility of supplements