Hi Vegas, i'm not sure that Magnsium is really to be used for increasing energy, but many people find it very good for other problems. I could'nt do without my magnesium because it has really helped with my cramps, muscle twitching/spasms and ovr the lng run it is calming. Baths of Epsom salts are supposed to be very good for muscls pain and helping with sleep if you have thm before bed.
Magnesium is important for the proper functioning of mitochondria, but i dont htink its dirctly related to energy improvement in M.E. I have always used it orally and it has worked fine, although i was recommended it by injection but didnt fancy it.