I was talking to a fellow therapist that had used magnesium to treat anything that had to do with muscular "spasm." He had results with leg cramps, which I've seen. Also, he had some success with such conditions as irritable bowel and migraines. These I've never even thought to mention or think about.
The one condition I found some research was with Asthma. Asthma seems to be on the rise. I seem to see more and more kids with inhalers. I don't think I had a single kid in my class in high school who had one.
Regardless, asthma can be a serious condition for many people. This study looked at 55 people that were given 2x a day Mg supplementation vs a placebo. Total supplementation per day was 340mg. This study lasted 6.5 months. Pretty decent size and length.
There were two objective markers and also subjective. The people rated their quality of life. Both objective markers for gaging bronchial activity improved and the subjects reported better quality of life.
For athletes dealing with asthma Mg supplementation is a must in my opinion. Make sure you supplement with a quality Mg as this is one ingredient that is easy for supplement companies to skip on quality. Check out PURE Magnesium.
Here is the original Research on PUBmed.