[deadlyshaolin]

Theoretically, milk of magnesia should NOT help with your exercise-induced nausea/vomiting. The reasons being:

A) The antacid effect of magnesium hydroxide takes effect within the stomach, neutralizing the hydrochloric acid secreted by the parietal cells of the stomach. Almost no effect systemically (i.e. in your bloodstream).

B) Magnesium hydroxide has a laxative/diuretic effect because the osmotic force of the Mg suspension draws fluid away from the body into the lumen of the stomach/intestine. This leads to increased peristalsis, diarrhea, and exacerbates the dehydrated state that your body is in during intense exercise. Bottom line: it leads to even faster lactic acidosis.

Of course, this is all in theory, since I don't have clinical experience with patients taking milk of magnesium for this indication.