Re: weak muscles-need info for marathon tomorrow!

His kidneys regulate potassium and depending on the levels in his blood and inside his cells, he is probably excreting the excess in his urine.

Foods high in potassium are: one-half cup of orange juice, one large banana, one baked potato, one-half winter squash, one cup tomato juice, one cup vegetable juice cocktail, one-half cup avocado, one-half cup cooked dried beans and one tablespoon black strap molasses.

Orange juice is not as acidic as the hydrochloric acid in your stomach. Orange juice helps to neutralize the acid in your stomach that your body secretes to digest food you eat. The only food more acidic than your stomach acid is lime juice. However, if you feel that you don't tolerate orange juice, don't drink it.
My guess is, he is overdoing the orange juice and not tolerating it well

Having too much potassium in the blood is called hyperkalemia and having too little in the blood is known as hypokalemia. Proper balance of potassium in the body depends on sodium. Therefore, excessive use of sodium may deplete the body's stores of potassium.