Magnesium helps your muscles to process glycogen. It is also known to be involved in the synthesis of protein and it is helpful if you have problems with cramps and are looking to prevent them.

Sources of Magnesium

Black beans
Legumes
Oats
Seafood
Soybeans
Whole Grain

Recommended Intake for a Bodybuilder

Magnesium is most popular in the supplement ZMA.