[Magnesium and exercise].

The determination of the magnesium status is difficult, since a cheep, sensitive and usable test remains to be found. Serum magnesium only signals severe deficiencies, which are in athletes. Blood cell magnesium may detect a subclinical deficiency, the significance of which is however very controversial. The "magnesium loading test" is the standard method, but it is too complex for the practice. A mixed diet with sufficient energy covers the needs of athletes of all levels. When the plasma magnesium levels are in normal range, supplements offer no significant benefits in terms of performance. The usefulness of magnesium in the treatment of exercise related muscle cramps is most probably widely exaggerated. Various other electrolyte dysbalances as well as venous insufficiency are certainly more important factors.