SlowMag MG Muscle + Heart Magnesium Chloride + Calcium 60 Tablets SlowMag Mg Muscle + Heart dietary supplement is specially formulated to provide magnesium to help support proper muscle function and cardiovascular health*; magnesium also helps your body properly absorb calcium. Formulated with magnesium chloride for better absorption than magnesium oxide1, and with added calcium to support normal nerve and muscle function.