Epsom Salts do wonders for sore muscles. Espom salts are a natural magnesium salt. In water, it breaks down into magnesium and sulfate. The theory is that when you soak in an epsom salt bath, these get into your body through your skin. That hasn't been proven, but just soaking in warm water can help relax muscles and loosen stiff joints.

People use epsom salt baths as a home treatment for: arthritis pain and swelling, bruises and sprains, fibromyalgia (a condition that makes your muscles, ligaments, and tendons hurt, and causes tender points throughout your body), Ingrown toenails, Insomnia, psoriasis, sore muscles after working out, sunburn pain and redness, tired, swollen feet. For a muscle soak bath, use 1-2 cups of epsom salts in very warm water. (source: WebMD)