Muscle spasm can occur for a number of reasons. We often associate cramps in the legs and arms after strenuous exercises, but it can also happen to any muscle group with or without exercising. The most important factor is figuring out whether or not you actually have cramps after running. Based on your description, it sounds as though you are describing what some sprinters called "liver cramps." These are not really "muscle" cramps but appear to be due to a discomfort coming from the organ as it is working in over-drive trying to neutralize the lactic acids in your muscles and to covert glycogen in the liver storage to simple sugar for the demanding muscles and brain. In practical terms, it is best to keep yourself well hydrated, take your time with routine warm-ups, and exercise at a less intense level. Then, you can work up your intensity as your body adjusts. Eating a heavy meal just before exercising also puts a heavy burden on the liver, gall bladder, and pancreas. This takes a lot of energy and actually diverts your precious blood away from your muscles therefore causing more difficulty in clearing away metabolic waste from the muscles. If your muscle cramps occur elsewhere in your body and are not related to exercises, then you should look into excessive alcohol, caffeine, kidney failure, diabetes, medications and electrolyte abnormality as potential causes. Regardless, to be safe you should follow up with a primary care provider who can further assess and treat your condition. Good luck.