Parents complain that their children are disconnected; this is exactly what happens with your muscles. Like excited hyperactive children, your nerve excites your muscles resulting in spasms.
Secondly, lack of calcium, potassium and magnesium can stimulate muscle cramps
Dehydration can also result in muscle cramps.
Injury to the nerve or muscle strokes can lead to muscle spasms.
Poor circulation to your muscles ignites muscle cramps, you may have experienced it after sitting crossed legged for extended time durations.