Ask Dr. Lisa

Q:I have calf cramps so painful that they wake me up. How can I prevent them?

A: No one knows for sure what triggers these common nighttime spasms, though dehydration, muscle fatigue and low intake of sodium, calcium and magnesium have all been blamed. Gently stretching and massaging the muscle relieves the pain. Prevention is trickier because the cause is not known, but many doctors advocate increasing water and salt intake (sports drinks cover both bases), and bedtime stretching. You can also eat more foods rich in calcium and magnesium, such as lowfat dairy products. Occasionally, leg cramps signal nerve or blood vessel problems, so if they persist longer than a couple of weeks, see your doctor.

Lisa Callahan, M.D. (drlisa@self.com), is author of The Fitness Factor (The Lyons Press).