By Dr. Brian McDonough

PHILADELPHIA (CBS) – When you have a muscle spasm, you know it. But do you know why it happens?

A muscle spasm is a painful, involuntary movement or contraction of a muscle. Skeletal muscles are muscles attached to bones that you control to move your body. Normally your skeletal muscles create movement by voluntary contraction. This occurs when muscles respond to a message sent from the brain through the nerves, which causes the muscles to contract, then relax.

This all requires normal amounts of oxygen and electrolytes like potassium and calcium. Skeletal muscle spasms and cramps are usually caused by overuse of the muscle and spasms can also occur if a muscle is overstretched or held in the same position for too long.

Muscle cramps are often a problem when you are dehydrated and not getting enough fluids.

Reported By Dr. Brian McDonough, KYW Newsradio Medical Editor

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