• Your face has more than 30 muscles that help you smile, look surprised, sad, or unhappy.
• Eye muscles are the busiest, moving more than 100,000 times a day.
• Jaw muscles can provide about 200 pounds of force to bring the back teeth together for chewing.
• Muscles make up about a 40 percent of your body weight.
• Nearly 85 percent of the heat produced by the body is the result of muscle contraction.

Without muscles, your body would be just a bag of bones. You have more than 640 muscles and they allow you to breathe, speak, smile, shake hands, blink, play the piano, plant a garden, chew your food, digest your food. Life, as you know it, would not be possible without muscles.

You have both voluntary and involuntary muscles. You choose when you use voluntary muscles, like raising your hand or walking across the room. Involuntary muscles are automatically controlled by the brain so you don't have to think about breathing and other bodily functions.

The body has three types of muscles:

• Skeletal muscles are voluntary and help the body move.
• Smooth muscles are involuntary and located inside internal organs such as the stomach and intestines.
• Cardiac muscle is found only in the heart and also is involuntary.

Why do muscles get weaker and slower?

• Less efficient nerve-muscle connections
• With less exercise, muscle cells get thinner and weaker
• Loss of muscle cells
• Slower increase in muscle size and strength
• Fewer nerve cells to stimulate the muscles

What does it mean?

"It is essential to keep a healthy and efficient muscular system, particularly as you age," says Ned Amendola, M.D., orthopaedic surgeon with UI Sports Medicine.

"If the muscles that cross joints are working well, then the joints will work more efficiently and you'll have less pain and fatigue, even if the joint has some arthritis or wear and tear.

"When you were young, your muscles did not need much attention, but as you grow and age, regular exercise, involving some specific muscular conditioning, is important to keep you mobile and agile.

"Gradual decrease in muscle mass, especially after age 50 and with less exercise means:

• Less strength
• Slower movements
• Less coordination
• Less stamina
• Longer recovery time to catch one's breath
• More stiffness and soreness after exercise
• Altered posture
• Altered appearance and body proportions
• Need for fewer calories and diet modification

For more information:

• Nemours Foundation: KidsHealth for Parents
  Bones, Muscles and Joints: the Musculoskeletal System
• MedlinePlus: Muscle Disorders

Listed above are Web sites that offer additional information on this topic. University of Iowa Health Care does not sponsor or endorse these sites, or guarantee the accuracy of the information contained on these sites. These links are here for general information only, and should not be used for personal diagnosis or treatment. If you have any questions, please contact UI Health Access.

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