How do muscles work?

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Across
  1. 2. A pulled muscle is a ____ in the muscle fibres.
  2. 4. Commonly known as 'the pecs'.
  3. 6. Muscles contract and _______ to control movement.
  4. 8. Also called the 'lats'.
  5. 10. The external layer that covers the muscle to keep the fibres together.
  6. 12. When the arm flexes at the elbow, the biceps ________.
  7. 13. The strongest muscle in the human body
  8. 14. The most common muscle that people pull (injure).
Down
  1. 1. The largest muscle in the human body
  2. 2. These attach to bones so that the muscles can move the skeleton
  3. 3. The large muscle group that covers the front and sides of the thigh.
  4. 5. Skeletal muscles make up about _____ percent of your total body mass.
  5. 7. When the bicep relaxes and the tricep contracts the arm _______ at the elbow joint.
  6. 9. The smallest muscle in the body
  7. 11. There are more than 640 of these in your body.