Muscle tone is defined as the resting tension in a muscle. In any muscle, certain motor units are al-ways active. Although this activity is too small to cause muscle shortening, it makes the muscle firm in consistency. This is one cause of muscle tone. Muscle tone is also a result of the viscoelastic property of muscle. This reflects the elastic tension of muscle fibers and the osmotic pressure of cells.
Tone in a muscle stabilizes the position of bones and joints. For example, muscle tone maintains body posture. Muscle tone also helps prevent sudden, un-controlled changes in the position of bones and joints. If tone is reduced, the muscle feels limp and flaccid. Muscles with moderate tone feel firm and solid. If the tone is increased, the resting muscle feels rigid and resists passive movement.