Muscle tone

From Wikipedia, the free encyclopedia

Muscle tone (aka residual muscle tension or tonus) is the continuous and passive partial contraction of the muscles. It helps maintain posture and is often present during REM sleep. (Some people use the term muscle tone to refer to how "in shape" a person is - a "toned" person having large muscles or a low fat-to-muscle ratio.)

Unconscious nerve impulses maintain the muscles in a partially contracted state. If a sudden pull or stretch occurs, the body responds by automatically increasing the muscle's tension, a reflex which helps guard against danger as well as helping to maintain balance.

Some present the idea that constant daily resistance training, or training at high intensities, will increase one's muscle tone, as the neurological system becomes more tense after constant exertion to stay in a state of greater readiness for the tension.

Physical disorders can result in abnormally low (hypotonia) or high (hypertonia) muscle tone.

The presence of near-continuous innervation makes it clear that tonus describes a "default" or "steady state" condition. There is, for the most part, no actual "rest state" insofar as activation is concerned.

In ophthalmology, tonus may be a central consideration in eye surgery, as in the manipulation of extraocular muscles to repair strabismus. Tonicity aberrations are associated with many diseases of the eye (e.g. Adie syndrome).

In terms of skeletal muscle, both the extensor muscle and flexor muscle use the term tonus to refer to the "at rest" or normal enervation that maintains current positions of bones.

Cardiac muscle and smooth muscle, although not directly connected to the skeleton also have tonus in the sense that although their contractions are not matched with those of antagonist muscles, their non-contractive state is characterized by (sometimes random) enervation.

[edit] References

[edit] External links

• Tone vs. strength - Diane E Gagnon, M.Ed., PT (Physiotherapist)
• ToneAndSlim
• BBC series on muscles