Muscle tone is the residual stress of muscle apparatus. Even at rest, the muscles have a certain residual stress and a resistance to external stimuli, which is also referred to as resting tone. Muscle tone disorders are expressed either in the form of diminished or increased levels of tension.

What is the muscle tone?

Muscle tone is the residual stress of muscle apparatus. Even at rest, the muscles have a certain residual stress.

The musculature of the body has a degree of tension. This degree of tension is also known as tone or muscle tone. The tension is caused by the viscoelastic properties of the tissue and stimuli of the central nervous system. Even at rest, the muscles have a certain tonus, which is also called resting tone or muscle tone.

The medicine distinguishes the passive from the active tonus of the muscles. The passive muscle tone is determined by the material properties, anatomical tissue structures, the composition of the muscle fibers and the anatomical position.

In addition, the filling state of extra- and intracellular fluid cavities also influence the passive tone. The same applies to the circulation and the oxygen supply as well as the temperature, the type of stress and the degree of fatigue of the muscle.

Neurophysiologically, muscle tonus usually means active tonus. Unlike the passive tone, the active size is determined by the innervation of the muscles and the sensorimotor program. A prolonged and painful muscle tone is also called tension. By contrast, the neurologist understands an involuntary tension in the context of motor units.

Function & Task

The muscle tone of skeletal muscle is produced by the successive contractions of individual muscle fibers. Due to the alternating contraction movements a certain degree of tension can be maintained even at rest. The smooth muscle cells, on the other hand, permanently contract, thereby producing muscle tone.

The resting tone means the force with which a muscle opposes an acting force. It does not go back to the muscles themselves, but is controlled by afferent and efferent fibers of reflex arches on the muscle. These reflex arcs are neuronal processes that trigger a body reflex - in this case the tension.

The skeletal muscle with its muscle tone is the active part of the musculoskeletal system. This musculature is capable of contraction and relaxation, making movements possible in the first place.

Only by muscle tensions is the person capable of locomotion. Without muscle tone, a person could not even maintain their own posture without effort. Neither standing nor sitting would be possible for the person. The muscle tone plays a role especially for coordinated and fine motor movements.

It requires a lot of energy for the muscles to do their varied tasks and to maintain the required muscle tone. Based on the energy balance of the body, even the muscle background makes up about one quarter of the total energy requirement. With active movements, the energy requirement even increases.

Diet-tested and athletes know this connection. The more muscle a person has, the more calories he burns even when at rest. This phenomenon is related to the muscle tone of every muscle. The more muscles, the higher the energy turnover. Building muscle is therefore part of the standard program for weight loss.

Among other things, the energy turnover of the muscles produces heat as a by-product. In this context, the muscle background tone even plays an important role in maintaining your own body heat.

Diseases & complaints

A disturbed muscle tone called the neurologist as a muscular dystonia. Such dystonia of the muscle may manifest itself as increased tension, but also as diminished tone. A completely lost tone is present, for example, in a paralysis. This syndrome is also referred to as flaccid paralysis. All motor nerves of a body part are ineffective in a flaccid paralysis.

This is to be distinguished from the paresis. Again, this is a paralysis. However, this phenomenon is not accompanied by complete failure, but partial failure of the motor nerve tracts of certain extremities. Pareses can be caused by nervous systematic disorders, stimulus transmission disorders or the muscles themselves. Often the muscle background tone remains largely intact.

Paralyzes are caused by a destruction of the affected nerves or even a transection of the pyramidal nerve tracts in the spinal cord. The muscle background tone is not preserved in a paralysis.

In addition to paralysis, muscular hypotension can also cause decreased muscle tone. This phenomenon reduces the fundamental tone, but does not turn it off. For example, if a leg is affected, the doctor may still place the patient's leg in any position despite the signs of paralysis.

Hypotension may develop as a result of seizure-induced or trauma-related cerebellar hemorrhage. Also conceivable is hypotension in the inflammatory autoimmune disease multiple sclerosis, which can attack both the motor tracts of the spinal cord and the cerebellum.

Symptoms of morbidly increased muscle tone are to be distinguished from complaints due to reduced muscle tone. Such phenomena can manifest themselves, for example, in a spasticity or rigidity. In rigidity, the muscle's own tension is so high that the extremity stiffens. If, for example, the arm is affected, it can hardly be bent anymore. An increased muscle resistance to external influences is present.

Spasticity, on the other hand, means increased tension that forces the extremities into unnatural postures. Spasticity usually arises from flaccid paralyzes. In turn, these flaccid paralyzes are usually associated with damage to the central nervous system.

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