Muscle Tone: Definition, Abnormal Contractions, Benefits of Stretching and Controlling Muscle Tension

It is a measure of the resistance of a muscle to stretching in a state of passive rest.

Muscle tone is controlled by neuronal impulses and is influenced by receptors found in muscle and tendons.

The main regulator of muscle tone is the muscle spindle, a small sensory unit that is closely associated with and parallel to a muscle.

If the tone decreases and the muscle stretches the spindle, an impulse produces a muscle contraction. Muscle tone ensures that, even when at rest, the muscle contracts at least partially.

Abnormal skeletal muscle contractions

Involuntary muscle contractions are called spasms and can be due to abnormal nerve or muscle activity.

In medicine, a spasm is a sudden and involuntary contraction of a muscle, a group of muscles or a hollow organ, or an equally sudden contraction of a hole.

Examples of spasms include:

  • Muscle contractions due to abnormal nerve stimulation.
  • Abnormal activity of the muscle itself.

In this case, hypertonic muscle tone is excessive and the muscles cannot relax.

Hypertonic muscle spasms are the chronic state, excessive muscle tone or tension in a resting muscle, the amount of contraction that remains when a muscle is not actively working.

muscle atrophy

People with sedentary jobs and older people with decreased activity can lose muscle tone and develop significant atrophy.

Astronauts, freed from Earth’s gravitational pull, can develop decreased muscle tone and loss of calcium from their bones after a few days of weightlessness.

Disease of the muscle itself

The muscles, mainly the voluntary muscles, progressively weaken.

In some types of muscular dystrophy, the muscles of the heart, other involuntary muscles, and other organs are affected.

Aging and the digestive system

Aging can lead to changes in the digestive system due to decreased nerve sensitivity, muscle loss, and increased infection rate.

Changes associated with aging of the digestive system are largely caused by decreased nerve sensitivity, loss of muscle tone, and increased susceptibility to bacterial infection due to a weakened immune system.

Therefore, the changes include:

  • Loss of strength and tone of muscle tissue and supporting muscle tissue.
  • Decreased secretory mechanisms.
  • Decreased motility of the digestive organs, along with changes in sensorineural feedback regarding the release of enzymes and hormones.
  • Decreased response to internal sensations and pain.

Benefits of stretching

Stretching is a form of physical exercise, where specific skeletal muscles are stretched, improving elasticity and muscle tone.

Stretching is a form of physical exercise in which a specific skeletal muscle (or muscle group) is deliberately stretched, often by abducting the torso, to improve the elasticity of the muscle felt and to firm up a comfortable muscle tone.

Stretching can strengthen muscles, and in turn, strong muscles are important to stretching safely and effectively.

Other research concludes that active stretching routines will reduce muscle tendon stickiness and increase muscle flexibility and elasticity.

This can cause muscle injury in individual performance.


Hypertonia is the reduced ability of the muscles to stretch due to increased muscle tension; and hypotonia, due to the chronic reduction of muscle tension.

Hypertonia is a reduction in the ability of a muscle to stretch due to increased muscle tension; it is caused by injury to upper motor neurons.

The effects of hypertonia include dystonia, spasticity (a state of prolonged muscle contractions) and rigidity (a state of muscle stiffness and decreased flexibility).


Hypotonia is the state of reduced muscle tone and tension, which reduces the ability to generate force from muscle contractions.

A muscle spindle, with γ-motor neurons, sensory fibers, and proprioceptors that detect the amount and rate of change in length in a muscle.

Local regulation of blood flow

The arterioles contain smooth muscle fibers in their tunica media, allowing precise control of their diameter.

Local responses to stretch, carbon dioxide, pH, and oxygen also influence smooth muscle tone and thus vasoconstriction and vasodilation.

However, arterioles in skeletal muscle, heart muscle, and pulmonary circulation are vasodilated in response to these hormones that act on beta-adrenergic receptors.

In general, stretching and high oxygen tension increase tone, and carbon dioxide and low pH promote vasodilation.

Several hormones influence the tone of the arteriole, including vasoconstrictor epinephrine, angiotensin II, and endothelin, and the vasodilators bradykinin and prostacyclin.

Control of muscle tension

Muscle tension is influenced by the number of cross bridges that can be formed.

The pull that a muscle exerts is called tension.

Muscle tension occurs when the maximum number of cross-bridges is formed, either within a muscle with a large diameter or when the maximum number of muscle fibers is stimulated.

Muscle tone is residual muscle tension that resists passive stretching during the resting phase.