ACTION PRINCIPLES
Muscular electrostimulation
Electrostimulation is a technique that, by means of electric pulses that act on the muscle
motor points (motoneurons), causes a muscular contraction similar to voluntary
contraction.
The majority of human muscles are striated or voluntary, with approximately 200
muscles on each side of the body (about 400 on the whole).
The physiology of muscular contraction
The skeletal muscle performs its functions through contraction.
When a movement is made, the motor center of the brain sends an electric signal to the
muscle to be contracted.
When the electric signal reaches the muscle, the motor plaque of the muscle surface
produces the depolarization of the muscle membrane and the release of CA++ ions
inside it. The Ca++ ions, interacting with the actin and myosin molecules, activate the
contraction mechanism which leads to the shortening of the muscle.
The energy required to contract the muscle is provided by adenosine triphosphate (ATP)
and supported by a recharging system based on aerobic and anaerobic mechanisms
using carbohydrates and fats. In other words, electrostimulation is not a direct source of
energy, but it acts as a tool triggering muscle contraction.
The same principle is activated when muscle contraction is generated by EMS, which act
as a natural impulse transmitted by the motor nervous system. At the end of the
contraction, the muscle relaxes and returns to its original state.
Isotonic and isometric contraction
An isotonic contraction occurs when, during a movement, the muscles overcome
external resistance, thus shortening and leading to a constant state of tension in the
tendon heads. An isometric contraction occurs instead when external resistance
impedes the movement; thus muscle contraction does not generate the muscle
shortening but an intensity increase on its tendons. Isometric stimulation is normally
used in electrostimulation because it permits a more powerful and efficient contraction.
The distribution of the different fiber types in the muscle
The relationship between the two main categories (type I and type II) can vary in a
considerable way.
There are muscular groups that are typically made up of type I fibers, like the soleus, and
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