Electro Muscle Stimulation

ELECTRO MUSCLE STIMULATION
Electro stimulation is a technique which, by means of electric impulses that act on the muscle’s motoneuron points, provokes muscular contraction responses similar to voluntary contractions (exercise).
Most on the muscles in the human body belong to the striated or voluntary muscle category, of which there are about 200 on each side of the body (about 400 in all).
The physiology of muscle contractions
The skeletal muscle performs its functions by way of a contraction mechanism.
When a person decides to make a movement, the motor centre of the brain sends an electric signal to the muscle which must contract in order to affect the motion the person has decided on.
When the signal reaches the muscle the motor plate of the muscle surface produces the depolarisation of the muscle’s membrane and the release of CA++ ions into it.  The Ca++ ions, reacting with the actins and myosin, activate the contraction mechanism which consequently results in the shortening of the muscle.
The amount of energy needed for this contraction is provided by the adenosine triphosphate (ATP) and is sustained by an energy recharging system based on aerobic and anaerobic energy mechanisms which consume carbohydrates and fat. In other words, electric stimulation is not a direct source of energy but functions as a tool to set off a muscular contraction.
The same type of mechanism is activated when the contraction, or twitching, is set off by the electro muscle stimulator (EMS); they perform the same function as an impulse naturally transmitted by the motor nervous system.
When the contraction is over, the muscle relaxes and returns to its original state.
Isotonic and isometric contractions
An isotonic contraction manifests itself when, during a movement, the interested muscles exceed resistance from the outside by shortening, thus provoking a constant state of tension in the ends of the tendons.  When outside resistance impedes its movement, the muscular contraction, instead of provoking a shortening effect, brings about an increase in the tension at the extremes; this is called isometric contraction.  In the case of electro stimulation normally a stimulation for isometric conditions is used, due to its ability to provoke a more powerful and efficient contraction.
The distribution in the muscle of different types of fibres
The rapport between the two principle categories (type I and type II) can vary noticeably.
There are muscle groups which are typically made up of type I fibres, like the soleus, and muscles which are made up of only type II fibres, like the orbicular muscle, but on the whole the muscles in the human body are composed of a combination of the two types.
Studies conducted on the distribution of the fibres in muscle mass have brought to light the close relationship which exists between the motoneurons (tonic or fascicle) and the characteristic functions of the fibres they innervate and have shown how a particular motor action (particularly sports) can provoke a functional adaptation to the fibres and can bring about a change in their metabolic characteristics.

Type of motor unit             Type of twitching          Twitching frequency
Tonic       ST                       Slow twitching I           0 - 50 Hz
Fascicle      FT                    Fast twitching II           50 - 70 Hz
Fascicle       FTb                 Fast twitching II b         80 - 120 Hz
Electro stimulation, thanks to its ability to stimulate with specific frequencies, lets you specifically work those fibres which intervene in the gesture you want to train (rapid fibres for explosive gestures, slow fibres for long duration action) or to transform the metabolism and characteristics of the intermediate fibres in order to make them more adapted to the motion you want to perform.