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Electrostimulation is a technique which, by means of electric pulses that act on the muscle’s motor points (motoneuron), causes muscular contraction responses similar to voluntary contractions (exercise).

Most of human body muscles belong to the striated or voluntary muscle category, with approximately 200 muscles on each side of the body (about 400 in all).

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The physiology of muscular contraction

The skeletal muscle performs its functions by way of a contraction mechanism.

When a person decides to make a movement, the motor center of the brain sends an electric signal to the muscle that is to contract.

When the signal reaches the muscle, the motor plate 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 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 muscular contraction is set off by the electro muscle stimulator (EMS). They carry out 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 of different types of fibers in the muscle

The ratio between the two main categories (type I and type II) can vary noticeably.

There are muscle groups which are typically made up of type I fibers, like the soleus, and muscles which are made up of only type II fibers, like the orbicular muscle. However, on the whole, the muscles in the human body are composed of a combination of the two types.

Studies on the distribution of fibers in the muscle mass have highlighted the close relationship between the (tonic or phasic) motoneuron and the functional characteristics of the fibers it innervates and have shown that a specific (particularly sports) motor action can bring about a functional adaptation of fibers and a change in their metabolic characteristics.

Type of motor unit Type of contraction    Contraction frequency

Tonic ST                     Slow contraction I          0 – 50 Hz

Phasic FT                   Fast contraction II        50 – 70 Hz

Phasic FTb                 Fast contraction II b    80 – 120 Hz


Electrostimulation, thanks to its ability to stimulate with specific frequencies, lets you train specifically those fibers which intervene in the movement you want to train (rapid fibers for explosive movements, slow fibers for long-lasting action) or to transform the metabolism and characteristics of intermediate fibers in order to make them more suitable to carry out the desired movement.


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Transcutaneous Electrical Nerve Stimulation

TENS is an antalgic stimulation applied with pulses reaching the peripheral nervous system by means of electrodes placed on the areas to be treated.

TENS stimulation is typically achieved by applying biphasic and symmetrical (square wave) pulses with frequencies that can vary from 8 to 200 Hz. This type of antalgic stimulation, fighting pain without resorting to drugs, uses 2 different physiological mechanisms to achieve the its goal:

  1. Endogenous beta-endorphin and encephalon production due to the activation of the endorphin system by very low frequency stimulation (< 8 Hz). This type of stimulation, which has a slow action, produces a generalized analgesic effect.
  2. The production of serotonin and the block of pain signals (gate control) heading towards the central nervous system. Higher frequency stimulation are applied in this case (starting from 80 Hz). The serotonin and the ‘gate control’ mechanism have a very rapid analgesic effect, but it is of short duration.
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TENS stimulation uses biphasic symmetrical and compensated current and has two different applications:

  • segmental sensory inhibition against acute localized pain
  • endorphin release to treat chronic and diffuse pain.


In the human body there are two types of afferent nervous fibers, i.e. fibers which transmit peripheral information to the encephalic part of the brain. The first type is made of fibers with large diameter, called A-beta fibers, which are responsible for transmitting tactile sensory information from the peripheral to the central nervous system. The second type, called A-delta fibers, is made of fibers with smaller diameter and transmit pain sensations to the encephalic level. Another factor differentiating these two types of fibers is that the first has a low excitement threshold, while the second has a higher excitement threshold. Along the path conducting the pain signal from the periphery to the center, at spinal cord level there is an interneuron inhibitor, which serves as a selector of the signal.

The TENS current stimulates the large diameter A-beta fibers and excites the inhibitory interneuron. Its activation, which preempts pain signals from reaching the encephalic level, blocks pain transmission.

This mechanism was called “Gate Control” by Melzack and Wall, who were the first to identify this phenomenon in 1965.

In this mode of TENS stimulation, pulses will be short (< 1 msec) with a frequency between 80 and 150 Hz. The intensity has to be comfortable and give only a slight tingling sensation (tactile sensory threshold). In order to be effective, the treatment should last at least 30 minutes.


Endorphins and enkephalins are proteins produced in the brain. Their functions are similar to morphine’s and they are present in various parts of the central nervous system. For this reason, they are particularly effective for pain sedation.

These endogenous morphines are the body’s natural analgesic neuromediators and can bind to brain cellular receptors, like the thalamus, the limbic system, the reticulated tissue, producing a pain-killing effect comparable to morphine.

Electrostimulation with TENS currents can stimulate the release of these endogenous morphine-like substances.

Indeed, research has proved that 30-minute treatments with low frequency currents of high intensity, capable of producing rhythmic muscular contractions near to pain threshold, can increase endorphin levels by 20% over normal levels. This increase in endorphin levels is maintained for 30 minutes after the end of the treatment.

Micro Current MCR

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Microcurrent electrical neuromuscular stimulation or MENS, as opposed to conventional electrotherapy where milliampere (mA) currents are administered, uses currents whose intensity varies between 10 and 500 µA (microamperes, i.e. one millionth of an ampere).

Much scientific research shows that the ATP (adenosine 5′-triphosphate) synthesis level is increased by the application of microcurrents. On the other hand, it seems to slow down when endogenous mA currents are applied.

In particular, the increment of the ATP synthesis reaches its maximum levels thanks to the administration of 500-µA currents, while, beyond this intensity level, it rapidly decreases. In the light of this, it is important to remember that ATP is the main source of intracellular chemical energy in every living organism and can be used in a wide variety of biological activities, including the healing process of damaged tissues.

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Another very interesting aspect regarding the application of MENS is that the alpha-aminoisobutyric acid uptake increases noticeably thanks to the application of an exogenous current starting from an intensity level of 10 µA. On the other hand, starting with an intensity level of 750 µA, there is an inhibitory effect. Considering that the alpha-aminoisobutyric acid uptake is essential for the protein synthesis mechanism (which are at the basis of tissue repair processes), its increase by 30-40%, as is produced by MENS applications, could play an essential role in cell reconstruction process.

The basic mechanism causing an increase in ATP synthesis is essentially constituted by the fact that, during MENS-induced electrostimulation, a proton gradient is created, i.e. a variation in proton concentration, which causes the creation of a proton flow from the anode to the cathode. This proton flow through the mitochondrial membrane brings about an increase in ATP formation, which stimulates the transport of amino acids, two essential factors to increment protein synthesis.


MENS therapy normally involves two distinct phases, the first of which aims at reducing the pain sensation felt by the patient, while the second phase promotes protein and ATP synthesis, thereby speeding up the tissue healing process. Treatment duration is normally between 15 and 30 minutes for the first phase and between 5 to 10 minutes for the second phase. The most frequently used parameters, which can however vary according to the type of pathology treated, for the first phase are: intensity between 1 and 5 µA with a frequency of about 5 Hz and with 250 millisecond wide pulses. As regards the second phase, the parameters normally used are: intensity between 10 and 200 µA with a frequency between 0.3 and 1 Hz and with 100 millisecond wide pulses.

The effectiveness of MENS therapy has been scientifically proven in the following fields:

  • Reduction of edemas and swelling of a traumatized area.
  • Osteoarthritis.
  • Stimulation of the production of cartilaginous proliferation processes.
  • Acceleration of tendon repair processes.
  • Osteogenesis process facilitation.


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Dr. Yakov Kots became famous for using electrostimulation for training USSR athletes. His studies were made public at the 1976 Montreal Olympics.

The electric current used for stimulating athletes was called Russian current or Kots current, and was soon also used by the athletes of other countries, thus becoming a widespread sports training method.


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Dr. Yakov Kots became famous for using electrostimulation for training USSR athletes. His studies were made public at the 1976 Montreal Olympics.

The electric current used for stimulating athletes was called Russian current or Kots current, and was soon also used by the athletes of other countries, thus becoming a widespread sports training method.

After conducting research and experiments, dr. Kots defined the characteristics of the current carrying his name:

– current form: sinusoidal (it passes through muscle tissue in alternating directions)

– it has a frequency of 2500 Hz when applied to muscle mass (1000 Hz if applied directly to nerves)

– stimulation with pulse trains lasting 10 milliseconds.

In order to avoid early exhaustion of the muscle, which takes place after 12-15 seconds of continuous stimulation, Kots identified the ideal work phase duration as 10 seconds (in sets of 10 msecs alternating with a 10 msec pause), followed by 50 seconds of break with a 1:5 duty cycle.

With respect to other low frequency motor exciting currents, this current seemed to guarantee a better work-out of the muscle mass, with deeper action, and was also considered more tolerable.

The use of Kotz currents in the medical field

New scientific discoveries on muscle contraction mechanism as well as a new technology that can generate pulses of different shape (square, triangular, trapezoidal, etc.) led to the gradual abandonment of the sinusoidal current for the electric stimulation of muscles for sports training in favor of the higher-performing current with square biphasic symmetric waves with frequencies ranging from 30 to 120 Hz.

The Kotz current, nonetheless, continued to be used in the medical field, where it still has valid applications for its characteristics:

1) Good muscle recruitment

2) Deep action

The motor exciting effect of the Kotz current, unlike other types of current, takes place deep within the muscle, because the skin gives less resistance to this currents. Indeed, it has been proved that the skin’s electrical impedance diminishes as the frequency increases.

Maximum tolerability

Among the motor exciting currents, the medium-frequency sinusoidal currents are better tolerated by the patient. This happens because, when the current frequency is increased, a discrepancy is generated between the muscular contraction threshold and the pain sensation threshold.

At a frequency of 3.000-8.000 Hz, the pain sensitivity threshold is higher than the motor exciting one. At these frequencies, the electric pulses stimulate more the nervous motor fibers and less those related to pain sensitivity, thus causing practically painless muscular contractions.

Applications of Kotz currents

The Kotz sinusoidal current has an important field of application in orthopedics, in the treatment of scoliosis according to the SPES (Surface Paravertebral Electro Stimulation) method. Paravertebral Electro Stimulation is a relatively new method and its worth is still the subject of discussion. However, in certain well selected cases it can actually reduce the use of a corset without any risk for the patient. Another sector in which the electrotherapy of innerved muscle can be applied is Functional Electrical Stimulation (FES).

Numerous scientific studies exist which describe electrostimulation in hemiplegics through the electric stimulation of non-nervously controlled non-spastic muscles with the aim to provoke a muscular contraction which can then produce a useful functional movement. It must be remembered that hemiplegics do not have muscle paralysis due to lesion of the second motoneuron but a movement paralysis. The electric excitement of peripheral nerves as well as the contraction ability of the muscles are not altered. Therefore, there are conditions for the application of electric stimulation.

Electrotherapy with Kotz currents is also used in muscle transplants, to ensure adequate tropism for the newly transplanted muscle’s function and to help the patient become aware of the different functional condition, thanks to the afferents produced by the induced muscular contraction.


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This specific type of current is called interferential because it forms and interferes with tissues in the points where the fields of two different medium-frequency currents intersect.

Interferential current (IFC) is a medium-frequency (2500 Hz – 4000 Hz – 10000 Hz) alternating sinusoidal current of wide modulation, characterized by its high ability to penetrate tissues and a very good tolerability even as regards patients most sensitive to pain.

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The antalgic action of the bipolar interferential current, with modulation frequency between 0 and 200 Hz, is due to the gate control mechanism, to the stimulation of the inhibitory mechanism, to the peripheral block of pain transmission, and to the removal of algogenic substances from the affected area, like in the case of transcutaneous electro nerve stimulation (TENS) current.

By varying the modulation frequency used, a motor exciting effect can be produced, which contributes to the return of venous blood flow by activating the “muscle pump”.

Clinical Applications
Interferential currents are particularly suitable for treating deep joint arthritis (hip, lumbar rachis), deep-seated tendinopathies and muscular hypotrophy of deep and normally innervated muscles.

Interferential current therapy is usually applied in physiotherapy for motor excitement and for its antalgic effects.

Therapeutic effects
Motor excitement effects: it brings about the contraction of deep and normally innervated muscles.

Analgesic effects
It may cause vasodilatation, which, due to the increase in local blood flow, would remove algogenic substances from the tissues.

It is used for the treatment of the following pathologies:

Deep arthritis (hip, lumbar and cervical rachis)

Hip and shoulder tendonitis


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Current for denervated muscles or partially denervated muscles.

The stimulation of a denervated muscle is different from the stimulation of a healthy muscle, because the muscle fiber activation requires special currents.

When there is a traumatic lesion to the peripheral nerves, the measurement of cronassial values helps establishing whether the level of denervation is scarce, partial or complete.

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The aim of motor exciting treatment is to maintain tropism and to limit muscular sclerosis, to allow the muscle to be as functional as possible after the re-enervation treatment program, which can sometimes last for a few months.

The effectiveness of this type of treatment depends a lot on the correct stimulation parameter settings: they have to be very specifically defined for each patient and have to evolve in time.


A rectangular current is characterized by a single rectangular pulse, which varies rapidly from zero to the maximum value of set intensity, by a contraction duration equal to the duration of the pulse, by a rest period corresponding to the time in which the muscle returns to normal. The rectangular shape of the pulse causes muscle contraction. The pulse duration determines a selective contraction of the denervated fibers, and the average zero value of the pulses (alternate polarity) avoids any skin ionization.

Rectangular pulses are mainly used on completely denervated muscles. The program varies according to the pulse width and the length of the rest period.


A triangular current reaches its maximum intensity value with a linear ascension scale, which, combined with relatively long duration pulses, brings about a valid contraction response of the denervated fibers (controlled by damaged nerves) without stimulating the adjacent healthy innervated fibers. Since this is a motor exciting current, the triangular pulse responsible for the contraction of the denervated fiber will be followed by a rest period in which the current has a zero value. The polarity of the pulses is alternated to avoid skin ionization.

Due to the ability of nervous fibers to adapt to the slow intensity increase of the stimulus and the lack of pain felt by the patient, the triangular current is used to stimulate totally denervated muscles and partially denervated muscles. The selective stimulation of the fibers happens without affecting the healthy innerved fibers, which can be the source of problems when using an alternated rectangular pulse due to the rapid increase of the pulse. The program varies in accordance with the pulse width and the length of the rest period.


Trapezoidal currents are mainly used on partially denervated muscles. The program varies in accordance with the pulse width and the length of the rest period.


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Ionophoresis is type of electrotherapy that brings pharmacological substances into tissues thanks to a unidirectional direct electric current.

It is based on the ionic disassociation capacity of certain low molecular weight medical substances once they are dissolved in water.

It is of fundamental importance to know whether the active part of the medicine is positively or negatively charged once it has been disassociated in ionic form, in order to be able to position it correctly on the basis of the electric flow.

The medicine’s ions are transferred inside of the organism through the skin areas that have low resistance to current, in order to reach the cell membranes, which are consequently changed electrically.

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The ionophoresis mechanism

The objective of ionophoretic therapy is to be able to transfer a pharmaceutically active substance through the skin into tissues, thereby transferring the medicine directly to the interested part of the body. The advantages of this mechanism lie in the fact that the medicine can be administered in lower doses, thus also diminishing possible side effects.

The substantial therapeutic value can be essentially ascribed to the confluence of two factors: the first is the antalgic and vasomotorial effect of the direct current administered, and the second is the benefits deriving from the administration of the medicine itself. For this reason, ionophoresis therapy is often chosen as a treatment for flogosis, when it can have an anti-inflammatory and sedative action, serving as an alternative therapeutic means to the hypodermic injection of ionic solutions.

Ionophoresis is especially recommended for treating the afflictions of superficial joints, where the subcutis thickness and muscle tissue are particularly thin.

Quantification of the transported substance

The relationship between transdermal ionic absorption and the intensity of administrated current is theoretically expressed in Faraday’s Law:

D= I M/ZF where D is the transdermal ionic absorption

I current intensity,

M the molecular weight of the medicine,

Z the number of charges for each molecule of medicine

F the Faraday constant (96,487 C/mol).


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Bibliography on the Electrical Muscle Stimulation.

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Electrical Stimulation: Neurophysiological Basis and Application.

Electrical stimulation has been used for thousands of years for a variety of purposes including muscle reeducation, muscle strength training and wound healing. However, because it has been used most commonly by individuals in money making schemes, it has been sometimes considered the domain of quacks and charlatans.


Jerrold Scott Petrofsky

(Department of Physical Therapy, Loma Linda University)

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The Effects of Electromyostimulation Training and Basketball Practice on Muscle Strength and Jumping

The aim of this study was to investigate the influence of a 4-week electromyostimulation training program on the strength of the knee extensors and the vertical jump performance of 10 basketball players.


Maffiuletti NA, Cometti G, Amiridis IG, Martin A, Pousson M, Chatard J-C.

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Application of Muscle/Nerve Stimulation in Health and Disease

Application of Muscle/Nerve Stimulation in Health and Disease

Gerta Vrbová,Olga Hudlicka,Kristin Schaefer Centofanti