ELECTRO-MUSCLE STIMULATION -THE APPLICATION IN PRACTICE

Abstract

The need to get 'fit' has resulted in a planetary fitness centre expansion, which has by the principle of cause and effect brought out a massive number of different fitness exercising programmes, methods, equipment and props, with an aim to achieve better and faster training results, i.e. the wanted transformational anthropological status. The new fitness programs are emerging almost every day, which in spite of a vast marketing support and a current publicity are forgotten very fast. Within those conditions, in order to achieve satisfaction and trust of your clients, the offered programmes need to produce wanted effects in regards to the transformation of targeted abilities or characteristics of those who perform exercises. This presents constant challenges to the fitness industry, along with the obligation to seek for optimum, scientifically accepted and proven exercising methods. It is because of those reasons that the professional fitness centres are interested in introducing and applying only proven training methods, using highly sophisticated and technologically advanced equipment. This paper deals with analysis of Electro muscular stimulation (EMS) as one of the three methods which have been developed through a research designed for the astronauts. It was released into public after the fall of the " Berlin Wall 1989 " and opening the secret USSR and USA documents. The current research defines the related units starting from epistemology of the electro muscle stimulation (EMS), its application as an alternative to developing conditional capacities, clinical use in physiotherapy and EMS and EMS as one of the means to athlete recovery (body's regeneration processes) so as to prevent negative training effects (the development of overtraining and chronic fatigue). Each of the units will contain information which is relevant to the theory and practice in sport, recreation and convalescence of athletes and patients.

Full text

Pavlović, R. et al.: Electro-muscle stimulation - the application in practice Acta Kinesiologica 10 (2016) Suppl 1: 49-55
49
ELECTRO-MUSCLE STIMULATION - THE APPLICATION IN PRACTICE
Ratko Pavlović1, Drena Trkulja-Petković2 and Stanislav Dragutinović1
1Faculty of Physical Education and Sport, University East Sarajevo, Bosnia and Herzegovina
2Faculty of Kinesiology, University of Zagreb, Croatia
Review paper
Abstract
The need to get 'fit' has resulted in a planetary fitness centre expansion, which has by the principle of cause
and effect brought out a massive number of different fitness exercising programmes, methods, equipment
and props, with an aim to achieve better and faster training results, i.e. the wanted transformational
anthropological status. The new fitness programs are emerging almost every day, which in spite of a vast
marketing support and a current publicity are forgotten very fast. Within those conditions, in order to achieve
satisfaction and trust of your clients, the offered programmes need to produce wanted effects in regards to
the transformation of targeted abilities or characteristics of those who perform exercises. This presents
constant challenges to the fitness industry, along with the obligation to seek for optimum, scientifically
accepted and proven exercising methods. It is because of those reasons that the professional fitness centres
are interested in introducing and applying only proven training methods, using highly sophisticated and
technologically advanced equipment. This paper deals with analysis of Electro muscular stimulation (EMS) as
one of the three methods which have been developed through a research designed for the astronauts. It was
released into public after the fall of the “Berlin Wall 1989” and opening the secret USSR and USA documents.
The current research defines the related units starting from epistemology of the electro muscle stimulation
(EMS), its application as an alternative to developing conditional capacities, clinical use in physiotherapy and
EMS and EMS as one of the means to athlete recovery (body's regeneration processes) so as to prevent
negative training effects (the development of overtraining and chronic fatigue). Each of the units will contain
information which is relevant to the theory and practice in sport, recreation and convalescence of athletes
and patients.
Key words: electro-muscle stimulation (EMS), fitness and sport, the application in practice,
contraindications, convalescence.
Introduction
In the last few decades with the right one can
speak of fitness as a serious, first of all, very
profitable industry. The need to be "fit" resulted in
the planetary expansion of the fitness, which
causally caused the emergence of a large number
of different fitness programs, exercise method,
devices, and equipment, with the aim of better and
faster training results, i.e. the desired
transformation of anthropological status. In such
circumstances, in order to achieve satisfaction and
customer trust, programs that are offered must
lead to the desired effects on the transformation of
targeted skills or characteristics of trainees. Thus,
almost every day, new fitness programs appear,
which despite massive marketing support, as well
as the current publicity, quickly fall into oblivion.
The most common reasons for this lie in the lack of
desired results, and termination of client interest
for this type of exercise. This continuously sets new
challenges to the fitness industry and imposes a
duty to seek optimal, therefore scientifically
accepted and proven method of exercise. It should
not be overlooked that such programs and methods
must follow the trends of modern understanding of
fitness. For these reasons, serious fitness centers
have the interest to introduce and practice only the
proven training methods, using at the same time
highly sophisticated, technologically advanced
equipment. In this study will be presented in detail
one of three methods that have arisen in research
intended for astronauts, i.e. the space program of
major world powers (Vrcić, Kovačević, &Abazović,
2015). These findings later found their place in the
military industry, and finally at the top sports, i.e.
the Olympic programs of the USSR and the USA.
Only by the cessation of the "cold war" and the
opening of secret documents, vibration training,
isokinetic training and electrical muscle stimulation
saw the daylight. This research will try to elucidate
knowledge in the field of electrical muscle
stimulation (EMS) and on objective and professional
way present scientific research findings of
mentioned training methods. The research aims to
answer key questions, give serious and proven
recommendations for safe application of EMS
methods in fitness and make explicitly the expected
benefits and possible contraindications.
Epistemology of electro-muscle stimulation (EMS)
The EMS stands for electric muscle stimulation, a
method widely used for years in rehab medicine
and sport. This method successfully restores and
improves muscle tonus, but it is also used in the
treatment of medical conditions which involve the
loss of muscle mass. In sports and fitness, the EMS
is used as an additional part of the conventional
training in order to stimulate specific muscle groups

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50
to increase their strength and efficiency or
aesthetic appearance. Different level of muscle
contraction is achieved by sending electric pulses of
different types depending on the selected program.
These contractions reactivate muscles, increase
their efficiency and stamina and are very important
for muscles which, for whatever reason, were not
regularly used (muscle atrophy). In sport, it
represents benefit because it increases the effect of
training and improves performance. By typing the
term "electro-muscle stimulation" - EMS, the
browser opens a vast number of websites that offer
this type of training or services. By a more detailed
analysis of the offered content we can easily come
up with a few striking and for kinesiology practice a
bit worrying facts. Firstly, most of the conclusions
presented are at the level of scientific and
professional speculations, which means that they
are scientifically untested or, at worst, completely
untrue.
It's a bit like this: "Muscle electro-stimulation is
electrotherapy treatment with a highly
sophisticated machine, which through a low-
frequency current breaks down fat and cellulite,
accelerates weight loss, stimulates peripheral
microcirculation, improves muscle tonus, shapes
the body and restores its thinness." (Vrcić, et al.,
2015). This is just one of a myriad of definitions
that can be found on mentioned sites, and even at
first glance, it shows that marketing is a very
cleverly written, and that it provides consumer a
quick and easy path to perfect figure without
excess fat. Another extremely important fact refers
to the type and use of facilities that provide these
treatments. Deliberately is used the term
treatment, not training, because it is evident that in
addition to fitness centers and physical medicine,
beauty salons or some wellness centers dominate
(Vrcić, et al. 2015). It is clear that electrical muscle
stimulation, as a service, is offered in a very large
number of facilities that have a completely different
purpose and essence of its work. This in itself
carries a third possibly decisive factor of "failures",
with the exception of the first marketing impression
on consumers, and that is actually a person "coach"
who realizes this type of treatment. It is clear that
we are talking about a very small number of
medical (physical medicine doctors and
physiotherapists) personnel, and occupations such
as beauticians, makeup artists and people of similar
professional profile dominate. It is almost
unbelievable that kinesiologists or people with
education in the field of physical training participate
the least in the provision and control of the
implementation of this type of training.
The situation is even worse if we take into account
that there are people with an adequate kinesiology
education, who because of marketing and quick
profits, through their facebook profiles and web
portals, promote unverified information, and
consciously or unconsciously confuse the public.
This leads to the appearance that this method is
discussed at the level of "hearsay" and there are
contradictory customer experiences, from complete
disappointment to rebirth in training, but also life in
general. The truth, as usual, is somewhere in
between, that is halfway between a disappointed
customer experience who is really overweight and
in chronically bad health condition, which, after
several EMS treatment has not improved at all, and
aggressive marketing campaigns to promote this
method as a breakthrough in the fight with all the
problems of the modern fitness centre users. In a
serious expert literature this training method is
generally defined as follows: "Electrical stimulation
is a type of training that is carried out through
passive movements of body segments, caused by
the application of electric current. The apparatus
used is called an electric muscle stimulator. It is
mainly used for the purpose of treatment of injuries
and muscle atrophy, during and after the
immobilization. It is believed that electrical
stimulation accelerates the renewal of muscle
tissue and shortens the duration of rehabilitation.
Improper use can result in burns to the skin and
deeper tissues." (Ostojic, 2006). EMS is primarily a
method of physical therapy and has been used for
many years as a method of rehabilitation of
muscles after injury or surgery. In the early 1960s,
it was often used in an attempt to prevent the
atrophy of skeletal muscle that occurred as a result
of weakened or interrupted innervations (Davis,
Hamzaid, & Fornusek, 2008). With the development
of stimulation devices the EMS has become a
popular method for the treatment of patients who
have suffered damage to the central nervous
system, most often due to stroke or spinal cord
injury (Scremin, Kurta, Gentili, et al., 1999;
Wheeler, Andrews, Lederer, et al. 2002). Over the
past 20 years, manufacturers have developed high-
quality devices, capable of modulating various
forms of pulses of electrical current, which can be
used to stimulate muscle contraction. For these
reasons, the EMS is being increasingly applied in
order to improve the strength of the lower
extremities (Laughman, Youdas, Garrett, et al.
1983) in the process of rehabilitation of patients
who have had orthopedic surgery, especially the
reconstruction of the anterior cruciate ligament
(Porcari, Mclean, Foster, et al., 2002; Avramidis,
Strike, Taylor, &Swain, 2003). To understand
better the idea of the use of electrical muscle
stimulation in rehabilitation, but also sport, it is
necessary to know the basic physiological
mechanisms of muscle contraction and its nervous
regulation, because it is the one that inspired the
researchers, using external excitation of muscles,
to try to cause its contraction and generate greater
force than during maximal voluntary contraction.
Physiological mechanisms of electro-muscle
stimulation (EMS) and functioning
EMS is achieved by an electric impulse which, via
electrodes on the skin stimulates nerves that
innervate specific muscle group (Figure 1). The
muscles work differently depending on the severity,
frequency and pulse width of electric impulse.
Muscle is made up of two types of muscle fibers:
red - which slowly contract and work under aerobic

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conditions, and white - which react faster and are
capable of anaerobic work. The ratio of white and
red muscle fibers depends on the way the muscles
are used. Muscle fibers can be converted from one
form to another, depending on the signals they
receive. This is known as a trophic effect (Pavlović,
2014). Contraction (lat. contraho-contract) or
muscle spasm is a process of muscle shortening
whereby there is a manifestation of the forces at its
ends (tendons). All skeletal muscles are composed
of a large number of muscle fibers; each muscle
fiber contains several hundred to several thousand
muscle fibers or myofibrils. Each myofibril consists
of about 1500myosin and 3000 actin filaments or
microfilaments. The main commander and
controller of motor activity is the central nervous
system (CNS), which generates and transmits
nerve impulses necessary for muscle contraction.
Every nerve ending is tied with muscle fibers in the
neuromuscular junction, located approximately in
the middle of the muscle fiber. The nerve fiber
branches at its end, making web branched nerve
endings, which make the structure called the motor
plate. The electric impulse in the form of an action
potential travels along the motor nerve to its end
on the muscle fibers. Each impulse that arrives at
the neuromuscular junction typically creates the
potential motor plate, which is about three times
higher than the potential required to incite the
muscle fiber. When a nerve impulse reaches the
neuromuscular junction, from the nerve endings in
the synaptic cleft is emptied one part of the
neurotransmitter acetylcholine bubbles (10,000
molecules).
Acetylcholine acts locally on the membrane of
muscle fibers and allows the entry of sodium ions
into the interior of the muscle fibers membrane.
This reaction promotes the formation of the action
potential in the muscle fiber, which along the
muscle fiber membrane travels in the same way as
along the nervous fiber membrane, leading to
depolarization of muscle membrane (2-4ms).The
membrane suddenly becomes very permeable to
sodium ions, which immediately neutralize the
impact of the normal polarized state of -90 mV and
the potential increases rapidly in the positive
direction (5mV). In this way, a large part of the
electric current of the action potential goes deep
within the muscle fiber, releasing from the
sarcoplasmic reticulum large amount of calcium
ions. Calcium ions induce forces of attraction
between the actin and myosin filaments, causing
their mutual sliding necessary to create muscle
contraction. Immediately thereafter (milliseconds)
calcium pump membrane returns the calcium ions
to sarcoplasmic reticulum where they remain stored
until a new action potential (Guyton, & Hall, 2003).
Spots of contact of muscular and nervous fibers
make the motor unit (muons). The motor unit
consists of a single α (alpha) -motor neurons (with
associated nerve fibers) and all the muscle cells
that irritate these individual neurons. During the
voluntary activity, CNS first activates the smallest
alpha motoneuron, while, with the increase of the
force, higher motoneurons are progressively
triggered. This principle is called the "recruitment in
size", and refers to the engagement of motor units
and depends on the size of the alpha motor
neurons. Among motor units, there are differences
in the frequency of nerve impulses, and these
differences depend on the type of muscle cells in
motor units (Mišigoj-Duraković, et al., 1999). The
male motor unit usually contains slow (red)
oxidative fibers of low threshold stimulation. Nerve
fibers, which sensitize them, have relatively low
impulse frequencies (10-20 Hz).Opposite of them
are the motor units with a fast (white) glycolytic
fibers, with the nerve fibers of high-frequency
impulses (40-60 Hz). Between these two types,
there are transitional fast oxidative-glycolytic fibers
(Type IIa), with the nerve fibers of medium impulse
frequency (20-40 Hz). Lower relative forces of
contraction (relative force is the strength
percentage) trigger the slow fibers. Between 40-
60% of relative forces are activated type IIa fibers,
and most of the high-speed fibers are activated
only above 90% of relative force (Pavlović, 2014;
Vrcić,et al., 2015). Increasing the force of
contraction leads to the increase of impulse
frequency of all types of motor units, up to a
maximum contraction, when the nerve fibers of all
activated motor units achieve the highest frequency
impulses, in terms characteristic for individual
fibers (so fibers of slow units will again have the
lowest and high-speed fiber units the highest
frequency). The order of muscle fibers activation is
reversed when the muscle is electro-stimulated
therefore activated by external stimuli through
electro-stimulator. In this case, first are recruited
fast contractile muscle fibers and with the highest
engagement, and after that, slow contractile
muscle fibers with low engagement (Porcari,
Mclean, Foster, et al., 2002). This phenomenon
significantly affects the size of the forces generated
during electro-stimulated contraction, i.e. the
difference between the force in this type of
contraction and the force generated during maximal
voluntary contraction.
The principle of electrical stimulation consists of
stimulating the nerve fibers by electrical impulses
that are transmitted through the electrodes. In
active training muscular work comes from the
brain, which sends the command in the form of
electrical signals to nerve fibers that contract. The
principle of electrical stimulation corresponds
exactly to the process that takes place at the
desired contraction. The stimulator sends an
electrical current impulse to the nerve fibers, which
causes their irritation. This irritation is submitted
further to the muscle fibers that perform
elementary mechanical response (muscle twitch) as
an essential element of muscle contraction. The
reaction of the muscle is fully synchronized with the
work of the muscles from the brain. In other words,
the muscle cannot distinguish the command from
the stimulator from those from the brain. Various
parameters (number of impulses per second, the
duration of contractions, the duration of resting
stages) allow different types of muscles to start
working, depending on the muscle fibers.

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Fast fibers will be more prevalent among sprinters
while marathon runners will have more slow fibers.
Knowledge of human physiology and a perfect
mastering of stimulation parameters of the
program allow very precisely the work of muscles
to be directed to the desired objective (to
strengthen muscles, increase blood flow,
mounting). To achieve the pain relief effects the
electrical impulses can also arouse sensitive nerve
fibers. The stimulation of nerve fibers blocks the
transfer of the pain through the nervous system, in
contrast to the stimulation of some other types of
sensible fibers which causes an increase in the
production of endorphins alleviating pain. (Baker,
McNeal, Benton, et al. 1993).
Figure 1. Stimulation of motor neuron (EMS)-
afferent and efferent impulse
The use of EMS in sports and fitness
Electrical stimulation in recent years has begun to be
applied in sports, especially with athletes who need
strength. It is implemented by using special
appliances, and the length of stimulation lasts for 10-
15 seconds with breaks of 45-50 seconds, usually with
10 repetitions. It can be particularly useful when
properlydosed; otherwise, its use can cause harmful
effects, especially if used for longer than the scheduled
time. By applying electrical stimulation blood
circulation and metabolism of nutrients in muscle cells
are improved, thereby contributing to the increase of
muscle mass, and thus strength.Most often it is used
for the purpose of recovery, but after three weeks of
its effect lowers. The application of EMS in the sport
and fitness helps strengthen specific muscles or
muscle groups in order to achieve the desired
proportions of the body, the development of muscular
endurance, warming, strengthening and increasing
strength, improves muscle recovery and rehabilitation
of sports injuries (Vrcić, et al., 2015). It is important
to note that the effect of the EMS functioning can be
expected only in regular use, it does not replace
regular exercise but it is good as a complementary
part. There are only a few studies in the scientific
literature in the field of electrical stimulation of
muscles. There are even fewer allegations that
document the effects of applying this method to
healthy people, and the physically active
population, or recreational athletes (Banerjee,
Caulfield, Crowe, & Clark, 2005; Davis, Hamzaid, &
Fornusek, 2008). Previous research in the field of
the EMS identified the significant effects on
strength and power, but in isolated muscle groups
(m. quadriceps femoris or m.bicepsfemoris).There
are top sportsmen (canoe or kayak) with a very
positive attitude towards electrical stimulation, but
even they apply it locally (on several muscles),
before major competitions, including the Olympics.
Some allegations indicate that if the EMS is applied
regularly (twice a day) on the small muscles of the
foot arch, improvements are probable, or on higher
muscle groups the EMS treatment can vary from
15-60 minutes, twice a week to several times
(Malacko & Rađo, 2004). In addition, the EMS has
been successfully applied to the extensor muscles
of the spine with the rowers and kayakers, who
tend to the occurrence of pain in the lower back
(Wheeler, Andrews, & Lederer, R., 2002 Zaciorski,
& Kremer, 2009). Advantages of using the EMS to
the whole body in order to achieve better physical
form or shape have never been tested. However, it
is evident that the EMS has an important place in
the field of recreational exercise, and a growing
number of fitness centers that follow the modern
trends offer this type of training.
The first allegations and the first documented
research in the Soviet Union state that the EMS is a
more effective method of developing strength and
power of skeletal muscles in athletes than exercise
without the use of electrical stimulation (Kots,
1977).This method was used in the Soviet Union on
the athletes at the end of the sixties of the
twentieth century, but contrary to some beliefs it
was not regularly used as a substitute for
traditional strength training. Often the authors
state that the advantage of using the EMS lies in a
different mode of motor unit recruitment in relation
to the exercise with maximum voluntary
contraction. The EMS method found its application
in the field of sports and fitness mainly through a
technique called tetanic stimulation. It represents a
series of repeated stimulus-electrical impulses,
which are determined by two key factors: the
duration of each impulse and the time between
consecutive impulses.Tetanic stimulation makes it
possible to manipulate the impulse duration and
breaks between two consecutive impulses, which
determines the total load on the stimulated muscle.
If the time between two consecutive impulses is
short, the muscle will not be ready for the next
contraction. This period is called the absolute non-
irritability refraction period lasting from 1-3ms.
(Pavlović, 2014).

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This method theoretically should cause the
maximum possible power development as a series
of consecutive impulses causes the maximum
contractions of the stimulated muscle. It is
recommended to use with athletes or recreational
athletes with a higher level of quality. Electrical
muscle stimulation in sport and fitness is applied
mainly through external electrodes, i.e. through the
skin. Bipolar electrodes are commonly used (which
means that the electrode has two different poles).
The electrodes are typically attached to the skin
above the stimulated muscle. For proper and
comfortable work it is very important to use the
appropriate size electrodes and properly position
them in the muscle (Knez, 2000). For the
successful implementation of the EMS method, it is
necessary to take into account the quality of the
stimulation device. In fact, studies have shown that
the actual frequency of electrical impulses
(modulation), provided by stimulator, can
significantly (for several times) be different from
those declared on the device.Specifically, the
muscle fatigue is increased with the increase in the
stimulation frequency (DeVahl, 1992). Most of the
previously used protocols, intended for the
development of strengths and the power, indicate
that the frequency must be sufficiently high to
achieve a tetanic contraction, but at the same time
sufficiently low to minimize the muscle fatigue
(Baker, et al., 1993). Usually, this is achieved by
using frequencies of between 50 and 75 Hz.
Excessive stimulation frequency in combination
with short breaks between contractions leads to
extreme fatigue at stimulated muscle fibers, which
can result in an insignificant increase in muscle
strength after the EMS. Another factor that can
affect muscle fatigue, and thus the size of the
effects, is the order of engaged muscle fibers
during the EMS (considerably changed in relation to
the voluntary contraction).So, first are engaged the
fast contractile muscle fibers (Van Swearingen,
1993). In addition, there is a synchronous
activation of all of the same sized axons, at equal
distance from the electrode (Baker, et al., 1993).
Thus, in relation to the voluntary contraction,
electrically caused contraction leads to a much
greater fatigue of the muscle fibers, due to
selective engagement of fast contractile muscle
fibers in combination with synchronous activation of
the same muscle fibers repeatedly. Accordingly,
protocols used to develop strength and muscle
strength using the EMS, usually are designed to
reduce fatigue. The first manner of reducing fatigue
is to allow plenty of time to recover muscle fibers
after each contraction. This is often accomplished
by the ratio of contraction and relaxation of 1: 5
(Baker et al., 1993). However, a large number of
stimulators used in research allows a relatively
short recovery time. This ratio is ranged from 1: 3
to 1: 5. Although in the offer can be found different
types of electro-stimulation treatments or training,
in professional sports literature is mainly mentioned
the so-called "Russian protocol".
Russian Protocol (Zaciorski and Kremer. 2009):
• Carrying signal - sinusoidal or triangular
• Frequency - greater than 2500 Hz
• Modulation - 50 Hz
• Amplitude of stimulus - adapted to the individual
to induce a force greater than 100% of maximal
isometric force or up to the limit of athlete's
endurance; the amplitude of the stimuli depends on
the output of the impedance of the stimulator, and
is often greater than 90 V
• Duration of contraction -10 s
• Pause between contractions - 50 s
• The number of contractions – 10 daily
• The number of training days - 5 times a week
Extremely important factor for the development of
strength and power is the intensity of the training,
which is carried out regardless of whether
combined with external irritation or not. The EMS in
previous studies was mostly combined with a
generally isometric type of muscle contraction. The
results of the studies which combined the EMS and
strength training, thefirst state that to achieve an
increase in strength of contractions the muscle
should be stimulated above the critical threshold.
This threshold can be very low 30% of the maximal
voluntary contraction (MVC) in untrained
individuals, but must strictly be in the range of 60-
80% MVC in athletes (Mueller, 1959).After a series
of studies to determine the minimum threshold
required to achieve improvements in strength
(Currier, Lehman, & Lightfoot, 1979) it was
concluded that electrically induced contraction must
be at least 60% of MVC (Currier, et al., 1979;
Currier, & Mann 1983; Soo, Currier, &Threlkeld,
1988). Studies have established that if the power of
electrically induced contraction was less than 20%
of MVC, the stimulus is below the critical threshold
needed to increase muscle strength and changes in
the appearance of a healthy person.
In fact, in a study on healthy people was
administered a battery of tests that included: body
weight, percentage of subcutaneous adipose tissue
- skin folds, circumferences, isometric and
isokinetic strength (biceps, triceps, quadriceps and
hamstring) and appearance (photos - forward,
backward) in order to determine the actual effects
of the EMS on physical strength, re