Needle emg. electrical activity of muscles. How can muscles grow even better? What does electromyography show?

Needle electromyography (EMG) is prescribed to patients for the diagnosis of diseases of the musculoskeletal system. This method is widely used to determine the causes of pain in the muscles or back, to track the dynamics of treatment. Needle EMG was first performed in 1907 by G. Pieper, but it began to be introduced into medicine in the middle of the 20th century. Needle electromyography in Moscow is performed for patients in the neurology clinic of the Yusupov hospital, equipped with modern equipment.

Needle electromyography: features of the study

Needle EMG is based on the establishment of bioelectric potentials of muscles during contraction and at rest. The essence of this method is that an electrical impulse comes from the nerves to the muscles, causing them to contract. The passage of impulses is disturbed in case of violations of the structure of the spinal cord and brain, pathologies of muscle fibers and nerves. With these deviations, the amplitude, duration and number of impulses change, as well as their occurrence at rest.

Needle electromyography can be performed using one of the following methods:

• scanning EMG;
• EMG of the muscle fiber, aimed at the study of a single fiber;
• macro EMG;
• Standard needle electromyography is an invasive procedure in which a needle electrode is inserted into the muscle.

To conduct the study, a special device is needed - an electromyograph that captures impulses with the help of electrodes. The data received from the device is displayed on the monitor, recorded and analyzed by the program. Needle EMG allows the neurologist to determine the cause of the disorder, its degree, localization, based on these data, make a diagnosis and prescribe a set of therapeutic measures.

Needle EMG: indications and contraindications

Needle electromyography is an invasive procedure, so it is characterized by certain indications and contraindications. The possibility of conducting a study is determined by a neurologist on an individual basis for each patient.

Electromyography is performed in the presence of symptoms characteristic of diseases of the musculoskeletal system, the cause of which is damage to nerve fibers, muscles, and impaired motor activity. This study is used to clarify the diagnosis or monitor the effectiveness of treatment.

Needle EMG allows you to establish the causes of the following conditions:

• muscle pain that is not caused by injury or strain;
• fatigue and muscle weakness;
• convulsions;
• a sharp decrease in muscle mass.

There are practically no contraindications to the use of this diagnostic method. A limitation for examining a patient is his unconscious state, when voluntary muscle tension is impossible. Also, needle EMG is undesirable in the presence of pronounced purulent wounds, burns and non-healing ulcers.

If you are looking for a clinic where you can do a needle EMG, contact the Yusupov Hospital. During the consultation, experienced neurologists will determine ways to solve the existing problem and, if necessary, give a referral for research.

Needle electromyography: technique

Special preparation before the procedure is not required. Before the needle electromyography, the subject is not recommended to smoke and eat dishes and products that affect the nervous system, and three days before the study, you should stop taking a number of drugs.

The duration of the procedure is 30-60 minutes. Needle electromyography is performed using an electromyograph, electrodes that are connected to the device by wires, and a computer that records the results. The patient takes a comfortable position in a chair or on a couch. The muscles to be examined must be relaxed. Before applying the electrodes, the doctor treats the required area with an antiseptic.

The doctor first diagnoses impulses that come to the muscles in a relaxed state, then with a slight muscle tension by the patient, as well as with artificial stimulation of their activity. This diagnostic method for some patients is painless. However, in some cases, after the study, discomfort occurs in the muscles, to eliminate which it is recommended to take painkillers or use warm compresses.

Needle electromyography in Moscow is performed at the neurology clinic of the Yusupov hospital. For diagnostics, the clinic uses only modern high-precision equipment that captures even minor impulses. The results of the study are carefully deciphered by experienced neurologists.

Needle electromyography in Moscow

The person who is assigned this study is looking for a medical institution where needle EMG can be done safely and at a good price. The right choice of a neurologist and a clinic for diagnosis and treatment determines the effectiveness of therapy and the quality of human life for several decades. The neurology clinic, which is part of the Yusupov hospital, offers patients to undergo this study.

Each patient who applied to the Yusupov Hospital has access to a wide range of services for the diagnosis, treatment of diseases and rehabilitation. The examination is performed in comfortable rooms using high-precision equipment, since the data obtained significantly affect the diagnosis. There is a widespread opinion that the price of diagnostic needle electromyography in private hospitals is significantly overestimated, but in the neurology clinic its cost is affordable for patients with different financial capabilities.

In the Yusupov Hospital, each patient, in addition to the results of the study, can receive a range of services: a consultation with a neurologist, an individual treatment plan, therapy in comfortable conditions and a respectful attitude of the clinic staff.

Needle electromyography: price

The neurology clinic, located on the territory of the Yusupov Hospital, is a place where experienced neurologists consult clients, use modern diagnostic methods to detect diseases, develop individual treatment programs and help patients recover from illnesses.

Turning to the Yusupov hospital, the patient receives the help of qualified doctors at affordable prices. You can find out the cost of diagnostics, as well as make an appointment by phone.

Electromyography (EMG) is a modern method for diagnosing the activity of muscle tissue. A technique is used to determine the functional abilities of nerves, muscles and soft tissues. With the help of EMG, the degree of damage after injuries is diagnosed or the dynamics of long-term treatment of muscle tissue is determined.

The essence of the method

Electromyography is a research method that determines the localization of possible damage. If the foci of inflammation are in soft tissues, diagnostics using radiography is not carried out: EMG shows the severity of the disease, the characteristic features of damage to muscle tissue and peripheral nerves.

For diagnostics, an apparatus is used - an electromyograph. The device consists of an integral computer system capable of recording certain signals (biopotentials) of muscle tissue. With the help of the device there is an increase in biopotentials, which allows you to determine the degree of damage to soft tissues without a surgical diagnostic operation.

Diodes are attached to the computer system, which register deviations from the norm. With the help of the device, the signal is amplified, and an image is displayed on the screen that displays the state of the muscle tissue and peripheral nerves of the body area under study. Modern devices display the image directly on the monitor, but the old generation electromyograph captures the received impulses on paper.

During normal functioning, a certain muscle impulse is created - it is the change in the impulse (deviation from the norm) that fixes the device during the diagnosis. The doctor analyzes the resulting image, which allows you to identify damage and pathology of muscles or nerves.

Variety of EMG

Modern devices differ in the types of transmission diodes: the range of such details determines the accuracy of the results obtained. 2 types of devices are used for surface and local examination. Global diagnostics takes place in a non-invasive way (non-contact) and allows you to see the activity of muscle tissue over a large area of ​​the body. This type of diagnosis is used in cases where the cause of pain or damage within the muscles is unknown. Examination of a large area allows you to trace the dynamics in the treatment of chronic diseases.

Local EMG is carried out using the contact method: the electrode is inserted directly into the part under study. Previously, the body area is anesthetized and treated with disinfectants. It is a thin needle electrode that makes a minimal puncture. An invasive technique is suitable for examining a small part of muscle tissue.

The choice of technique depends on the prescription of the doctor. The indications for EMG are patient complaints, injuries and injuries that affect walking and human mobility. In some cases, for an accurate diagnosis of the problem, 2 types of EMG are assigned at once: local and global.

The feasibility of an EMG

A safe technique is being carried out to examine a patient who suffers from muscle pain. EMG is used as an independent or auxiliary procedure. Weakness in the muscles and cramps are a common reason for visiting a specialist.

If there are no additional symptoms in the patient, a safe and simple procedure is prescribed by the doctor. EMG is indicated for children and the elderly who find it difficult to move around. It is advisable to conduct electromyography before competitions or heavy physical exertion.

Indications for the procedure

Pain is a direct indication for EMG. Sudden or frequent muscle pain is a warning sign that should be addressed immediately. Intense muscle pain and muscle twitching require additional examination of muscle tissue. With the help of the EMG procedure, the diagnoses are confirmed: myasthenia gravis, myoclonus or amyotrophic sclerosis. Electromyography is prescribed for suspected development of polymitosis.

It is advisable to diagnose muscles in case of loss of their tone (dystonia) or after traumatism of peripheral nerves. Damage to the central nervous system, brain or spine is the reason for a complete examination of muscle tissue using EMG.

Diagnosis is prescribed with the introduction of diodes for suspected multiple sclerosis, for botulism, after poliomyelitis. For facial neuropathy or carpal tunnel syndrome, invasive electromyography is used. Direct appointment to the procedure are diseases: spinal cord herniation or tremor. A pre-EMG is used to safely administer Botox.

The patient is assigned the required number of procedures that do not harm neighboring tissues. The first examination falls on the initial stage of diagnosis before the appointment of treatment. During therapy, EMG is performed repeatedly. For prevention, electromyography is used for adults and children.

Direct contraindications

In total, electromyography is a safe procedure that is prescribed to patients of different sex and age categories. EMG does not harm. Painful sensations during the introduction of diodes are removed with the help of local anesthetics. A diagnostic procedure is allowed even for children with muscle problems.

Contraindications to the procedure:

• infectious diseases with pronounced symptoms;
• noncommunicable chronic diseases;
• epilepsy;
• a disease of the central nervous system that can interfere with the examination of muscle tissue;
• mental disorders (an invasive procedure is especially carefully performed for patients with mental disorders);
• acute heart failure;
• angina;
• the presence of an electrical stimulator;
• skin diseases.

In most cases, contraindications relate to the needle procedure. The technique is not prescribed for patients with diseases that are transmitted through the blood - AIDS, infectious diseases, hepatitis. For people with a blood clotting problem, an EMG is undesirable.

Insertion of the needle occurs with minimal bleeding, but the simple procedure can be a problem for people with platelet dysfunction. Hemophilia is a direct contraindication for invasive diagnostics. Individual pain threshold is a contraindication to EMG.

Possible Complications

EMG is a safe research method. Cautions apply to the healing of the wound, which is formed at the site of the introduction of the diode. The hematoma formed at the puncture site disappears within 10-15 days. After the puncture, the skin does not need additional processing.

If EMG is prescribed in combination with other procedures, the doctor talks about restrictions and warnings after the procedure. In addition, electroneuromyography is prescribed, which allows you to fully assess the degree of damage.

Contraindications to an additional diagnostic method are the same as to electromyography.

Preparing for an EMG

EMG does not need long preparation. Before prescribing the procedure, the features of its implementation are taken into account: before electromyography, psychotropic drugs or medications that affect the functioning of the nervous system are stopped. Before the start of the procedure (a few hours before the EMG), you should not eat or drink energy drinks. Avoid caffeine, chocolate and tea.

If during treatment the patient takes drugs that affect blood clotting, it is necessary to additionally consult with a doctor before the procedure. Any contraindications are taken into account before the start of the diagnosis. For small children, EMG is performed in the presence of parents.

Procedure steps

The procedure is carried out on an inpatient and outpatient basis. During the EMG, the patient should be in comfortable conditions (sitting, standing or lying down). Before the invasive technique, the skin area through which the diode is inserted is treated with an antibacterial agent. Antiseptics are used for processing. The health worker inserts the diode and fixes it for further diagnostics.

During the procedure, the patient experiences slight discomfort - this is how the diodes read the impulses of the muscle tissue. At the beginning of electromyography, the muscle potential is read in a relaxed form: these data will become the basis for the study of muscle tone. At the second stage of the procedure, the patient needs to tighten the muscles: the impulses are re-read.

Results

The results obtained are a snapshot (electronic image). The first condition of the muscle tissue is assessed by a specialist who conducts diagnostics. Based on his conclusion, the attending physician makes an accurate diagnosis and prescribes effective treatment.

The patient himself does not decipher the results of electromyography. The diagnostician does not prescribe further therapy: he assesses the condition of the muscles and nerve nodes located in the part of the body being studied.

An electromyogram looks like a picture of a cardiogram. It consists of oscillations: the amplitude of the oscillations is determined by the state of the human muscle tissue. For the diagnosis, the height and frequency of oscillations are important.

Deciphering the results

Image interpretation begins with the analysis of amplitude fluctuations. Normally (average data), the magnitude of the oscillations is from 100 to 150 μV. The maximum reduction sets the rate equal to 3000 μV. The value of the indicators is determined by the patient's age, muscle tone of the body and lifestyle. The results obtained may be distorted by a large fat layer (obese patients). Poor blood clotting affects the results obtained through diodes.

Reduced amplitude indicates muscle diseases. The lower the indicators obtained, the more severe the degree of neglect of the pathology. At the initial stage, the amplitude decreases to 500 μV, and then to 20 μV - in such cases, the patient needs urgent hospitalization. On local EMG, the indicators may remain within the limiting norm (for such cases, it is advisable to conduct additional examinations).

Rare oscillations indicate pathologies of a toxic or hereditary nature. At the same time, polyphasic potentials are recorded on local electromyography. With a large number of dead fibers, muscle activity is absent. An increase in amplitude (sharp waves) indicates amyotrophy. With the development of myasthenia, the amplitude decreases (after muscle stimulation). Low activity (low amplitude) at the time of exercise indicates the development of myotonic syndrome.

In diseases or lesions of parts of the nervous system, accompanied by impaired transmission of nerve impulses, a person loses the ability to clearly perceive information. When the received data is distorted, the response changes, which causes a loss in the quality of motor movements, leading to a violation of adaptation.

To select the most correct therapeutic path, diagnostics is prescribed that can identify the location and degree of damage to various parts of the nervous system. This method is electroneuromyography (ENMG), which allows you to accurately determine the localization of the pathological process and the nature of the violations. There are two methods of this method - stimulation and needle ENMG, differing in the methods of conducting and the quality of the materials obtained.

ENMG characteristic

To obtain data during the study, an electroneuromyograph is used, a device that captures the slightest reactions of the nervous system, mainly peripheral. This diagnosis allows you to accurately assess the functional status of nerves and muscles that are close to the surface of the skin. During diagnostics, nerve endings are irritated by electrical impulses and these reactions of the muscles innervated by the nerve under study are recorded for study.

ENMG allows:

• find out the speed of the impulse;
• identify the site of nerve damage;
• evaluate the quality of the muscle reaction in response to stimulation;
• fix a decrease in the speed of movement of the impulse and the amplitude of the potential of nerve endings.

Principle of electroneuromyography

Types of electroneuromyography

In modern medicine, two ENMG techniques are used. Stimulation (superficial) - performed by fixing the electrodes on the skin. With this method, the subject does not experience pain and the procedure itself proceeds quickly. The advantages of this method include non-invasiveness, simplicity and speed of execution.

The short duration of exposure and a weak electrical discharge will not harm even patients with an implanted pacemaker, and therefore the method has no restrictions on its use. It also does not bring negative consequences for pregnant women and children.

Needle - for diagnostics, a specially designed electrode in the form of a thin needle is inserted into the muscle. With this method, the patient may feel unpleasant or even painful sensations, but this method is more informative than the previous one - it makes it possible to obtain important materials for studying the activity of particular muscle fibers at rest, as well as in free movement.

Evoked Potentials

According to the principle of electroneuromyography, the potentials of the passage of nerve signals caused by electrical stimuli are studied: visual, auditory and sensorimotor. Visual evoked potentials are a non-invasive method that fixes the reaction to visual stimulation and makes it possible to check the quality of its conduction along the optic nerve to brain formations.

Skin electrodes are placed on the back of the head, and the stimulus is carried out when the subject looks at the monitor screen with white and black squares resembling a chessboard. This stimulus is called in medicine - "chess pattern".

Diagnosis of evoked visual potentials using the "chess pattern"

Auditory evoked potentials - an examination that fixes the electrical potential of the transmission of information from the auditory nerve to the brain as a response to sound stimulation conducted using headphones. This method makes it possible to track disturbances in the functioning of the auditory nerve and the brain. The study of auditory and visual potentials is often used to establish the quality of the prescribed treatment for multiple sclerosis.

Somatosensory evoked potentials (SSEPs) is a technique that captures electrical responses from the upper and lower extremities, head and spine in response to electrical stimulation of sensitive and motor uneven fibers of the arms and legs. This method is used to assess the conduction of the brain and spinal cord, as well as nerve formations in the cervical-brachial and lumbosacral regions.

SSEPs make it possible to study in detail multiple sclerosis, degenerative-dystrophic pathologies of the spine (osteochondrosis) and other diseases of the central and peripheral nervous system.

What pathologies are diagnosed by electromyography?

The list of diseases investigated using electromyography is significant. It is usually required to confirm the following diagnoses:

• Parkinson's disease;
• back injuries and bruises;
• concussions, injuries, bruises of the brain and spinal cord;
• varieties of neuropathies, plexitis and neuritis (metabolic, post-traumatic, toxic, etc.);
• syringomyelia;
• different types of osteochondrosis;
• vibration disease due to occupational factors;
• multiple sclerosis of all kinds;
• muscle diseases (dermatomyositis, myositis, myasthenia gravis, fatigue);
• hereditary pathology (in particular, Charcot-Marie neural amyotrophy);
• residual manifestations of spinal and cerebral microstrokes;
• polyneuropathy.

Electroneuromyography is prescribed for muscle atrophy, the presence of involuntary muscle spasms and impaired motor and sensory function.

ENMG limbs

When studying the nerves of the upper and lower extremities in this way, it is possible to more accurately diagnose such pathologies as:

• damage or compression of nerve endings;
• polyneuropathy of all kinds;
• protrusion of the intervertebral disc;
• osteochondrosis;
• neuritis;
• peripheral neuropathy;
• carpal tunnel syndrome.

Diagnostics allows you to almost accurately determine the inflammatory processes, damage and localization of compression of nerve fibers in the extremities.

Equipped cabinet for ENMG

Additionally, you can check the degree and progress of the recovery process and find out if appropriate medications are required. For the most accurate result, skin electrodes are placed not only at the site of pain in the muscle, but also at points where the nerve endings are closer to the skin.

Contraindications for electroneuromyography

As a rule, there are no recommendations to prohibit this examination. Almost the only contraindications are mental disorders and epilepsy, since with an injection there is a possibility of an attack. Conducting a needle technique for people with immune diseases, as well as HIV, is dangerous for the medical staff themselves due to working with blood and the possibility of infection.

Needle electrodes are also prohibited for use in places with a violation of the integrity of the skin surface, purulent discharge, ulcerative defects, boils and skin diseases. With a pathology associated with a decrease in blood clotting, such an intervention can lead to prolonged bleeding. There are no contraindications for electroneuromyography, and it is allowed to be performed on unconscious patients.

Study preparation

The patient does not need any special preparation for the procedure. But taking certain medications (anticholinergics, muscle relaxants) can affect the received materials. A large weight, in which the skin has a wide fatty layer, and reduced blood clotting can cause unforeseen consequences. Therefore, before the examination, it is necessary to consult a specialist.

Be sure to warn the doctor if there is a history of hemophilia, the patient is taking blood-thinning drugs (Aspirin, Warfarin), or he has a pacemaker.

You may have to replace the drugs or temporarily postpone the intake, take measures to reduce weight, and only then perform this technique. Be sure to stop taking drugs that affect the transmission of nerve impulses for a day. Do not eat for a few hours before the procedure.

If the patient wears contact lenses or glasses, then he must wear them to ensure the acceptance of evoked potentials. Before going to the examination, the patient should take a bath or shower to minimize oily secretions on the skin and not use lotions or creams on the day of the examination.

Carrying out electroneuromyography

The study is conducted within 30-90 minutes. Immediately before the start of the procedure, the subject is informed about all possible sensations during the diagnostic process. The patient is asked to sit or lie down comfortably and try to relax completely. Skin electrodes are attached over the motor point of the examined muscle. The indifferent one is fixed over the tendon, and the leading one is fixed over the belly of the muscle.

Carrying out surface ENMG

Before installing the electrodes, the skin puncture site must be wiped with alcohol, and then a special gel is applied. A ground electrode is attached to the area between the two electrodes responsible for stimulation and regulation. At the beginning of the examination, felt wicks are dipped into an isotonic solution (sodium chloride is used for this). The anode is applied distally, and the cathode is placed above the motor point.

During the examination, a slight tingling or slight pain may be felt, but after the end they completely disappear.

With needle ENMG, electrodes are inserted directly into the muscle. This is a local invasive study and the patient feels pain during the insertion of the electrode. But because of the high information content, this method has to be chosen. The site of the planned puncture is disinfected and treated with specially designed soap, after which the doctor makes a puncture and inserts the needle.

The electrodes are connected to an electroneuromyograph that captures bioelectrical reactions transmitted from particular muscle fibers or a specific muscle. The data is converted into a graph that looks like a cardiogram. They are also fixed on the tape of the device or broadcast on the monitor for quick reference and subsequently printed out.

First, the procedure takes place at rest - the patient is comfortable, relaxes and does not move for a certain time. In this part of the study, spontaneous muscle activity can be recorded, confirming violations of the nervous system, after ENMG is performed with spontaneous slow muscle contraction, as well as with its tone. During the study, surface electrodes can be attached to different muscles, and needle electrodes can be attached to different parts of the same muscle.

Possible complications after electroneuromyography

After applying the needle technique, small hematomas sometimes form in the areas where the electrodes enter, or painful sensations appear. Rarely, but still possible risk of infection. After this examination, the concentration of certain enzymes in the patient's blood may increase.

This is due to a violation of the integrity of the muscle tissue as a result of a puncture and does not appear on the state of the person who underwent the procedure, but when taking blood for biochemistry shortly after ENMG, it should be taken into account. But basically, this examination does not bring painful sensations and negative consequences, but it reliably allows you to determine the presence of pathologies and their features.

ELECTROMYOGRAPHY (EMG, classical EMG) is a method for diagnosing neuromuscular diseases based on the registration of spontaneous fluctuations in the electrical potentials of muscle and nerve fibers.

For the first time EMG recording was carried out in 1907 H. Piper. However, the method became widespread in practice in the 1930s. In 1948, R. Hodes proposed a method for determining the speed of propagation of excitation (ERV) along the motor fibers of peripheral nerves in a clinical setting. In the same year M. Dawson and G. Scott developed a method for determining NRV by afferent fibers of peripheral nerves, which marked the beginning of electroneuromyography.

By total EMG the biopotentials of many motor units are analyzed, forming an interference, or total, curve. According to one of the classifications of total EMG proposed by Yu.S. Yusilevich in the middle of the last century, 4 types are distinguished

1type – EMG with fast, frequent, variable in amplitude potential fluctuations(oscillation frequency 50 - 100 Hz); EMG of this type is recorded normally, and in cases of a decrease in the amplitude of potential fluctuations, it is recorded in patients with various forms of myopathy, radiculoneuritis, and central muscle paresis.

type 2– reduced oscillation frequency on EMG(less than 50 Hz), when individual potential fluctuations are visually well traced, the frequency of which can be less than 10 Hz (type IIA, type "palisade") or higher - up to 35 Hz (type IIB); appears in cases of neuritic and neuronal lesions.

3 type– volleys of frequent oscillations with a duration of 80 - 100 ms(oscillation frequency 4 - 10 Hz), is characteristic of all diseases in which there is an increase in muscle tone according to the extrapyramidal type and violent movements - hyperkinesis.

4 type– "bioelectric silence"- lack of bioelectrical activity of the muscle, despite an attempt to cause voluntary or tonic muscle tension. It is observed in flaccid paralysis in case of damage to all or most of the peripheral motor neurons innervating them.

When conducting an EMG study, the potential in the muscle that occurs during its direct, indirect and reflex stimulation is investigated. In this case, the reaction of the muscle in response to stimulation of the nerve innervating it is more often checked.

Among the electrical responses evoked are:
M-answer- the potential arising from electrical stimulation of the motor fibers of the nerve
H-answer- reflex, arising in the muscle when it is irritated by low-threshold sensory nerve fibers
F-answer- manifested in the muscle during electrical stimulation of the motor axons of the nerve, due to the antidromic conduction of the excitation wave from the site of stimulation to the body of the motor neuron, its excitation and reverse conduction of the excitation wave to the muscle fibers innervated by this motor neuron.

The development of the method and the improvement of diagnostic equipment contributed to the formation of its directions:
1) electromyographic studies proper, that is, registration of spontaneous muscle activity at rest and during various forms of physical activity (global EMG)
2) stimulation electromyography and electroneurography.

The combination of these two trends is often referred to as electroneuromyography .

!!! The most informative was classical EMG with needle electrodes.

Currently, EMG is the main method in the diagnosis of diseases of peripheral motor neurons, nerves, muscles, and neuromuscular transmission.

Method capabilities

EMG allows you to obtain objective information that contributes to the solution of the following issues:
one? - is there damage to the sensory fibers of the nerve
2? - decrease in muscle strength in a patient of a neurogenic nature or is it a primary myopathy?
3? - whether neuromuscular transmission is impaired
four? - Is there a Wallerian degeneration of nerve fibers and is the process of denervation continuing?
5? - if the nerve is damaged, do the axial cylinders of nerve fibers or their myelin sheath mainly suffer?
6? - in the case of neuropathy: is chronic partial muscle denervation associated with damage to the nerve roots, nerve trunk, or is it due to a polyneuropathic process?

!!! Thus, the use of EMG studies makes it possible to identify lesions of the neuromotor apparatus: primary muscular, neural, anterior horn.

This makes it possible to differentiate:
single or multiple neuropathies (mono- and polyneuropathies),
axonal and demyelinating neuropathies
conduct a topical diagnosis of damage to the spinal roots, nerve plexus or peripheral nerve
determine the level of nerve compression in carpal tunnel syndromes
determine the state of neuromuscular transmission

The use of the needle myography method makes it possible to to determine some features of the denervation-reinervation process, which is important for assessing the severity of peripheral nerve damage, prognosis and, accordingly, planning treatment tactics.

!!! Diagnosis should be carried out taking into account the clinical picture of the disease, since changes in the electrical activity of the muscles are associated with certain symptoms, and not with nosological forms.

Methodology

An EMG machine is used to conduct an EMG. electromyograph, consisting of electronic amplifier and recording system(oscilloscope). It provides the ability to amplify muscle biocurrents 1 million times or more and register them in the form of a graphic record. Removal of muscle biopotentials is carried out using surface and needle electrodes

Wherein:
surface electrodes allow to register the total electrical activity of many muscle fibers
needle electrodes, immersed in the muscle, can record the bioelectric potentials of individual motor units (MU) - a concept introduced by C. Sherrington to refer to a complex consisting of a peripheral motor neuron, its axon, branches of this axon and a set of muscle fibers innervated by a motor neuron

EMG analysis takes into account:
frequency of biopotentials
the magnitude of their amplitude (voltage)
the general structure of the oscillograms is the monotonicity of the oscillations or their division into volleys, the frequency and duration of these volleys, etc.

EMG is performed in various conditions of the examined muscles:
during their relaxation and voluntary contraction
with reflex changes in their tone that occur during the contraction of other muscles
during inhalation
with emotional arousal, etc.

In a healthy person:
at rest (with voluntary muscle relaxation), EMG shows weak, low-amplitude (up to 10-15 μV), high-frequency oscillations
reflex increase in tone is accompanied by a slight increase in the amplitude of muscle biopotentials (up to 50-100 μV)
with arbitrary muscle contraction, frequent high-amplitude oscillations occur (up to 1000 - 3000 μV)

At diseases accompanied by denervation of the muscle, the involvement of sensitive nerve fibers in the pathological process makes it possible to differentiate neuropathy from damage to the cells of the anterior horns of the spinal cord. With EMG, it is possible to objectively early (sometimes before the clinical stage) identify dysfunctions of the neuromuscular apparatus, determine the level of its damage (central, segmental, neuropathic, neuromuscular synapses, myopathic), as well as the nature (axonopathy, myelinopathy), degree and stage peripheral nerve damage. Establishing the nature of the neuropathic process is important, as it contributes to the diagnosis of the underlying disease and the development of the most rational treatment program.

If electrodiagnostic data indicate axonopathy, especially in the case of progressive polyneuropathy with a subacute or chronic course, there is reason to consider the presence of metabolic disorders or exogenous intoxication as probable. if, however, primary demyelination of the nerve is detected during electrodiagnosis, among the possible causes of the disease, one should consider acquired demyelinating neuropathy due to impaired immunity, or hereditary neuropathies, some forms of which are accompanied by a uniform and pronounced decrease in the speed of conduction of excitation along the nerves.

EMG also makes it possible to judge state of neuromuscular transmission, contributes to the detection of its violation. In addition, EMG makes it possible to control the regenerative process after traumatic nerve injury, thus helping to decide on the appropriateness of neurosurgical intervention in such cases.

At primary muscle pathology a decrease in the amplitude of biopotentials, a shortening of the duration of a single potential and an increase in the percentage of polyphasic potentials (normally up to 15–20%) are characteristic. With damage to peripheral nerves, a decrease in the amplitude of oscillations occurs, and arrhythmic fibrillation potentials with an amplitude of up to 200 μV may appear. If peripheral paralysis develops with degeneration of nerve and muscle fibers, biopotentials disappear (comes "bioelectric silence")

Damage to the structures of the anterior horns of the spinal cord accompanied by a decrease in the oscillation frequency; fasciculations in such cases are reflected on the graph by rhythmic potentials with an amplitude of up to 300 μV and a frequency of 5–35 Hz - the “palisade rhythm”. With central paresis during voluntary movements, the amplitude of oscillations decreases, while at the same time, with reflex increases in muscle tone, the amplitude of biopotentials increases sharply and frequent non-synchronous oscillations appear.

When researching peripheral nerve function important information can be obtained by determining the speed of impulse conduction and the parameters of evoked action potentials. For this purpose, electroneuromyography is carried out - a method. in which classical EMG is accompanied by electrical stimulation of the peripheral nerve, followed by an analysis of the parameters of evoked potentials recorded from the muscle (stimulation electromyography) or from the nerve innervating it (stimulation electroneurography). At the same time, it is possible to register and analyze the parameters of evoked potentials (EPs) of the muscle and nerve (latent period, shape, amplitude and duration of EPs), determine the speed of impulse conduction along the motor and sensory fibers of peripheral nerves, calculate the motor-sensory and craniocaudal asymmetry coefficients and detect deviations them from the norm, determining the number of functioning motor units (MU).

Methods for determining the speed of impulse conduction are applicable to the study of any accessible peripheral nerve. It is usually defined by middle, ulnar, tibial and peroneal nerves, less often - at the ulnar and sciatic nerves. Electroneuromyography should be performed in the study of the functional state of both motor and sensory fibers. For determining impulse conduction rate (SPI) first, the onset time of the muscle action potential (in milliseconds) is measured when a motor nerve is stimulated near the muscle itself ( latent time– T2– response at the distal point) and at a point located proximal along the nerve at some distance ( latent time– T1 – at the proximal point). Knowing distance between two stimulation points (S) and the difference of latent periods (T1-T2), we can calculate the speed of nerve impulse conduction ( speed of propagation of excitation– Vietnam) according to the formula:

SPI, or SRV, \u003d S / (T1-T2) mm / ms

For most nerves, the normal SPI, or NRV, is 45-60 mm/ms or m/s

At axonal degeneration, for example, with alcoholic or diabetic neuropathy, against the background of pronounced denervation changes, the rate of excitation conduction decreases slightly. In this case, the amplitude of the action potentials of the nerves and muscles progressively decreases as the lesion spreads along the fibers that make up the nerve. With axonal polyneuropathy, its subclinical course, activity and degree of reinnervation can be established.

At segmental demyelination, for example, with Guillain-Barré syndrome, the rate of excitation decreases much more - up to 60% of the norm. From an electrophysiological point of view, demyelination is characterized by other features. These include desynchronization (dispersion) of muscle evoked action potentials, a disproportionate increase in the latent response time at the distal point, slowing of F-responses (action potentials traveling to the spinal cord and returning back to the muscle), and conduction blockade. Conduction blockade is determined by a sudden sharp drop in the amplitude of the evoked muscle action potential when the nerve is stimulated at points at an increasing distance (in the proximal direction) from the recording electrode.

Checking the speed of impulse conduction along the nerve:
mono rate severity of secondary Wallerian degeneration
can be diagnosed and differentiated myotonia from prolonged neuropathic muscle activity
can be analyzed and clearly distinguished muscle spasm from physiological contracture, which is characterized by electrical "silence"

A decrease in the speed of conduction of excitation along individual nerves is a sign mononeuropathies, may be, for example, a manifestation of carpal tunnel syndrome, while a decrease in the speed of conduction along symmetrical nerves in all, or as it happens more often, in the lower extremities indicates the presence of polyneuropathy.

Extrapyramidal hyperkinesis on EMG are characterized by bursts of frequent high-amplitude oscillations that occur against the background of a low-amplitude curve. With myotonia, EMG during movement reveals a characteristic increasing decrease in the amplitude of biopotentials - “myotonic delay”.

Computer processing of the EMG frequency spectrum using the Fourier method is also possible, which makes it possible to determine the total power of the spectrum, the distribution and power of individual frequency bands.

!!! NOTE

During an electrodiagnostic study, it is necessary to record the patient's body temperature

SPNI (speed of nerve impulses) for sensory and motor nerves changes by 2.0-2.4 m/s with a decrease in temperature by 1 °C. These changes can be significant, especially in cold conditions. With borderline results of the study, the following question of the attending physician could be appropriate: "What was the patient's temperature during the study and was the limb warm before measuring CSNI?". Underestimation of the latter position can lead to false positive results and misdiagnosis of carpal tunnel syndrome or generalized sensory motor neuropathy.

The speed of nerve impulse conduction (SPNI) in different parts of the nerve

SPNI differs depending on the nerve and the area of ​​the nerve. Normally, conduction along the proximal parts of the nerve is faster than along the distal parts. This effect is due to a higher temperature in the body, approaching the temperature of the internal organs. In addition, the nerve fibers expand in the proximal part of the nerve. Differences in SPNI are most noticeable in the example of normal values ​​of SPNI for the upper and lower extremities, respectively, 45-75 m/s and 38-55 m/s.

EMG is used to diagnose and predict the course of myasthenia gravis, myotonic dystrophy and Bell's palsy:

Myasthenia gravis - slow re-stimulation of motor nerves with a frequency of 2-3 Hz reveals a decrease in motor response by 10% in 65-85% of patients EMG of a single fiber, which measures the delay in impulse transmission between nerve endings and their corresponding muscle fibers, detects a deviation from the norm in 90 -95% of patients
myotonic dystrophy- PDME on EMG fluctuate in amplitude and frequency and acoustically resemble the sound of an "underwater explosion"
Bell's palsy - SPNI on the facial nerve performed 5 days after the onset of the disease provides prognostic information about the likelihood of recovery If amplitudes and latencies are normal by this time, the prognosis for recovery is excellent

EMG and SIRS are used to diagnose carpal tunnel syndrome and ulnar nerve compression at the elbow joint

carpal tunnel syndrome(CTS) - the most common carpal tunnel syndrome, affecting 1% of the total population SPNI is reduced in 90-95% of patients. Latent period of the action potential of the sensory component median nerve(“palmar retention”) increases twice as often as that of the motor component, although as the disease progresses, the motor latency period also changes. The use of needle EMG has a limited role, but may reveal signs of denervation of the muscles of the eminence of the thumb, which indicates an advanced stage of CTS.
With compression of the ulnar nerve in the area of ​​the elbow joint, SPNI along the motor and sensory nerves is reduced in 60-80% of cases. EMG helps to determine the degree of denervation of the muscles of the hand and forearm innervated by the ulnar nerve.

Welcome, welcome, anyone? ABC of Bodybuilding in touch! And this Friday afternoon we will analyze an unusual topic called electrical muscle activity.

After reading, you will learn what EMG is as a phenomenon, why and for what purposes this process is used, why most studies on the “best” exercises operate on electrical activity data.

So, sit back, it will be interesting.

Electrical activity of muscles: questions and answers

This is the second article in the “Muscle inside” cycle, in the first we talked about, but in general the cycle is devoted to the phenomena and events that take place (may leak) inside the muscles. These notes will allow you to better understand pumping processes and progress faster in improving your physique. Why did we, in fact, decide to talk about the electrical activity of muscles? Everything is very simple. In our technical (and not only) articles, we constantly provide lists of the best exercises, which are formed precisely on the basis of EMG research data.

For almost five years now, we have been informing you of this information, but not once during this time have we revealed the very essence of the phenomenon. Well, today we will fill this gap.

Note:
All further narration on the topic of electrical muscle activity will be divided into subchapters.

What is electromyography? Measurement of muscle activity

EMG is an electrodiagnostic medicine method for assessing and recording electrical activity generated by skeletal muscles. An EMG procedure is performed using an instrument called an electromyograph to create a recording called an electromyogram. An electromyograph detects the electrical potential generated by muscle cells when they are electrically or neurologically activated. To understand the essence of the EMG phenomenon, it is necessary to have an idea about the structure of the muscles and the processes occurring inside.

A muscle is an organized “collection” of muscle fibers (mf), which in turn are made up of groups of components known as myofibrils. In the skeletal system, nerve fibers initiate electrical impulses in the m.v., known as muscle action potentials. They create chemical interactions that activate the contraction of myofibrils. The more activated fibers in the muscle part, the stronger the contraction that the muscle can produce. Muscles can only create force when they contract/shorten. Pulling and pushing force in the musculoskeletal system is generated by the conjugation of muscles that act in an antagonistic pattern: one muscle contracts while the other relaxes. For example, when lifting a dumbbell to the biceps, the biceps of the shoulder muscle contracts / shortens when the projectile is lifted, and the triceps (antagonist) is in a relaxed state.

EMG in various sports

The method of assessing the basic muscle activity that occurs during physical movement has become widespread in many sports, especially fitness and bodybuilding. By measuring the number and magnitude of impulses that occur during muscle activation, one can estimate how much a muscle unit is stimulated to give a particular strength. An electromyogram is a visual illustration of the signals generated during muscle activity. And further in the text we will consider some “portraits” of EMG.

EMG procedure. What does it consist of and where is it carried out?

For the most part, it is possible to measure the electrical activity of muscles only in special research sports laboratories, i.e. specialized institutions. Modern fitness clubs do not provide such an opportunity due to the lack of qualified specialists and low demand from the club's audience.

The procedure itself consists of:

• placement on the human body in a specific area (on or near the studied muscle group) special electrodes connected to a unit that measures electrical impulses;
• recording and transmission of signals to a computer via a wireless EMG data transmission unit from located surface electrodes for subsequent display and analysis.

In the picture version, the EMG procedure is as follows.

Muscle tissue at rest is electrically inactive. When a muscle voluntarily contracts, action potentials begin to appear. As the force of muscle contraction increases, more and more muscle fibers generate action potentials. When the muscle is fully contracted, a random group of action potentials with different speeds and amplitudes should appear. (full set and interference pattern).

Thus, the process of obtaining a picture comes down to the fact that the subject performs a specific exercise according to a specific scheme. (sets/reps/rest), and the devices record the electrical impulses generated by the muscles. Ultimately, the results are displayed on the PC screen in the form of a specific pulse graph.

Purity of EMG results and the concept of MVC

As you probably remember from our technical notes, sometimes we gave different values ​​for the electrical activity of the muscles even for the same exercise. This is due to the subtleties of the procedure itself. In general, the final results are influenced by a number of factors:

• selection of a specific muscle;
• the size of the muscle itself (men and women have different volumes);
• correct electrode placement (in a specific place of the superficial muscle - the belly of the muscle, longitudinal midline);
• body fat percentage (the more fat, the weaker the EMG signal);
• thickness - how strongly the central nervous system generates a signal, how quickly it enters the muscle;
• training experience - how well developed a person is.

Thus, in view of the indicated initial conditions, different studies may give different results.

Note:

More accurate results of muscle activity in a particular movement are given by the intramuscular method of assessment. This is when a needle electrode is inserted through the skin into muscle tissue. The needle is then moved to several points in the relaxed muscle to assess both insertion activity and resting activity in the muscle. By evaluating resting and insertion activity, an electromyograph evaluates muscle activity during voluntary contraction. The shape, size and frequency of the resulting electrical signals are used to judge the degree of activity of a particular muscle.

In an electromyography procedure, one of its main functions is how well a muscle can be activated. The most common method is to perform a maximum voluntary contraction (MVC) of the muscle being tested. It is MVC that, in most studies, is accepted as the most reliable means of analyzing peak strength and force generated by muscles.

However, the most complete picture of muscle activity can be obtained by providing both sets of data. (MVC and ARV are medium) EMG values.

Actually, we figured out the theoretical part of the note, now let's plunge into practice.

Electrical Muscle Activity: The Best Exercises for Each Muscle Group, Research Results

Now we will start collecting bumps :) from our esteemed audience, and all because we will be engaged in a thankless task - proving that a particular exercise is the best for a particular muscle group.

And why it is ungrateful, you will understand in the course of the story.

So, by taking EMG readings during various exercises, we can paint an illustrative picture of the level of activity and arousal within a muscle. This can indicate how effective a particular exercise is at stimulating a particular muscle.

I. Research results (Professor Tudor Bompa, Mauro Di Pasquale, Italy 2014)

The data are presented according to the template, muscle group-exercise-percentage of activation m.v.:

Note:

The percentage value indicates the proportion of activated fibers, a value of 100% means full activation.

No. 1. Latissimus dorsi:

• – 91 ;
• – 89 ;
• – 86 ;
• – 83 .

No. 2. pectoral muscles (large pectoral):

• – 93 ;
• – 87 ;
• – 85 ;
• – 84 .

Number 3. Front Delta:

• standing dumbbell press - 79 ;
• – 73 .

No. 4. Middle/lateral delta:

• lifting straight arms through the sides with dumbbells - 63 ;
• lifting straight arms through the sides on the upper block of the crossover - 47 .

No. 5. Rear Delta:

• dilution of hands in an inclination while standing with dumbbells - 85 ;
• spreading arms in a tilt while standing from the lower block of the crossover - 77 .

No. 6. Biceps (long head):

• curling arms on the Scott bench with dumbbells - 90 ;
• bending arms with dumbbells sitting on a bench at an angle upwards - 88 ;
• (narrow grip) - 86 ;
• – 84 ;
• – 80 .

No. 7. Quadriceps (rectus femoris):

• – 88 ;
• – 86 ;
• – 78 ;
• – 76 .

No. 8. Back surface (biceps) of the thigh:

• – 82 ;
• – 56 .

No. 9. Back surface (semitendinosus muscle) hips:

• – 88 ;
• deadlift on straight legs - 63 .

With respect and gratitude, Dmitry Protasov.