Date: December 11, 2020
`
`To whom it may concern:
`
`This is to certify that the attached translation from Russian and into English is an accurate
`representation of the documents received by this office.
`
`The document is designated as:
`Certified copy of the document that is entitled “Влияние магнитной стимуляции на силовые
`возможности скелетных мышц” in Russian and “EFFECT OF MAGNETIC STIMULATION ON THE
`STRENGTH CAPACITY OF SKELETAL MUSCLES” in English.
`
`Taylor Liff, Project Manager in this company, attests to the following:
`
`“To the best of my knowledge, the aforementioned documents are a true, full and accurate translation
`of the specified documents.”
`
`_________________________________
`Signature of Taylor Liff
`
`www.morningsideIP.com
`
`
` info@morningsideIP.com
`
` The Leader in Global IP Solutions
`
`CERT-05, 2019-Mar-21, V2
`
`LUMENIS EX1028
`Page 1
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`

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`61 15-3/374
`
`FEDERAL STATE BUDGETARY EDUCATIONAL INSTITUTION OF HIGHER
`
`PROFESSIONAL EDUCATION “VELIKIYE LUKI STATE ACADEMY OF PHYSICAL
`
`CULTURE AND SPORT”
`
`As manuscript
`
`[Signature]
`
`ANDREY GENNADIEVICH BELYAEV
`
`EFFECT OF MAGNETIC STIMULATION ON THE STRENGTH CAPACITY OF
`
`SKELETAL MUSCLES
`
`03/03/01 - physiology
`
`Thesis for
`
`PhD in Biological Sciences
`
`The copy is authentic to the
`original.
`
`Academic secretary of the
`Russian State Library
`
`December 10, 2020 [Signature]
`Ivanova Ye.A.
`Seal affixed
`
`Doctoral advisor
`
`Doctor of Biological Sciences,
`
`Professor R.M. Gorodnichev
`
`Velikiye Luki - 2015
`
`LUMENIS EX1028
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`TABLE OF CONTENTS
`
`INTRODUCTION ..................................................................................................................... 4
`
`CHAPTER 1. LITERATURE REVIEW ................................................................................... 9
`
`1.1. General description of muscle strength .................................................................. 9
`
`1.2. Methods to develop muscle strength .................................................................... 18
`
`1.3. Magnetic stimulation in human research .............................................................. 27
`
`CHAPTER 2. ORGANIZATION AND RESEARCH METHODS ........................................ 35
`
`2.1. Population and research organization ................................................................... 35
`
`2.2. Research methods ................................................................................................. 36
`
`2.3. Recording of electromyographic parameters during experiment ......................... 40
`
`2.4. Mathematical statistics methods ........................................................................... 42
`
`CHAPTER 3. ASPECTS OF INDUCED MUSCLE RESPONSES IN MAGNETIC
`
`AND ELECTRIC STIMULATION OF PERIPHERAL NERVE ........................................... 43
`
`3.1. Changes in parameters of induced muscle responses with an increase in
`
`strength with a single magnetic and electrical stimulation of n. tibialis ...................... 44
`
`3.2. Changes in the magnitude of torque with an increase in frequency and
`
`intensity of rhythmic stimulation effects ..................................................................... 50
`
`3.3. Effect of magnetic stimulation on the impulse activity of individual
`
`motor units of m. gastrocnemius ................................................................................. 58
`
`CHAPTER 4. EFFECT OF MAGNETIC STIMULATION ON THE STRENGTH
`
`OF SKELETAL MUSCLES ................................................................................................... 63
`
`4.1. Changes in muscle strength parameters with magnetic stimulation of
`
`muscles ........................................................................................................................ 63
`
`4.2. Dynamics of muscle strength after termination of magnetostimulation
`
`training ......................................................................................................................... 72
`
`CHAPTER 5. RESULTS DISCUSSION ................................................................................ 80
`
`FINDINGS .............................................................................................................................. 89
`
`PRACTICAL RECOMMENDATIONS ................................................................................. 91
`
`LIST OF REFERENCES ....................................................................................................... 92
`
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`ABBREVIATIONS
`
`ATP - adenosine triphosphate;
`
`IMR - induced motor response;
`
`MU - motor unit;
`
`MT - maximum torque;
`
`MP - motor pool;
`
`MVS - maximum voluntary strength;
`
`MS - magnetic stimulation;
`
`RNA - ribonucleic acid;
`
`STH - somatotropic hormone;
`
`T - teslas;
`
`CNS - central nervous system;
`
`EMG - electromyogram;
`
`EMS - electromyostimulation;
`
`ES - electrical stimulation;
`
`GM - gastrocnemius muscle;
`
`SOL - soleus muscle;
`
`TA - tibialis anterior muscle.
`
`
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`LUMENIS EX1028
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`INTRODUCTION
`
`Research relevance. Strength capacity of the human allows for targeted manipulation of
`
`the environment and adaptation of the human body to various living conditions at all stages of
`
`postnatal ontogenesis (A.N. Vorob'yev, 1989; M.L. Foss, S.J. Keteyian, 2008; A.V. Samsonova,
`
`2011; A.A. Chelnokov, 2014). Strength capacity is of particular importance in sports, since the
`
`results in a number of sports are largely determined by the strength capacity of the athlete (V.M.
`
`Zatsiorskiy, 2009; A.I. Netreba et al., 2011).
`
`To date, extensive experimental material has been accumulated on the effectiveness of
`
`various methods and approaches to the development of strength capacity in humans (B.S.
`
`Shenkman et al., 2006; M.N. Stone et al., 2007; V.E. Chursinov, 2011; O.L. Vinogradova et al.,
`
`2014). There is information about the physiological mechanisms underlying the development of
`
`skeletal muscle strength (R.M. Enoka, 1988; Yu.V. Koryagina, 2003; R.M. Gorodnichev, 2005;
`
`B.R. Macintosh et al., 2006; J. Gondin et al., 2014).
`
`A number of studies are devoted to the development of unconventional methods to
`
`increase strength capacity (I.P. Ratov, 1979; V.G. Fedorov, 2010; G. Attene et al., 2014), among
`
`which the most comprehensively described are methodological approaches to the development of
`
`skeletal muscle strength by electrostimulation at rest and during activities requiring muscle
`
`activation (Ya.M. Kots, 1971; G.F. Kolesnikov, 1977; A.A. Nikolaev, 1999; J. Gondin et al.,
`
`2005; U. Doermann et al., 2011).
`
`Electrostimulation muscle strength training has some limitations associated with pain and
`
`discomfort,
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`which is a natural result of electrical irritation. Such disadvantages are not characteristic of high-
`
`intensity magnetic stimulation, which is similar to electrical stimulation according to the
`
`mechanism of excitation of muscle and nerve cells. In this connection, studies have been
`
`conducted to investigate the effect of systematic magnetic stimulation of muscles at rest on the
`
`manifestation of strength capacity in healthy young individuals (R.M. Gorodnichev et al., 2007),
`
`which have demonstrated the effectiveness of magnetostimulation training for skeletal muscle
`
`strength. With this training, it is necessary to act on the muscle with very powerful stimuli,
`
`however the technical capabilities of even the latest magnetic stimulators are limited to
`
`generating only a certain number of intense stimuli. In this regard, and based on literature data, it
`
`seemed justified to study the possibility of modifying strength capacity by a mild magnetic effect
`
`on agonist muscles for a certain activity as it is performed.
`
`Research object - mechanisms by which magnetic muscle stimulation affects functional
`
`properties.
`
`Research subject - dynamics of muscle strength capacity as a result of exposure to
`
`magnetic stimulation.
`
`Hypothesis - it was proposed that high-intensity rhythmic magnetic muscle stimulation,
`
`causing the activation of additional motor units, would contribute to the development of muscle
`
`strength.
`
`Goal of the research was to study the possibility of increasing muscle strength through
`
`rhythmic magnetic stimulation of muscles during their voluntary contraction.
`
`Research objectives:
`
`1. Reveal aspects of reflex muscle responses caused by a single magnetic stimulation of
`
`varying intensity applied to the peripheral nerve.
`
`
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`2. Study the effect of rhythmic magnetic muscle stimulation, differing in the frequency
`
`and intensity of stimuli, on muscle strength capacity.
`
`3. Determine aspects of changes in muscle strength under the effect of magnetic and
`
`electrical stimulation in order to develop an optimal mode of magnetostimulation training to
`
`develop muscle capacity of calf muscles.
`
`4. Investigate change in human strength capacity as a result of a course of high-intensity
`
`rhythmic magnetic stimulation applied to muscles during their contraction.
`
`Scientific novelty. In this work, new information was obtained on the dynamics of reflex
`
`excitability of spinal cord motor neurons with an increase in the intensity of a single magnetic
`
`stimulation of the peripheral nerve. It was shown that the maximum reflex muscle response
`
`caused by high-intensity magnetic exposure is achieved when the threshold is exceeded by a
`
`smaller amount compared to electrical stimulation of the peripheral nerve. A smaller increase in
`
`torque was revealed as a result of an increase in the frequency and intensity of rhythmic
`
`magnetic stimulation of muscles compared to electrical stimulation, and, at the same time, the
`
`absence of pain and discomfort when exposed to magnetic stimuli. For the first time, it was
`
`established that a fifteen-day course of magnetic stimulation of voluntarily contracted skeletal
`
`muscles increases muscle strength capacity, which is reflected in an increase in the torque and an
`
`increase in the magnitude of descending drive to the motor neurons of the spinal cord.
`
`Expectable changes were determined in the parameters of electrical activity of muscles, which
`
`underlie the increase in the force of their contraction as a result of magnetostimulation training.
`
`Theoretical significance. Data obtained in this work expand the modern understanding
`
`of the mechanisms of action of high-intensity
`
`
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`magnetic stimulation on the human body. Information on increase in strength capacity as a result
`
`of magnetostimulation muscle training is important for the development of theoretical ideas
`
`about factors that determine the effectiveness of external stimulation of various nature on the
`
`human neuromuscular apparatus.
`
`Practical significance. The developed methodological approach to increasing muscle
`
`strength as a result of magnetostimulation muscle training complements the spectrum of non-
`
`traditional methods for the development of human motor abilities. Magnetic muscle stimulation
`
`can be used in clinical practice for the rehabilitation of motor functions in patients after injury
`
`and diseases of the spinal cord and skeletal muscles. Data obtained on the dynamics of reflex
`
`muscle response and torque as a result of an increase in the degree and frequency of magnetic
`
`and electrical stimulation of the peripheral nerve and the muscles themselves can be used to
`
`model the targeted effect of strength training programs on the functional status of the muscular
`
`apparatus of athletes.
`
`Main points to be defended:
`
`1. Post-activation effect caused by fifteen-day magnetostimulation training lasts up to 13
`
`days, which is reflected in an increase in both muscle strength and parameters of electrical
`
`activity of agonist muscles during exertion of maximum effort.
`
`2. An increase in muscle strength under the effect of magnetostimulation muscle training
`
`is accompanied by a change in reflex excitability of motor neuronal pools, responsible for the
`
`activation of motor action.
`
`3. Maximum amplitude of reflex muscle response caused by high-intensity magnetic
`
`stimulation and electrical stimulation of the peripheral nerve does not differ significantly, which
`
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`indicates that the number of activated afferent and efferent nerve fibers with both types of
`
`stimulation is about the same.
`
`Work approbation. Based on materials of the dissertation, 9 publications have been
`
`published, including 2 articles in journals included in the list of leading peer-reviewed scientific
`
`journals and publications recommended by the Higher Attestation Commission (HAC) of the
`
`Ministry of Education and Science of the Russian Federation. Research results were reported and
`
`discussed at: VII and VIII All-Russian, with international participation, School-conference on
`
`the physiology of muscles and muscle activity “New Approaches to the Study of Classical
`
`Problems” (Moscow, 2013, 2015); All-Russian scientific-practical conference “Innovative
`
`technologies for improving athletic performance” (Velikiye Luki, 2013); XXII Congress of
`
`Pavlov Physiological Society (Volgograd, 2013); V Russian conference, with international
`
`participation, “Movement control” (Petrozavodsk, 2014).
`
`Results of the study and procedure for assessing strength capacity using magnetic muscle
`
`stimulation are introduced and used in the sports and health center “Strelets” OOO “Gazprom
`
`transgaz Saint Petersburg” - Pskov Linear Production Management of Main Gas Pipelines,
`
`municipal autonomous educational institution of supplementary education for children “Children
`
`and Youth Sports School No. 2 “Express”.
`
`Structure and scope of thesis. Thesis, 115 pages of printed text, consists of an
`
`introduction and 5 chapters, including literature review, description of research methods,
`
`presentation of results of own research and their discussion, findings, practical recommendations,
`
`list of references and two implementation acts. The work contains 13 figures and 12 tables.
`
`References include 196 literary sources (107 domestic, 89 foreign).
`
`
`
`LUMENIS EX1028
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`

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`CHAPTER 1. LITERATURE REVIEW
`
`1.1. General description of muscle strength
`
`Strength capacity of a person is essential in their daily and work activities. High strength
`
`capacity is especially important for achieving high results in many athletics pursuits (Yu.V.
`
`Verkhoshansky, 1993; V.N. Platonov, 2004; A.A. Vasilenko, 2006). Strength is understood as a
`
`person’s ability to overcome external resistance or counteract it with muscle activity (V.M.
`
`Zatsiorskiy, 2009). Physiology distinguishes absolute and relative muscle strength (P.V. Komi,
`
`1986; S.Yu. Bershitsskiy, 2005). Absolute strength is the ratio of the maximum muscle strength
`
`to the physiological diameter of the muscle (cross-sectional area of all muscle fibers). It is
`
`measured in newtons or kilograms of force per 1 cm2 (N/cm2 or kg/cm2). Ratio of the maximum
`
`muscle strength to its anatomical diameter - thickness as a whole, as determined by the number
`
`and thickness of individual muscle fibers - is called relative strength. It is measured in the same
`
`units. To compare strength capacity of people of different body weight, it is common to calculate
`
`the magnitude of force per 1 kg of their own weight (V.V. Kuznetsov, 1975; Yu.V. Koryagina,
`
`2003; A.N. Khorunzhiy, 2007; R.N. Dorokhov et al., 2009).
`
`Bodily strength is manifested in various types of muscle contractions: isometric,
`
`concentric, eccentric and isokinetic (N.P. Anisimova, 1980; D.Yu. Bravaya, 1985; T.L.
`
`Nemirovskaya, 2003; N.M. Tarbeeva, 2013). Isometric contraction of a muscle
`
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`generates force without a change in muscle length. Concentric contraction is a contraction in
`
`which the muscle shortens when the external force is less than the force generated by the muscle.
`
`Eccentric contraction is a contraction in which the muscle is lengthened when the external force
`
`is greater than the force generated by the muscle. This type of muscle contraction generates the
`
`greatest force compared to other types of muscle contraction. Isokinetic contraction is a
`
`contraction that changes articular angle at a constant speed with compensation for changing
`
`muscle tension by regulation of external resistance. Such contraction is achieved only by using
`
`special force measuring devices. To ensure a constant speed of movement, the external resistance
`
`is increased in those articular angles where the muscle can generate significant tension and,
`
`conversely, the resistance is decreased in those angles where the muscle generates less tension
`
`(A.A. Skurvidas, 1988; R.M. Gorodnichev, 2005; S.A. Moiseev, 2010).
`
`Muscle strength of a person is determined during voluntary effort exerted by the person,
`
`the desire to contract muscles of interest as much as possible (Yu. Grishina, 2012). This is a
`
`condition for the development of the maximum voluntary strength (MVS). When considering
`
`strength capacity as a motor quality of a person, it is common to distinguish the following types
`
`of strength: static strength capacity and speed strength capacity (V.M. Zatsiorsky, 2009). Static
`
`strength capacity is manifested during static exertion or slow movements (V.N. Platonov, 2004).
`
`Speed strength capacity is understood as the ability of a person to generate maximum force in the
`
`shortest possible time (D.V. Popov et al., 2004)). It can be achieved by increasing the force
`
`generated or speed of muscle contraction, or both. Usually, the greatest gain is achieved by
`
`increasing muscle strength. A variation of speed strength capacity is called “explosive force” (V.
`
`Rodionov, 1966; A.V. Faleev, 2006). This term is used to denote the ability to achieve maximum
`
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`apparent force during movement in the shortest time possible. In explosive force it is not so
`
`much the magnitude of the force that is important as its increase over time, i.e. force gradient.
`
`The success of speed strength exercises is the higher, the shorter the duration of gain in force to
`
`its maximum value. Reactive muscle properties are distinguished as a specific factor of certain
`
`abilities constituting speed strength capacity of an athlete. They are manifested in movements
`
`that include instant change from the surrendering (in the direction of external force) to
`
`overcoming (against the direction of external force) mode of muscle function and are
`
`characterized by the fact that the magnitude of resisting force is significantly increased under the
`
`effect of preliminary quick “forced” stretching of muscles due to kinetic energy of the moving
`
`mass (E.A. Shirkovets, 2003).
`
`Maximum voluntary strength depends on muscle (peripheral) and coordination (central
`
`nervous) factors (Ya.M. Kots, 1986). Muscle (peripheral) factors that determine maximum
`
`voluntary strength include the following: 1) muscle length, since the force generated by the
`
`muscle depends on its length; 2) muscle exertion conditions - lever arm for the muscle force and
`
`angle of force applied to bone levers; 3) physiological diameter of contracting muscles, due to
`
`the fact that, all other things being equal, the force developed by the muscle is the greater, the
`
`larger its diameter; 4) the ratio of fast- and slow-twitch muscle fibers in contracting muscles,
`
`since the apparent muscle strength is the greater, the greater the number fast-twitch fibers in the
`
`contracting muscle (P.D. Gollnick, 1981; Е.А. Kos’mina, 2012).
`
`Coordination (central nervous) factors include a set of central nervous mechanisms for
`
`controlling the muscular apparatus - mechanisms of coordination of individual motor units (MU)
`
`and mechanisms of intermuscular coordination. Structural and functional organization of the
`
`neural networks of the brain and spinal cord ensures
`
`
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`interconnection between these two mechanisms. Mechanisms of coordination of activity of MU
`
`determine the number and frequency of nerve impulses entering the skeletal muscles from the
`
`motor neurons of the spinal cord and thereby ensure the transition from weak single contractions
`
`of their fibers to powerful tetanic contraction. Using these mechanisms, it is possible to achieve
`
`the maximum voluntary strength. MVS of an individual human skeletal muscle depends on the
`
`contraction force of other muscles. Maximum strength of an individual muscle is generated only
`
`under the condition of perfect intermuscular coordination that ensures the optimal choice of
`
`synergist muscles, decreases the activity of antagonist muscles and increases the activity of the
`
`muscles that fix the adjacent joints involved in the movement (Yu.S. Saplinskas, 1990; V.N.
`
`Popenko, 1994; V.N. Kurys’, 2004).
`
`It should be emphasized that the muscle control, when it is necessary to achieve the
`
`maximum voluntary strength, is a difficult task for the central nervous system. Therefore, under
`
`normal conditions, MVS of muscles is smaller in comparison with the effort developed in
`
`response to tetanic electrical stimulation of the muscles themselves. The difference between
`
`MVS and strength due to electrostimulation is called strength deficit (Ya.M. Kots, 1986).
`
`The better the central control of the muscular apparatus, the smaller the strength deficit of
`
`a given muscle group. How big the strength deficit depends on: psychological, emotional status
`
`of the subject; number of simultaneously activated muscle groups; skill of controlling muscles
`
`involved in the movement (Ya.M. Kots, 1986; M.H. Stone et al., 2007; D.J. Kidgell et al., 2010).
`
`To solve motor tasks that require different exertion of muscle strength, the following
`
`three mechanisms are used:
`
`1) regulation of the number of active MU;
`
`2) regulation of impulse frequency of motor neurons;
`
`
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`3) synchronization of the activity of individual MU in time (V.S.Gurfinkel, Yu.S. Levik,
`
`1985; R.M. Enoka, 1988).
`
`1. Number of motor units. Since each muscle is innervated by many motor neurons with
`
`different recruitment thresholds, changing the number of active motor neurons (MU) is an
`
`important way to regulate the strength of muscle contraction. The greater the number of active
`
`MU, the greater the generated muscle strength.
`
`In the early 30s of the last century, it was found that small motor neurons that innervate
`
`slow muscles are activated more easily than larger motor neurons that make up fast MU. The
`
`question of the order of MU recruitment was investigated most fully by E. Henneman, who
`
`proved the invariability and stereotype nature of the order of MU activation depending on the
`
`size of their motor neurons (E. Henneman, 1957). As the intensity of excitation of motor neurons
`
`from the central motor structures and peripheral receptors is increased, slow, small MU are
`
`activated the first. As the intensity of excitation is further increased, fast, fatigue-resistant MU
`
`are involved. Fast, easily fatigued MU are activated last, when the force of contraction reaches
`
`20-25 percent of the maximum.
`
`Therefore, the order of activation of MU is determined by the intrinsic property of their
`
`motor neurons such as the size: the smaller the size of the motor neuron, the lower the threshold
`
`for its activation (recruitment). This principle of activation of motor neurons is called
`
`Henneman’s size principle. According to this principle, the smallest MU of the muscle are active
`
`with any contraction, while the large, fast MU that make up the muscle are active only with the
`
`greatest effort. Therefore, in the same muscle, the degree of use of large, fast MU compared to
`
`small, slow MU is smaller (R.M. Enoka, 1998).
`
`
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`The intensity of excitation of motor neurons of a given muscle depends on the nature of
`
`the motor task at hand (L.P. Kudina, 1983; A.Dzh. Mak-Komas, 2001). If, during a certain
`
`movement, the muscle must develop a small force, then a weak stream of nerve impulses is
`
`delivered to its motor neurons. Due to the fact that all muscles include both fast and slow MU,
`
`which differ in the size of their motor neurons, the MU response to this stream of nerve impulses
`
`is different. Only slow MU, which have small motor neuron size and, consequently, low
`
`recruitment thresholds, are activated. In this case, fast MU in this muscle are not activated.
`
`Therefore, the range of weak muscle movements is affected by the activity of only slow, fatigue-
`
`resistant MU (type S).
`
`When performing a movement that requires a large contraction force of a given muscle,
`
`its motor neurons receive a more intense flow of nerve impulses (R.S. Persson, 1976). This leads
`
`to an increase in the number of activated MU. In addition to slow, low-threshold MU, fast high-
`
`threshold MU are also activated. The greater the intensity of excitation of motor neurons, the
`
`larger MU are activated. Consequently, a large force of muscle contraction is affected by the
`
`activity of all three types of MU (S, FR, FF).
`
`2. Impulse frequency of motor neurons. In case of weak contraction of skeletal muscles,
`
`impulse frequency is 5-10 Hz. In this frequency range, even the slow MU of most muscles are
`
`activated as unfused tetanic contractions or even single contractions. The smooth nature of
`
`contraction of the entire muscle under these conditions is ensued by asynchronous activity of
`
`different MU.
`
`As the magnitude of muscle contraction is increased, MU impulse frequency is also
`
`increased (I.I. Yashchaninas, 1983). When the magnitude of contraction is equal to 30-60% of
`
`the maximum, MU impulse frequency reaches 20-30 Hz, while in the case of
`
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`maximum contraction it reaches 50 Hz. During short-term bursts of activity, recorded at the
`
`beginning of a very fast and strong contraction, instantaneous impulse frequency reaches 90 Hz
`
`or even 120 Hz. The above facts prove that a mechanism for regulation of MU impulse
`
`frequency participates in the regulation of muscle contraction. The higher (up to a certain limit)
`
`the frequency of impulses of an individual MU, the greater contractile force of its muscle fibers
`
`and the greater its contribution to the force generated by the entire muscle. Each individual MU
`
`is characterized by a certain frequency of impulses at which the strength capacity of all its
`
`muscle fibers are realized in full. Regulation of contractile force of a muscle by a change in MU
`
`impulse frequency is most pronounced in fast MU.
`
`Frequency of excitation of an individual MU is determined by the intensity of descending
`
`flow of nerve impulses affecting the motor neuron of this MU. If the intensity of excitation is
`
`low, then only low-threshold slow MU are activated, which receive impulses with a relatively
`
`low frequency, sufficient to ensure unfused tetanic contractions and single contractions. Such
`
`MU impulse frequency is sufficient to ensure muscle contraction of moderate intensity for a
`
`prolonged time. It is in this range that MU of skeletal muscles work when maintaining an upright
`
`body posture.
`
`Increase in intensity of muscle contraction is achieved by increasing intensity of
`
`excitation of its motor neurons. In this case, high-threshold fast MU are activated, whose impulse
`
`frequency is increased with an increase in the intensity of the flow of nerve impulses to the
`
`motor neurons of these MU (B. Calancie et al., 1987). Maximum contractile force of a muscle is
`
`achieved when the impulse frequency in most high-threshold fast MU effects fused tetanic
`
`contractions of their muscle fibers. The time period during which such contractions can be
`
`maintained is not long.
`
`
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`Determination of the relative role of mechanisms of recruitment and increase in MU
`
`impulse frequency with increase in muscle effort requires knowledge of the maximum
`
`capabilities of each of them. Comparison of the force of muscle contraction at the lowest
`
`pulsation frequency of their MU (average force of unfused tetanic contractions) with the force
`
`generated with high impulse frequency (fused tetanic contractions) showed that the latter is
`
`several times higher. Consequently, recruitment of all MU at a low impulse frequency results in
`
`a smaller increase in strength compared to the increase resulting from frequency increase. This
`
`means that when it comes to the generation of contractile force, the potential of the frequency
`
`mechanism is greater than that of the recruitment mechanism. In different force ranges and under
`
`different contraction conditions, it is possible to use both mechanisms in parallel to increase the
`
`strength of muscle contraction as well as predominantly one of them. Under real conditions of
`
`human muscle exertion, most MU are activated in the range from 0% to 50% of the maximum
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`contractile force, after which only a small (about 10%) number of the most high-threshold MU
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`are activated, and an increase in strength from 75% to 100% is achieved exclusively due to the
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`gain in impulse frequency (A.A. Gidikov, 1975; R.S. Persson, 1985; V.S. Gurfinkel, Yu.S.
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`Levik, 1985; D.A. Petrov, 2001).
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`3. Synchronization of contraction of muscle fibers of individual MU in time. Muscle
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`contraction always involves activation of several or many MU. The nature of the temporal
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`relationship of the activity of various MU to a certain extent affects the intensity of muscle
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`contraction. Coincidence of individual impulses of two or more MU in time is called
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`synchronization (R.S. Persson, 1985; M.L. Foss, S.J. Keteyian, 2008). Let us consider the effect
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`of synchronization on the contractile force using three MU as an example. If each of the three
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`MU contracts synchronously with other as single contraction, then the contraction of muscle
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`fibers of each MU coincides with the contraction of other MU. Therefore, contractions of three
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`LUMENIS EX1028
`Page 17
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`MU overlap. The contractions of individual MU are summed up and the muscle generate a
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`comparatively large force. In contrast, if three MU contract asynchronously, then no summation
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`takes place and the muscle develops smaller force. In the first case, there are significant
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`fluctuations in the force of muscle contraction, in the second case they are significantly smaller.
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`This example demonstrates that when MU are activated as single contractions, the asynchronous
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`nature of their activity ensures smooth contraction of the entire muscle. An increase in the
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`number of asynchronous MU leads to a decrease in fluctuations in muscle tension, which
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`contributes to a smoother execution and maintenance of a certain position. Under regular
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`everyday conditions, most MU work asynchronously. This helps to achieve smooth contraction
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`of muscles under conditions where muscles fibers of MU, due to low impulse frequency of motor
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`neurons, are activated as single contractions or unfused tetanic contractions.
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`Normal temporal relationship of the activity of muscle fibers of individual MU is
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`disrupted during muscle fatigue. This is manifested as periodic grouping (“thickening”) of
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`impulses of different MU. Under such conditions, the smoothness and accuracy of the movement
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`is lost and a fatigue tremor follows: trembling movements with a relatively large amplitude
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`(Yu.S. Saplinskas, I.I. Yashchaninas, 1980; D. Kozarov, Yu.T. Shapkov, 1983; Yu.T. Shapkov,
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`1984).
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`If MU are activated as fused tetanic contractions, the nature of their temporal relationship
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`does not have any significant effect on the magnitude of static effort generated by the muscle.
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`This is due to the fact that in the case of fused tetanic contractions, the contractile force of each
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`working MU is maintained at an almost constant level. Therefore, with relatively long-lasting
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`and strong muscle contractions, the nature of temporal relationship of impulse activity of
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`different MU has no effect on the maximum muscle effort (R.M. Gorodnichev, 2005).
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`LUMENIS EX1028
`Page 18
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`Synchronization of MU activity plays an important role during quick contractions or at
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`the first moment of any contraction, since it affects the rate of contraction. Naturally, the more
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`the contractile cycles of different MU coincide at the start of muscle contraction, the faster it
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`develops. At the beginning of execution of quick movements to overcome significant external
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`resistance, there is usually pronounced synchronization