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Influence of motor unit synchronization on amplitude characteristics of surface and intramuscularly recorded EMG signals

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Abstract

The increase in muscle strength without noticeable hypertrophic adaptations is very important in some sports. Motor unit (MU) synchronisation and higher rate of MU activation are proposed as possible mechanisms for such a strength and electromyogram (EMG) increase in the early phase of a training regimen. Root mean square and/or integrated EMG are amplitude measures commonly used to estimate the adaptive changes in efferent neural drive. EMG amplitude characteristics could change also because of alteration in intracellular action potential (IAP) spatial profile. We simulated MUs synchronization under different length of the IAP profile. Different synchronization was simulated by variation of the percent of discharges in a referent MU, to which a variable percent of remaining MUs was synchronized. Population synchrony index estimated the degree of MU synchronization in EMG signals. We demonstrate that the increase in amplitude characteristics due to MU synchronization is stronger in surface than in intramuscularly detected EMG signals. However, the effect of IAP profile lengthening on surface detected EMG signals could be much stronger than that of MU synchronization. Thus, changes in amplitude characteristics of surface detected EMG signals with progressive strength training could hardly be used as an indicator of changes in neural drive without testing possible changes in IAPs.

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References

  • Aagaard P, Simonsen EB, Andersen JL et al (2002) Increased rate of force development and neural drive of human skeletal muscle following resistance training. J Appl Physiol 93:1318–1326

    PubMed  Google Scholar 

  • Arabadzhiev TI, Dimitrov GV, Dimitrova NA (2005) Simulation analysis of the performance of a novel high sensitive spectral index for quantifying M-wave changes during fatigue. J Electromyogr Kinesiol 15:149–158

    Article  CAS  PubMed  Google Scholar 

  • Arabadzhiev TI, Dimitrov GV, Chakarov VE et al (2008a) Effects of changes in intracellular action potential on potentials recorded by single-fiber, macro, and belly-tendon electrodes. Muscle Nerve 37:700–712

    Article  PubMed  Google Scholar 

  • Arabadzhiev TI, Dimitrov GV, Dimitrov AG et al (2008b) Factors affecting the turns analysis of the interference EMG signal. Biomed Signal Process Control 3:145–153

    Article  Google Scholar 

  • Arabadzhiev TI, Dimitrov VG, Dimitrova NA et al (2009) Interpretation of EMG integral or RMS and estimates of “neuromuscular efficiency” can be misleading in fatiguing contraction. J Electromyogr Kinesiol (in press). doi:10.1016/j.jelekin.2009.01.008

  • Bernasconi S, Tordi N, Perrey S et al (2006) Is the VO2 slow component in heavy arm-cranking exercise associated with recruitment of type II muscle fibers as assessed by an increase in surface EMG? Appl Physiol Nutr Metab 31:414–422

    Article  PubMed  Google Scholar 

  • Bigland-Ritchie BR (1995) Looking back. Adv Exp Med Biol 384:1–9

    CAS  PubMed  Google Scholar 

  • Boonstra TW, Daffertshofer A, Van Ditshuizen JC et al (2008) Fatigue-related changes in motor-unit synchronization of quadriceps muscles within and across legs. J Electromyogr Kinesiol 18:717–731

    Article  CAS  PubMed  Google Scholar 

  • Burnley M, Doust JH, Ball D et al (2002) Effects of prior heavy exercise on VO(2) kinetics during heavy exercise are related to changes in muscle activity. J Appl Physiol 93:167–174

    PubMed  Google Scholar 

  • Dartnall TJ, Nordstrom MA, Semmler JG (2008) Motor unit synchronization is increased in biceps brachii after exercise-induced damage to elbow flexor muscles. J Neurophysiol 99:1008–1019

    Article  PubMed  Google Scholar 

  • Day JR, Rossiter HB, Coats EM et al (2003) The maximally attainable VO2 during exercise in humans: the peak vs. maximum issue. J Appl Physiol 95:1901–1907

    CAS  PubMed  Google Scholar 

  • De Luca CJ (1979) Physiology and mathematics of myoelectric signals. IEEE Trans Biomed Eng 26:313–325

    Article  PubMed  Google Scholar 

  • De Luca CJ (1984) Myoelectrical manifestations of localized muscular fatigue in humans. Crit Rev Biomed Eng 11:251–279

    PubMed  Google Scholar 

  • Del Balso C, Cafarelli E (2007) Adaptations in the activation of human skeletal muscle induced by short-term isometric resistance training. J Appl Physiol 103:402–411

    Article  PubMed  Google Scholar 

  • Deschenes MR, Giles JA, Mccoy RW et al (2002) Neural factors account for strength decrements observed after short-term muscle unloading. Am J Physiol Regul Integr Comp Physiol 282:R578–R583

    CAS  PubMed  Google Scholar 

  • Dimitrov GV, Dimitrova NA (1977) Bipolar recording of potentials generated by excitable fibres in a volume conductor. Agressologie 18:235–252

    CAS  PubMed  Google Scholar 

  • Dimitrov GV, Dimitrova NA (1979) Influence of the afterpotentials on the shape and magnitude of the extracellular potentials generated under activation of excitable fibres. Electromyogr Clin Neurophysiol 19:249–267

    CAS  PubMed  Google Scholar 

  • Dimitrov GV, Dimitrova NA (1998) Precise and fast calculation of the motor unit potentials detected by a point and rectangular plate electrode. Med Eng Phys 20:374–381

    Article  CAS  PubMed  Google Scholar 

  • Dimitrov GV, Arabadzhiev TI, Mileva KN et al (2006) Muscle fatigue during dynamic contractions assessed by new spectral indices. Med Sci Sports Exerc 38:1971–1979

    Article  PubMed  Google Scholar 

  • Dimitrov GV, Arabadzhiev TI, Hogrel JY et al (2008) Simulation analysis of interference EMG during fatiguing voluntary contractions. Part II—changes in amplitude and spectral characteristics. J Electromyogr Kinesiol 18:35–43

    Article  CAS  PubMed  Google Scholar 

  • Dimitrova N (1973) Influence of the length of the depolarized zone on the extracellular potential field of a single unmyelinated nerve fibre. Electromyogr Clin Neurophysiol 13:547–558

    CAS  PubMed  Google Scholar 

  • Dimitrova NA, Dimitrov GV (2002) Amplitude-related characteristics of motor unit and M-wave potentials during fatigue. A simulation study using literature data on intracellular potential changes found in vitro. J Electromyogr Kinesiol 12:339–349

    Article  CAS  PubMed  Google Scholar 

  • Dimitrova NA, Dimitrov GV (2003) Interpretation of EMG changes with fatigue: facts, pitfalls, and fallacies. J Electromyogr Kinesiol 13:13–36

    Article  CAS  PubMed  Google Scholar 

  • Dimitrova NA, Dimitrov GV (2006) Electromyography (EMG) modeling. In: Metin A (ed) Wiley encyclopedia of biomedical engineering. Wiley, Hoboken

    Google Scholar 

  • Dimitrova NA, Hogrel JY, Arabadzhiev TI et al (2005) Estimate of M-wave changes in human biceps brachii during continuous stimulation. J Electromyogr Kinesiol 15:341–348

    Article  CAS  PubMed  Google Scholar 

  • Dimitrova NA, Arabadzhiev TI, Hogrel JY et al (2009) Fatigue analysis of interference EMG signals obtained from biceps brachii during isometric voluntary contraction at various force levels. J Electromyogr Kinesiol 19:252–258

    Article  CAS  PubMed  Google Scholar 

  • Doherty M, Nobbs L, Noakes TD (2003) Low frequency of the “plateau phenomenon” during maximal exercise in elite British athletes. Eur J Appl Physiol 89:619–623

    Article  CAS  PubMed  Google Scholar 

  • Duchateau J, Semmler JG, Enoka RM (2006) Training adaptations in the behavior of human motor units. J Appl Physiol 101:1766–1775

    Article  PubMed  Google Scholar 

  • Edwards RH (1981) Human muscle function and fatigue. Ciba Found Symp 82:1–18

    CAS  PubMed  Google Scholar 

  • Edwards RG, Lippold OC (1956) The relation between force and integrated electrical activity in fatigued muscle. J Physiol 132:677–681

    CAS  PubMed  Google Scholar 

  • Farina D, Merletti R, Enoka RM (2004) The extraction of neural strategies from the surface EMG. J Appl Physiol 96:1486–1495

    Article  PubMed  Google Scholar 

  • Folland JP, Williams AG (2007) The adaptations to strength training : morphological and neurological contributions to increased strength. Sports Med 37:145–168

    Article  PubMed  Google Scholar 

  • Gabriel DA, Kamen G, Frost G (2006) Neural adaptations to resistive exercise: mechanisms and recommendations for training practices. Sports Med 36:133–149

    Article  PubMed  Google Scholar 

  • Garland SW, Wang W, Ward SA (2006) Indices of electromyographic activity and the “slow” component of oxygen uptake kinetics during high-intensity knee-extension exercise in humans. Eur J Appl Physiol 97:413–423

    Article  PubMed  Google Scholar 

  • Hakkinen K, Komi PV (1983) Electromyographic changes during strength training and detraining. Med Sci Sports Exerc 15:455–460

    CAS  PubMed  Google Scholar 

  • Hakkinen K, Kallinen M, Izquierdo M et al (1998) Changes in agonist–antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people. J Appl Physiol 84:1341–1349

    CAS  PubMed  Google Scholar 

  • Häkkinen A, Häkkinen K, Hannonen P et al (2001a) Strength training induced adaptations in neuromuscular function of premenopausal women with fibromyalgia: comparison with healthy women. Ann Rheum Dis 60:21–26

    Article  PubMed  Google Scholar 

  • Häkkinen K, Kraemer WJ, Newton RU et al (2001b) Changes in electromyographic activity, muscle fibre and force production characteristics during heavy resistance/power strength training in middle-aged and older men and women. Acta Physiol Scand 171:51–62

    Article  PubMed  Google Scholar 

  • Häkkinen K, Alen M, Kraemer WJ et al (2003) Neuromuscular adaptations during concurrent strength and endurance training versus strength training. Eur J Appl Physiol 89:42–52

    Article  PubMed  Google Scholar 

  • Hanson J, Persson A (1971) Changes in the action potential and contraction of isolated frog muscle after repetitive stimulation. Acta Physiol Scand 81:340–348

    Article  CAS  PubMed  Google Scholar 

  • Holtermann A, Roeleveld K, Vereijken B et al (2005) Changes in agonist EMG activation level during MVC cannot explain early strength improvement. Eur J Appl Physiol 94:593–601

    Article  PubMed  Google Scholar 

  • Holtermann A, Gronlund C, Karlsson JS et al (2009) Motor unit synchronization during fatigue: described with a novel sEMG method based on large motor unit samples. J Electromyogr Kinesiol 19:232–241

    Article  CAS  PubMed  Google Scholar 

  • Jones DA (1992) Strength of skeletal muscle and the effects of training. Br Med Bull 48:592–604

    CAS  PubMed  Google Scholar 

  • Jones DA, Rutherford OM, Parker DF (1989) Physiological changes in skeletal muscle as a result of strength training. Q J Exp Physiol 74:233–256

    CAS  PubMed  Google Scholar 

  • Kleine BU, Stegeman DF, Mund D et al (2001) Influence of motoneuron firing synchronization on SEMG characteristics in dependence of electrode position. J Appl Physiol 91:1588–1599

    CAS  PubMed  Google Scholar 

  • Lucia A, Sanchez O, Carvajal A et al (1999) Analysis of the aerobic-anaerobic transition in elite cyclists during incremental exercise with the use of electromyography. Br J Sports Med 33:178–185

    Article  CAS  PubMed  Google Scholar 

  • Milner-Brown HS, Stein RB, Lee RG (1975) Synchronization of human motor units: possible roles of exercise and supraspinal reflexes. Electroencephalogr Clin Neurophysiol 38:245–254

    Article  CAS  PubMed  Google Scholar 

  • Moore DR, Burgomaster KA, Schofield LM et al (2004) Neuromuscular adaptations in human muscle following low intensity resistance training with vascular occlusion. Eur J Appl Physiol 92:399–406

    Article  PubMed  Google Scholar 

  • Mori S (1973) Discharge patterns of soleus motor units with associated changes in force exerted by foot during quiet stance in man. J Neurophysiol 36:458–471

    CAS  PubMed  Google Scholar 

  • Moritani T, Devries HA (1979) Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med 58:115–130

    CAS  PubMed  Google Scholar 

  • Nandedkar S, Stålberg E (1983) Simulation of macro EMG motor unit potentials. Electroencephalogr Clin Neurophysiol 56:52–62

    Article  CAS  PubMed  Google Scholar 

  • Narici MV, Roi GS, Landoni L et al (1989) Changes in force, cross-sectional area and neural activation during strength training and detraining of the human quadriceps. Eur J Appl Physiol Occup Physiol 59:310–319

    Article  CAS  PubMed  Google Scholar 

  • Nordstrom MA, Miles TS, Turker KS (1990) Synchronization of motor units in human masseter during a prolonged isometric contraction. J Physiol 426:409–421

    CAS  PubMed  Google Scholar 

  • Nordstrom MA, Fuglevand AJ, Enoka RM (1992) Estimating the strength of common input to human motoneurons from the cross-correlogram. J Physiol 453:547–574

    CAS  PubMed  Google Scholar 

  • Onambele GL, Maganaris CN, Mian OS et al (2008) Neuromuscular and balance responses to flywheel inertial versus weight training in older persons. J Biomech 41:3133–3138

    Article  PubMed  Google Scholar 

  • Osborne MA, Schneider DA (2006) Muscle glycogen reduction in man: relationship between surface EMG activity and oxygen uptake kinetics during heavy exercise. Exp Physiol 91:179–189

    Article  CAS  PubMed  Google Scholar 

  • Sale DG (1988) Neural adaptation to resistance training. Med Sci Sports Exerc 20:S135–S145

    Article  CAS  PubMed  Google Scholar 

  • Saunders MJ, Evans EM, Arngrimsson SA et al (2000) Muscle activation and the slow component rise in oxygen uptake during cycling. Med Sci Sports Exerc 32:2040–2045

    Article  CAS  PubMed  Google Scholar 

  • Seki K, Narusawa M (1996) Firing rate modulation of human motor units in different muscles during isometric contraction with various forces. Brain Res 719:1–7

    Article  CAS  PubMed  Google Scholar 

  • Semmler JG (2002) Motor unit synchronization and neuromuscular performance. Exerc Sport Sci Rev 30:8–14

    Article  PubMed  Google Scholar 

  • Semmler JG, Nordstrom MA (1998) Motor unit discharge and force tremor in skill- and strength-trained individuals. Exp Brain Res 119:27–38

    Article  CAS  PubMed  Google Scholar 

  • Seynnes OR, De Boer M, Narici MV (2007) Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training. J Appl Physiol 102:368–373

    Article  CAS  PubMed  Google Scholar 

  • Shinohara M, Moritani T (1992) Increase in neuromuscular activity and oxygen uptake during heavy exercise. Ann Physiol Anthropol 11:257–262

    CAS  PubMed  Google Scholar 

  • Stålberg E, Dioszeghy P (1991) Scanning EMG in normal muscle and in neuromuscular disorders. Electroencephalogr Clin Neurophysiol 81:403–416

    PubMed  Google Scholar 

  • Stulen FB, De Luca CJ (1978) The relation between the myoelectric signal and physiological properties of constant-force isometric contractions. Electroencephalogr Clin Neurophysiol 45:681–698

    Article  CAS  PubMed  Google Scholar 

  • Vercruyssen F, Missenard O, Brisswalter J (2009) Relationship between oxygen uptake slow component and surface EMG during heavy exercise in humans: influence of pedal rate. J Electromyogr Kinesiol 19:676–684

    Article  PubMed  Google Scholar 

  • Watts PB (2004) Physiology of difficult rock climbing. Eur J Appl Physiol 91:361–372

    Article  PubMed  Google Scholar 

  • Whipp BJ (1994) The slow component of O2 uptake kinetics during heavy exercise. Med Sci Sports Exerc 26:1319–1326

    CAS  PubMed  Google Scholar 

  • Yao W, Fuglevand RJ, Enoka RM (2000) Motor-unit synchronization increases EMG amplitude and decreases force steadiness of simulated contractions. J Neurophysiol 83:441–452

    CAS  PubMed  Google Scholar 

Download references

Acknowledgments

This study was supported by the Bulgarian National Science Fund, Project 1530/05.

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Authors and Affiliations

  1. Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 105, Sofia, 1113, Bulgaria

    Todor I. Arabadzhiev, Nonna A. Dimitrova & George V. Dimitrov

  2. Institute of Biophysics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, Sofia, 1113, Bulgaria

    Vladimir G. Dimitrov

Authors
  1. Todor I. Arabadzhiev
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  2. Vladimir G. Dimitrov
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  3. Nonna A. Dimitrova
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  4. George V. Dimitrov
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Correspondence to Todor I. Arabadzhiev.

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Communicated by Arnold de Haan, Susan A. Ward.

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Arabadzhiev, T.I., Dimitrov, V.G., Dimitrova, N.A. et al. Influence of motor unit synchronization on amplitude characteristics of surface and intramuscularly recorded EMG signals. Eur J Appl Physiol 108, 227–237 (2010). https://doi.org/10.1007/s00421-009-1206-3

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