Summation of elementary phonomyograms during isometric twitches in humans

Petitjean, Michel; Maton, B.; Fourment, A.

doi:10.1007/s004210050371

Cited by 24 publications

(38 citation statements)

References 32 publications

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“…The amplitude of the MMG increases with the number of recruited MUs, whereas it decreases with higher firing rate due to fusion of the MU mechanical activity (Bichler 2000;Orizio et al 1993;Petitjean et al 1998;Stokes and Cooper 1992). The MMG-amplitude/force relationship may be broadly divided into two contiguous force regions, in which recruitment is the major mechanism for force production, and rate coding plays the prominent role (Akataki et al 1999;Matheson et al 1997;Orizio et al 1989).…”

Section: Amplitude Characteristicsmentioning

confidence: 96%

Mechanomyographic responses during voluntary ramp contractions of the human first dorsal interosseous muscle

Akataki

Mita

Watakabe

et al. 2003

European Journal of Applied Physiology

113

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The aim of this study was to examine the mechanomyogram (MMG) and force relationship of the first dorsal interosseous (FDI) muscle as well as the biceps brachii (BB) muscle during voluntary isometric ramp contractions, and to elucidate the MMG responses resulting from the intrinsic motor unit (MU) activation strategy of FDI muscle with reference to the MMG of BB muscle. The subjects were asked to exert ramp contractions of FDI and BB muscle from 5% to 70% of the maximal voluntary contraction (MVC) at a constant rate of 10% MVC/s. In FDI muscle, the root-mean-squared amplitude (RMS) of the MMG decreased slowly with force up to 21%, and then a progressive increase was followed by a relatively rapid decrease beyond 41% MVC. The RMS/%MVC relationship in BB muscle consisted of an initial slow increase followed by a rapid increase from 23% MVC and a progressive decrease beyond 61% MVC. With respect to the mean power frequency (MPF), FDI muscle demonstrated no obvious inflection point in the MPF/%MVC relationship compared with that in BB muscle. Namely, the MPF of FDI muscle increased linearly through the force levels exerted. In contrast to FDI muscle, the MPF/%MVC relationship in BB muscle was decomposed into four specific regions: (1) a relative rapidly increase (<34% MVC), (2) a slow increment (34-53% MVC), (3) a temporary reduction (53-62% MVC), and (4) a further rapid increase (>62% MVC). The different MMG responses between FDI and BB muscles are considered to reflect the fact that the MU activation strategy varies among different muscles in relation to their morphology and histochemical type. Namely, the rate coding of the MUs plays a more prominent role in force production in relatively small FDI muscle than does MU recruitment compared with their respective roles in the relatively large BB muscle.

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Section: Amplitude Characteristicsmentioning

confidence: 96%

Mechanomyographic responses during voluntary ramp contractions of the human first dorsal interosseous muscle

Akataki

Mita

Watakabe

et al. 2003

European Journal of Applied Physiology

113

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“…The authors suggested that the MMG recorded from a contracting muscle re¯ects the summation of elementary MMG signals that occur during voluntary contractions. Moreover, a connection between the increase in MMG amplitude and motor unit recruitment process was observed by Petitjean et al (1998) during evoked contractions of the human ®rst dorsal interosseus muscle. Orizio et al (1993) drew similar conclusions to those of Petitjean et al (1998) in an earlier study of contractions of the cat gastrocnemius muscle.…”

Section: Introductionmentioning

confidence: 92%

“…Moreover, a connection between the increase in MMG amplitude and motor unit recruitment process was observed by Petitjean et al (1998) during evoked contractions of the human ®rst dorsal interosseus muscle. Orizio et al (1993) drew similar conclusions to those of Petitjean et al (1998) in an earlier study of contractions of the cat gastrocnemius muscle. It was therefore generally supposed that each activity of a single motor unit generates a MMG signal.…”

Section: Introductionmentioning

confidence: 92%

Mechanomyograms recorded during evoked contractions of single motor units in the rat medial gastrocnemius muscle

Bichler

2000

European Journal of Applied Physiology

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Acoustic phenomena accompanying contractions of single motor units (MUs) have previously received little attention. Therefore, in the present study, the mechanomyographic (MMG) signals during evoked contractions of single MUs have been recorded from the medial gastrocnemius muscle of the rat. A piezoelectric transducer immersed in a paraffin-oil pool was used for the measurement of these signals. Muscle fibre action potentials, tension and MMG were recorded in parallel during twitch (the weakest) and fused tetanic (the strongest) MU contractions. It was observed that the onset of the MMG signals was coincident with the beginning of the increase in tension for both the twitch and tetanus. Weaker MMG signals than those accompanying the beginning of the first phase of the fused tetanus were seen during the beginning of the relaxation after tetanic contraction. During contraction and relaxation, MMG signals were characterised by the reverse-direction of the first extreme phase, positive and negative, respectively. No MMG signals were observed when the tension was constant during the fused tetanus. The amplitude of MMG signals was correlated with both the tension increase and the velocity of tension increase during both the twitch and the fused tetanus. The strongest MUs (fast fatiguable) generated MMG signals of the highest amplitude. MMG signals were not detected for some of the weakest slow MUs (with tension increases of < or = 2 mN). These results indicate a strong correlation between the MMG and the change of tension. Therefore, we believe that MMG signals are generated by muscle deformation that occurs during the contraction of MU muscle fibres. We conclude that the number of active muscle fibres, their topography, and their localisation in relation to the muscle surface (which is variable for different types of MUs) influence these MMG phenomena.

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“…The subsequent component, t EMG-MMG, includes events that are mainly electrochemical in nature, spanning from the propagation of the motor unit action potential at the sarcolemmal level to myosin head rotation, together with the pressure wave transmission to the skin surface detected by MMG (Hufschmidt 1985;Petitjean et al 1998). The longer t EMG-MMG in DM1 may be explained by the alteration in the splicing of several proteins, such as SERCA1 and CACNA1S, involved in Ca 2+ homeostasis and in excitation-contraction coupling mechanism [6][7][8][9][10] thus possibly leading to a lengthened duration of the dihydropyridine and ryanodine receptors interaction, Ca 2+ release by sarcoplasmic reticulum, and troponin activation [9,10,35].…”

Section: Delays During Muscle Contractionmentioning

confidence: 99%

“…When also MMG is recorded, the three signals allow the partitioning of the total electromechanical delay (Delay TOT ) into (i) a mainly electrochemical component, which includes the events from the propagation of the motor unit action potential at the sarcolemmal level to myosin head rotation and pressure wave transmission to the skin surface [28,29], and (ii) a mainly mechanical component, which reasonably provides a potential index of the time required for taking up the muscle-tendon unit slack, before F transmission becomes efficient at the tendon insertion point [12][13][14]16]. When the muscle is electrically activated, the simultaneous recording also of the stimulation current (Stim) offers an additional Delay TOT component between Stim and EMG onset, related to the presynaptic and synaptic events [16].…”

Section: Introductionmentioning

confidence: 99%

Electromechanical delay components during skeletal muscle contraction and relaxation in patients with myotonic dystrophy type 1

Esposito

Cè

Rampichini

et al. 2016

Neuromuscular Disorders

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights Patients with myotonic dystrophy type 1 (DM1) were investigated isometrically  We calculated the electromechanical delays during muscle contraction and relaxation  Delays were partitioned into electrochemical and mechanical components  Measurements reliability was very high in both patients and controls  Delays were longer in DM1, especially during muscle relaxation AbstractThe electromechanical delay during muscle contraction and relaxation can be partitioned into mainly electrochemical and mainly mechanical components by an EMG, mechanomyographic, and force combined approach. Components duration and measurements reliability were investigated during contraction and relaxation in a group of patients with myotonic dystrophy type 1 (DM1, n=13) and in healthy controls (n=13). EMG, mechanomyogram, and force were recorded in DM1 and in age-and body-matched controls from tibialis anterior (distal muscle) and vastus lateralis (proximal muscle) muscles during maximum voluntary and electrically-evoked isometric contractions. The electrochemical and mechanical components of the electromechanical delay during muscle contraction and relaxation were calculated off-line. Maximum strength was significantly lower in DM1 than in controls under both experimental conditions. All electrochemical and mechanical components were significantly longer in DM1 in both muscles.Measurements reliability was very high in both DM1 and controls. The high reliability of the measurements and the differences between DM1 patients and controls suggest that the EMG, mechanomyographic, and force combined approach could be utilized as a valid tool to assess the level of neuromuscular dysfunction in this pathology, and to follow the efficacy of pharmacological or non-pharmacological interventions.

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Summation of elementary phonomyograms during isometric twitches in humans

Cited by 24 publications

References 32 publications

Mechanomyographic responses during voluntary ramp contractions of the human first dorsal interosseous muscle

Mechanomyographic responses during voluntary ramp contractions of the human first dorsal interosseous muscle

Mechanomyograms recorded during evoked contractions of single motor units in the rat medial gastrocnemius muscle

Electromechanical delay components during skeletal muscle contraction and relaxation in patients with myotonic dystrophy type 1

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