Mechanomyographic signals generated during unfused tetani of single motor units in the rat medial gastrocnemius muscle

Bichler, Edyta K.; Celichowski, Jan

doi:10.1007/s004210100491

Cited by 33 publications

(55 citation statements)

References 23 publications

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“…An increased MMG amplitude of working muscle at the cessation of contraction was also recorded by others working on isolated muscle (Bichler 2000;Bichler and Celichowski 2001). The present results additionally shows that during the slow relaxation the increase was smaller than that during the fast relaxation in the BB and TB muscle, but was similar in the BR muscle.…”

Section: Mmg Amplitude During Slow and Fast Relaxationsupporting

confidence: 78%

“…Large MMG signals were observed during relaxation from fused and unfused tetani of isolated motor units in rats; MMG amplitude was dependent on the amplitude and velocity of tension changes (Bichler 2000;Bichler and Celichowski 2001). Because there is unfused muscle contraction during voluntary movements, MMG amplitude (MMG RMS) during relaxation from MVC might also depend on the amplitude and speed of force changes.…”

Section: Muscle Length and Electrical Activity Of Synergists And Antamentioning

confidence: 97%

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EMG and MMG of synergists and antagonists during relaxation at three joint angles

Jaskólska

Kisiel

Brzenczek³

et al. 2003

Eur J Appl Physiol

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The aim of the study was to estimate the influence of force changes during relaxation from maximal voluntary contraction (MVC) of elbow flexors on electrical (EMG) and mechanical (MMG) activity of synergists and antagonists at different joint angles. Repeated studies were conducted on 22 young female students to estimate the EMG and MMG activity of the biceps brachii (BB), brachioradialis (BR), and triceps brachii (TB) muscles during relaxation from MVC at an optimal angle (the angle at which a subject achieved MVC=Lo), as well as at angles that were smaller (Ls=Lo-30 degrees ) and bigger (Ll=Lo+30 degrees ). Four testing sessions consisted of 2-s or 3-s MVC at each angle with simultaneous recording of EMG and MMG signals from BB, BR, and TB muscles. The EMG/MMG probes were used to record EMG and MMG signals. The results showed that the slow relaxation rate was related to a percentage decrease of the EMG amplitude (as measured by root mean square; EMG RMS) of the synergists, while the fast relaxation was related to the EMG RMS of the antagonist, independent of the joint angle. The MMG amplitude (MMG RMS) increased gradually during slow and fast relaxation (compared to the MMG RMS at MVC), indicating a bigger muscle oscillation during relaxation; the changes were related to the muscle tested and joint angle. It was found that, during the slow relaxation, the MMG RMS reflects the force amplitude changes in the BB muscle and the velocity of force changes in the BB and TB muscle (but not in the BR). During the fast relaxation, the MMG amplitude reflects a change in muscle force in the TB and BB muscles (but not in the BR), and the velocity of force changes in the synergists (not in the antagonist). The different contribution of the force and velocity of force changes during slow and fast relaxation to the MMG signal in the three muscle tested can be related to the different deactivation time of each muscle. In conclusion, the present results indicate that MMG recordings might be useful to measure the fast relaxation of individual muscle during voluntary contraction, but this needs be tested on isolated muscle.

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Section: Mmg Amplitude During Slow and Fast Relaxationsupporting

confidence: 78%

Section: Muscle Length and Electrical Activity Of Synergists And Antamentioning

confidence: 97%

EMG and MMG of synergists and antagonists during relaxation at three joint angles

Jaskólska

Kisiel

Brzenczek³

et al. 2003

Eur J Appl Physiol

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“…The amplitude of the MMG signal is determined by the number of active motor units and their firing rates (Orizio, 1993;Orizio et al, 2003), and although not directly verified (Akataki et al, 2003), it has been suggested that the MMG frequency content qualitatively reflects the global firing rate of the unfused activated motor units (Akataki et al, 2001;Bichler, 2000;Bichler & Celichowski, 2001;Orizio, 1993;Orizio et al, 2003). Thus, examination of the MMG amplitude and mean power frequency vs. isometric torque relationships may provide information regarding the unique motor unit activation strategies (recruitment and firing rate) …”

Section: Discussionmentioning

confidence: 99%

Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships

Beck

Housh²,

Johnson³

et al. 2005

Journal of Applied Biomechanics

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This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 ± 3.5 yrs) and 8 women (mean 21.0 ± 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R 2 = 0.983), where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r 2 = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric torque relationship in both the men (r 2 = 0.813) and women (r 2 = 0.578). The results demonstrated gender differences in the MMG amplitude vs. isometric torque relationship, but similar torque-related patterns for MMG mean power frequency. These findings suggested that the plateau in MMG amplitude at high levels of isometric torque production for the biceps brachii in the men, but not the women, may have been due to greater isometric torque, muscle stiffness, and/or intramuscular fluid pressure in the men, rather than to differences in motor unit activation strategies for modulating isometric torque production.

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“…Previous studies have demonstrated that the MMG amplitude during repetitive stimulation reflects the magnitude of the fusion state of the muscle fiber (Bichler and Celichowski 2001a;Orizio 1993;Orizio et al 1996). As the fusion state of muscle fiber is caused by an inadequate fiber relaxation between impulses, its magnitude can be determined by the motor unit firing frequency and shortening and relaxation velocity of the activated muscle fibers.…”

Section: Introductionmentioning

confidence: 99%

Mechanomyographic responses in human biceps brachii and soleus during sustained isometric contraction

et al. 2004

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The purpose of this study was to elucidate the responses of the mechanomyogram (MMG) from two apparently different muscles (biceps brachii and soleus) during a sustained voluntary contraction at 50% maximum voluntary contraction. The MMG and surface electromyogram (EMG) were recorded from human biceps brachii and soleus during sustained elbow flexion and plantar flexion, respectively. Results indicated that the slope coefficient of rise in EMG amplitude as a function of time for the biceps was significantly greater than that for the soleus ( P<0.001). On the contrary, the MMG amplitude of the biceps showed a significant increase during the initial phase of sustained contraction ( P<0.05); however, when exhaustion was approached the amplitude declined significantly ( P<0.05). In the soleus muscle the decrease in MMG amplitude toward exhaustion occurred to a much lesser extent than that observed in the biceps. This difference could be attributed to the nature of the fusion state of the underlying muscle fibers. That is, the great extent of fusion observed in the biceps may be as a result of a greater quantity of fatigable motor units. In addition, the absence of MMG reduction in the soleus would indicate the absence of fatigue-induced slowing of contractile machinery and/or the lack of full activation (tetanus) of muscle fibers even at the exhaustion phase of plantar flexion.

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Mechanomyographic signals generated during unfused tetani of single motor units in the rat medial gastrocnemius muscle

Cited by 33 publications

References 23 publications

EMG and MMG of synergists and antagonists during relaxation at three joint angles

EMG and MMG of synergists and antagonists during relaxation at three joint angles

Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships

Mechanomyographic responses in human biceps brachii and soleus during sustained isometric contraction

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