Sustained Muscle Contractions Maintained by Autonomous Neuronal Activity Within the Human Spinal Cord

Nozaki, Daichi; Kawashima, Noritaka; Aramaki, Yu; Akai, Masami; Nakazawa, Kimitaka; Nakajima, Yasoichi; Yano, Hideo

doi:10.1152/jn.00200.2003

Cited by 24 publications

(25 citation statements)

References 35 publications

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“…Surprisingly, in the standing position the soleus EMG levels of four subjects decreased after the stimulus ended, contrary to the increase described for seated subjects 9,11,[13][14][15][16]22 . One possibility for this lack of increase in soleus activity is that while standing, the plateau potential mechanism would already be activated by the action of monoaminergic modulation 23 .…”

Section: Discussioncontrasting

confidence: 87%

“…Although the chosen stimulation level was lower than that used by other authors 13,15 , which may also have limited its efficacy in triggering the PP mechanism, it assured on the other hand that mainly large diameter afferents were stimulated (e.g., Ia spindle afferents).…”

Section: Discussionmentioning

confidence: 98%

“…This behavior can be explained by neither the peripheral properties of nerve and muscle nor volitional drive to the motoneurons 13,14 . However, a plausible hypothesis is that the sustained muscle activity originated from the generation of persistent inward currents due to the temporal summation of excitatory postsynaptic potentials occurring at a high rate, such as the Ia terminals discharged following the stimulus train 9,[13][14][15] . The subjects' responses ranged from little evidence of this behavior to large sustained activity following the stimulus train.…”

Section: Discussionmentioning

confidence: 99%

“…The neuron may then be turned off by, for example, a hyperpolarization caused by inhibitory synapses [9][10][11] . Strong evidence for this phenomenon has been obtained from electrical stimulation of mixed nerves and from voluntary muscle activation in human MNs 9,[11][12][13][14][15][16] . The PP phenomenon reduces the need for continuous synaptic input during muscle contraction, which may be useful in postural muscles, whose activity can be maintained without a continuous descending drive to keep the MNs firing 10,14,16 .…”

Section: Introductionmentioning

confidence: 94%

“…The feet have to be considered as a specific sensory-motor sub-system due to their importance for signaling the position of the body' s center of gravity [27][28][29] and to muscles such as the FDB, which contribute to postural control [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]30 . That increased and sustained FDB activity can be triggered by appropriate stimuli reinforces the relevance of foot muscles for postural control.…”

mentioning

confidence: 99%

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Changes in FDB and soleus muscle activity after a train of stimuli during upright stance

Okai

Kohn

2012

Rev. bras. fisioter.

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© Revista Brasileira de FisioterapiaChanges in FDB and soleus muscle activity after a train of stimuli during upright stance Alterações pós-trem de estímulo, na atividade dos músculos FDB e sóleus durante a postura ortostática Liria A. Okai 1,2 , André F. Kohn 1 AbstractBackground: Evidence of self-sustained muscle activation following a brief electrical stimulation has been reported in the literature for certain muscles. Objectives: This report shows that the foot muscle (Flexor Digitorum Brevis -FDB) shows a self-sustained increase in muscle activity during upright stance in some subjects following a train of stimuli to the tibial nerve. Methods: Healthy subjects were requested to stand upright and surface EMG electrodes were placed on the FDB, Soleus and Tibialis Anterior muscles. After background muscle activity (BGA) acquisition, a 50 Hz train of stimuli was applied to the tibial nerve at the popliteal fossa. The root mean square values (RMS) of the BGA and the post-stimulus muscle activation were computed. Results: There was a 13.8% average increase in the FDB muscle EMG amplitude with respect to BGA after the stimulation was turned off. The corresponding post-stimulus Soleus EMG activity decreased by an average of 9.2%. We hypothesize that the sustained contraction observed in the FDB following stimulus may be evidence of persistent inward currents (PIC) generated in FDB spinal motoneurons. The post-stimulus decrease in soleus activity may have occurred due to the action of inhibitory interneurons caused by the PICs, which were triggered by the stimulus train. Conclusions: These sustained post-stimulation changes in postural muscle activity, found in different levels in different subjects, may be part of a set of possible responses that contribute to overall postural control.Keywords: physical therapy; posture; foot; human; electromyography; motor activity. ResumoContextualização: Existem evidências de ativação autossustentada em certos músculos pós-estimulação elétrica. Objetivos: Mostrar que, em alguns sujeitos, o músculo do pé (Flexor Digitorum Brevis -FDB) também pode apresentar aumento de atividade autossustentada na posição ortostática pós-trem de estímulo no nervo tibial. Métodos: Sujeitos foram solicitados a permanecer na posição ortostática e sinais eletromiográficos foram coletados dos músculos FDB, sóleus e tibial anterior do membro inferior direito. Após a aquisição dos sinais eletromiográficos base (sem estimulação -BGA), um trem de estímulos de 50 Hz foi aplicado no nervo tibial (fossa poplítea).Foram analisados os valores RMS dos dados BGA e dos sinais coletados pós-estímulo. Resultados: Ao fim do estímulo, houve um aumento de 13,8% da atividade muscular do FDB em comparação com BGA. O mesmo fenômeno não aconteceu com o músculo sóleus, que apresentou uma diminuição de 9,2% da sua atividade pós-estímulo. Uma das hipóteses para a geração pós-estímulo da contração sustentada do FDB seria a da geração de corrente de entrada persistente (PIC) nos motoneurônios espinais do FDB. A diminuição da at...

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Section: Discussioncontrasting

confidence: 87%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

mentioning

confidence: 99%

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Changes in FDB and soleus muscle activity after a train of stimuli during upright stance

Okai

Kohn

2012

Rev. bras. fisioter.

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Turning off the central contribution to contractions evoked by neuromuscular electrical stimulation

2008

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Neuromuscular electrical stimulation can generate contractions through both peripheral and central mechanisms. The peripheral mechanism involves the direct activation of motor axons, while the central mechanism involves the activation of sensory axons that recruit spinal neurons through a reflex pathway. For use in functional electrical stimulation. One must have control over turning the central mechanism on and off. We investigated whether inhibition developed through antagonist muscle (tibialis anterior, TA) contractions elicited by electrical stimulation or by volition can turn off the central mechanism in triceps surae. Both electrical stimulation and voluntary contractions of TA reduced or eliminated plantar flexion torque produced by the central mechanism, indicating that inhibition induced via these contractions can effectively turn off the central contribution to force. These findings suggest that patterns of electrical stimulation may be able to generate periodic muscle contractions by turning the central contribution to muscular contractions on and off.

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Influence of stimulus pulse width on M‐waves, H‐reflexes, and torque during tetanic low‐intensity neuromuscular stimulation

Lagerquist

Collins

2010

Muscle and Nerve

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Neuromuscular electrical stimulation (NMES) has been shown to generate contractions that include a central recruitment of motoneurons; however, the effect of pulse width on electromyographic (EMG) and torque responses during NMES are not well documented. Soleus EMG and isometric plantarflexion torque were recorded from 14 subjects with NMES delivered to the tibial nerve using 50, 200, 500, and 1000 μs pulse widths. M-waves were significantly smaller during 20 Hz NMES compared with responses evoked by single pulses of 200, 500, and 1000 μs, but not 50 μs pulse widths. At all pulse widths, stimulation at 20 Hz depressed soleus H-reflexes compared with single pulses. Two seconds of 100 Hz NMES significantly increased H-reflexes and torque during the subsequent 20 Hz NMES with 200, 500, and 1000 μs, but not 50 μs, pulse widths. NMES delivered using wide pulses generated larger contractions with a relatively greater central contribution than narrow pulses. This may help reduce atrophy and produce fatigue-resistant contractions for rehabilitation.

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Sustained Muscle Contractions Maintained by Autonomous Neuronal Activity Within the Human Spinal Cord

Cited by 24 publications

References 35 publications

Changes in FDB and soleus muscle activity after a train of stimuli during upright stance

Changes in FDB and soleus muscle activity after a train of stimuli during upright stance

Turning off the central contribution to contractions evoked by neuromuscular electrical stimulation

Influence of stimulus pulse width on M‐waves, H‐reflexes, and torque during tetanic low‐intensity neuromuscular stimulation

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