Motor unit recruitment when neuromuscular electrical stimulation is applied over a nerve trunk compared with a muscle belly: triceps surae

Bergquist, Austin J.; Clair, J. M.; Collins, David F.

doi:10.1152/japplphysiol.01103.2010

Cited by 102 publications

(125 citation statements)

References 48 publications

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“…In the first case, motor units are activated in random order with uniform probability distribution as indicated by the empirical evidence presented by Knaflitz et al (1990) and Gregory and Bickel (2005). In the second case, motor units are activated in inverse order of physiological recruitment, i.e., in the order of decreasing recruitment threshold , as suggested by the empirical studies of Bergquist et al (2011Bergquist et al ( , 2012.…”

Section: Effect Of Elicited Input Excitationmentioning

confidence: 99%

Is the notion of central fatigue based on a solid foundation?

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Luca

2016

Journal of Neurophysiology

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-Exercise-induced muscle fatigue has been shown to be the consequence of peripheral factors that impair muscle fiber contractile mechanisms. Central factors arising within the central nervous system have also been hypothesized to induce muscle fatigue, but no direct empirical evidence that is causally associated to reduction of muscle forcegenerating capability has yet been reported. We developed a simulation model to investigate whether peripheral factors of muscle fatigue are sufficient to explain the muscle force behavior observed during empirical studies of fatiguing voluntary contractions, which is commonly attributed to central factors. Peripheral factors of muscle fatigue were included in the model as a time-dependent decrease in the amplitude of the motor unit force twitches. Our simulation study indicated that the force behavior commonly attributed to central fatigue could be explained solely by peripheral factors during simulated fatiguing submaximal voluntary contractions. It also revealed important flaws regarding the use of the interpolated twitch response from electrical stimulation of the muscle as a means for assessing central fatigue. Our analysis does not directly refute the concept of central fatigue. However, it raises important concerns about the manner in which it is measured and about the interpretation of the commonly accepted causes of central fatigue and questions the very need for the existence of central fatigue. central fatigue; motor units; interpolated twitch; voluntary drive THE SOURCES of exercise-induced muscle fatigue have been debated since the early 1900s. There is general agreement on the influence of peripheral factors on muscle fatigue, i.e., those that develop within the muscle and impair the muscle fiber contractile mechanism, such as metabolite accumulation during prolonged exercise (see, e.g., Bergström et al. 1967;Hermansen et al. 1967;Pernow and Saltin 1971). These contractile impairments can be measured as changes in the amplitude and duration of the elicited muscle force twitch De Luca 2003, 2005;Burke 1981;Macintosh et al. 1994; Vandervoort et al. 1983).In addition to the influence of peripheral factors of muscle fatigue, some studies have put forth the notion of "central fatigue," i.e., a limitation in muscle performance caused by central factors. These would arise within the central nervous system (CNS) and diminish the voluntary drive to the motoneuron pool of a muscle. Potential sources include failure of the motor cortex (see, e.g., Gandevia et al. 1996;Todd et al. 2007) and the influence of afferent inputs at the spinal level (see, e.g., Gandevia 2001). Mosso (1904) was the first to draw attention to this concept, but others have followed (e.g., Bellemare and Bigland-Ritchie 1987; Gandevia 2001; Reid 1927). Today, central fatigue is commonly accepted as a physiological phenomenon that plays a relevant role in muscle fatigue and, according to BiglandRitchie et al. (1983) and Gandevia (2001), protects muscles against excessive effort.However, unlike the dire...

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Section: Effect Of Elicited Input Excitationmentioning

confidence: 99%

Is the notion of central fatigue based on a solid foundation?

Contessa

Puleo

Luca

2016

Journal of Neurophysiology

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“…Thus, during NMES the recruitment of motor units through central pathways can augment contractions generated through peripheral pathways, leading to the development of greater torque (extra or central torque). A central contribution to electrically evoked contractions has now been shown for the triceps surae (TS) (Collins et al 2002a;Baldwin et al 2006;Klakowicz et al 2006;Bergquist et al 2011), tibialis anterior (TA) (Collins et al 2002a;Klakowicz et al 2006), quadriceps (Bergquist et al, in revision), wrist extensors and flexor pollicis longus ). The strength of the central contribution, measured as the amplitude of H-reflexes, asynchronous activity (see below) and evoked torque, depends on the muscle being stimulated, the stimulation parameters (Collins et al 2002b;Dean et al 2007;Lagerquist et al 2009) and the stimulation location Bergquist et al 2011;Bergquist et al, in revision).…”

Section: Nmes and The Central Recruitment Of Motor Unitsmentioning

confidence: 99%

Neuromuscular electrical stimulation: implications of the electrically evoked sensory volley

et al. 2011

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Neuromuscular electrical stimulation (NMES) generates contractions by depolarising axons beneath the stimulating electrodes. The depolarisation of motor axons produces contractions by signals travelling from the stimulation location to the muscle (peripheral pathway), with no involvement of the central nervous system (CNS). The concomitant depolarisation of sensory axons sends a large volley into the CNS and this can contribute to contractions by signals travelling through the spinal cord (central pathway) which may have advantages when NMES is used to restore movement or reduce muscle atrophy. In addition, the electrically evoked sensory volley increases activity in CNS circuits that control movement and this can also enhance neuromuscular function after CNS damage. The first part of this review provides an overview of how peripheral and central pathways contribute to contractions evoked by NMES and describes how differences in NMES parameters affect the balance between transmission along these two pathways. The second part of this review describes how NMES location (i.e. over the nerve trunk or muscle belly) affects transmission along peripheral and central pathways and describes some implications for motor unit recruitment during NMES. The third part of this review summarises some of the effects that the electrically evoked sensory volley has on CNS circuits, and highlights the need to identify optimal stimulation parameters for eliciting plasticity in the CNS. A goal of this work is to identify the best way to utilize the electrically evoked sensory volley generated during NMES to exploit mechanisms inherent to the neuromuscular system and enhance neuromuscular function for rehabilitation.

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“…In one of the included studies, both currents were used to maximize the response and the patient did, in fact, make a strong recovery (Srilakshmi & Chaganti, 2013). As for electrode placement, Bergquist, Clair, and Collins (2011) argued for placement of the electrode over the nerve trunk rather than the muscle belly in order to promote a greater central contribution to motor unit recruitment (Bergquist, Clair, & Collins, 2011). This central contribution is associated with recruitment of low-threshold motor units first, which is more consistent with the natural physiological process and promotes more effective recovery of motor functions (Bergquist et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…As for electrode placement, Bergquist, Clair, and Collins (2011) argued for placement of the electrode over the nerve trunk rather than the muscle belly in order to promote a greater central contribution to motor unit recruitment (Bergquist, Clair, & Collins, 2011). This central contribution is associated with recruitment of low-threshold motor units first, which is more consistent with the natural physiological process and promotes more effective recovery of motor functions (Bergquist et al, 2011). None of the included studies referenced the exact placement of electrodes, but given the potential to harness a central contribution to motor unit recruitment, electrode placement over the nerve trunk may be an important component of a future standardized NMES protocol.…”

Section: Discussionmentioning

confidence: 99%