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   2017

Changes in tibialis anterior architecture affect the amplitude of surface electromyograms. Vieira TM, Bisi MC, Stagni R, Botter A. J Neuroeng Rehabil. 2017 Aug 14;14(1):81
2017 Aug 14;14(1):81. doi: 10.1186/s12984-017-0291-5.

Changes in tibialis anterior architecture affect the amplitude of surface electromyograms.

Author information

1
Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and Telecommunication, Politecnico di Torino, Via Cavalli 22/h, 10138, Torino, Italy. taian.vieira@polito.it.
2
Department of Electrical, Electronic and Information Engineering “Guglielmo Marconi”, University of Bologna, Viale Risorgimento 2, Bologna, 40136, Italy.
3
Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and Telecommunication, Politecnico di Torino, Via Cavalli 22/h, 10138, Torino, Italy.

Abstract

BACKGROUND:

Variations in the amplitude of surface electromyograms (EMGs) are typically considered to advance inferences on the timing and degree of muscle activation in different circumstances. Surface EMGs are however affected by factors other than the muscle neural drive. In this study, we use electrical stimulation to investigate whether architectural changes in tibialis anterior (TA), a key muscle for balance and gait, affect the amplitude of surface EMGs.

METHODS:

Current pulses (500 μs; 2 pps) were applied to the fibular nerve of ten participants, with the ankle at neutral, full dorsi and full plantar flexion positions. Ultrasound images were collected to quantify changes in TA architecture with changes in foot position. The peak-to-peak amplitude of differential M waves, detected with a grid of surface electrodes (16 × 4 electrodes; 10 mm inter-electrode distance), was considered to assess the effect of changes in TA architecture on the surface recordings.

RESULTS:

On average, both TA pennation angle and width increased by respectively 7 deg. and 9 mm when the foot moved from plantar to dorsiflexion (P < 0.02). M-wave amplitudes changed significantly with ankle position. M waves elicited in dorsiflexion and neutral positions were ~25% greater than those obtained during plantar flexion, regardless of where they were detected in the grid (P < 0.001). This figure increased to ~50% when considering bipolar M waves.

CONCLUSIONS:

Findings reported here indicate the changes in EMG amplitude observed during dynamic contractions, especially when changes in TA architecture are expected (e.g., during gait), may not be exclusively conceived as variations in TA activation.

KEYWORDS:

Electrical stimulation; Surface electromyograms; Tibialis anterior; Ultrasound

PMID:
28807025
DOI:
10.1186/s12984-017-0291-5
Is the firing rate of motor units in different vastus medialis regions modulated similarly during isometric contractions? Cabral HV, de Souza LML, Mello RGT, Gallina A, de Oliveira LF, Vieira TM. Muscle Nerve. 2017 May 13
2017 May 13. doi: 10.1002/mus.25688. [Epub ahead of print]

Is the firing rate of motor units in different vastus medialis regions modulated similarly during isometric contractions?

Abstract

INTRODUCTION:

Previous evidence suggests the fibers of different motor units reside within distinct vastus medialis (VM) regions. It remains unknown whether the activity of these motor units may be modulated differently. Herein we assess the discharge rate of motor units detected proximodistally from the VM to address this issue.

METHODS:

Surface electromyograms (EMGs) were recorded proximally and distally from the VM while 10 healthy subjects performed isometric contractions. Single motor units were decomposed from surface EMGs. The smoothed discharge rates of motor units identified from the same and from different VM regions were then cross-correlated.

RESULTS:

During low-level contractions, the discharge rate varied more similarly for distal (cross-correlation peak; interquartile interval: 0.27-0.40) and proximal (0.28-0.52) than for proximodistal pairs of VM motor units (0.20-0.33; P = 0.006).

CONCLUSIONS:

The discharge rates of motor units from different proximodistal VM regions show less similarity in their variations than those of pairs of units either distally or proximally. Muscle Nerve, 2017.

KEYWORDS:

compartmentalization; knee; motor unit; quadriceps; surface electromyography; vastus medialis

PMID:
28500671
DOI:
10.1002/mus.25688
Is heart rate variability affected by distinct motor imagery strategies? Peixoto Pinto T, Mello Russo Ramos M, Lemos T, Domingues Vargas C, Imbiriba LA. Physiol Behav. 2017 Aug 1;177:189-195.
2017 Aug 1;177:189-195. doi: 10.1016/j.physbeh.2017.05.004. Epub 2017 May 2.

Is heart rate variability affected by distinct motor imagery strategies?

Abstract

Although some studies have reported significant changes in autonomic responses according to the perspective-taking during motor imagery [first person perspective (1P) and third person perspective (3P)], investigations on how the strategies adopted to mentally simulate a given movement affect the heart rate variability (HRV) seem so far unexplored. Twenty healthy subjects mentally simulated the movement of middle-finger extension in 1P and 3P, while electrocardiogram was recorded. After each task, the level of easiness was self-reported. Motor imagery ability was also assessed through the revised version of Movement Imagery Questionnaire (MIQ-R) and a mental chronometry index. The traditional measures of HRV in the time- and frequency-domain were compared between 1P and 3P tasks by using Student’s t-test for dependent samples. The MIQ-R results showed that subjects had the same facility to imagine movements in 1P or 3P. The mental chronometry index revealed a similar temporal course only between 1P and execution, while the 3P strategy had a shorter duration. Additionally, the subjective report was similar between the experimental tasks. Regarding the HRV measures, the low frequency component, in log-transformed unit, was significantly higher (p=0.017) in 1P than 3P, suggesting a higher activity of the sympathetic system during 1P. This log-transformed HRV parameter seems to be more sensitive than normalized values for the assessment of the motor imagery ability, together with questionnaires, scales and mental chronometry.

KEYWORDS:

Autonomic nervous system; Heart rate variability; Motor imagery strategies

PMID:
28476285
DOI:
10.1016/j.physbeh.2017.05.004
Physiological arousal accompanying postural responses to external perturbations after stroke. Pollock CL, Carpenter MG, Hunt MA, Gallina A, Vieira TM, Ivanova TD, Garland SJ. Clin Neurophysiol. 2017 Jun;128(6):935-944
2017 Jun;128(6):935-944. doi: 10.1016/j.clinph.2017.03.008. Epub 2017 Mar 18.

Physiological arousal accompanying postural responses to external perturbations after stroke.

Author information

1
Department of Physical Therapy, University of British Columbia, Vancouver, Canada.
2
School of Kinesiology, University of British Columbia, Vancouver, Canada.
3
Department of Physical Therapy, University of British Columbia, Vancouver, Canada; Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy.
4
Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Italy; Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
5
Faculty of Health Sciences, Western University, London, Canada.
6
Faculty of Health Sciences, Western University, London, Canada. Electronic address: jgarland@uwo.ca.

Abstract

OBJECTIVE:

The purpose of this study was to examine simultaneously the level of physiological arousal and the postural response to external perturbations in people post-stroke compared to age-matched controls to build a more comprehensive understanding of the effect of stroke on postural control and balance self-efficacy.

METHODS:

Participants stood with each foot on separate force platforms. Ten applications of loads of 2% body weight at the hips perturbed the participant anteriorly under two conditions: investigator-triggered or self-triggered (total 20). Electrodermal activity (EDA; measurement of physiological arousal), electromyography (EMG) of the ankle plantarflexor muscles and anterior-posterior center of pressure measurements were taken pre-perturbation (anticipatory) and post-perturbation (response) and compared between the initial (first two) and final (last two) perturbations.

RESULTS:

Participants post-stroke demonstrated significantly higher levels of anticipatory EDA and anticipatory paretic plantarflexor EMG during both self- and investigator-triggered conditions compared to controls. Anticipatory EDA levels were higher in the final perturbations in participants post-stroke in both conditions, but not in controls. Habituation of the EDA responses post-perturbation was exhibited in the self-triggered perturbations in controls, but not in participants post-stroke.

CONCLUSIONS:

Physiological arousal and postural control strategies of controls revealed habituation in response to self-triggered perturbations, whereas this was not seen in participants post-stroke.

SIGNIFICANCE:

Understanding the physiological arousal response to challenges to standing balance post-stroke furthers our understanding of postural control mechanisms post-stroke.

KEYWORDS:

External perturbation; Physiological arousal; Postural control; Stroke

PMID:
28407522
DOI:
10.1016/j.clinph.2017.03.008
Optimization of surface electrodes location for H-reflex recordings in soleus muscle. Botter A, Vieira TM. J Electromyogr Kinesiol. 2017 Jun;34:14-23
2017 Jun;34:14-23. doi: 10.1016/j.jelekin.2017.03.003. Epub 2017 Mar 16.

Optimization of surface electrodes location for H-reflex recordings in soleus muscle.

Author information

1
Laboratory for Engineering of the Neuromuscular System (LISiN), Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Torino, Italy. Electronic address: alberto.botter@polito.it.
2
Laboratory for Engineering of the Neuromuscular System (LISiN), Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Torino, Italy.

Abstract

The Hoffmann reflex (H reflex) is extensively used to investigate the spinal motor neuron excitability in healthy and pathological subjects. Obtaining a representative and robust amplitude estimation of the H reflex is of marked relevance in clinical as well as in research applications. As for the motor responses, this issue is strictly related to the electrode positioning, especially for large, pinnate muscles such as the triceps surae. In this study we investigated the effect of electrode position on soleus H-reflex amplitude. A grid of 96 electrodes was used to identify maximal H reflexes (Hmax) across the whole soleus region available for surface recording. The spatial distribution of Hmax amplitude detected in monopolar and single-differential derivations was used to determine where greatest reflex responses were detected from soleus. For both derivations and for all participants, largest Hmax were detected consistently over the central soleus region, in correspondence of the muscle superficial aponeurosis. Indeed, the amplitude of Hmax provided by conventional electrodes (1cm2 area, 2cm apart) located centrally was significantly greater (median: 35% for monopolar and 79% for single-differential derivations) than that obtained medially, where surface electromyograms are typically recorded from soleus. Computer simulations, used to assist in the interpretation of results, suggest the soleus pinnate architecture was the key determinant of the medio-lateral variability observed for the experimental Hmax. The presented results provide a clear indication for electrode positioning, of crucial relevance in applied studies aimed at eliciting H reflexes.

KEYWORDS:

Achilles tendon; EMG; Electrode positioning; H reflex; Soleus

PMID:
28342367
DOI:
10.1016/j.jelekin.2017.03.003
Is myoelectric activity distributed equally within the rectus femoris muscle during loaded, squat exercises? de Souza LM, da Fonseca DB, Cabral HD, de Oliveira LF, Vieira TM. J Electromyogr Kinesiol. 2017 Apr;33:10-19
2017 Apr;33:10-19. doi: 10.1016/j.jelekin.2017.01.003. Epub 2017 Jan 9.

Is myoelectric activity distributed equally within the rectus femoris muscle during loaded, squat exercises?

Author information

1
Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
2
Programa de Engenharia Biomédica (COPPE), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
3
Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Programa de Engenharia Biomédica (COPPE), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Electronic address: liliam@peb.ufrj.br.
4
Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Dipartimento di Elettronica e Telecomunicazioni, Politecnico di Torino, Torino, Italy.

Abstract

Recent evidence suggests different regions of the rectus femoris (RF) muscle respond differently to squat exercises. Such differential adaptation may result from neural inputs distributed locally within RF, as previously reported for isometric contractions, walking and in response to fatigue. Here we therefore investigate whether myoelectric activity distributes evenly within RF during squat. Surface electromyograms (EMGs) were sampled proximally and distally from RF with arrays of electrodes, while thirteen healthy volunteers performed 10 consecutive squats with 20% and 40% of their body weight. The root mean square (RMS) value, computed separately for thirds of the concentric and eccentric phases, was considered to assess the proximo-distal changes in EMG amplitude during squat. The channels with variations in EMG amplitude during squat associated with shifts in the muscle innervation zone were excluded from analysis. No significant differences were observed between RF regions when considering squat phases and knee joint angles individually (P>0.16) while a significant interaction between phase and knee joint angle with detection site was observed (P<0.005). For the two loads considered, proximal RMS values were greater during the eccentric phase and for the more flexed knee joint position (P<0.001). Our results suggest inferences on the degree of RF activation during squat must be made cautiously from surface EMGs. Of more practical relevance, there may be a potential for the differential adaption of RF proximal and distal regions to squat exercises.

KEYWORDS:

Rectus femoris; Resistance training; Squat; Surface electromyography

PMID:
28110043
DOI:
10.1016/j.jelekin.2017.01.003
The Spatial Distribution of Ankle Muscles Activity Discriminates Aged from Young Subjects during Standing. Dos Anjos FV, Pinto TP, Gazzoni M, Vieira TM. Front Hum Neurosci. 2017 Apr 19;11:190
2017 Apr 19;11:190. doi: 10.3389/fnhum.2017.00190. eCollection 2017.

The Spatial Distribution of Ankle Muscles Activity Discriminates Aged from Young Subjects during Standing.

Author information

1
Laboratorio di Ingegneria del Sistema Neuromuscolare, Dipartimento di Elettronica e Telecomunicazioni, Politecnico di TorinoTorino, Italy.

Abstract

During standing, age-related differences in the activation of ankle muscles have been reported from surface electromyograms (EMGs) sampled locally. Given though activity seems to distribute unevenly within ankle muscles, the local sampling of surface EMGs may provide a biased view on how often and how much elderly and young individuals activate these muscles during standing. This study aimed therefore at sampling EMGs from multiple regions of individual ankle muscles to evaluate whether the distribution of muscle activity differs between aged and young subjects during standing. Thirteen young and eleven aged, healthy subjects were tested. Surface EMGs were sampled at multiple skin locations from tibialis anterior, soleus and medial and lateral gastrocnemius muscles while subjects stood at ease. The root mean square amplitude of EMGs was considered to estimate the duration, the degree of activity and the size of the region where muscle activity was detected. Our main findings revealed the medial gastrocnemius was active for longer periods in aged (interquartile interval; 74.1-98.2%) than young (44.9-81.9%) individuals (P = 0.02). Similarly, while tibialis anterior was rarely active in young (0.7-4.4%), in elderly subjects (2.6-82.5%) it was often recruited (P = 0.01). Moreover, EMGs with relatively higher amplitude were detected over a significantly wider proximo-distal region of medial gastrocnemius in aged (29.4-45.6%) than young (20.1-31.3%) subjects (P = 0.04). These results indicate the duration and the size of active muscle volume, as quantified from the spatial distribution of surface EMGs, may discriminate aged from young individuals during standing; elderlies seem to rely more heavily on the active loading of ankle muscles to control their standing posture than young individuals. Most importantly, current results suggest different conclusions on the active control of standing posture may be drawn depending on the skin location from where EMGs are collected, in particular for the medial gastrocnemius.

KEYWORDS:

aging; electromyography; muscle activity; postural control; standing

PMID:
28469567
PMCID:
PMC5395606
DOI:
10.3389/fnhum.2017.00190

   2016

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

   2015

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications

Surface EMG and muscle fatigue: multi-channel approaches to the study of myoelectric manifestations of muscle fatigue

In a broad view, fatigue is used to indicate a degree of weariness. On a muscular level, fatigue posits the reduced capacity of muscle fibres to produce force, even in the presence of motor neuron excitation via either spinal mechanisms or electric pulses applied externally. Prior to decreased force, when sustaining physically demanding tasks, alterations in the muscle electrical properties take place. These alterations, termed myoelectric manifestation of fatigue, can be assessed non-invasively with a pair of surface electrodes positioned appropriately on the target muscle; traditional approach. A relatively more recent approach consists of the use of multiple electrodes. This multi-channel approach provides access to a set of physiologically relevant variables on the global muscle level or on the level of single motor units, opening new fronts for the study of muscle fatigue; it allows for: (i) a more precise quantification of the propagation velocity, a physiological variable of marked interest to the study of fatigue; (ii) the assessment of regional, myoelectric manifestations of fatigue; (iii) the analysis of single motor units, with the possibility to obtain information about motor unit control and fibre membrane changes.
This review provides a methodological account on the multi-channel approach for the study of myoelectric manifestation of fatigue and on the experimental conditions to which it applies, as well as examples of their current applications