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Pineau A, Martin A, Lepers R, Papaiordanidou M. Effect of combined electrical stimulation and brief muscle lengthening on torque development. J Appl Physiol (1985) 2024; 136:844-852. [PMID: 38357725 DOI: 10.1152/japplphysiol.00671.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 01/31/2024] [Accepted: 02/13/2024] [Indexed: 02/16/2024] Open
Abstract
This study aimed to evaluate torque production in response to the application of a brief muscle lengthening during neuromuscular electrical stimulation (NMES) applied over the posterior tibial nerve. Fifteen participants took part in three experimental sessions, where wide-pulse NMES delivered at 20 and 100 Hz (pulse duration of 1 ms applied during 15 s at an intensity evoking 5-10% of maximal voluntary contraction) was either applied alone (NMES condition) or in combination with a muscle lengthening at three distinct speeds (60, 180, or 300°/s; NMES + LEN condition). The torque-time integral (TTI) and the muscle activity following the stimulation trains [sustained electromyography (EMG)] were calculated for each condition. Results show that TTI and sustained EMG activity were higher for the NMES + LEN condition only when using 100-Hz stimulation, regardless of the lengthening speed (P = 0.029 and P = 0.007 for the two parameters, respectively). This indicates that superimposing a muscle lengthening to high-frequency NMES can enhance the total torque production, partly due to neural mechanisms, as evidenced by the higher sustained EMG activity. This finding has potential clinical relevance, especially when it comes to finding ways to enhance torque production to optimize the effectiveness of NMES training programs.NEW & NOTEWORTHY This study showed, for the first time, that the combined application of a brief muscle lengthening and wide-pulse neuromuscular electrical stimulation (NMES) delivered over the posterior tibial nerve can entail increased torque production as compared with the sole application of NMES. This observation, present only for high stimulation frequencies (100 Hz) and independently of the lengthening speed, is attributed to neural mechanisms, most probably related to increased afferents' solicitation, although muscular phenomena cannot be excluded.
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Affiliation(s)
- Antoine Pineau
- INSERM UMR1093-CAPS, Université Bourgogne, UFR des Sciences du Sport, Dijon, France
| | - Alain Martin
- INSERM UMR1093-CAPS, Université Bourgogne, UFR des Sciences du Sport, Dijon, France
| | - Romuald Lepers
- INSERM UMR1093-CAPS, Université Bourgogne, UFR des Sciences du Sport, Dijon, France
| | - Maria Papaiordanidou
- INSERM UMR1093-CAPS, Université Bourgogne, UFR des Sciences du Sport, Dijon, France
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Paris MT, Kulkarni SV, Rice CL. Electrically Evoked Isotonic Plantar Flexion Contractions Are Impaired Less than Voluntary After a Dynamic Fatiguing Task. Med Sci Sports Exerc 2023; 55:2096-2102. [PMID: 37379258 DOI: 10.1249/mss.0000000000003243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
PURPOSE Evaluating central and peripheral processes responsible for reduced power after dynamic fatiguing tasks are often limited to isometric torque, which may not accurately reflect dynamic contractile performance. Here, we compare voluntary and electrically evoked peak power (and its determinants: dynamic torque and velocity) and rate of velocity development (RVD) before and after a dynamic fatiguing task using concentric Plantar flexion contractions. METHODS Young (18-32 yr) males ( n = 11) and females ( n = 2) performed maximal-effort isotonic Plantar flexion contractions using a load of 20% isometric torque until an approximately 75% reduction in peak power. Voluntary and electrically evoked (300 Hz tibial nerve stimulation) contractions loaded to 20% and 40% isometric torque through 25° ankle joint range of motion were compared before and 0, 2.5, 5, and 10 min after task termination. RESULTS At task termination, peak power and RVD of voluntary contractions at both loads were reduced more (~40% to 50% reduction) than electrically evoked (~25% to 35% reduction) contractions ( P < 0.001 and P = 0.003). Throughout the recovery period, electrically evoked peak power and RVD returned to baseline sooner (<5 min) than voluntary contractions, which were still depressed at 10 min. Reductions in peak power for the 20% load were equally due to impaired dynamic torque and velocity, whereas velocity was impaired more than dynamic torque ( P < 0.001) for the 40% load. CONCLUSIONS The relative preservation of electrically evoked power and RVD compared with voluntary contractions at task termination and quicker recovery to baseline indicates that the reductions in dynamic contractile performance after task termination are due to both central and peripheral processes; however, the relative contribution of dynamic torque and velocity is load dependent.
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Affiliation(s)
- Michael T Paris
- School of Kinesiology, Faculty of Health Sciences, University of Western Ontario, London, ON, CANADA
| | - Sohum V Kulkarni
- School of Kinesiology, Faculty of Health Sciences, University of Western Ontario, London, ON, CANADA
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Magnuson JR, Kang HJ, Debenham MIB, McNeil CJ, Dalton BH. Effects of sleep deprivation on perceived and performance fatigability in females: An exploratory study. Eur J Sport Sci 2023; 23:1922-1931. [PMID: 35989687 DOI: 10.1080/17461391.2022.2115944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sleep deprivation (SD) is prevalent and impairs motor function; however, little is known about its effect on perceived and performance fatigability, especially in females. To examine the effects of 24 h of SD on these attributes of fatigue, nine females completed a 20-min isometric, sustained elbow flexion contraction, followed by 10 min of recovery. The superimposed twitch (SIT) elicited via transcranial magnetic stimulation (TMS) assessed supraspinal drive. Biceps brachii electromyographic data indicated neural excitability in response to stimulation over the motor cortex (motor evoked potential; MEP), corticospinal tract (cervicomedullary motor evoked potential; CMEP), and brachial plexus (maximal M-wave; Mmax). MEPs and CMEPs were recorded during a TMS-induced silent period. At baseline, ratings of perceived effort (RPE; 2.9 vs. 1.6) and fatigue (RPF; 6.9 vs. 2.9), were higher for SD than control. Across the 20-min contraction, RPE increased from 2.2 to 7.6, SIT and MEP/CMEP increased by 284 and 474%, respectively, whereas maximal voluntary isometric contraction (MVC) torque and CMEP/Mmax decreased by 26 and 57%, respectively. No differences were found across conditions for MVC, SIT, Mmax, CMEP/Mmax, or MEP/CMEP prior to, during, and after the fatiguing task. During recovery, RPE (4.9 vs. 3.4), RPF (7.6 vs. 2.8), and perception of task difficulty (5.5 vs. 4.5) were greater for SD than control. Acute SD does not appear to alter performance fatigability development and subsequent recovery; however, it increases perceptions of fatigue, effort, and task difficulty. Thus, the disconnect between perceived and actual neuromuscular capacity following a sustained, submaximal isometric task is exacerbated by SD.HighlightsSleep deprivation did not alter supraspinal drive or neural excitability during and after a 20-min submaximal elbow flexion contractionSleep deprivation increased perceived fatigue and perception of task difficultyThe disconnect between perceived and performance fatigability is exacerbated in a sleep-deprived state.
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Affiliation(s)
- Justine R Magnuson
- School of Health and Exercise Sciences and Centre for Heart, Lung and Vascular Health, The University of British Columbia, Kelowna, Canada
| | - Hogun J Kang
- School of Health and Exercise Sciences and Centre for Heart, Lung and Vascular Health, The University of British Columbia, Kelowna, Canada
| | - Mathew I B Debenham
- School of Health and Exercise Sciences and Centre for Heart, Lung and Vascular Health, The University of British Columbia, Kelowna, Canada
| | - Chris J McNeil
- School of Health and Exercise Sciences and Centre for Heart, Lung and Vascular Health, The University of British Columbia, Kelowna, Canada
| | - Brian H Dalton
- School of Health and Exercise Sciences and Centre for Heart, Lung and Vascular Health, The University of British Columbia, Kelowna, Canada
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Baude M, Guihard M, Gault-Colas C, Bénichou L, Coste A, Méningaud JP, Schmitz D, Natella PA, Audureau E, Gracies JM. Guided Self-rehabilitation Contract vs conventional therapy in chronic peripheral facial paresis: VISAGE, a multicenter randomized controlled trial. BMC Neurol 2023; 23:148. [PMID: 37038105 PMCID: PMC10084642 DOI: 10.1186/s12883-023-03096-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 01/27/2023] [Indexed: 04/12/2023] Open
Abstract
BACKGROUND One year after persistent peripheral facial paresis (PFP), prescriptions of conventional rehabilitation are often downgraded into maintenance rehabilitation or discontinued, the patient entering what is seen as a chronic stage. This therapeutic choice is not consistent with current knowledge about behavior-induced plasticity, which is available all life long and may allow intense sensorimotor rehabilitation to remain effective. This prospective, randomized, multicenter single-blind study in subjects with chronic unilateral PFP evaluates changes in facial motor function with a Guided Self-rehabilitation Contract (GSC) vs. conventional therapy alone, carried out for six months. METHODS Eighty-two adult subjects with chronic unilateral PFP (> 1 year since facial nerve injury) will be included in four tertiary, maxillofacial surgery (2), otolaryngology (1) and rehabilitation (1) centers to be randomized into two rehabilitation groups. In the experimental group, the PM&R specialist will implement the GSC method, which for PFP involves intensive series of motor strengthening performed daily on three facial key muscle groups, i.e. Frontalis, Orbicularis oculi and Zygomatici. The GSC strategy involves: i) prescription of a daily self-rehabilitation program, ii) teaching of the techniques involved in the program, iii) encouragement and guidance of the patient over time, in particular by requesting a quantified diary of the work achieved to be returned by the patient at each visit. In the control group, participants will benefit from community-based conventional therapy only, according to their physician's prescription. The primary outcome measure is the composite score of Sunnybrook Facial Grading System. Secondary outcome measures include clinical and biomechanical facial motor function quantifications (Créteil Scale and 3D facial motion analysis through the Cara system), quality of life (Facial Clinimetric Evaluation and Short-Form 12), aesthetic considerations (FACE-Q scale) and mood representations (Hospital Anxiety and Depression scale). Participants will be evaluated every three months by a blinded investigator, in addition to four phone calls (D30/D60/D120/D150) to monitor compliance and tolerance to treatment. DISCUSSION This study will increase the level of knowledge on the effects of intense facial motor streng- Facial paralysisthening prescribed through a GSC in patients with chronic peripheral facial paresis. TRIAL REGISTRATION ClinicalTrials.gov, NCT04074018 . Registered 29 August 2019. PROTOCOL VERSION Version N°4.0-04/02/2021.
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Affiliation(s)
- Marjolaine Baude
- BIOTN Research Unit 7377, Université Paris-Est Créteil (UPEC), 94000, Créteil, France.
- Service de Rééducation Neurolocomotrice, AP-HP, Hôpitaux Universitaires Henri Mondor, 1 Rue Gustave Eiffel, 94000, Créteil, France.
| | - Marina Guihard
- BIOTN Research Unit 7377, Université Paris-Est Créteil (UPEC), 94000, Créteil, France
| | - Caroline Gault-Colas
- Service de Rééducation Neurolocomotrice, AP-HP, Hôpitaux Universitaires Henri Mondor, 1 Rue Gustave Eiffel, 94000, Créteil, France
| | - Ludovic Bénichou
- Hôpital Paris Saint-Joseph, Service de Chirurgie Maxillo-Faciale Stomatologie, 75015, Paris, France
| | - André Coste
- Centre Hospitalier Intercommunal Créteil, Service d'ORL, Stomatologie Et Chirurgie Cervico-Faciale, 94000, Créteil, France
| | - Jean-Paul Méningaud
- AP-HP, Service de Chirurgie Plastique, Reconstructrice, Esthétique Et Maxillo-Faciale, Hôpitaux Universitaires Henri Mondor, 94000, Créteil, France
| | - David Schmitz
- AP-HP, Unité de Recherche Clinique, Hôpitaux Universitaires Henri Mondor, 94000, Créteil, France
| | - Pierre-André Natella
- AP-HP, Unité de Recherche Clinique, Hôpitaux Universitaires Henri Mondor, 94000, Créteil, France
| | - Etienne Audureau
- AP-HP, Unité de Recherche Clinique, Hôpitaux Universitaires Henri Mondor, 94000, Créteil, France
- AP-HP, Service de Santé Publique, Hôpitaux Universitaires Henri Mondor, 94000, Créteil, France
- DHU A-TVB, IRMB- EA 7376 CEpiA (Clinical Epidemiology And Ageing Unit), Université Paris Est-Créteil, 94000, Créteil, France
| | - Jean-Michel Gracies
- BIOTN Research Unit 7377, Université Paris-Est Créteil (UPEC), 94000, Créteil, France
- Service de Rééducation Neurolocomotrice, AP-HP, Hôpitaux Universitaires Henri Mondor, 1 Rue Gustave Eiffel, 94000, Créteil, France
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Theodosiadou A, Henry M, Duchateau J, Baudry S. Revisiting the use of Hoffmann reflex in motor control research on humans. Eur J Appl Physiol 2023; 123:695-710. [PMID: 36571622 DOI: 10.1007/s00421-022-05119-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 12/17/2022] [Indexed: 12/27/2022]
Abstract
Research in movement science aims at unravelling mechanisms and designing methods for restoring and maximizing human functional capacity, and many techniques provide access to neural adjustments (acute changes) or long-term adaptations (chronic changes) underlying changes in movement capabilities. First described by Paul Hoffmann over a century ago, when an electrical stimulus is applied to a peripheral nerve, this causes action potentials in afferent axons, primarily the Ia afferents of the muscle spindles, which recruit homonymous motor neurons, thereby causing an electromyographic response known as the Hoffmann (H) reflex. This technique is a valuable tool in the study of the neuromuscular function in humans and has provided relevant information in the neural control of movement. The large use of the H reflex in motor control research on humans relies in part to its relative simplicity. However, such simplicity masks subtleties that require rigorous experimental protocols and careful data interpretation. After highlighting basic properties and methodological aspects that should be considered for the correct use of the H-reflex technique, this brief narrative review discusses the purpose of the H reflex and emphasizes its use as a tool to assess the effectiveness of Ia afferents in discharging motor neurones. The review also aims to reconsider the link between H-reflex modulation and Ia presynaptic inhibition, the use of the H-reflex technique in motor control studies, and the effects of ageing. These aspects are summarized as recommendations for the use of the H reflex in motor control research on humans.
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Affiliation(s)
- Anastasia Theodosiadou
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Mélanie Henry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium
| | - Stéphane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology (LABNeuro), Faculty of Motor Sciences, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 Route de Lennik, CP 640, 1070, Brussels, Belgium.
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6
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Angus SA, Chang JC, Mann LM, Thompson BP, Doherty CJ, Dominelli PB. Altering magnetic field strength impacts the assessment of diaphragmatic function using cervical magnetic stimulation. Respir Physiol Neurobiol 2023; 309:104012. [PMID: 36592844 DOI: 10.1016/j.resp.2022.104012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 12/20/2022] [Accepted: 12/28/2022] [Indexed: 12/31/2022]
Abstract
Quantifying diaphragm neuromuscular function using cervical magnetic stimulation (CMS) typically uses only a single stimulator (1-Stim) which may be inadequate to maximally stimulate the phrenic nerves. We questioned if using two stimulators (2-Stim) together alters diaphragm neuromuscular function at baseline and following inspiratory pressure threshold loading. Six (n = 3 female) healthy young participants were instrumented with esophageal and gastric balloon tipped catheters and electrodes over the 7-8th intercostal space. With either 1-Stim or 2-Stim an incremental protocol, where the stimulator intensity was progressively increased was completed prior to a series of potentiated twitches. The inspiratory threshold loading test consisted of loaded breathing to failure. Compared to 1-Stim, 2-Stim resulted in significantly greater unpotentiated Pditw and M-waves during the incremental protocol (both p < 0.01). Similarly, 2-Stim resulted in greater potentiated Pditw (31 ± 8 vs. 41 ± 9 cmH2O; p = 0.02) and M-waves (6.4 ± 2.9 vs. 8.6 ± 2.4 V; p = 0.02). Our findings suggest that CMS using 1-Stim is unlikely to generate a sufficient magnetic field to maximally stimulate the phrenic nerves and may underestimate diaphragm function.
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Affiliation(s)
- Sarah A Angus
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada
| | - Jou-Chung Chang
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada
| | - Leah M Mann
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada
| | - Benjamin P Thompson
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada
| | - Connor J Doherty
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada
| | - Paolo B Dominelli
- Department of Kinesiology and Health Sciences, Faculty of Health, University of Waterloo, Waterloo, ON, Canada.
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Batista-Ferreira L, Rabelo NF, da Cruz GM, Costa JNDA, Elias LA, Mezzarane RA. Effects of voluntary contraction on the soleus H-reflex of different amplitudes in healthy young adults and in the elderly. Front Hum Neurosci 2022; 16:1039242. [PMID: 36590063 PMCID: PMC9797586 DOI: 10.3389/fnhum.2022.1039242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 11/30/2022] [Indexed: 12/23/2022] Open
Abstract
A number of H-reflex studies used a moderate steady voluntary contraction in an attempt to keep the motoneuron pool excitability relatively constant. However, it is not clear whether the voluntary muscle activation itself represents a confounding factor for the elderly, as a few ongoing mechanisms of reflex modulation might be compromised. Further, it is well-known that the amount of either inhibition or facilitation from a given conditioning depends on the size of the test H-reflex. The present study aimed at evaluating the effects of voluntary contraction over a wide range of reflex amplitudes. A significant reflex facilitation during an isometric voluntary contraction of the soleus muscle (15% of the maximal voluntary isometric contraction-MVC) was found for both young adults and the elderly (p < 0.05), regardless of their test reflex amplitudes (considering the ascending limb of the H-reflex recruitment curve-RC). No significant difference was detected in the level of reflex facilitation between groups for all the amplitude parameters extracted from the RC. Simulations with a computational model of the motoneuron pool driven by stationary descending commands yielded qualitatively similar amount of reflex facilitation, as compared to human experiments. Both the experimental and modeling results suggest that possible age-related differences in spinal cord mechanisms do not significantly influence the reflex modulation during a moderate voluntary muscle activation. Therefore, a background voluntary contraction of the ankle extensors (e.g., similar to the one necessary to maintain upright stance) can be used in experiments designed to compare the RCs of both populations. Finally, in an attempt to elucidate the controversy around changes in the direct motor response (M-wave) during contraction, the maximum M-wave (Mmax) was compared between groups and conditions. It was found that the Mmax significantly increases (p < 0.05) during contraction and decreases (p < 0.05) with age arguably due to muscle fiber shortening and motoneuron loss, respectively.
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Affiliation(s)
- Leandra Batista-Ferreira
- Laboratory of Signal Processing and Motor Control, Faculty of Physical Education, University of Brasília, Brasília, Goiás, Brazil
| | - Natielle Ferreira Rabelo
- Neural Engineering Research Laboratory, Center for Biomedical Engineering, University of Campinas, Campinas, São Paulo, Brazil,Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Gabriel Menezes da Cruz
- Laboratory of Signal Processing and Motor Control, Faculty of Physical Education, University of Brasília, Brasília, Goiás, Brazil
| | | | - Leonardo Abdala Elias
- Neural Engineering Research Laboratory, Center for Biomedical Engineering, University of Campinas, Campinas, São Paulo, Brazil,Department of Electronics and Biomedical Engineering, School of Electrical and Computer Engineering, University of Campinas, Campinas, São Paulo, Brazil
| | - Rinaldo André Mezzarane
- Laboratory of Signal Processing and Motor Control, Faculty of Physical Education, University of Brasília, Brasília, Goiás, Brazil,Postgraduate Program in Biomedical Engineering, University of Brasília, Brasília, Goiás, Brazil,*Correspondence: Rinaldo André Mezzarane,
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8
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Rodriguez-Falces J, Place N. Sarcolemmal Excitability, M-Wave Changes, and Conduction Velocity During a Sustained Low-Force Contraction. Front Physiol 2021; 12:732624. [PMID: 34721063 PMCID: PMC8554155 DOI: 10.3389/fphys.2021.732624] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Accepted: 09/14/2021] [Indexed: 11/20/2022] Open
Abstract
This study was undertaken to investigate whether sarcolemmal excitability is impaired during a sustained low-force contraction [10% maximal voluntary contraction (MVC)] by assessing muscle conduction velocity and also by analyzing separately the first and second phases of the muscle compound action potential (M wave). Twenty-one participants sustained an isometric knee extension of 10% MVC for 3min. M waves were evoked by supramaximal single shocks to the femoral nerve given at 10-s intervals. The amplitude, duration, and area of the first and second M-wave phases were computed. Muscle fiber conduction velocity, voluntary surface electromyographic (EMG), perceived effort, MVC force, peak twitch force, and temperature were also recorded. The main findings were: (1) During the sustained contraction, conduction velocity remained unchanged. (2) The amplitude of the M-wave first phase decreased for the first ~30s (−7%, p<0.05) and stabilized thereafter, whereas the second phase amplitude increased for the initial ~30s (+7%, p<0.05), before stabilizing. (3) Both duration and area decreased steeply during the first ~30s, and then more gradually for the rest of the contraction. (4) During the sustained contraction, perceived effort increased fivefold, whereas knee extension EMG increased by ~10%. (5) Maximal voluntary force and peak twitch force decreased (respectively, −9% and −10%, p<0.05) after the low-force contraction. Collectively, the present results indicate that sarcolemmal excitability is well preserved during a sustained 10% MVC task. A depression of the M-wave first phase during a low-force contraction can occur even in the absence of changes in membrane excitability. The development of fatigue during a low-force contraction can occur without alteration of membrane excitability.
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Affiliation(s)
- Javier Rodriguez-Falces
- Department of Electrical and Electronical Engineering, Public University of Navarre, Pamplona, Spain
| | - Nicolas Place
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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Luu MJ, Jones KE, Collins DF. Decreased excitability of motor axons contributes substantially to contraction fatigability during neuromuscular electrical stimulation. Appl Physiol Nutr Metab 2021; 46:346-355. [DOI: 10.1139/apnm-2020-0366] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The present study was designed to (i) determine the time course of changes in motor axon excitability during and after neuromuscular electrical stimulation (NMES); and (ii) characterize the relationship between contraction fatigability, NMES frequency, and changes at the axon, neuromuscular junction, and muscle. Eight neurologically intact participants attended 3 sessions. NMES was delivered over the common peroneal nerve at 20, 40, or 60 Hz for 8 min (0.3 s “on”, 0.7 s “off”). Threshold tracking was used to measure changes in axonal excitability. Supramaximal stimuli were used to assess neuromuscular transmission and force-generating capacity of the tibialis anterior muscle. Torque decreased by 49% and 62% during 8 min of 40 and 60 Hz NMES, respectively. Maximal twitch torque decreased only during 60 Hz NMES. Motor axon excitability decreased by 14%, 27%, and 35% during 20, 40, and 60 Hz NMES, respectively. Excitability recovered to baseline immediately (20 Hz) and at 2 min (40 Hz) and 4 min (60 Hz) following NMES. Overall, decreases in axonal excitability best predicted how torque declined over 8 min of NMES. During NMES, motor axons become less excitable and motor units “drop out” of the contraction, contributing substantially to contraction fatigability and its dependence on NMES frequency. Novelty: The excitability of motor axons decreased during NMES in a frequency-dependent manner. As excitability decreased, axons failed to reach threshold and motor units dropped out of the contraction. Overall, decreased excitability best predicted how torque declined and thus is a key contributor to fatigability during NMES.
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Affiliation(s)
- M. John Luu
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Kelvin E. Jones
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - David F. Collins
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
- Faculty of Kinesiology, Sport, and Recreation, Neuroscience and Mental Health Institute, Sensorimotor Rehabilitation Neuroscience Group, University of Alberta, Edmonton, AB T6G 2H9, Canada
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Focal Vibration Alters Human Digital Sensory Nerve Action Potentials: A Pilot Study. Neural Plast 2021; 2021:8819169. [PMID: 33763127 PMCID: PMC7949868 DOI: 10.1155/2021/8819169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 12/17/2020] [Accepted: 02/05/2021] [Indexed: 12/04/2022] Open
Abstract
Introduction We studied the impact of vibratory stimulation on the electrophysiological features of digital sensory nerve action potential (SNAP). Methods The antidromic digit 3 SNAP was recorded in 19 healthy adults before, during, and after applying a vibration to either 3rd or 5th metacarpal phalangeal joint (MCPJ) at 60 Hz and amplitude of 2 mm. 100% supramaximal stimulus intensity was performed in 5 subjects (randomly selected from the 19 subjects) where the SNAP sizes were recorded. Results The amplitude of digit 3 SNAP declined to 58.9 ± 8.6% when a vibration was applied to MCPJ digit 3. These impacts did not change by increasing the electrical stimulus intensity. The SNAP regained its baseline value immediately after the cessation of vibration stimulation. The magnitude of size reduction of digit 3 SNAP was less when vibration was moved to from MCPJ of digit 3 to MCPJ of digit 5. Discussion. The marked drop of the SNAP size during vibratory stimulation reflects the decreased responsiveness of Aβ afferents to electrical stimulation, which deserve further investigation in the study of focal vibration in neurorehabilitation.
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Latella C, Pinto MD, Nuzzo JL, Taylor JL. Effects of postexercise blood flow occlusion on quadriceps responses to transcranial magnetic stimulation. J Appl Physiol (1985) 2021; 130:1326-1336. [PMID: 33571056 DOI: 10.1152/japplphysiol.01082.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
For a fatigued hand muscle, group III/IV afferent firing maintains intracortical facilitation (ICF) without influencing corticospinal excitability. Exercise of larger muscles produces greater afferent firing. Thus, this study investigated if fatigue-related firing of group III/IV afferents from a large muscle group (quadriceps) modulates intracortical and corticospinal networks. In two sessions, participants (n = 18) completed a 2-min maximal voluntary isometric contraction (MVIC) of knee extensors with (OCC) or without (CON) postexercise blood flow occlusion to maintain afferent firing. Pre- and postexercise, single- and paired-pulse transcranial magnetic stimulation (TMS) elicited motor evoked potentials (MEPs) from vastus lateralis (VL), vastus medialis, and rectus femoris. Test pulse intensities evoked VL MEPs of ∼0.5 mV and were adjusted postexercise. The conditioning stimulus for ICF and short-interval intracortical inhibition (SICI) was constant and set to evoke ∼50% of maximum ICF. Muscle pain was also assessed (0-10 scale). Postexercise, muscle pain was greater for OCC than CON (Median = 8.6 vs. 2.3; P < 0.001). MEPs were depressed for CON (all muscles: Δ -24.3 to -34.1%; P ≤ 0.018) despite increased stimulus intensity (∼10%, P < 0.001), but both MEPs and intensity remained unchanged for OCC. ICF was depressed postexercise in OCC (VL and RF: Δ -59.8% and -28.8%, respectively P = 0.016-0.018) but not in CON (all muscles: Δ -3.8 to -44.3%, P = 0.726-1.0), but was not different between conditions (interactions: P = 0.143-0.252). No interactions were observed for SICI (all muscles: P ≥ 0.266). Group III/IV afferent firing counteracts the postcontraction depression of MEPs in quadriceps. However, intracortical inhibitory and facilitatory networks are not implicated in this response.NEW & NOTEWORTHY Maintained exercise-induced firing of group III/IV quadriceps muscle afferents counteracts known reductions in corticospinal excitability that occur with fatigue. However, the results suggest that this increased excitability is not underpinned by changes in intracortical facilitatory or inhibitory networks. These findings are not consistent with previous findings for hand muscle, which reported preserved intracortical facilitation with fatigue-related sustained group III/IV muscle afferent firing.
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Affiliation(s)
- Christopher Latella
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.,Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, Western Australia, Australia
| | - Matheus D Pinto
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia
| | - James L Nuzzo
- Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, Western Australia, Australia.,Neuroscience Research Australia, Randwick, New South Wales, Australia
| | - Janet L Taylor
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia.,Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, Western Australia, Australia.,Neuroscience Research Australia, Randwick, New South Wales, Australia
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Archiza B, Reinhard PA, Welch JF, Sheel AW. Sex differences in diaphragmatic fatigue: Effects of hypoxia during inspiratory loading. J Physiol 2020; 599:1319-1333. [PMID: 33180958 DOI: 10.1113/jp280704] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Accepted: 10/26/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Under normoxic conditions, both healthy female and male diaphragms fatigue at a similar degree when matched for absolute diaphragmatic work during inspiratory loading. We investigated whether similarities in diaphragm fatigability persist under acute hypoxic conditions. We found that, in acute hypoxia, fatigue of the diaphragm is greater in women compared to men, whereas the magnitude of fatigue in normoxia did not differ between sexes. When matched for maximal diaphragm strength, women and men had a similar pressor response to work-matched inspiratory loading, independent of oxygen availability. ABSTRACT In normoxia, women and men display a comparable magnitude of diaphragmatic fatigue (DF) after work-matched inspiratory loading. Whether these sex similarities are maintained under acute hypoxic conditions is unknown. We investigated the influence of acute hypoxia during work-matched inspiratory pressure-threshold loading (PTL) on DF in healthy women (n = 8) and men (n = 8). Two 5 min isocapnic PTL tasks targeting a transdiaphragmatic pressure (Pdi ) of 92 cmH2 O in normoxia and hypoxia (8% O2 ) were performed on separate days (≥48 h). DF was quantified by twitch Pdi (Pdi,tw ) via cervical magnetic stimulation post-PTL. Women and men had similar maximal Pdi (Pdi,max ; women: 171 ± 16, men: 178 ± 20 cmH2 O) and relative target workload (women: 54 ± 5%, men: 53 ± 6% Pdi,max ). The absolute cumulative diaphragmatic work did not differ between sexes in normoxia (women: 12,653 ± 1796 cmH2 O s-1 , men: 13,717 ± 1231 cmH2 O s-1 ; P = 0.202) or hypoxia (women: 11,624 ± 1860 cmH2 O s-1 , men: 12 722 ± 1502 cmH2 O s-1 ; P = 0.189). In normoxia, the magnitude of reduction in Pdi,tw post-PTL was similar between sexes (women: -21.1 ± 8.4%, men: -22.5 ± 4.9 %; P = 0.193); however, a higher degree of DF was observed in women compared to men following PTL in acute hypoxia (women: -27.6 ± 7.7%, men: -23.4 ± 9.6%, P = 0.019). We conclude that the female diaphragm is more susceptible to fatigue after inspiratory loading under acute hypoxic conditions. This finding may be related to sex differences in diaphragm muscle metabolism, such as fibre type composition, contractile properties, substrate utilisation and blood perfusion.
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Affiliation(s)
- Bruno Archiza
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Paige A Reinhard
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Joseph F Welch
- Department of Physical Therapy, University of Florida, Gainesville, FL, USA
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
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Hernández RB, Carrascal M, Abian J, Michalke B, Farina M, Gonzalez YR, Iyirhiaro GO, Moteshareie H, Burnside D, Golshani A, Suñol C. Manganese-induced neurotoxicity in cerebellar granule neurons due to perturbation of cell network pathways with potential implications for neurodegenerative disorders. Metallomics 2020; 12:1656-1678. [PMID: 33206086 DOI: 10.1039/d0mt00085j] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Manganese (Mn) is essential for living organisms, playing an important role in nervous system function. Nevertheless, chronic and/or acute exposure to this metal, especially during early life stages, can lead to neurotoxicity and dementia by unclear mechanisms. Thus, based on previous works of our group with yeast and zebrafish, we hypothesized that the mechanisms mediating manganese-induced neurotoxicity can be associated with the alteration of protein metabolism. These mechanisms may also depend on the chemical speciation of manganese. Therefore, the current study aimed at investigating the mechanisms mediating the toxic effects of manganese in primary cultures of cerebellar granule neurons (CGNs). By exposing cultured CGNs to different chemical species of manganese ([[2-[(dithiocarboxy)amino]ethyl]carbamodithioato]](2-)-kS,kS']manganese, named maneb (MB), and [[1,2-ethanediylbis[carbamodithioato]](2-)]manganese mixture with [[1,2-ethanediylbis[carbamodithioato]](2-)]zinc, named mancozeb (MZ), and manganese chloride (MnCl2)), and using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, we observed that both MB and MZ induced similar cytotoxicity (LC50∼ 7-9 μM), which was higher than that of MnCl2 (LC50∼ 27 μM). Subsequently, we applied systems biology approaches, including metallomics, proteomics, gene expression and bioinformatics, and revealed that independent of chemical speciation, for non-cytotoxic concentrations (0.3-3 μM), Mn-induced neurotoxicity in CGNs is associated with metal dyshomeostasis and impaired protein metabolism. In this way, we verified that MB induced more post-translational alterations than MnCl2, which can be a plausible explanation for cytotoxic differences between both chemical species. The metabolism of proteins is one of the most energy consuming cellular processes and its impairment appears to be a key event of some cellular stress processes reported separately in other studies such as cell cycle arrest, energy impairment, cell signaling, excitotoxicity, immune response, potential protein accumulation and apoptosis. Interestingly, we verified that Mn-induced neurotoxicity shares pathways associated with the development of Alzheimer's disease, Amyotrophic Lateral Sclerosis, Huntington's disease, and Parkinson's disease. This has been observed in baker's yeast and zebrafish suggesting that the mode of action of Mn may be evolutionarily conserved.
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Affiliation(s)
- Raúl Bonne Hernández
- Laboratory of Bioinorganic and Environmental Toxicology - LABITA, Department of Exact and Earth Sciences, Federal University of São Paulo, Rua Prof. Artur Riedel, 275, CEP 09972-270, Diadema, SP, Brazil.
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Monjo F, Shemmell J. Probing the neuromodulatory gain control system in sports and exercise sciences. J Electromyogr Kinesiol 2020; 53:102442. [DOI: 10.1016/j.jelekin.2020.102442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 01/22/2023] Open
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Recovery of the first and second phases of the M wave after prolonged maximal voluntary contractions. J Electromyogr Kinesiol 2020; 50:102385. [DOI: 10.1016/j.jelekin.2019.102385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 11/18/2019] [Accepted: 12/23/2019] [Indexed: 11/24/2022] Open
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16
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Vastano R, Perez MA. Changes in motoneuron excitability during voluntary muscle activity in humans with spinal cord injury. J Neurophysiol 2020; 123:454-461. [PMID: 31461361 PMCID: PMC7052637 DOI: 10.1152/jn.00367.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/19/2019] [Accepted: 08/19/2019] [Indexed: 11/22/2022] Open
Abstract
The excitability of resting motoneurons increases following spinal cord injury (SCI). The extent to which motoneuron excitability changes during voluntary muscle activity in humans with SCI, however, remains poorly understood. To address this question, we measured F waves by using supramaximal electrical stimulation of the ulnar nerve at the wrist and cervicomedullary motor-evoked potentials (CMEPs) by using high-current electrical stimulation over the cervicomedullary junction in the first dorsal interosseous muscle at rest and during 5 and 30% of maximal voluntary contraction into index finger abduction in individuals with chronic cervical incomplete SCI and aged-matched control participants. We found higher persistence (number of F waves present in each set) and amplitude of F waves at rest in SCI compared with control participants. With increasing levels of voluntary contraction, the amplitude, but not the persistence, of F waves increased in both groups but to a lesser extent in SCI compared with control participants. Similarly, the CMEP amplitude increased in both groups but to a lesser extent in SCI compared with controls. These results were also found at matched absolutely levels of electromyographic activity, suggesting that these changes were not related to decreases in voluntary motor output after SCI. F-wave and CMEP amplitudes were positively correlated across conditions in both groups. These results support the hypothesis that the responsiveness of the motoneuron pool during voluntary activity decreases following SCI, which could alter the generation and strength of voluntary muscle contractions.NEW & NOTEWORTHY How the excitability of motoneurons changes during voluntary muscle activity in humans with spinal cord injury (SCI) remains poorly understood. We found that F-wave and cervicomedullary motor-evoked potential amplitude, outcomes reflecting motoneuronal excitability, increased during voluntary activity compared with rest in SCI participants but to a lesser extent that in controls. These results suggest that the responsiveness of motoneurons during voluntary activity decreases following SCI, which might affect functionally relevant plasticity after the injury.
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Affiliation(s)
- Roberta Vastano
- The Miami Project to Cure Paralysis, University of Miami, Miami, Florida
- Department of Neurological Surgery, University of Miami, Miami, Florida
- Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, Florida
| | - Monica A Perez
- The Miami Project to Cure Paralysis, University of Miami, Miami, Florida
- Department of Neurological Surgery, University of Miami, Miami, Florida
- Bruce W. Carter Department of Veterans Affairs Medical Center, Miami, Florida
- Shirley Ryan Ability Laboratory, Northwestern University, Chicago, Illinois
- Hines Veterans Affairs Medical Center, Chicago, Illinois
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17
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Latella C, van der Groen O, Ruas CV, Taylor JL. Effect of fatigue-related group III/IV afferent firing on intracortical inhibition and facilitation in hand muscles. J Appl Physiol (1985) 2019; 128:149-158. [PMID: 31725359 DOI: 10.1152/japplphysiol.00595.2019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Fatiguing exercise causes a reduction in motor drive to the muscle. Group III/IV muscle afferent firing is thought to contribute to this process; however, the effect on corticospinal and intracortical networks is poorly understood. In two experiments, participants performed sustained maximal isometric finger abductions of the first dorsal interosseous (FDI) muscle, with postexercise blood flow occlusion (OCC) to maintain the firing of group III/IV afferents or without occlusion (control; CON). Before and after exercise, single- and paired-pulse transcranial magnetic stimulation (TMS) tested motor evoked potentials (MEPs), intracortical facilitation [ICF (12 ms)], and short-interval intracortical inhibition [SICI2 (2 ms), SICI3 (3 ms)]. Ulnar nerve stimulation elicited maximal M waves (MMAX). For experiment 1 (n = 16 participants), TMS intensities were 70% and 120% of resting motor threshold (RMT) for the conditioning and MEP stimuli, respectively. For experiment 2 (n = 16 participants), the MEP was maintained at 1 mV before and after exercise and the conditioning stimulus individualized. In experiment 1, MEP/MMAX was reduced after exercise (~48%, P = 0.007) but was not different between conditions. No changes occurred in ICF or SICI. In experiment 2, MEP/MMAX increased (~27%, P = 0.027) and less inhibition (SICI2: ~21%, P = 0.021) occurred after exercise for both conditions, whereas ICF decreased for CON only (~28%, P = 0.006). MEPs and SICI2 were modulated by fatiguing contractions but not by group III/IV afferent firing, whereas sustained afferent firing appeared to counteract postexercise reductions in ICF in FDI. The findings do not support the idea that actions of group III/IV afferents on motor cortical networks contribute to the reduction in voluntary activation observed in other studies.NEW & NOTEWORTHY This is the first study to investigate, in human hand muscles, the action of fatigue-related group III/IV muscle afferent firing on intracortical facilitation and inhibition. In fatigued and nonexercised hand muscles, intracortical inhibition is reduced after exercise but is not modulated differently by the firing of group III/IV afferents. However, facilitation is maintained for the fatigued muscle when group III/IV afferents fire, but these results are unlikely to explain the reduction in voluntary activation observed in other studies.
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Affiliation(s)
- Christopher Latella
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Perth, Western Australia, Australia.,Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, Perth, Western Australia, Australia
| | - Onno van der Groen
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Perth, Western Australia, Australia.,Neurorehabilitation and Robotics Laboratory, Edith Cowan University, Joondalup, Perth, Western Australia, Australia
| | - Cassio V Ruas
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Perth, Western Australia, Australia
| | - Janet L Taylor
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, Perth, Western Australia, Australia.,Neurophysiology Research Laboratory, Edith Cowan University, Joondalup, Perth, Western Australia, Australia.,Neuroscience Research Australia, Randwick, New South Wales, Australia
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18
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Vitry F, Martin A, Papaiordanidou M. Torque gains and neural adaptations following low-intensity motor nerve electrical stimulation training. J Appl Physiol (1985) 2019; 127:1469-1477. [DOI: 10.1152/japplphysiol.00513.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of the study was to assess neural adaptations of the plantar-flexors induced by an electrical stimulation training applied over the motor nerve at low intensity using two different stimulation frequencies. Thirty subjects were randomly assigned into 3 groups: 20 Hz, 100 Hz, and control group. The training consisted of 15 sessions of 25 stimulation trains applied over the tibial nerve and delivered at an intensity evoking 10% maximal voluntary isometric contraction (MVIC). Before and after training, MVIC was assessed and neural adaptations were evaluated by the voluntary activation level (VAL) and the V-wave (normalized by the superimposed muscle compound action potential, V/MSUP). H-reflex and motor-evoked potential (MEP) recorded during MVIC were studied to assess spinal and corticospinal excitabilities [i.e., maximal H-reflex during maximal voluntary isometric contraction (HSUP)/MSUPand maximal motor-evoked potential during maximal voluntary isometric contraction (MEPSUP)/MSUP]. MVIC significantly increased after training only for the two training groups ( P = 0.017). This increase was accompanied by a significant increase of VAL only for these groups ( P = 0.014), whereas statistical analysis revealed a time effect for V/MSUP( P = 0.022). HSUP/MSUPand MEPSUP/MSUPwere significantly increased at post conditions only for the 100 Hz group ( P = 0.021 and P = 0.029). Results show that low-intensity electrical stimulation training applied over the motor nerve can induce torque gains, accompanied by neural adaptations. Stimulation frequency differentially affected spinal and corticospinal excitabilities, indicating that neural adaptations could have a supraspinal origin for the 20-Hz protocol, whereas spinal and supraspinal mechanisms were implicated in the torque increases after the 100-Hz training.NEW & NOTEWORTHY This study brings new insights into the neurophysiological mechanisms responsible for torque gains after electrical stimulation training using wide pulse duration and low stimulation intensity applied over the motor nerve. Stimulation frequency had a distinct impact on spinal and/or supraspinal origins of the observed neural adaptations. The use of the aforementioned stimulation parameters in rehabilitation settings can be proved beneficial in terms of strength gains while avoiding any serious discomfort because of stimulation.
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Affiliation(s)
- Florian Vitry
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21000, Dijon, France
| | - Alain Martin
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21000, Dijon, France
| | - Maria Papaiordanidou
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21000, Dijon, France
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Vitry F, Martin A, Papaiordanidou M. Impact of stimulation frequency on neuromuscular fatigue. Eur J Appl Physiol 2019; 119:2609-2616. [PMID: 31605203 DOI: 10.1007/s00421-019-04239-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 10/01/2019] [Indexed: 11/26/2022]
Abstract
PURPOSE The aim of the present study was to examine the frequency effects (20 Hz and 100 Hz) on neuromuscular fatigue using stimulation parameters favoring an indirect motor unit recruitment through the afferent pathway. METHODS Nineteen subjects were divided into two groups: 20 Hz (n = 10) and 100 Hz (n = 9). The electrical stimulation session consisted of 25 stimulation trains (20 s ON/20 s OFF, pulse width: 1 ms) applied over the tibial nerve and delivered at an intensity evoking 10% maximal voluntary isometric contraction (MVIC). Before and after these protocols, MVIC was assessed, while neural changes were evaluated by the level of activation (VAL) and muscle changes were evaluated by the twitch associated with the maximal M-wave (Pt). For all stimulation trains, the real and the theoretical values of the torque-time integral (TTIr and TTIth, respectively) were calculated. The TTIr/TTIth ratio of the first train was calculated to evaluate the presence of extra torque. RESULTS The main results showed a similar decrease in MVIC torque after both protocols accompanied by neural and muscle changes, as evidenced by the decrease in VAL and Pt. TTIr values across the 20-Hz trains remained constant, whereas they significantly decreased during the 100-Hz stimulation trains. The relative MVIC decrease was negatively correlated with TTIr/TTIth. CONCLUSION Results give evidence of an identical neuromuscular fatigue development between protocols, while lower stimulation frequency permitted preservation of a given torque level during the stimulation trains. The negative correlation between this fatigue development and TTIr/TTIth suggests that extra torque production induces greater voluntary torque losses.
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Affiliation(s)
- Florian Vitry
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, 21000, Dijon, France.
| | - Alain Martin
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, 21000, Dijon, France
| | - Maria Papaiordanidou
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, 21000, Dijon, France
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Bell JM, Lorenz C, Jones KE. Nerve excitability differences in slow and fast motor axons of the rat: more than just Ih. J Neurophysiol 2019; 122:1728-1734. [PMID: 31533011 DOI: 10.1152/jn.00269.2019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The objective was to determine biophysical differences between fast and slow motor axons using threshold tracking and demonstrate confounds related to anesthetic. Nerve excitability of motor axons innervating the slow-twitch soleus (SOL) and fast-twitch tibialis anterior (TA) muscles was tested. The experiments were conducted with pentobarbital sodium (SP) anesthetic and compared with previous results that used ketamine-xylazine (KX). Nerve excitability indices measured with SP show definitive differences between TA and SOL motor axons that extend beyond previous reports. Nerve excitability indices sensitive to changes in Ih indicated an increase in SOL axons compared with TA axons [e.g., S3 t = 7.949 (df = 10), P < 0.001; hyperpolarizing threshold electrotonus (90-100 ms), t = 2.659 (df = 20); P = 0.01; hyperpolarizing I/V slope, t = 4.308 (df = 19); P < 0.001]. SOL axons also had a longer strength-duration time constant [t = 3.35 (df = 20); P = 0.003] and a longer and larger magnitude relative refractory period [RRP (ms) t = 3.53 (df = 12); P = 0.004; Refractoriness at 2 ms, t = 0.0055 (df = 9); P = 0.006]. Anesthetic choice affected many measures of peripheral nerve excitability with differences most apparent in tests of threshold electrotonus and recovery cycle. For example, recovery cycle with KX lacked a clear superexcitable and late subexcitable period. We conclude that KX had a confounding effect on nerve excitability results consistent with ischemic depolarization. Results using SP revealed the full extent of differences in nerve excitability measures between putative slow and fast motor axons of the rat. These results provide empirical evidence, beyond conduction velocity, that the biophysical properties of motor axons vary with the type of muscle fiber innervated. These differences suggest that fast axons may be predisposed to dysfunction during hyperpolarizing stresses, e.g., electrogenic sodium pumping following sustained impulse conduction.NEW & NOTEWORTHY Nerve excitability testing is a tool used to provide insight into the properties of ion channels in peripheral nerves. It is used clinically to assess pathophysiology of axons. Researchers customarily think of motor axons as homogeneous; however, we demonstrate there are clear differences between fast and slow axons in the rat. This is important for interpreting results with selective motor neuronopathy, like aging where fast axons are at high risk of degeneration.
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Affiliation(s)
- James M Bell
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Department of Computing Science, University of Alberta, Edmonton, Alberta, Canada
| | - Chad Lorenz
- Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Kelvin E Jones
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, Alberta, Canada.,Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, Alberta, Canada
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Kirk BJC, Trajano GS, Pulverenti TS, Rowe G, Blazevich AJ. Neuromuscular Factors Contributing to Reductions in Muscle Force After Repeated, High-Intensity Muscular Efforts. Front Physiol 2019; 10:783. [PMID: 31293449 PMCID: PMC6601466 DOI: 10.3389/fphys.2019.00783] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 06/04/2019] [Indexed: 01/07/2023] Open
Abstract
Multiple neuromuscular processes contribute to the loss of force production following repeated, high-intensity muscular efforts; however, the relative contribution of each process is unclear. In Experiment 1, 16 resistance trained men performed six sets of unilateral isometric plantar flexor contractions of the right leg (3 s contraction/2 s rest; 85% maximal voluntary contraction torque; 90-s inter-set rest) until failure with and without caffeine ingestion (3 mg kg-1) on two separate days. Corticospinal excitability and cortical silent period (cSP) were assessed before and immediately, 10 and 20 min after the exercise. In Experiment 2, electrically evoked tetanic force and persistent inward current (PIC)-mediated facilitation of the motor neuron pool (estimated using neuromuscular electrical stimulation with tendon vibration) were assessed before and after the same exercise intervention in 17 resistance trained men. Results showed decreases in peak plantar flexion torque (Experiment 1: -12.2%, Experiment 2: -16.9%), electrically evoked torque (20 Hz -15.3%, 80 Hz -15.3%, variable-frequency train -17.9%), and cSP (-3.8%; i.e., reduced inhibition) post-exercise which did not recover by 20 min. Electromyographic activity (EMG; -6%), corticospinal excitability (-9%), and PIC facilitation (-24.8%) were also reduced post-exercise but recovered by 10 min. Caffeine ingestion increased torque and EMG but did not notably affect corticospinal excitability, PIC amplification, or electrically evoked torque. The data indicate that a decrease in muscle function largely underpins the loss of force after repeated, high-intensity muscular efforts, but that the loss is exacerbated immediately after the exercise by simultaneous decreases in corticospinal excitability and PIC amplitudes at the motor neurons.
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Affiliation(s)
- Benjamin J C Kirk
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - Gabriel S Trajano
- School of Exercise and Nutrition Sciences, Faculty of Health and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia
| | - Timothy S Pulverenti
- Department of Physical Therapy, College of Staten Island, Staten Island, NY, United States
| | - Grant Rowe
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
| | - Anthony J Blazevich
- Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
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Nuzzo JL, Taylor JL, Gandevia SC. CORP: Measurement of upper and lower limb muscle strength and voluntary activation. J Appl Physiol (1985) 2019; 126:513-543. [DOI: 10.1152/japplphysiol.00569.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.
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Affiliation(s)
- James L. Nuzzo
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Janet L. Taylor
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, Australia
- School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
| | - Simon C. Gandevia
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- Prince of Wales Hospital Clinical School, University of New South Wales, Sydney, Australia
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Cortical and Subcortical Contributions to Neuroplasticity after Repetitive Transspinal Stimulation in Humans. Neural Plast 2019; 2019:4750768. [PMID: 30881443 PMCID: PMC6383395 DOI: 10.1155/2019/4750768] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 10/26/2018] [Accepted: 12/17/2018] [Indexed: 01/13/2023] Open
Abstract
The objectives of this study were to establish cortical and subcortical contributions to neuroplasticity induced by noninvasive repetitive transspinal stimulation in human subjects free of any neurological disorder. To meet our objectives, before and after 40 minutes of transspinal stimulation we established changes in tibialis anterior (TA) motor-evoked potentials (MEPs) in response to paired transcranial magnetic stimulation (TMS) pulses at interstimulus intervals (ISIs) consistent with I-wave periodicity. In order to establish to what extent similar actions are exerted at the spinal cord and motor axons, changes in soleus H-reflex and transspinal evoked potential (TEP) amplitude following transspinal and group Ia afferent conditioning stimulation, respectively, were established. After 40 min of transspinal stimulation, the TA MEP consecutive peaks of facilitation produced by paired TMS pulses were significantly decreased supporting for depression of I-waves. Additionally, the soleus H-reflex and ankle TEP depression following transspinal and group Ia afferent conditioning stimulation was potentiated at intervals when both responses interacted at the spinal cord and nerve axons. These findings support the notion that repetitive transspinal stimulation decreases corticocortical inputs onto corticospinal neurons and promotes a surround inhibition in the spinal cord and nerve axons. This novel method may be a suitable neuromodulation tool to alter excitability at cortical and subcortical levels in neurological disorders.
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Sarcoglycan Alpha Mitigates Neuromuscular Junction Decline in Aged Mice by Stabilizing LRP4. J Neurosci 2018; 38:8860-8873. [PMID: 30171091 DOI: 10.1523/jneurosci.0860-18.2018] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 08/07/2018] [Accepted: 08/22/2018] [Indexed: 01/08/2023] Open
Abstract
During aging, acetylcholine receptor (AChR) clusters become fragmented and denervated at the neuromuscular junction (NMJ). Underpinning molecular mechanisms are not well understood. We showed that LRP4, a receptor for agrin and critical for NMJ formation and maintenance, was reduced at protein level in aged mice, which was associated with decreased MuSK tyrosine phosphorylation, suggesting compromised agrin-LRP4-MuSK signaling in aged muscles. Transgenic expression of LRP4 in muscles alleviated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. LRP4 ubiquitination was augmented in aged muscles, suggesting increased LRP4 degradation as a mechanism for reduced LRP4. We found that sarcoglycan α (SGα) interacted with LRP4 and delayed LRP4 degradation in cotransfected cells. AAV9-mediated expression of SGα in muscles mitigated AChR fragmentation and denervation and improved neuromuscular transmission in aged mice. These observations support a model where compromised agrin-LRP4-MuSK signaling serves as a pathological mechanism of age-related NMJ decline and identify a novel function of SGα in stabilizing LRP4 for NMJ stability in aged mice.SIGNIFICANCE STATEMENT This study provides evidence that LRP4, a receptor of agrin that is critical for NMJ formation and maintenance, is reduced at protein level in aged muscles. Transgenic expression of LRP4 in muscles ameliorates AChR fragmentation and denervation and improves neuromuscular transmission in aged mice, demonstrating a critical role of the agrin-LRP4-MuSK signaling. Our study also reveals a novel function of SGα to prevent LRP4 degradation in aged muscles. Finally, we show that NMJ decline in aged mice can be mitigated by AAV9-mediated expression of SGα in muscles. These observations provide insight into pathological mechanisms of age-related NMJ decline and suggest that improved agrin-LRP4-MuSK signaling may be a target for potential therapeutic intervention.
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25
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Sleutjes BT, Drenthen J, Boskovic E, van Schelven LJ, Kovalchuk MO, Lumens PG, van den Berg LH, Franssen H. Excitability tests using high-density surface-EMG: A novel approach to studying single motor units. Clin Neurophysiol 2018; 129:1634-1641. [DOI: 10.1016/j.clinph.2018.04.754] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 04/19/2018] [Accepted: 04/29/2018] [Indexed: 12/13/2022]
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26
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Giuriato G, Pedrinolla A, Schena F, Venturelli M. Muscle cramps: A comparison of the two-leading hypothesis. J Electromyogr Kinesiol 2018; 41:89-95. [PMID: 29857264 DOI: 10.1016/j.jelekin.2018.05.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 04/28/2018] [Accepted: 05/22/2018] [Indexed: 12/13/2022] Open
Abstract
Exercise-Associated Muscle Cramps (EAMC) are a common painful condition of muscle spasms. Despite scientists tried to understand the physiological mechanism that underlies these common phenomena, the etiology is still unclear. From 1900 to nowadays, the scientific world retracted several times the original hypothesis of heat cramps. However, recent literature seems to focus on two potential mechanisms: the dehydration or electrolyte depletion mechanism, and the neuromuscular mechanism. The aim of this review is to examine the recent literature, in terms of physiological mechanisms of EAMC. A comprehensive search was conducted on PubMed and Google Scholar. The following terminology was applied: muscle cramps, neuromuscular hypothesis (or thesis), dehydration hypothesis, Exercise-Associated muscle cramps, nocturnal cramps, muscle spasm, muscle fatigue. From the initial literature of 424 manuscripts, sixty-nine manuscripts were included, analyzed, compared and summarized. Literature analysis indicates that neuromuscular hypothesis may prevails over the initial hypothesis of the dehydration as the trigger event of muscle cramps. New evidence suggests that the action potentials during a muscle cramp are generated in the motoneuron soma, likely accompanied by an imbalance between the rising excitatory drive from the muscle spindles (Ia) and the decreasing inhibitory drive from the Golgi tendon organs. In conclusion, from the latest investigations there seem to be a spinal involvement rather than a peripheral excitation of the motoneurons.
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Affiliation(s)
- Gaia Giuriato
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Anna Pedrinolla
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Federico Schena
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy
| | - Massimo Venturelli
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Italy; Department of Internal Medicine, University of Utah, USA.
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27
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Dominelli PB, McNeil CJ, Vermeulen TD, Stuckless TJR, Brown CV, Dominelli GS, Swenson ER, Teppema LJ, Foster GE. Effect of acetazolamide and methazolamide on diaphragm and dorsiflexor fatigue: a randomized controlled trial. J Appl Physiol (1985) 2018; 125:770-779. [PMID: 29792554 DOI: 10.1152/japplphysiol.00256.2018] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Acetazolamide, a carbonic anhydrase (CA) inhibitor used clinically and to prevent acute mountain sickness, worsens skeletal muscle fatigue in animals and humans. In animals, methazolamide, a methylated analog of acetazolamide and an equally potent CA inhibitor, reportedly exacerbates fatigue less than acetazolamide. Accordingly, we sought to determine, in humans, if methazolamide would attenuate diaphragm and dorsiflexor fatigue compared with acetazolamide. Healthy men (dorsiflexor: n = 12; diaphragm: n = 7) performed fatiguing exercise on three occasions, after ingesting acetazolamide (250 mg three times a day) and then in random order, methazolamide (100 mg twice a day) or placebo for 48 h. For both muscles, subjects exercised at a fixed intensity until exhaustion on acetazolamide, with subsequent iso-time and -workload trials. Diaphragm exercise was performed using a threshold-loading device, while dorsiflexor exercise was isometric. Neuromuscular function was determined pre- and postexercise by potentiated transdiaphragmatic twitch pressure and dorsiflexor torque in response to stimulation of the phrenic and fibular nerve, respectively. Diaphragm contractility 3-10 min postexercise was impaired more for acetazolamide than methazolamide or placebo (82 ± 10, 87 ± 9, and 91 ± 8% of pre-exercise value; P < 0.05). Similarly, dorsiflexor fatigue was greater for acetazolamide than methazolamide (mean twitch torque of 61 ± 11 vs. 57 ± 13% of baseline, P < 0.05). In normoxia, methazolamide leads to less neuromuscular fatigue than acetazolamide, indicating a possible benefit for clinical use or in the prophylaxis of acute mountain sickness. NEW & NOTEWORTHY Acetazolamide, a carbonic anhydrase inhibitor, may worsen diaphragm and locomotor muscle fatigue after exercise; whereas, in animals, methazolamide does not impair diaphragm function. Compared with both methazolamide and the placebo, acetazolamide significantly compromised dorsiflexor function at rest and after exhaustive exercise. Similarly, diaphragm function was most compromised on acetazolamide followed by methazolamide and placebo. Methazolamide may be preferable over acetazolamide for clinical use and altitude illness prophylaxis to avoid skeletal muscle dysfunction.
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Affiliation(s)
- Paolo B Dominelli
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Chris J McNeil
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Tyler D Vermeulen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Troy J R Stuckless
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Courtney V Brown
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
| | - Giulio S Dominelli
- Southern Medical Program, University of British Columbia, Kelowna, Canada
| | - Erik R Swenson
- Division of Pulmonary & Critical Care Medicine, VA Puget Sound Health Care System, University of Washington , Seattle, Washington
| | - Lucas J Teppema
- Department of Anesthesiology, Leiden University Medical Center , Leiden , The Netherlands
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia , Kelowna , Canada
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28
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Hageman S, Kovalchuk MO, Sleutjes BTHM, van Schelven LJ, van den Berg LH, Franssen H. Sodium-potassium pump assessment by submaximal electrical nerve stimulation. Clin Neurophysiol 2018; 129:809-814. [PMID: 29477980 DOI: 10.1016/j.clinph.2018.01.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 12/15/2017] [Accepted: 01/07/2018] [Indexed: 12/14/2022]
Abstract
OBJECTIVE Sodium-potassium pump dysfunction in peripheral nerve is usually assessed by determining axonal hyperpolarization following maximal voluntary contraction (MVC) or maximal electrical nerve stimulation. As MVC may be unreliable and maximal electrical stimulation too painful, we assessed if hyperpolarization can also be induced by submaximal electrical nerve stimulation. METHODS In 8 healthy volunteers different submaximal electrical stimulus trains were given to the median nerve at the wrist, followed by 5 min assessment of thresholds for compound muscle action potentials of 20%, 40% or 60% of maximal. RESULTS Threshold increase after submaximal electrical nerve stimulation was most prominent after an 8 Hz train of at least 5 min duration evoking submaximal CMAPs of 60%. It induced minimal discomfort and was not painful. Threshold increase after MVC was not significantly higher than this stimulus train. CONCLUSIONS Submaximal electrical stimulation evokes activity dependent hyperpolarization in healthy test subjects without causing significant discomfort. SIGNIFICANCE Sodium-potassium pump function may be assessed using submaximal electrical stimulation.
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Affiliation(s)
- Steven Hageman
- Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Centre Utrecht, The Netherlands
| | - Maria O Kovalchuk
- Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Centre Utrecht, The Netherlands
| | - Boudewijn T H M Sleutjes
- Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Centre Utrecht, The Netherlands
| | - Leonard J van Schelven
- Department of Medical Technology & Clinical Physics, University Medical Centre Utrecht, The Netherlands
| | - Leonard H van den Berg
- Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Centre Utrecht, The Netherlands
| | - Hessel Franssen
- Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Centre Utrecht, The Netherlands.
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29
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Rodriguez-Falces J, Place N. Determinants, analysis and interpretation of the muscle compound action potential (M wave) in humans: implications for the study of muscle fatigue. Eur J Appl Physiol 2017; 118:501-521. [DOI: 10.1007/s00421-017-3788-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2017] [Accepted: 12/06/2017] [Indexed: 10/18/2022]
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30
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Giroux C, Roduit B, Rodriguez-Falces J, Duchateau J, Maffiuletti NA, Place N. Short vs. long pulses for testing knee extensor neuromuscular properties: does it matter? Eur J Appl Physiol 2017; 118:361-369. [PMID: 29218407 DOI: 10.1007/s00421-017-3778-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 11/29/2017] [Indexed: 01/13/2023]
Abstract
PURPOSE The present study aimed at comparing knee extensor neuromuscular properties determined with transcutaneous electrical stimulation using two pulse durations before and after a standardized fatigue protocol. METHODS In the first sub-study, 19 healthy participants (ten women and nine men; 28 ± 5 years) took part to two separate testing sessions involving the characterization of voluntary activation (twitch interpolation technique), muscle contractility (evoked forces by single and paired stimuli), and neuromuscular propagation (M-wave amplitude from vastus lateralis and vastus medialis muscles) obtained at supramaximal intensity with a pulse duration of either 0.2 or 1 ms. The procedures were identical in the second sub-study (N = 11), except that neuromuscular properties were also evaluated after a standardized fatiguing exercise. Electrical stimulation was delivered through large surface electrodes positioned over the quadriceps muscle and a visual analog scale was used to evaluate the discomfort to paired stimuli evoked at rest. RESULTS There was no difference between pulse durations in the estimates of voluntary activation, neuromuscular propagation, and muscle contractility both in the non-fatigued and fatigued states. The discomfort associated with supramaximal paired electrical stimuli was also comparable between the two pulse durations. CONCLUSIONS It appears that 0.2- and 1-ms-long pulses provide a comparable evaluation of knee extensor neuromuscular properties.
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Affiliation(s)
- Caroline Giroux
- Laboratory ‛Bioingenierie, Tissus et Neuroplasticité' (EA 7377), Université Paris-Est Créteil, Créteil, France.,Laboratory Sport, Expertise and Performance (EA 7370), Research Department, French Institute of Sport (INSEP), Paris, France
| | - Boris Roduit
- Institut des Sciences du Sport de l'Université de Lausanne, Quartier UNIL-Centre, Bâtiment Synathlon, 1015, Lausanne, Switzerland
| | - Javier Rodriguez-Falces
- Department of Electrical and Electronical Engineering, Public University of Navarra, Pamplona, Spain
| | - Jacques Duchateau
- Laboratory of Applied Biology and Neurophysiology, ULB Neuroscience Institute, Université Libre de Bruxelles (ULB), Bruxelles, Belgium
| | | | - Nicolas Place
- Institut des Sciences du Sport de l'Université de Lausanne, Quartier UNIL-Centre, Bâtiment Synathlon, 1015, Lausanne, Switzerland.
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31
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Barss TS, Ainsley EN, Claveria-Gonzalez FC, Luu MJ, Miller DJ, Wiest MJ, Collins DF. Utilizing Physiological Principles of Motor Unit Recruitment to Reduce Fatigability of Electrically-Evoked Contractions: A Narrative Review. Arch Phys Med Rehabil 2017; 99:779-791. [PMID: 28935232 DOI: 10.1016/j.apmr.2017.08.478] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 08/08/2017] [Accepted: 08/16/2017] [Indexed: 10/18/2022]
Abstract
Neuromuscular electrical stimulation (NMES) is used to produce contractions to restore movement and reduce secondary complications for individuals experiencing motor impairment. NMES is conventionally delivered through a single pair of electrodes over a muscle belly or nerve trunk using short pulse durations and frequencies between 20 and 40Hz (conventional NMES). Unfortunately, the benefits and widespread use of conventional NMES are limited by contraction fatigability, which is in large part because of the nonphysiological way that contractions are generated. This review provides a summary of approaches designed to reduce fatigability during NMES, by using physiological principles that help minimize fatigability of voluntary contractions. First, relevant principles of the recruitment and discharge of motor units (MUs) inherent to voluntary contractions and conventional NMES are introduced, and the main mechanisms of fatigability for each contraction type are briefly discussed. A variety of NMES approaches are then described that were designed to reduce fatigability by generating contractions that more closely mimic voluntary contractions. These approaches include altering stimulation parameters, to recruit MUs in their physiological order, and stimulating through multiple electrodes, to reduce MU discharge rates. Although each approach has unique advantages and disadvantages, approaches that minimize MU discharge rates hold the most promise for imminent translation into rehabilitation practice. The way that NMES is currently delivered limits its utility as a rehabilitative tool. Reducing fatigability by delivering NMES in ways that better mimic voluntary contractions holds promise for optimizing the benefits and widespread use of NMES-based programs.
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Affiliation(s)
- Trevor S Barss
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Emily N Ainsley
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Francisca C Claveria-Gonzalez
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada; Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, AB, Canada
| | - M John Luu
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Dylan J Miller
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada
| | - Matheus J Wiest
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada; Biomechanics Laboratory, Department of Physical Education, Federal University of Santa Catarina, Florianópolis, Brazil
| | - David F Collins
- Human Neurophysiology Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB, Canada; Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada.
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32
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Weerasinghe D, Menon P, Vucic S. Hyperpolarization-activated cyclic-nucleotide-gated channels potentially modulate axonal excitability at different thresholds. J Neurophysiol 2017; 118:3044-3050. [PMID: 28904107 DOI: 10.1152/jn.00576.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/06/2017] [Accepted: 09/12/2017] [Indexed: 11/22/2022] Open
Abstract
Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels mediate differences in sensory and motor axonal excitability at different thresholds in animal models. Importantly, HCN channels are responsible for voltage-gated inward rectifying (Ih) currents activated during hyperpolarization. The Ih currents exert a crucial role in determining the resting membrane potential and have been implicated in a variety of neurological disorders, including neuropathic pain. In humans, differences in biophysical properties of motor and sensory axons at different thresholds remain to be elucidated and could provide crucial pathophysiological insights in peripheral neurological diseases. Consequently, the aim of this study was to characterize sensory and motor axonal function at different threshold. Median nerve motor and sensory axonal excitability studies were undertaken in 15 healthy subjects (45 studies in total). Tracking targets were set to 20, 40, and 60% of maximum for sensory and motor axons. Hyperpolarizing threshold electrotonus (TEh) at 90-100 ms was significantly increased in lower threshold sensory axons times (F = 11.195, P < 0.001). In motor axons, the hyperpolarizing current/threshold (I/V) gradient was significantly increased in lower threshold axons (F = 3.191, P < 0.05). The minimum I/V gradient was increased in lower threshold motor and sensory axons. In conclusion, variation in the kinetics of HCN isoforms could account for the findings in motor and sensory axons. Importantly, assessing the function of HCN channels in sensory and motor axons of different thresholds may provide insights into the pathophysiological processes underlying peripheral neurological diseases in humans, particularly focusing on the role of HCN channels with the potential of identifying novel treatment targets.NEW & NOTEWORTHY Hyperpolarization-activated cyclic-nucleotide-gated (HCN) channels, which underlie inward rectifying currents (Ih), appear to mediate differences in sensory and motor axonal properties. Inward rectifying currents are increased in lower threshold motor and sensory axons, although different HCN channel isoforms appear to underlie these changes. While faster activating HCN channels seem to underlie Ih changes in sensory axons, slower activating HCN isoforms appear to be mediating the differences in Ih conductances in motor axons of different thresholds. The differences in HCN gating properties could explain the predilection for dysfunction of sensory and motor axons in specific neurological diseases.
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Affiliation(s)
| | - Parvathi Menon
- Department of Neurology, Westmead Hospital, Sydney, Australia; and.,Westmead Clinical School, The University of Sydney, Sydney, Australia
| | - Steve Vucic
- Department of Neurology, Westmead Hospital, Sydney, Australia; and .,Westmead Clinical School, The University of Sydney, Sydney, Australia
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33
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Peters CM, Welch JF, Dominelli PB, Molgat-Seon Y, Romer LM, McKenzie DC, Sheel AW. Influence of inspiratory resistive loading on expiratory muscle fatigue in healthy humans. Exp Physiol 2017. [PMID: 28646592 DOI: 10.1113/ep086346] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
NEW FINDINGS What is the central question of this study? This study is the first to measure objectively both inspiratory and expiratory muscle fatigue after inspiratory resistive loading to determine whether the expiratory muscles are activated to the point of fatigue when specifically loading the inspiratory muscles. What is the main finding and its importance? The absence of abdominal muscle fatigue suggests that future studies attempting to understand the neural and circulatory consequences of diaphragm fatigue can use inspiratory resistive loading without considering the confounding effects of abdominal muscle fatigue. Expiratory resistive loading elicits inspiratory as well as expiratory muscle fatigue, suggesting parallel coactivation of the inspiratory muscles during expiration. It is unknown whether the expiratory muscles are likewise coactivated to the point of fatigue during inspiratory resistive loading (IRL). The purpose of this study was to determine whether IRL elicits expiratory as well as inspiratory muscle fatigue. Healthy male subjects (n = 9) underwent isocapnic IRL (60% maximal inspiratory pressure, 15 breaths min-1 , 0.7 inspiratory duty cycle) to task failure. Abdominal and diaphragm contractile function was assessed at baseline and at 3, 15 and 30 min post-IRL by measuring gastric twitch pressure (Pga,tw ) and transdiaphragmatic twitch pressure (Pdi,tw ) in response to potentiated magnetic stimulation of the thoracic and phrenic nerves, respectively. Fatigue was defined as a significant reduction from baseline in Pga,tw or Pdi,tw . Throughout IRL, there was a time-dependent increase in cardiac frequency and mean arterial blood pressure, suggesting activation of the respiratory muscle metaboreflex. The Pdi,tw was significantly lower than baseline (34.3 ± 9.6 cmH2 O) at 3 (23.2 ± 5.7 cmH2 O, P < 0.001), 15 (24.2 ± 5.1 cmH2 O, P < 0.001) and 30 min post-IRL (26.3 ± 6.0 cmH2 O, P < 0.001). The Pga,tw was not significantly different from baseline (37.6 ± 17.1 cmH2 O) at 3 (36.5 ± 14.6 cmH2 O), 15 (33.7 ± 12.4 cmH2 O) and 30 min post-IRL (32.9 ± 11.3 cmH2 O). Inspiratory resistive loading elicits objective evidence of diaphragm, but not abdominal, muscle fatigue. Agonist-antagonist interactions for the respiratory muscles appear to be more important during expiratory versus inspiratory loading.
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Affiliation(s)
- Carli M Peters
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Joseph F Welch
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Paolo B Dominelli
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Yannick Molgat-Seon
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
| | - Lee M Romer
- Centre for Human Performance, Exercise and Rehabilitation, College of Health and Life Sciences, Brunel University London, Uxbridge, UK.,Division of Sport, Health and Exercise Sciences, Department of Life Sciences, Brunel University London, Uxbridge, UK
| | - Donald C McKenzie
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada.,Faculty of Medicine, Division of Sports Medicine, University of British Columbia, Vancouver, BC, Canada
| | - A William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, BC, Canada
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Zhang Y, Bucher D, Nadim F. Ionic mechanisms underlying history-dependence of conduction delay in an unmyelinated axon. eLife 2017; 6. [PMID: 28691900 PMCID: PMC5519330 DOI: 10.7554/elife.25382] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 07/06/2017] [Indexed: 11/13/2022] Open
Abstract
Axonal conduction velocity can change substantially during ongoing activity, thus modifying spike interval structures and, potentially, temporal coding. We used a biophysical model to unmask mechanisms underlying the history-dependence of conduction. The model replicates activity in the unmyelinated axon of the crustacean stomatogastric pyloric dilator neuron. At the timescale of a single burst, conduction delay has a non-monotonic relationship with instantaneous frequency, which depends on the gating rates of the fast voltage-gated Na+ current. At the slower timescale of minutes, the mean value and variability of conduction delay increase. These effects are because of hyperpolarization of the baseline membrane potential by the Na+/K+ pump, balanced by an h-current, both of which affect the gating of the Na+ current. We explore the mechanisms of history-dependence of conduction delay in axons and develop an empirical equation that accurately predicts this history-dependence, both in the model and in experimental measurements.
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Affiliation(s)
- Yang Zhang
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, United States
| | - Dirk Bucher
- Federated Department of Biological Sciences, NJIT and Rutgers University, Newark, United States
| | - Farzan Nadim
- Department of Mathematical Sciences, New Jersey Institute of Technology, Newark, United States.,Federated Department of Biological Sciences, NJIT and Rutgers University, Newark, United States
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Affiliation(s)
- Matthew C Kiernan
- Bushell Professor of Neurology, Royal Prince Alfred Hospital; and Brain and Mind Centre, University of Sydney, Sydney, NSW, 2040, Australia
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Picton LD, Zhang H, Sillar KT. Sodium pump regulation of locomotor control circuits. J Neurophysiol 2017; 118:1070-1081. [PMID: 28539392 DOI: 10.1152/jn.00066.2017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 05/03/2017] [Accepted: 05/16/2017] [Indexed: 12/21/2022] Open
Abstract
Sodium pumps are ubiquitously expressed membrane proteins that extrude three Na+ ions in exchange for two K+ ions, using ATP as an energy source. Recent studies have illuminated additional, dynamic roles for sodium pumps in regulating the excitability of neuronal networks in an activity-dependent fashion. We review their role in a novel form of short-term memory within rhythmic locomotor networks. The data we review derives mainly from recent studies on Xenopus tadpoles and neonatal mice. The role and underlying mechanisms of pump action broadly match previously published data from an invertebrate, the Drosophila larva. We therefore propose a highly conserved mechanism by which sodium pump activity increases following a bout of locomotion. This results in an ultraslow afterhyperpolarization (usAHP) of the membrane potential that lasts around 1 min, but which only occurs in around half the network neurons. This usAHP in turn alters network excitability so that network output is reduced in a locomotor interval-dependent manner. The pumps therefore confer on spinal locomotor networks a temporary memory trace of recent network performance.
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Affiliation(s)
- Laurence D Picton
- School of Psychology and Neuroscience, University of St. Andrews, St Andrews, Fife, Scotland, United Kingdom; and
| | - HongYan Zhang
- Centre for Neuroregeneration, University of Edinburgh, Edinburgh, Scotland, United Kingdom
| | - Keith T Sillar
- School of Psychology and Neuroscience, University of St. Andrews, St Andrews, Fife, Scotland, United Kingdom; and
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Park SB, Kiernan MC, Vucic S. Axonal Excitability in Amyotrophic Lateral Sclerosis : Axonal Excitability in ALS. Neurotherapeutics 2017; 14:78-90. [PMID: 27878516 PMCID: PMC5233634 DOI: 10.1007/s13311-016-0492-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Axonal excitability testing provides in vivo assessment of axonal ion channel function and membrane potential. Excitability techniques have provided insights into the pathophysiological mechanisms underlying the development of neurodegeneration and clinical features of amyotrophic lateral sclerosis (ALS) and related neuromuscular disorders. Specifically, abnormalities of Na+ and K+ conductances contribute to development of membrane hyperexcitability in ALS, thereby leading to symptom generation of muscle cramps and fasciculations, in addition to promoting a neurodegenerative cascade via Ca2+-mediated processes. Modulation of axonal ion channel function in ALS has resulted in significant symptomatic improvement that has been accompanied by stabilization of axonal excitability parameters. Separately, axonal ion channel dysfunction evolves with disease progression and correlates with survival, thereby serving as a potential therapeutic biomarker in ALS. The present review provides an overview of axonal excitability techniques and the physiological mechanisms underlying membrane excitability, with a focus on the role of axonal ion channel dysfunction in motor neuron disease and related neuromuscular diseases.
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Affiliation(s)
- Susanna B Park
- Brain and Mind Centre, University of Sydney, Sydney, Australia
| | | | - Steve Vucic
- Westmead Clinical School, University of Sydney, Sydney, Australia.
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Khan SI, Taylor JL, Gandevia SC. Unexpected factors affecting the excitability of human motoneurones in voluntary and stimulated contractions. J Physiol 2016; 594:2707-17. [PMID: 26940402 DOI: 10.1113/jp272164] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 02/25/2016] [Indexed: 12/12/2022] Open
Abstract
KEY POINTS The output of human motoneurone pools decreases with fatiguing exercise, but the mechanisms involved are uncertain. We explored depression of recurrent motoneurone discharges (F-waves) after sustained maximal voluntary contractions (MVCs). MVC depressed the size and frequency of F-waves in a hand muscle but a submaximal contraction (at 50% MVC) did not. Surprisingly, activation of the motoneurones antidromically by stimulation of the ulnar nerve (at 20 or 40 Hz) did not depress F-wave area or persistence. Furthermore, a sustained (3 min) MVC of a hand muscle depressed F-waves in its antagonist but not in a remote hand muscle. Our findings suggest that depression of F-waves after voluntary contractions is not simply due to repetitive activation of the motoneurones but requires descending voluntary drive. Furthermore, this effect may depress nearby, but not distant, spinal motoneurone pools. ABSTRACT There are major spinal changes induced by repetitive activity and fatigue that could contribute to 'central' fatigue but the mechanisms involved are poorly understood in humans. Here we confirmed that the recurrent motoneuronal discharge (F-wave) is reduced during relaxation immediately after a sustained maximal voluntary contraction (MVC) of an intrinsic hand muscle (abductor digiti minimi, ADM) and explored the relationship between motoneurone firing and the depression of F-waves in three ways. First, the depression (in both F-wave area and F-wave persistence) was present after a 10 s MVC (initial decrease 36.4 ± 19.1%; mean ± SD) but not after a submaximal voluntary contraction at 50% maximum. Second, to evoke motoneurone discharge without volitional effort, 10 s tetanic contractions were produced by supramaximal ulnar nerve stimulation at the elbow at physiological frequencies of 25 and 40 Hz. Surprisingly, neither produced depression of F-waves in ADM to test supramaximal stimulation of the ulnar nerve at the wrist. Finally, a sustained MVC (3 min) of the antagonist to ADM (4th palmar interosseous) depressed F-waves in the anatomically close ADM (20 ± 18.2%) but not in the more remote first dorsal interosseous on the radial side of the hand. We argue that depression of F-waves after voluntary contractions may not be due to repetitive activation of the motoneurones but requires descending voluntary drive. Furthermore, this effect may depress nearby, but not distant, spinal motoneurone pools and it reveals potentially novel mechanisms controlling the output of human motoneurones.
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Affiliation(s)
- Serajul I Khan
- Neuroscience Research Australia and University of New South Wales, Randwick, NSW, Australia
| | - Janet L Taylor
- Neuroscience Research Australia and University of New South Wales, Randwick, NSW, Australia
| | - Simon C Gandevia
- Neuroscience Research Australia and University of New South Wales, Randwick, NSW, Australia
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Prak RF, Doestzada M, Thomas CK, Tepper M, Zijdewind I. Reduced voluntary drive during sustained but not during brief maximal voluntary contractions in the first dorsal interosseous weakened by spinal cord injury. J Appl Physiol (1985) 2015; 119:1320-9. [PMID: 26404618 DOI: 10.1152/japplphysiol.00399.2015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 09/22/2015] [Indexed: 11/22/2022] Open
Abstract
In able-bodied (AB) individuals, voluntary muscle activation progressively declines during sustained contractions. However, few data are available on voluntary muscle activation during sustained contractions in muscles weakened by spinal cord injury (SCI), where greater force declines may limit task performance. SCI-related impairment of muscle activation complicates interpretation of the interpolated twitch technique commonly used to assess muscle activation. We attempted to estimate and correct for the SCI-related-superimposed twitch. Seventeen participants, both AB and with SCI (American Spinal Injury Association Impairment Scale C/D) produced brief and sustained (2-min) maximal voluntary contractions (MVCs) with the first dorsal interosseous. Force and electromyography were recorded together with superimposed (doublet) twitches. MVCs of participants with SCI were weaker than those of AB participants (20.3 N, SD 7.1 vs. 37.9 N, SD 9.5; P < 0.001); MVC-superimposed twitches were larger in participants with SCI (SCI median 10.1%, range 2.0-63.2%; AB median 4.7%, range 0.0-18.4% rest twitch; P = 0.007). No difference was found after correction for the SCI-related-superimposed twitch (median 6.7%, 0.0-17.5% rest twitch, P = 0.402). Thus during brief contractions, the maximal corticofugal output that participants with SCI could exert was similar to that of AB participants. During the sustained contraction, force decline (SCI, 58.0%, SD 15.1; AB, 57.2% SD 13.3) was similar (P = 0.887) because participants with SCI developed less peripheral (P = 0.048) but more central fatigue than AB participants. The largest change occurred at the start of the sustained contraction when the (corrected) superimposed twitches increased more in participants with SCI (SCI, 16.3% rest twitch, SD 20.8; AB, 2.7%, SD 4.7; P = 0.01). The greater reduction in muscle activation after SCI may relate to a reduced capacity to overcome fast fatigue-related excitability changes at the spinal level.
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Affiliation(s)
- Roeland F Prak
- Department of Neuroscience, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Marwah Doestzada
- Department of Neuroscience, University Medical Center Groningen, University of Groningen, The Netherlands
| | - Christine K Thomas
- The Miami Project to Cure Paralysis, Departments of Neurological Surgery, Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida; and
| | - Marga Tepper
- Department of Rehabilitation Medicine, University Medical Center Groningen, Groningen, The Netherlands
| | - Inge Zijdewind
- Department of Neuroscience, University Medical Center Groningen, University of Groningen, The Netherlands;
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Czesnik D, Howells J, Negro F, Wagenknecht M, Hanner S, Farina D, Burke D, Paulus W. Increased HCN channel driven inward rectification in benign cramp fasciculation syndrome. Brain 2015; 138:3168-79. [DOI: 10.1093/brain/awv254] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 07/08/2015] [Indexed: 12/13/2022] Open
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Neyroud D, Temesi J, Millet GY, Verges S, Maffiuletti NA, Kayser B, Place N. Comparison of electrical nerve stimulation, electrical muscle stimulation and magnetic nerve stimulation to assess the neuromuscular function of the plantar flexor muscles. Eur J Appl Physiol 2015; 115:1429-39. [DOI: 10.1007/s00421-015-3124-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 02/03/2015] [Indexed: 01/15/2023]
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Papaiordanidou M, Stevenot JD, Mustacchi V, Vanoncini M, Martin A. Electrically induced torque decrease reflects more than muscle fatigue. Muscle Nerve 2014; 50:604-7. [DOI: 10.1002/mus.24276] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2014] [Indexed: 11/08/2022]
Affiliation(s)
- Maria Papaiordanidou
- UMR7287, Institut des Sciences du Mouvement, CNRS, Faculté des Sciences du Sport; Aix-Marseille University; 163 avenue de Luminy 13288 Marseille France
| | - Jean-Damien Stevenot
- UMR7287, Institut des Sciences du Mouvement, CNRS, Faculté des Sciences du Sport; Aix-Marseille University; 163 avenue de Luminy 13288 Marseille France
| | - Valerie Mustacchi
- UMR7287, Institut des Sciences du Mouvement, CNRS, Faculté des Sciences du Sport; Aix-Marseille University; 163 avenue de Luminy 13288 Marseille France
| | - Michele Vanoncini
- UMR7287, Institut des Sciences du Mouvement, CNRS, Faculté des Sciences du Sport; Aix-Marseille University; 163 avenue de Luminy 13288 Marseille France
| | - Alain Martin
- INSERM U1093 Cognition, Action et Plasticité Sensorimotrice, Université de Bourgogne, UFR STAPS; Campus Universitaire; Dijon France
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Huynh W, Lin CSY, Krishnan AV, Vucic S, Kiernan MC. Transynaptic Changes Evident in Peripheral Axonal Function After Acute Cerebellar Infarct. THE CEREBELLUM 2014; 13:669-76. [DOI: 10.1007/s12311-014-0577-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Awiszus F. Of thresholds and "hot spots". Quo vadis transcranial magnetic stimulation? Clin Neurophysiol 2014; 125:2451-3. [PMID: 24680196 DOI: 10.1016/j.clinph.2014.03.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 03/03/2014] [Accepted: 03/04/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Friedemann Awiszus
- Neuromuscular Research Group at the Department of Orthopaedics, Otto-von-Guericke University, Magdeburg, Germany.
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45
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Kudina LP, Andreeva RE. Excitability properties of single human motor axons: are all axons identical? Front Cell Neurosci 2014; 8:85. [PMID: 24678291 PMCID: PMC3958702 DOI: 10.3389/fncel.2014.00085] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 03/06/2014] [Indexed: 12/02/2022] Open
Affiliation(s)
- Lydia P Kudina
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute) Moscow, Russia
| | - Regina E Andreeva
- Institute for Information Transmission Problems of the Russian Academy of Sciences (Kharkevich Institute) Moscow, Russia
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Milder DA, Sutherland EJ, Gandevia SC, McNulty PA. Sustained maximal voluntary contraction produces independent changes in human motor axons and the muscle they innervate. PLoS One 2014; 9:e91754. [PMID: 24622330 PMCID: PMC3951451 DOI: 10.1371/journal.pone.0091754] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 02/13/2014] [Indexed: 11/18/2022] Open
Abstract
The repetitive discharges required to produce a sustained muscle contraction results in activity-dependent hyperpolarization of the motor axons and a reduction in the force-generating capacity of the muscle. We investigated the relationship between these changes in the adductor pollicis muscle and the motor axons of its ulnar nerve supply, and the reproducibility of these changes. Ten subjects performed a 1-min maximal voluntary contraction. Activity-dependent changes in axonal excitability were measured using threshold tracking with electrical stimulation at the wrist; changes in the muscle were assessed as evoked and voluntary electromyography (EMG) and isometric force. Separate components of axonal excitability and muscle properties were tested at 5 min intervals after the sustained contraction in 5 separate sessions. The current threshold required to produce the target muscle action potential increased immediately after the contraction by 14.8% (p<0.05), reflecting decreased axonal excitability secondary to hyperpolarization. This was not correlated with the decline in amplitude of muscle force or evoked EMG. A late reversal in threshold current after the initial recovery from hyperpolarization peaked at −5.9% at ∼35 min (p<0.05). This pattern was mirrored by other indices of axonal excitability revealing a previously unreported depolarization of motor axons in the late recovery period. Measures of axonal excitability were relatively stable at rest but less so after sustained activity. The coefficient of variation (CoV) for threshold current increase was higher after activity (CoV 0.54, p<0.05) whereas changes in voluntary (CoV 0.12) and evoked twitch (CoV 0.15) force were relatively stable. These results demonstrate that activity-dependent changes in motor axon excitability are unlikely to contribute to concomitant changes in the muscle after sustained activity in healthy people. The variability in axonal excitability after sustained activity suggests that care is needed when using these measures if the integrity of either the muscle or nerve may be compromised.
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Affiliation(s)
- David A. Milder
- Neuroscience Research Australia, Sydney and University of New South Wales, Sydney, Australia
| | - Emily J. Sutherland
- Neuroscience Research Australia, Sydney and University of New South Wales, Sydney, Australia
| | - Simon C. Gandevia
- Neuroscience Research Australia, Sydney and University of New South Wales, Sydney, Australia
| | - Penelope A. McNulty
- Neuroscience Research Australia, Sydney and University of New South Wales, Sydney, Australia
- * E-mail:
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47
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Papaiordanidou M, Varray A, Fattal C, Guiraud D. Neural and muscular mechanisms of electrically induced fatigue in patients with spinal cord injury. Spinal Cord 2014; 52:246-50. [DOI: 10.1038/sc.2013.172] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 12/19/2013] [Accepted: 12/23/2013] [Indexed: 11/09/2022]
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48
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Franssen H, Straver DCG. Pathophysiology of immune-mediated demyelinating neuropathies--Part II: Neurology. Muscle Nerve 2013; 49:4-20. [PMID: 24037667 DOI: 10.1002/mus.24068] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2013] [Indexed: 12/13/2022]
Abstract
In the second part of this review we deal with the clinical aspects of immune-mediated demyelinating neuropathies. We describe the relationship between pathophysiology and symptoms and discuss the pathophysiology of specific disease entities, including Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy, anti-myelin-associated glycoprotein neuropathy, and POEMS syndrome.
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Affiliation(s)
- Hessel Franssen
- Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Heidelberglaan 100, 3584, CX Utrecht, The Netherlands
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Cintas P. [The role of dynamic electromyography in the follow-up of chronic immune polyneuropathies]. Rev Neurol (Paris) 2013; 169:978-83. [PMID: 24246114 DOI: 10.1016/j.neurol.2013.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Revised: 08/12/2013] [Accepted: 09/28/2013] [Indexed: 10/26/2022]
Abstract
Nerve conduction studies providing insight into demyelinating process are essential for the diagnostic of chronic inflammatory demyelinating polyradiculoneuropathy. For the diagnostic, several sets of electrophysiologic criteria have been established. To assess the response to treatment, nerve conduction studies are often used in trials and in clinical practice. Nevertheless, the useful of these classical electrophysiologic techniques is debated because of their lack of sensibility and specificity. In the last 20 years, several works have showed that dysfunction of channels and pump of the axonal membrane at the site and around the site of the conduction block can precipitate conduction failure and produce weakness. These important features explaining clinical status are not correctly assessed by conventional nerve conduction studies. New nerve conduction examinations in dynamic conditions can explore these hyperexcitability modifications.
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Affiliation(s)
- P Cintas
- Centre de référence de pathologie neuromusculaire du Grand Sud Ouest, pôle neurosciences, CHU Toulouse-Rangueil, 1, avenue Jean-Poulhes TSA 50032, 31052 Toulouse cedex 09, France.
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50
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Neyroud D, Vallotton A, Millet GY, Kayser B, Place N. The effect of muscle fatigue on stimulus intensity requirements for central and peripheral fatigue quantification. Eur J Appl Physiol 2013; 114:205-15. [PMID: 24197080 DOI: 10.1007/s00421-013-2760-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 10/21/2013] [Indexed: 12/20/2022]
Abstract
PURPOSE The present study was designed to determine the stimulation intensity necessary for an adequate assessment of central and peripheral components of neuromuscular fatigue of the knee extensors. METHODS Three different stimulation intensities (100, 120 and 150% of the lowest intensity evoking a plateau in M-waves and twitch amplitudes, optimal stimulation intensity, OSI) were used to assess voluntary activation level (VAL) as well as M-wave, twitch and doublet amplitudes before, during and after an incremental isometric exercise performed by 14 (8 men) healthy and physically active volunteers. A visual analog scale was used to evaluate the associated discomfort. RESULTS There was no difference (p > 0.05) in VAL between the three intensities before and after exercise. However, we found that stimulating at 100% OSI may overestimate the extent of peripheral fatigue during exercise, whereas 150% OSI stimulations led to greater discomfort associated with doublet stimulations as well as to an increased antagonist co-activation compared to 100% OSI. CONCLUSION We recommend using 120% OSI, as it constitutes a good trade-off between discomfort and reliable measurements.
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Affiliation(s)
- Daria Neyroud
- Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland
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