1
|
Andrushko JW, Levenstein JM, Zich C, Edmond EC, Campbell J, Clarke WT, Emir U, Farthing JP, Stagg CJ. Repeated unilateral handgrip contractions alter functional connectivity and improve contralateral limb response times. Sci Rep 2023; 13:6437. [PMID: 37081073 PMCID: PMC10119116 DOI: 10.1038/s41598-023-33106-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 04/07/2023] [Indexed: 04/22/2023] Open
Abstract
In humans, motor learning is underpinned by changes in sensorimotor network functional connectivity (FC). Unilateral contractions increase FC in the ipsilateral primary motor cortex (M1) and supplementary motor area (SMA); areas involved in motor planning and execution of the contralateral hand. Therefore, unilateral contractions are a promising approach to augment motor performance in the contralateral hand. In a within-participant, randomized, cross-over design, 15 right-handed adults had two magnetic resonance imaging (MRI) sessions, where functional-MRI and MR-Spectroscopic Imaging were acquired before and after repeated right-hand contractions at either 5% or 50% maximum voluntary contraction (MVC). Before and after scanning, response times (RTs) were determined in both hands. Nine minutes of 50% MVC contractions resulted in decreased handgrip force in the contracting hand, and decreased RTs and increased handgrip force in the contralateral hand. This improved motor performance in the contralateral hand was supported by significant neural changes: increased FC between SMA-SMA and increased FC between right M1 and right Orbitofrontal Cortex. At a neurochemical level, the degree of GABA decline in left M1, left and right SMA correlated with subsequent behavioural improvements in the left-hand. These results support the use of repeated handgrip contractions as a potential modality for improving motor performance in the contralateral hand.
Collapse
Affiliation(s)
- Justin W Andrushko
- College of Kinesiology, University of Saskatchewan, Saskatoon, Canada.
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK.
| | - Jacob M Levenstein
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
- Section on Functional Imaging Methods, National Institutes of Mental Health, National Institutes of Health, Bethesda, MD, USA
- Thompson Institute, University of the Sunshine Coast, Sippy Downs, Australia
| | - Catharina Zich
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
- Department of Clinical and Movement Neurosciences, University College London, London, UK
| | - Evan C Edmond
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - Jon Campbell
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - William T Clarke
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| | - Uzay Emir
- School of Health Sciences, College of Health and Human Sciences, Purdue University, West Lafayette, USA
| | | | - Charlotte J Stagg
- FMRIB, Nuffield Department of Clinical Neurosciences, Wellcome Centre for Integrative Neuroimaging, University of Oxford, Oxford, UK
| |
Collapse
|
2
|
Hadjizadeh Anvar S, Kordi MR, Alizadeh S, Ramsay E, Shabkhiz F, Behm DG. Lack of Evidence for Crossover Fatigue with Plantar Flexor Muscles. J Sports Sci Med 2022; 21:214-223. [PMID: 35719232 PMCID: PMC9157513 DOI: 10.52082/jssm.2022.214] [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] [Received: 03/04/2022] [Accepted: 04/01/2022] [Indexed: 06/15/2023]
Abstract
The occurrence and mechanisms underlying non-local or crossover muscle fatigue is an ongoing issue. This study aimed to investigate crossover fatigue of the plantar flexor muscles. Sixteen recreationally active males (n = 6) and females (n = 10) visited the laboratory for four sessions and performed a single 5-s pre-test maximal voluntary isometric contraction (MVIC) with each plantar flexors muscle. Thereafter, the fatigue intervention involved two 100-s MVICs (60-s recovery) with their dominant plantar flexors or rested for 260-s (control). Subsequently, in two separate sessions, Hoffman reflexes (H-reflex) were evoked in the non-dominant, non-exercised, leg before and following the dominant leg fatigue or control intervention (Fatigue-Reflex and Control-Reflex conditions). MVIC forces and volitional (V)-waves were monitored in the non-dominant leg in the other two sessions (Fatigue-MVIC and Control-MVIC) before and after the intervention (fatigue or control) as well as during 12 repeated MVICs and immediately thereafter. Despite the force reduction in the dominant leg (42.4%, p = 0.002), no crossover force deficit with single (F(1,9) = 0.02, p = 0.88, pƞ2 = 0.003) or repeated (F(1,9) = 0.006, p = 0.93, pƞ2 = 0.001) MVIC testing were observed. The H-reflex did not change after the fatigue (F(1,7) = 0.51; p = 0.49; pƞ2 = 0.06) or repeated MVICs (F(1,8) = 0.27; p = 0.61; pƞ2 = 0.03). There were also no crossover effects of fatigue on the V-wave with single (F(1,8) = 3.71, p = 0.09, pƞ2 = 0.31) or repeated MVICs (F(1,6) = 1.45, p = 0.27, pƞ2 = 0.19). Crossover fatigue was not evident with the plantar flexors nor any significant changes in H-reflex and V-waves in the soleus muscle. This finding suggests that crossover fatigue may not necessarily occur in slow-twitch predominant muscle groups.
Collapse
Affiliation(s)
- Saman Hadjizadeh Anvar
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's Newfoundland and Labrador (NL), Canada
- Faculty of Physical Education & Sport Sciences, University of Tehran, Tehran, Iran
| | - Mohammad Reza Kordi
- Faculty of Physical Education & Sport Sciences, University of Tehran, Tehran, Iran
| | - Shahab Alizadeh
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's Newfoundland and Labrador (NL), Canada
| | - Emma Ramsay
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's Newfoundland and Labrador (NL), Canada
| | - Fatemeh Shabkhiz
- Faculty of Physical Education & Sport Sciences, University of Tehran, Tehran, Iran
| | - David G Behm
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's Newfoundland and Labrador (NL), Canada
| |
Collapse
|
3
|
Carr JC, Bemben MG, Stock MS, DeFreitas JM. Ipsilateral and contralateral responses following unimanual fatigue with and without illusionary mirror visual feedback. J Neurophysiol 2021; 125:2084-2093. [PMID: 33909484 DOI: 10.1152/jn.00077.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Illusionary mirror visual feedback alters interhemispheric communication and influences cross-limb interactions. Combining forceful unimanual contractions with the mirror illusion is a convenient way to provoke robust alterations within ipsilateral motor networks. It is unknown, however, if the mirror illusion affects cross-limb fatigability. We examine this concept by comparing the ipsilateral and contralateral handgrip force and electromyographic (EMG) responses following unimanual fatigue with and without illusionary mirror visual feedback. Participants underwent three experimental sessions (mirror, no-mirror, and control), performing a unimanual fatigue protocol with and without illusionary mirror visual feedback. Maximal handgrip force and EMG activity were measured before and after each session for both hands during maximal unimanual and bimanual contractions. The associated EMG activity from the inactive forearm during unimanual contraction was also examined. The novel findings demonstrate greater relative fatigability during bimanual versus unimanual contraction following unimanual fatigue (-31.8% vs. -23.4%, P < 0.01) and the mirror illusion attenuates this difference (-30.3% vs. -26.3%, P = 0.169). The results show no evidence for a cross-over effect of fatigue with (+0.62%, -2.72%) or without (+0.26%, -2.49%) the mirror illusion during unimanual or bimanual contraction. The mirror illusion resulted in significantly lower levels of associated EMG activity in the contralateral forearm. There were no sex differences for any of the measures of fatigability. These results demonstrate that the mirror illusion influences contraction-dependent fatigue during maximal handgrip contractions. Alterations in facilitatory and inhibitory transcallosal drive likely explain these findings.NEW & NOTEWORTHY Illusionary mirror visual feedback is a promising clinical tool for motor rehabilitation, yet many features of its influence on motor output are unknown. We show that maximal bimanual force output is compromised to a greater extent than unimanual force output following unimanual fatigue, yet illusionary mirror visual feedback attenuates this difference. The mirror illusion also reduces the unintended EMG activity of the inactive, contralateral forearm during unimanual contraction.
Collapse
Affiliation(s)
- Joshua C Carr
- Department of Kinesiology, Texas Christian University, Fort Worth, Texas.,Department of Medical Education, TCU and UNTHSC School of Medicine, Fort Worth, Texas
| | - Michael G Bemben
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma
| | - Matt S Stock
- School of Kinesiology and Physical Therapy, University of Central Florida, Orlando, Florida.,Neuromuscular Plasticity Laboratory, Institute of Exercise Physiology and Rehabilitation Science, University of Central Florida, Orlando, Florida
| | - Jason M DeFreitas
- Applied Neuromuscular Physiology Laboratory, Oklahoma State University, Stillwater, Oklahoma
| |
Collapse
|
4
|
Behm DG, Alizadeh S, Hadjizedah Anvar S, Hanlon C, Ramsay E, Mahmoud MMI, Whitten J, Fisher JP, Prieske O, Chaabene H, Granacher U, Steele J. Non-local Muscle Fatigue Effects on Muscle Strength, Power, and Endurance in Healthy Individuals: A Systematic Review with Meta-analysis. Sports Med 2021; 51:1893-1907. [PMID: 33818751 DOI: 10.1007/s40279-021-01456-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2021] [Indexed: 12/11/2022]
Abstract
BACKGROUND The fatigue of a muscle or muscle group can produce global responses to a variety of systems (i.e., cardiovascular, endocrine, and others). There are also reported strength and endurance impairments of non-exercised muscles following the fatigue of another muscle; however, the literature is inconsistent. OBJECTIVE To examine whether non-local muscle fatigue (NLMF) occurs following the performance of a fatiguing bout of exercise of a different muscle(s). DESIGN Systematic review and meta-analysis. SEARCH AND INCLUSION A systematic literature search using a Boolean search strategy was conducted with PubMed, SPORTDiscus, Web of Science, and Google Scholar in April 2020, and was supplemented with additional 'snowballing' searches up to September 2020. To be included in our analysis, studies had to include at least one intentional performance measure (i.e., strength, endurance, or power), which if reduced could be considered evidence of muscle fatigue, and also had to include the implementation of a fatiguing protocol to a location (i.e., limb or limbs) that differed to those for which performance was measured. We excluded studies that measured only mechanistic variables such as electromyographic activity, or spinal/supraspinal excitability. After search and screening, 52 studies were eligible for inclusion including 57 groups of participants (median sample = 11) and a total of 303 participants. RESULTS The main multilevel meta-analysis model including all effects sizes (278 across 50 clusters [median = 4, range = 1 to 18 effects per cluster) revealed a trivial point estimate with high precision for the interval estimate [- 0.02 (95% CIs = - 0.14 to 0.09)], yet with substantial heterogeneity (Q(277) = 642.3, p < 0.01), I2 = 67.4%). Subgroup and meta-regression analyses showed that NLMF effects were not moderated by study design (between vs. within-participant), homologous vs. heterologous effects, upper or lower body effects, participant training status, sex, age, the time of post-fatigue protocol measurement, or the severity of the fatigue protocol. However, there did appear to be an effect of type of outcome measure where both strength [0.11 (95% CIs = 0.01-0.21)] and power outcomes had trivial effects [- 0.01 (95% CIs = - 0.24 to 0.22)], whereas endurance outcomes showed moderate albeit imprecise effects [- 0.54 (95% CIs = - 0.95 to - 0.14)]. CONCLUSIONS Overall, the findings do not support the existence of a general NLMF effect; however, when examining specific types of performance outcomes, there may be an effect specifically upon endurance-based outcomes (i.e., time to task failure). However, there are relatively fewer studies that have examined endurance effects or mechanisms explaining this possible effect, in addition to fewer studies including women or younger and older participants, and considering causal effects of prior training history through the use of longitudinal intervention study designs. Thus, it seems pertinent that future research on NLMF effects should be redirected towards these still relatively unexplored areas.
Collapse
Affiliation(s)
- David G Behm
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada.
| | - Shahab Alizadeh
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Saman Hadjizedah Anvar
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada.,University of Tehran, Tehran, Iran
| | - Courtney Hanlon
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Emma Ramsay
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada
| | | | - Joseph Whitten
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL, Canada
| | - James P Fisher
- School of Sport, Health and Social Science, Solent University, Southampton, UK
| | - Olaf Prieske
- Division of Exercise and Movement, University of Applied Sciences for Sport and Management Potsdam, Potsdam, Germany
| | - Helmi Chaabene
- Division of Training and Movement Science, University of Potsdam, Potsdam, Germany
| | - Urs Granacher
- Division of Training and Movement Science, University of Potsdam, Potsdam, Germany
| | - James Steele
- School of Sport, Health and Social Science, Solent University, Southampton, UK.,Ukactive Research Institute, London, UK
| |
Collapse
|
5
|
Morrison S, Kavanagh JJ, Newell KM. Cross-limb dynamics of postural tremor due to limb loading to fatigue: neural overflow but not coupling. J Neurophysiol 2019; 122:572-584. [DOI: 10.1152/jn.00199.2019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Many experiments have shown independence of the index finger dynamics under bilateral postural tremor protocols. Here we investigated in young adults the dynamics of bilateral multidirectional postural tremor and forearm muscle activity under the progressively fatiguing conditions supporting an external weight to the point of induced postural failure. When no loads were applied, tremor in the vertical (VT) and mediolateral (ML) directions was similar with prominent peaks within 2- to 4-Hz and 8- to 12-Hz bandwidths. Contrastingly tremor in the anterior-posterior (AP) direction was characterized by a single peak between 0 and 2 Hz. Although no tremor coupling occurred cross limbs, strong within-limb coupling was found between ML and VT directions when no loads were applied (coherence range: 0.77–0.85), implying that these oscillations are related and likely derived from mechanical sources. Applying an external load to the index finger(s) led to significant increases in the amplitude of VT tremor and EMG activity within that limb but also caused increases in tremor directions not aligned with the gravitational vector (AP and ML). Significant increases in VT and ML tremor and EMG activity in the contralateral (unloaded) limb were also found when a single index finger was loaded; however, this bilateral increase did not align with increases in interlimb coupling (coherence <0.21). The effects of fatigue caused by prolonged loading were widespread, affecting tremor and muscle activity in both limbs through a combination of neural and mechanical mechanisms. The single- and dual-limb loading to fatigue increased neural overflow but not tremor coupling between the index fingers. NEW & NOTEWORTHY This study investigated bilateral multidirectional tremor under unloaded and loaded conditions. We found that tremor in the mediolateral and vertical directions within a limb were strongly coupled, a result not reported previously. Furthermore, when holding a weight to failure, tremor in all directions increased. Tremor also increased in the contralateral (unloaded) limb despite no interlimb coupling. This contralateral increase in tremor following loading a limb until fatigue is hypothesized to stem from motor-overflow effects.
Collapse
Affiliation(s)
- Steven Morrison
- School of Rehabilitation Sciences, Old Dominion University, Norfolk, Virginia
| | - Justin J. Kavanagh
- Menzies Health Institute Queensland, Griffith University, Queensland, Australia
| | - Karl M. Newell
- Department of Kinesiology, University of Georgia, Athens, Georgia
| |
Collapse
|
6
|
Kavanagh JJ, McFarland AJ, Taylor JL. Enhanced availability of serotonin increases activation of unfatigued muscle but exacerbates central fatigue during prolonged sustained contractions. J Physiol 2019; 597:319-332. [PMID: 30328105 PMCID: PMC6312415 DOI: 10.1113/jp277148] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 10/15/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Animal preparations have revealed that moderate synaptic release of serotonin (5-HT) onto motoneurones enhances motor activity via activation of 5-HT2 receptors, whereas intense release of 5-HT causes spillover of 5-HT to extrasynaptic 5-HT1A receptors on the axon initial segment to reduce motoneurone activity. We explored if increasing extracellular concentrations of endogenously released 5-HT (via the selective serotonin reuptake inhibitor paroxetine) influences the ability to perform unfatigued and fatigued maximal voluntary contractions in humans. Following the ingestion of paroxetine, voluntary muscle activation and torque generation increased during brief unfatigued maximal contractions. In contrast, the ability to generate maximal torque with increased 5-HT availability was compromised under fatigued conditions, which was consistent with paroxetine-induced reductions in motoneurone excitability and voluntary muscle activation. This is the first in vivo human study to provide evidence that 5-HT released onto the motoneurones could play a role in central fatigue. ABSTRACT Brief stimulation of the raphe-spinal pathway in the turtle spinal cord releases serotonin (5-HT) onto motoneurones to enhance excitability. However, intense release of 5-HT via prolonged stimulation results in 5-HT spillover to the motoneurone axon initial segment to activate inhibitory 5-HT1A receptors, thus providing a potential spinal mechanism for exercise-induced central fatigue. We examined how increased extracellular concentrations of 5-HT affect the ability to perform brief, as well as sustained, maximal voluntary contractions (MVCs) in humans. Paroxetine was used to enhance 5-HT concentrations by reuptake inhibition, and three studies were performed. Study 1 (n = 14) revealed that 5-HT reuptake inhibition caused an ∼4% increase in elbow flexion MVC. However, when maximal contractions were sustained, time-to-task failure was reduced and self-perceived fatigue was higher with enhanced availability of 5-HT. Study 2 (n = 11) used twitch interpolation to reveal that 5-HT-based changes in motor performance had a neural basis. Enhanced 5-HT availability increased voluntary activation for the unfatigued biceps brachii and decreased voluntary activation of the biceps brachii by 2-5% following repeated maximal elbow flexions. The final study (n = 8) investigated whether altered motoneurone excitability may contribute to 5-HT changes in voluntary activation. F-waves of the abductor digiti minimi (ADM) were unaffected by paroxetine for unfatigued muscle and marginally affected following a brief 2-s MVC. However, F-wave area and persistence were significantly decreased following a prolonged 60-s MVC of the ADM. Overall, high serotonergic drive provides a spinal mechanism by which higher concentrations of 5-HT may contribute to central fatigue.
Collapse
Affiliation(s)
- Justin J. Kavanagh
- Menzies Health Institute QueenslandGriffith UniversityGold CoastAustralia
| | - Amelia J. McFarland
- School of Pharmacy and PharmacologyGriffith UniversityGold CoastAustralia
- Quality Use of Medicines NetworkGriffith UniversityGold CoastAustralia
| | - Janet L. Taylor
- School of Medical and Health SciencesEdith Cowan UniversityPerthAustralia
- Neuroscience Research AustraliaSydneyAustralia
| |
Collapse
|
7
|
Li Y, Power KE, Marchetti PH, Behm DG. The effect of dominant first dorsal interosseous fatigue on the force production of a contralateral homologous and heterologous muscle. Appl Physiol Nutr Metab 2018; 44:704-712. [PMID: 30468626 DOI: 10.1139/apnm-2018-0583] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Crossover and nonlocal muscle fatigue (NLMF) has generally focused on large muscle groups. It is unclear if fatigue of a small muscle can result in NLMF of a larger muscle. The purpose of the present study was to examine the effect of small muscle (first dorsal interosseous; FDI) fatigue on the force and activation of contralateral homologous and larger heterologous muscles (biceps brachii; BB). Fifteen right-handed male subjects performed 3 pre-test index finger abduction or elbow flexion maximum voluntary isometric contractions (MVICs) on the nondominant side. Subsequently, they performed two 100-s index finger abduction MVICs on the dominant side (experimental (fatigue) group) or rested for 5 min (control group). Afterwards, a single MVIC and a 12-repetition MVIC fatiguing protocol were completed with index finger abduction or elbow flexion on the nondominant side. Force and electromyography (EMG) were measured from both sides. The force and EMG (median frequency; MDF) of nonexercised index finger abductors (IFA)/FDI and elbow flexors (EF)/BB significantly decreased after the fatiguing protocol. Compared with the control condition, the nonexercised IFA (12.5% and 5.7%) had significantly greater force and MDF fatigue indexes than the EF (5.2% and 1.7%). There were no significant force differences with the single MVIC test between conditions. The small muscle fatiguing protocol produced NLMF effects on both contralateral homologous and larger heterologous muscles, with the force decrements greater with the homologous muscle.
Collapse
Affiliation(s)
- Yimeng Li
- a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1M 3L8, Canada
| | - Kevin E Power
- a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1M 3L8, Canada
| | - Paulo H Marchetti
- b College of Health and Human Development, Department of Kinesiology, California State University, Northridge, Northridge, CA 91330, USA
| | - David G Behm
- a School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, NL A1M 3L8, Canada
| |
Collapse
|
8
|
Madrid A, Madinabeitia-Mancebo E, Cudeiro J, Arias P. Effects of a Finger Tapping Fatiguing Task on M1-Intracortical Inhibition and Central Drive to the Muscle. Sci Rep 2018; 8:9326. [PMID: 29921946 PMCID: PMC6008331 DOI: 10.1038/s41598-018-27691-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 06/07/2018] [Indexed: 12/26/2022] Open
Abstract
The central drive to the muscle reduces when muscle force wanes during sustained MVC, and this is generally considered the neurophysiological footprint of central fatigue. The question is if force loss and the failure of central drive to the muscle are responsible mechanisms of fatigue induced by un-resisted repetitive movements. In various experimental blocks, we validated a 3D-printed hand-fixation system permitting the execution of finger-tapping and maximal voluntary contractions (MVC). Subsequently, we checked the suitability of the system to test the level of central drive to the muscle and developed an algorithm to test it at the MVC force plateau. Our main results show that the maximum rate of finger-tapping dropped at 30 s, while the excitability of inhibitory M1-intracortical circuits and corticospinal excitability increased (all by approximately 15%). Furthermore, values obtained immediately after finger-tapping showed that MVC force and the level of central drive to the muscle remained unchanged. Our data suggest that force and central drive to the muscle are not determinants of fatigue induced by short-lasting un-resisted repetitive finger movements, even in the presence of increased inhibition of the motor cortex. According to literature, this profile might be different in longer-lasting, more complex and/or resisted repetitive movements.
Collapse
Affiliation(s)
- Antonio Madrid
- Universidade da Coruña, NEUROcom (Neuroscience and Motor Control Group) and Biomedical Institute of A Coruña (INIBIC), Department of Biomedical Sciences, Medicine and Physiotherapy-INEF Galicia, A Coruña, Spain
| | - Elena Madinabeitia-Mancebo
- Universidade da Coruña, NEUROcom (Neuroscience and Motor Control Group) and Biomedical Institute of A Coruña (INIBIC), Department of Biomedical Sciences, Medicine and Physiotherapy-INEF Galicia, A Coruña, Spain
| | - Javier Cudeiro
- Universidade da Coruña, NEUROcom (Neuroscience and Motor Control Group) and Biomedical Institute of A Coruña (INIBIC), Department of Biomedical Sciences, Medicine and Physiotherapy-INEF Galicia, A Coruña, Spain.,Centro de Estimulación Cerebral de Galicia, A Coruña, Spain
| | - Pablo Arias
- Universidade da Coruña, NEUROcom (Neuroscience and Motor Control Group) and Biomedical Institute of A Coruña (INIBIC), Department of Biomedical Sciences, Medicine and Physiotherapy-INEF Galicia, A Coruña, Spain.
| |
Collapse
|