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Zafeiridis A, Kounoupis A, Papadopoulos S, Koutlas A, Boutou AK, Smilios I, Dipla K. Brain oxygenation during multiple sets of isometric and dynamic resistance exercise of equivalent workloads: Association with systemic haemodynamics. J Sports Sci 2022; 40:1020-1030. [PMID: 35271420 DOI: 10.1080/02640414.2022.2045061] [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: 10/18/2022]
Abstract
Brain function relies on sufficient blood flow and oxygen supply. Changes in cerebral oxygenation during exercise have been linked to brain activity and central command. Isometric- and dynamic-resistance exercise-(RE) may elicit differential responses in systemic circulation, neural function and metabolism; all important regulators of cerebral circulation. We examined whether (i) cerebral oxygenation differs between isometric- and dynamic-RE of similar exercise characteristics and (ii) cerebral oxygenation changes relate to cardiovascular adjustments occurring during RE. Fourteen men performed, randomly, an isometric-RE and a dynamic-RE of similar characteristics (bilateral-leg-press, 2-min×4-sets, 30% of maximal-voluntary-contraction, equivalent tension-time-index/workload). Cerebral-oxygenation (oxyhaemoglobin-O2Hb; total haemoglobin-tHb/blood-volume-index; deoxyhemoglobin-HHb) was assessed by NIRS and beat-by-beat haemodynamics via photoplethysmography. Cerebral-O2Hb and tHb progressively increased from the 1st to 4th set in both RE-protocols (p < 0.05); HHb slightly decreased (p < 0.05). Changes in NIRS-parameters were similar between RE-protocols within each exercise-set (p = 0.91-1.00) and during the entire protocol (including resting-phases) (p = 0.48-0.63). O2Hb and tHb changes were not correlated with changes in systemic haemodynamics. In conclusion, cerebral oxygenation/blood-volume steadily increased during multiple-set RE-protocols. Isometric- and dynamic-RE of matched exercise characteristics resulted in similar prefrontal oxygenation/blood volume changes, suggesting similar cerebral haemodynamic and possibly neuronal responses to maintain a predetermined force.
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Affiliation(s)
- Andreas Zafeiridis
- Laboratory of Exercise Physiology and Biochemistry, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Anastasios Kounoupis
- Laboratory of Exercise Physiology and Biochemistry, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Stavros Papadopoulos
- Laboratory of Exercise Physiology and Biochemistry, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Aggelos Koutlas
- Laboratory of Exercise Physiology and Biochemistry, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
| | - Afroditi K Boutou
- Department of Respiratory Medicine, General Papanikolaou Hospital, Thessaloniki, Greece
| | - Ilias Smilios
- Department of Physical Education and Sport Science, Democritus University of Thrace, Komotini, Greece
| | - Konstantina Dipla
- Laboratory of Exercise Physiology and Biochemistry, Department of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Serres, Greece
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Brandão RDAFS, Mendes CMC, Lopes TDS, Brandão Filho RA, Sena EPD. Neurophysiological aspects of isotonic exercises in temporomandibular joint dysfunction syndrome. Codas 2021; 33:e20190218. [PMID: 34008769 DOI: 10.1590/2317-1782/20202019218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 06/03/2020] [Indexed: 11/21/2022] Open
Abstract
PURPOSE The aim of the study was to investigate the electroneurophysiological aspects of volunteers with temporomandibular disorders before and after performing isotonic exercises for pain relief and self-care guidelines. METHODS The study was a parallel controlled randomized controlled trial under protocol 1,680,920. The inclusion criteria were age between 18 and 60 years, muscle temporomandibular dysfunction with or without limitation of mouth opening and self-reported pain with scores between 4 and 10. The individuals were randomized into experimental group and control. Twenty-three volunteers participated in the study, most of then were female. Control group had 11 and experimental group 12 individuals. Dropouts occurred in both groups, two in the experimental group and three in the control group. Since there were an intergroup imbalance the power density was analysed just in experimental group. Electroencephalographic recording was performed before and after the interventions, using the 32-channel apparatus, with sample frequency of 600 Hz and impedance of 5 kΩ. The data were processed through the MATLAB computer program. The individual records filtered off-line, using bandpass between 0.5 and 50 Hz. Epochs of 1,710 ms were created and the calculation of the absolute power density calculated by means of the fast Fourier transform. The statistical approach was inferential and quantitative. RESULTS The alpha power density analyzed presented a difference, but not significant, when compared in the two moments. CONCLUSION According to this study, isotonic exercises performed to reduce pain provided a small increase in alpha power density in the left temporal, parietal and occipital regions.
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Affiliation(s)
- Renata de Assis Fonseca Santos Brandão
- Programa de Pós-graduação de Processos Interativo de Órgãos e Sistemas, Instituto de Ciências da Saúde, Universidade Federal da Bahia - UFBA - Salvador (BA), Brasil.,Departamento de Ciências da Vida, Universidade do Estado da Bahia - UNEB - Salvador (BA), Brasil
| | - Carlos Maurício Cardeal Mendes
- Programa de Pós-graduação de Processos Interativo de Órgãos e Sistemas, Instituto de Ciências da Saúde, Universidade Federal da Bahia - UFBA - Salvador (BA), Brasil
| | - Tiago da Silva Lopes
- Programa de Pós-graduação de Medicina e Saúde, Universidade Federal da Bahia - UFBA - Salvador (BA), Brasil.,Faculdade Adventista da Bahia - Cachoeira (BA), Brasil
| | | | - Eduardo Pondé de Sena
- Programa de Pós-graduação de Processos Interativo de Órgãos e Sistemas, Departamento de Farmacologia e Fisiologia, Instituto de Ciências da Saúde, Universidade Federal da Bahia - UFBA - Salvador (BA), Brasil
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Grande-Alonso M, Ortega-López F, Vittecoq R, Mayo-Fernández E, Navarro-Fernández G, Cuenca-Martínez F, La Touche R, Paris-Alemany A. Auditory and visual distraction improve muscle endurance: a randomised controlled trial. Somatosens Mot Res 2020; 37:334-342. [PMID: 33064039 DOI: 10.1080/08990220.2020.1834378] [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: 10/23/2022]
Abstract
The main aim was to investigate the influence of various distracting stimuli on the endurance-strength and fatigue of the lumbar region in asymptomatic participants. Fifty-four healthy individuals were randomised to three groups: auditory distraction group (ADG), visual distraction group (VDG) and control group without distraction (CG). Lumbar muscle endurance and perceived fatigue were the outcome measures. Lumbar muscle endurance was assessed with the Biering-Sorensen test, and perceived fatigue was assessed with the modified Borg scale, once baseline and second with the distraction intervention. Lumbar muscle endurance showed significant changes over time, and there were intragroup differences for VDG and ADG. The direct comparison did show significant differences between both distraction groups with respect to the control group with a large effect size (ΔVDG-CG: p < 0.001, d = 1.55 and, ΔADG-CG: p = 0.008, d = 1.07) but not between the two distraction groups (ΔVDG-VDG: p = 0.56). Fatigue showed significant changes over time but not for group*time interaction, revealing intragroup differences for VDG and ADG. There were no intragroup differences in the CG for muscle resistance or fatigue, and there were no between-group differences. Auditory and visual distractors might produce a significant increase in muscle resistance during the Biering-Sorensen test. Both techniques are valid for increasing lumbar muscle endurance but also both stimuli produced a higher level of fatigue or perception of effort once the test was completed when compared with CG. Finally, we were unable to demonstrate that one type of stimulus produces superior results to the other.
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Affiliation(s)
- Mónica Grande-Alonso
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Fernando Ortega-López
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Romain Vittecoq
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Enrique Mayo-Fernández
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Gonzalo Navarro-Fernández
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Ferran Cuenca-Martínez
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain
| | - Roy La Touche
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Instituto de Neurociencia y Dolor Craneofacial (INDCRAN), Madrid, Spain
| | - Alba Paris-Alemany
- Departamento de Fisioterapia, Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Motion in Brains Research Group, Institute of Neuroscience and Sciences of the Movement (INCIMOV), Centro Superior de Estudios Universitarios La Salle, Universidad Autónoma de Madrid, Madrid, Spain.,Instituto de Neurociencia y Dolor Craneofacial (INDCRAN), Madrid, Spain
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Tanaka M, Ishii A, Watanabe Y. Neural effect of physical fatigue on mental fatigue: a magnetoencephalography study. FATIGUE-BIOMEDICINE HEALTH AND BEHAVIOR 2016. [DOI: 10.1080/21641846.2016.1167471] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Physical fatigue increases neural activation during eyes-closed state: a magnetoencephalography study. Behav Brain Funct 2015; 11:35. [PMID: 26542654 PMCID: PMC4635605 DOI: 10.1186/s12993-015-0079-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 10/14/2015] [Indexed: 11/13/2022] Open
Abstract
Background Fatigue, defined as difficulty initiating or sustaining voluntary activities, can be classified as physical or mental. In this study, we use magnetoencephalography (MEG) to quantify the effect of physical fatigue on neural activity under the condition of simulated physical load. Methods Thirteen healthy right-handed male volunteers participated in this study. The experiment consisted of one fatigue-inducing physical task session performed between two MEG sessions. During the 10-min physical task session, participants performed maximum-effort handgrips with the left hand lasting 1 s every 4 s; during MEG sessions, 3-min recordings were made during the eyes-closed state. MEG data were analyzed using narrow-band adaptive spatial filtering methods. Results Alpha-frequency band (8–13 Hz) power in the left postcentral gyrus, precentral gyrus, and middle frontal gyrus (Brodmann’s areas 1, 2, 3, 4, 6, and 46) were decreased after performing the physical fatigue-inducing task. Conclusions These results show that performing the physical fatigue-inducing task caused activation of the left sensorimotor and prefrontal areas, manifested as decreased alpha-frequency band power in these brain areas. Our results increase understanding of the neural mechanisms of physical fatigue.
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Frontier studies on fatigue, autonomic nerve dysfunction, and sleep-rhythm disorder. J Physiol Sci 2015; 65:483-98. [PMID: 26420687 PMCID: PMC4621713 DOI: 10.1007/s12576-015-0399-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 09/01/2015] [Indexed: 12/30/2022]
Abstract
Fatigue is defined as a condition or phenomenon of decreased ability and efficiency of mental and/or physical activities, caused by excessive mental or physical activities, diseases, or syndromes. It is often accompanied by a peculiar sense of discomfort, a desire to rest, and reduced motivation, referred to as fatigue sensation. Acute fatigue is a normal condition or phenomenon that disappears after a period of rest; in contrast, chronic fatigue, lasting at least 6 months, does not disappear after ordinary rest. Chronic fatigue impairs activities and contributes to various medical conditions, such as cardiovascular disease, epileptic seizures, and death. In addition, many people complain of chronic fatigue. For example, in Japan, more than one third of the general adult population complains of chronic fatigue. It would thus be of great value to clarify the mechanisms underlying chronic fatigue and to develop efficient treatment methods to overcome it. Here, we review data primarily from behavioral, electrophysiological, and neuroimaging experiments related to neural dysfunction as well as autonomic nervous system, sleep, and circadian rhythm disorders in fatigue. These data provide new perspectives on the mechanisms underlying chronic fatigue and on overcoming it.
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Takarada Y, Mima T, Abe M, Nakatsuka M, Taira M. Inhibition of the primary motor cortex can alter one's “sense of effort”: Effects of low-frequency rTMS. Neurosci Res 2014; 89:54-60. [DOI: 10.1016/j.neures.2014.09.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 08/30/2014] [Accepted: 09/16/2014] [Indexed: 11/25/2022]
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Tanaka M, Ishii A, Watanabe Y. Neural effect of mental fatigue on physical fatigue: a magnetoencephalography study. Brain Res 2014; 1542:49-55. [PMID: 24505624 DOI: 10.1016/j.brainres.2013.10.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We sought to clarify the neural effect of mental fatigue on physical fatigue using magnetoencephalography (MEG) and classical conditioning techniques. Eleven right-handed volunteers participated in this study. On the first day, participants performed fatigue-inducing maximum handgrip trials for 10 min; metronome sounds were started 5 min after the beginning of the trials. We used metronome sounds as conditioned stimuli and maximum handgrip trials as unconditioned stimuli to cause physical fatigue. On the next day, MEG recordings during the imagery of maximum grips of the right hand guided by the metronome sounds were performed for 10 min just before (control session) and after (mental fatigue session) a 30-min fatigue-inducing mental task session. In the right anterior cingulate cortex (Brodmann's area 23), the alpha-band event-related synchronization of the mental fatigue session relative to the control session within the time window of 500–600 ms after the onset of handgrip cue sounds was identified. We demonstrated that mental fatigue suppresses activities in the right anterior cingulate cortex during physical fatigue.
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9
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Bhambhani Y, Fan JL, Place N, Rodriguez-Falces J, Kayser B. Electromyographic, cerebral, and muscle hemodynamic responses during intermittent, isometric contractions of the biceps brachii at three submaximal intensities. Front Physiol 2014; 5:190. [PMID: 24966837 PMCID: PMC4052733 DOI: 10.3389/fphys.2014.00190] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/29/2014] [Indexed: 11/25/2022] Open
Abstract
This study examined the electromyographic, cerebral and muscle hemodynamic responses during intermittent isometric contractions of biceps brachii at 20, 40, and 60% of maximal voluntary contraction (MVC). Eleven volunteers completed 2 min of intermittent isometric contractions (12/min) at an elbow angle of 90° interspersed with 3 min rest between intensities in systematic order. Surface electromyography (EMG) was recorded from the right biceps brachii and near infrared spectroscopy (NIRS) was used to simultaneously measure left prefrontal and right biceps brachii oxyhemoglobin (HbO2), deoxyhemoglobin (HHb), and total hemoglobin (Hbtot). Transcranial Doppler ultrasound was used to measure middle cerebral artery velocity (MCAv) bilaterally. Finger photoplethysmography was used to record beat-to-beat blood pressure and heart rate. EMG increased with force output from 20 to 60% MVC (P < 0.05). Cerebral HbO2 and Hbtot increased while HHb decreased during contractions with differences observed between 60% vs. 40% and 20% MVC (P < 0.05). Muscle HbO2 decreased while HHb increased during contractions with differences being observed among intensities (P < 0.05). Muscle Hbtot increased from rest at 20% MVC (P < 0.05), while no further change was observed at 40 and 60% MVC (P > 0.05). MCAv increased from rest to exercise but was not different among intensities (P > 0.05). Force output correlated with the root mean square EMG and changes in muscle HbO2 (P < 0.05), but not changes in cerebral HbO2 (P > 0.05) at all three intensities. Force output declined by 8% from the 1st to the 24th contraction only at 60% MVC and was accompanied by systematic increases in RMS, cerebral HbO2 and Hbtot with a leveling off in muscle HbO2 and Hbtot. These changes were independent of alterations in mean arterial pressure. Since cerebral blood flow and oxygenation were elevated at 60% MVC, we attribute the development of fatigue to reduced muscle oxygen availability rather than impaired central neuronal activation.
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Affiliation(s)
- Yagesh Bhambhani
- Department of Occupational Therapy, Faculty of Rehabilitation Medicine, University of Alberta Edmonton, AB, Canada
| | - Jui-Lin Fan
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland ; Lemanic Neuroscience Doctoral School, University of Lausanne Lausanne, Switzerland
| | - Nicolas Place
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland
| | - Javier Rodriguez-Falces
- Department of Electrical and Electronic Engineering, Public University of Navarra Pamplona, Spain
| | - Bengt Kayser
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne Lausanne, Switzerland
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Signal N, Taylor D, McNair P. Central and peripheral contributions to neuromuscular fatigue in people with stroke. PHYSICAL THERAPY REVIEWS 2014. [DOI: 10.1179/174328808x309205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Tanaka M, Ishii A, Watanabe Y. Regulatory mechanism of performance in chronic cognitive fatigue. Med Hypotheses 2014; 82:567-71. [PMID: 24594236 DOI: 10.1016/j.mehy.2014.02.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 01/15/2014] [Accepted: 02/10/2014] [Indexed: 10/25/2022]
Abstract
Chronic cognitive fatigue is characterized by a sensation of long-lasting fatigue that impairs cognitive functions. Facilitation and inhibition systems in the central nervous system play primary roles in determining the output to the peripheral system, that is, performance. Sensory input from the peripheral system to the central nervous system activates the inhibition system to limit performance, whereas motivational input activates the facilitation system to enhance performance. The dysfunction of the facilitation system and central sensitization and classical conditioning of the inhibition system play important roles in the pathophysiology of chronic cognitive fatigue. Because the dorsolateral prefrontal cortex receives input from both the facilitation and inhibition systems to determine performance, metabolic, functional, and structural impairments of the dorsolateral prefrontal cortex induced by repetitive and prolonged overwork, stress, and stress responses contribute to the impaired functioning and cognitive performance that occur in people with chronic cognitive fatigue. This hypothesis of the regulatory mechanism of performance provides a new perspective on the neural mechanisms underlying chronic cognitive fatigue.
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Affiliation(s)
- Masaaki Tanaka
- Department of Physiology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan.
| | - Akira Ishii
- Department of Physiology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan
| | - Yasuyoshi Watanabe
- Department of Physiology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Abeno-ku, Osaka 545-8585, Japan; RIKEN Center for Life Science Technologies, 6-7-3 Minatojima-minamimachi, Chuo-ku, Hyogo 650-0047, Japan
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12
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Tanaka M, Ishii A, Watanabe Y. Neural mechanism of facilitation system during physical fatigue. PLoS One 2013; 8:e80731. [PMID: 24278313 PMCID: PMC3835560 DOI: 10.1371/journal.pone.0080731] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 10/05/2013] [Indexed: 11/19/2022] Open
Abstract
An enhanced facilitation system caused by motivational input plays an important role in supporting performance during physical fatigue. We tried to clarify the neural mechanisms of the facilitation system during physical fatigue using magnetoencephalography (MEG) and a classical conditioning technique. Twelve right-handed volunteers participated in this study. Participants underwent MEG recording during the imagery of maximum grips of the right hand guided by metronome sounds for 10 min. Thereafter, fatigue-inducing maximum handgrip trials were performed for 10 min; the metronome sounds were started 5 min after the beginning of the handgrip trials. The metronome sounds were used as conditioned stimuli and maximum handgrip trials as unconditioned stimuli. The next day, they were randomly assigned to two groups in a single-blinded, two-crossover fashion to undergo two types of MEG recordings, that is, for the control and motivation sessions, during the imagery of maximum grips of the right hand guided by metronome sounds for 10 min. The alpha-band event-related desynchronizations (ERDs) of the motivation session relative to the control session within the time windows of 500 to 700 and 800 to 900 ms after the onset of handgrip cue sounds were identified in the sensorimotor areas. In addition, the alpha-band ERD within the time window of 400 to 500 ms was identified in the right dorsolateral prefrontal cortex (Brodmann's area 46). The ERD level in the right dorsolateral prefrontal cortex was positively associated with that in the sensorimotor areas within the time window of 500 to 700 ms. These results suggest that the right dorsolateral prefrontal cortex is involved in the neural substrates of the facilitation system and activates the sensorimotor areas during physical fatigue.
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Affiliation(s)
- Masaaki Tanaka
- Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Akira Ishii
- Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan
| | - Yasuyoshi Watanabe
- Department of Physiology, Osaka City University Graduate School of Medicine, Osaka, Japan
- RIKEN Center for Life Science Technologies, Kobe, Japan
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13
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Palmer HS, Håberg AK, Fimland MS, Solstad GM, Moe Iversen V, Hoff J, Helgerud J, Eikenes L. Structural brain changes after 4 wk of unilateral strength training of the lower limb. J Appl Physiol (1985) 2013; 115:167-75. [DOI: 10.1152/japplphysiol.00277.2012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Strength training enhances muscular strength and neural drive, but the underlying neuronal mechanisms remain unclear. This study used magnetic resonance imaging (MRI) to identify possible changes in corticospinal tract (CST) microstructure, cortical activation, and subcortical structure volumes following unilateral strength training of the plantar flexors. Mechanisms underlying cross-education of strength in the untrained leg were also investigated. Young, healthy adult volunteers were assigned to training ( n = 12) or control ( n = 9) groups. The 4 wk of training consisted of 16 sessions of 36 unilateral isometric plantar flexions. Maximum voluntary isometric contraction torque was tested pre- and posttraining. MRI investigation included a T1-weighted scan, diffusion tensor imaging and functional MRI. Probabilistic fiber tracking of the CST was performed on the diffusion tensor imaging images using a two-regions-of-interest approach. Fractional anisotropy and mean diffusivity were calculated for the left and right CST in each individual before and after training. Standard functional MRI analyses and volumetric analyses of subcortical structures were also performed. Maximum voluntary isometric contraction significantly increased in both the trained and untrained legs of the training group, but not the control group. A significant decrease in mean diffusivity was found in the left CST following strength training of the right leg. No significant changes were detected in the right CST. No significant changes in cortical activation were observed following training. A significant reduction in left putamen volume was found after training. This study provides the first evidence for strength training-related changes in white matter and putamen in the healthy adult brain.
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Affiliation(s)
- H. S. Palmer
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
| | - A. K. Håberg
- Department of Medical Imaging, St. Olavs Hospital, Trondheim, Norway
- Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
| | - M. S. Fimland
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
| | - G. M. Solstad
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
| | - V. Moe Iversen
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
| | - J. Hoff
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
- Department of Physical Medicine and Rehabilitation, St. Olavs Hospital, Trondheim, Norway
| | - J. Helgerud
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
- Hokksund Medical Rehabilitation Centre, Hokksund, Norway; and
- Department of Sports and Outdoor Life Studies, Telemark University College, Bø, Norway
| | - L. Eikenes
- MI-Lab, Department of Circulation and Medical Imaging, Norwegian University of Science and Technology, Trondheim, Norway
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Takarada Y, Ohki Y, Taira M. Effect of transient vascular occlusion of the upper arm on motor evoked potentials during force exertion. Neurosci Res 2013; 76:224-9. [PMID: 23806753 DOI: 10.1016/j.neures.2013.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Revised: 04/30/2013] [Accepted: 05/25/2013] [Indexed: 11/18/2022]
Abstract
We previously observed that transient vascular occlusion in volunteers increased the estimation of force exertion with no change in peripheral nerves or muscles. We hypothesized that the primary factor responsible for the overestimation of force exertion during occlusion was the centrally generated motor command, as hypothesized by McCloskey et al. (1974) and McCloskey (1978, 1981). In the present study, we tested the hypothesis that transient vascular occlusion increases the excitability of the primary motor cortex (M1) during force exertion. Healthy human volunteers lay on a bed and squeezed a dynamometer in their right hand. Repetitive gripping forces were exerted at 20%, 40%, or 60% of maximum force, with or without transient (20s) vascular occlusion of the proximal portion of the right upper arm. During the task, single-pulse transcranial magnetic stimulation was applied to the contralateral M1 to induce motor evoked potentials (MEPs) in the flexor carpi ulnaris (FCU) muscle. The MEP amplitudes were enhanced with occlusion under all conditions, with the exception of 60% contraction. In contrast, no significant difference was observed between the MEP amplitudes obtained from the occluded or non-occluded, relaxed FCU muscle. These results suggest that transient vascular occlusion increases the excitability of M1 only during force exertion.
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Affiliation(s)
- Yudai Takarada
- Faculty of Sport Sciences, Waseda University, Saitama 359-1192, Japan.
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Flanagan SD, Dunn-Lewis C, Comstock BA, Maresh CM, Volek JS, Denegar CR, Kraemer WJ. Cortical Activity during a Highly-Trained Resistance Exercise Movement Emphasizing Force, Power or Volume. Brain Sci 2012; 2:649-66. [PMID: 24961265 PMCID: PMC4061814 DOI: 10.3390/brainsci2040649] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2012] [Revised: 10/10/2012] [Accepted: 11/13/2012] [Indexed: 11/17/2022] Open
Abstract
Cortical activity is thought to reflect the biomechanical properties of movement (e.g., force or velocity of movement), but fatigue and movement familiarity are important factors that require additional consideration in electrophysiological research. The purpose of this within-group quantitative electroencephalogram (EEG) investigation was to examine changes in cortical activity amplitude and location during four resistance exercise movement protocols emphasizing rate (PWR), magnitude (FOR), or volume (VOL) of force production, while accounting for movement familiarity and fatigue. EEG signals were recorded during each complete repetition and were then grouped by functional region, processed to eliminate artifacts, and averaged to compare overall differences in the magnitude and location of cortical activity between protocols over the course of six sets. Biomechanical, biochemical, and exertional data were collected to contextualize electrophysiological data. The most fatiguing protocols were accompanied by the greatest increases in cortical activity. Furthermore, despite non-incremental loading and lower force levels, VOL displayed the largest increases in cortical activity over time and greatest motor and sensory activity overall. Our findings suggest that cortical activity is strongly related to aspects of fatigue during a high intensity resistance exercise movement.
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Affiliation(s)
- Shawn D Flanagan
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - Courtenay Dunn-Lewis
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - Brett A Comstock
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - Carl M Maresh
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - Jeff S Volek
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - Craig R Denegar
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
| | - William J Kraemer
- Human Performance Laboratory, Department of Kinesiology, University of Connecticut, Storrs, CT 06269, USA.
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Gordon NM, Rudroff T, Enoka JA, Enoka RM. Handedness but not dominance influences variability in endurance time for sustained, submaximal contractions. J Neurophysiol 2012; 108:1501-10. [DOI: 10.1152/jn.01144.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to compare endurance time and accompanying neuromuscular adjustments when left- and right-handed subjects used the dominant and nondominant arms to sustain submaximal contractions that required either force or position control. Ten left-handed and 10 right-handed healthy adults (21 ± 5 yr) participated in the study. Each subject exerted a similar net torque about the elbow joint during the force and position tasks to achieve a target force of 20% maximal voluntary contraction (MVC) force (56 ± 18 N). MVC force declined to a similar level immediately after task failure for left- and right-handed subjects (27 ± 13 vs. 25 ± 15%, P = 0.9). Endurance time for the position task was similar for the dominant and nondominant arms (task × dominance interaction, P = 0.17). Although the difference in endurance time between the two tasks was similar for left-handed (136 ± 165 s) and right-handed individuals (92 ± 73 s, task × handedness interaction, P = 0.38), there was greater variance in the ratio of the endurance times for the force and position tasks for left-handed (0.77) than right-handed subjects (0.13, P < 0.001; see Fig. 2 ). Furthermore, endurance time for the force and position tasks was significantly correlated for right-handed subjects ( r2 = 0.62, P < 0.001), but not for left-handed subjects ( r2 = 0.004, P = 0.79). Multiple regression analyses identified sets of predictor variables for each endurance time, and these differed with handedness and task. Hand dominance, however, did not influence endurance time for either group of subjects. These findings indicate that endurance times for the elbow flexors when performing submaximal isometric contractions that required either force or position control were not influenced by hand dominance but did depend on handedness.
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Affiliation(s)
- Nicole M. Gordon
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Thorsten Rudroff
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Joel A. Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Roger M. Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
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Tanaka M, Watanabe Y. Supraspinal regulation of physical fatigue. Neurosci Biobehav Rev 2012; 36:727-34. [DOI: 10.1016/j.neubiorev.2011.10.004] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 10/13/2011] [Accepted: 10/18/2011] [Indexed: 11/26/2022]
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Abstract
Several studies suggest that when subjects mentally rehearse or execute a familiar action, they engage similar neural and cognitive operations. Here, we examined whether muscle fatigue could influence mental movements. Participants mentally and actually performed a sequence of vertical arm movements (rotation around the shoulder joint) before and after a fatiguing exercise involving the right arm. We found similar durations for actual and mental movements before fatigue, but significant temporal discrepancies after fatigue. Specifically, mental simulation was accelerated immediately after fatigue, while the opposite was observed for actual execution. Furthermore, actual movements showed faster adaptation (i.e., return to prefatigue values) than mental movements. The EMG analysis showed that postfatigue participants programmed larger, compared to prefatigue, neural drives. Therefore, immediately after fatigue, the forward model received dramatically greater efferent copies and predicted faster, compared to prefatigue, arm movements. During actual movements, the discrepancy between estimated (forward model output) and actual state (sensory feedback) of the arm guided motor adaptation; i.e., durations returned rapidly to prefatigue values. Since during mental movements there is no sensory information and state estimation derives from the forward model alone, mental durations remained faster after fatigue and their adaptation was longer than those of actual movements. This effect was specific to the fatigued arm because actual and mental movements of the left nonfatigued arm were unaffected. The current results underline the interdependence of motor and cognitive states and suggest that mental actions integrate the current state of the motor system.
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Addamo PK, Farrow M, Bradshaw JL, Georgiou-Karistianis N. Relative or absolute? Implications and consequences of the measures adopted to investigate motor overflow. J Mot Behav 2011; 43:203-12. [PMID: 21480026 DOI: 10.1080/00222895.2011.561376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Motor overflow is involuntary overt movement or covert muscle activity that cooccurs with voluntary movement. Overflow is present in several pathological conditions, as well as in neurologically healthy children and older adults, and can be induced in healthy young adults under effortful conditions. This motor phenomenon may provide insight into the underlying mechanisms and kinetic characteristics of voluntary and involuntary motor control in various populations. Although often measured behaviorally using force transduction techniques, different methods of calculating and presenting such overflow data have resulted in seemingly contradictory findings, with limited discussion of the advantages and limitations of different approaches. In this article, the authors examined the relevant literature to highlight significant methodological considerations for authors and readers conducting or appraising this type of research. Issues regarding the interpretation and reporting of findings are also discussed. Researchers are encouraged to continue using behavioral measures to create well-defined variables that enable the study of the kinematic characteristics of overflow, as these may offer promising new ways forward in better characterizing and understanding this intriguing movement phenomenon.
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Affiliation(s)
- Patricia K Addamo
- Experimental Neuropsychology Research Unit, School of Psychology and Psychiatry, Monash University, Clayton, Victoria 3800, Australia.
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Maeda L, Ono M, Koyama T, Oshiro Y, Sumitani M, Mashimo T, Shibata M. Human brain activity associated with painful mechanical stimulation to muscle and bone. J Anesth 2011; 25:523-30. [PMID: 21633873 PMCID: PMC3152719 DOI: 10.1007/s00540-011-1173-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2010] [Accepted: 05/12/2011] [Indexed: 12/19/2022]
Abstract
Purpose The purpose of this study was to elucidate the central processing of painful mechanical stimulation to muscle and bone by measuring blood oxygen level-dependent signal changes using functional magnetic resonance imaging (fMRI). Methods Twelve healthy volunteers were enrolled. Mechanical pressure on muscle and bone were applied at the right lower leg by an algometer. Intensities were adjusted to cause weak and strong pain sensation at either target site in preliminary testing. Brain activation in response to mechanical nociceptive stimulation targeting muscle and bone were measured by fMRI and analyzed. Results Painful mechanical stimulation targeting muscle and bone activated the common areas including bilateral insula, anterior cingulate cortex, posterior cingulate cortex, secondary somatosensory cortex (S2), inferior parietal lobe, and basal ganglia. The contralateral S2 was more activated by strong stimulation than by weak stimulation. Some areas in the basal ganglia (bilateral putamen and caudate nucleus) were more activated by muscle stimulation than by bone stimulation. Conclusions The putamen and caudate nucleus may have a more significant role in brain processing of muscle pain compared with bone pain.
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Affiliation(s)
- Lynn Maeda
- Department of Anesthesia and Pain Medicine, Nishinomiya Municipal Central Hospital, Nishinomiya, Japan
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Neuroimaging changes in mesial temporal lobe epilepsy are magnified in the presence of depression. Epilepsy Behav 2010; 19:422-7. [PMID: 20850388 DOI: 10.1016/j.yebeh.2010.08.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/07/2010] [Accepted: 08/09/2010] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The aim of this study was to investigate differences in gray matter volume between patients with mesial temporal lobe epilepsy (MTLE) with and without depression using voxel-based morphometry. METHOD We included 48 adults with refractory MTLE (31 women, 39.18 ± 8.4 years) and 96 healthy controls (75 women, 37.11 ± 8.9 years). For the psychiatric evaluation, the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Axis I, was used for the diagnosis of depression, and the Beck Depression Inventory, for the determination of symptom intensity. All patients underwent an MRI scan. Patients were separated into two groups: those with MTLE with depression (n = 24) and those with MTLE without depression (n = 24). We performed voxel-based morphometric analysis, comparing patients with controls using the t test. RESULTS The number of areas of gray matter volume loss was higher in patients with MTLE with depression than in those with MTLE without depression. CONCLUSIONS The evidence of more widespread gray matter volume loss in patients with MTLE and depression calls our attention to the importance of timely recognition and treatment of depression in patients with MTLE and also to the bidirectional relationship between the two disorders and their frequent co-occurrence.
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22
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Dynamic changes in white and gray matter volume are associated with outcome of surgical treatment in temporal lobe epilepsy. Neuroimage 2010; 49:71-9. [DOI: 10.1016/j.neuroimage.2009.08.014] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2009] [Revised: 06/16/2009] [Accepted: 08/06/2009] [Indexed: 11/22/2022] Open
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Narita N, Funato M, Ishii T, Kamiya K, Matsumoto T. Effects of jaw clenching while wearing an occlusal splint on awareness of tiredness, bite force, and EEG power spectrum. J Prosthodont Res 2009; 53:120-5. [PMID: 19345662 DOI: 10.1016/j.jpor.2009.02.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 01/06/2009] [Indexed: 10/20/2022]
Abstract
PURPOSE Treatment with an occlusal splint is used for temporomandibular disorders, bruxism, and occlusal disturbance to relieve orofacial symptoms such as myofascial pain and jaw movement restriction. However, the effects of various types of occlusal splints have not been elucidated. We investigated the effects of jaw clenching with soft and hard occlusal splints on the awareness of tiredness, bite force, and EEG activity. METHODS Six healthy adults were used as subjects, with a visual analogue scale utilized to evaluate the awareness of each patient's tiredness both preceding the session and following the clenching trials. In addition, a Dental Prescale was used to measure bite force and an EEG recording was conducted while performing jaw clenching. The jaw clenching task comprised 1min of maximal voluntary clenching under 3 kinds of clenching conditions: with natural dentition, and with soft and hard occlusal splints, which were each repeated 5 times. RESULTS Jaw clenching with natural dentition and a hard occlusal splint did not cause a significant awareness of tiredness following repetitive jaw clenching, and there was not a significant alteration of EEG spectrum values with those conditions. In contrast, jaw clenching with a soft occlusal splint caused a significant increase in awareness of tiredness, as well as significant decreases in bite force and EEG alpha 2 power spectrum values. CONCLUSIONS Jaw clenching with a soft resilient occlusal splint causes an awareness of tiredness, which might be accompanied by declines in bite force and EEG spectrum values.
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Affiliation(s)
- Noriyuki Narita
- Department of Stomatognathic Science and Occlusion, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, Japan.
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Maznychenko AV, Pilyavskii AI, Kostyukov AI, Lyskov E, Vlasenko OV, Maisky VA. Coupling of c-fos expression in the spinal cord and amygdala induced by dorsal neck muscles fatigue. Histochem Cell Biol 2007; 128:85-90. [PMID: 17525853 DOI: 10.1007/s00418-007-0292-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2007] [Indexed: 10/23/2022]
Abstract
c-fos gene expression in the cervical spinal cord and amygdala was examined in anaesthetized rats following muscle fatigue caused by intermittent high-rate (100 s(-1)) electrical stimulation of the dorsal neck muscles (m. trapezius and m. splenius). Fatigue-related increases in c-fos expression were observed on the stimulated muscle side in the cervical C2-C4 (layers 1, 3-5, 7 and 10) spinal segments, bilaterally in the lumbar L4-L6 (layer 1) segments and in contralateral central (Ce), medial (Me), and basomedial (BM) amygdaloid nuclei. A scarce number of staining cells were found within lateral and basolateral nuclei. The rostro-caudal extent of c-fos expression in the spinal cord supports functional coupling of the cervical and lumbar regions during the neck muscle fatigue development. The distinct c-fos expression in the Ce and Me amygdaloid nuclei suggests that they may contribute to mediating the neck muscle fatigue-related nociception, autonomic and behavioural responses.
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Affiliation(s)
- Andrey V Maznychenko
- Department of Movement Physiology, Bogomoletz Institute of Physiology, National Academy of Sciences, Bogomoletz str. 4, Kiev 01024, Ukraine.
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Addamo PK, Farrow M, Hoy KE, Bradshaw JL, Georgiou-Karistianis N. The effects of age and attention on motor overflow production—A review. ACTA ACUST UNITED AC 2007; 54:189-204. [PMID: 17300842 DOI: 10.1016/j.brainresrev.2007.01.004] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2006] [Revised: 01/11/2007] [Accepted: 01/15/2007] [Indexed: 12/29/2022]
Abstract
Motor overflow refers to overt involuntary movement, or covert muscle activity, that sometimes co-occurs with voluntary movement. Various clinical populations exhibit overflow. Motor overflow is also present in healthy children and the elderly, although in young adults, overt overflow is considered abnormal unless elicited under conditions of extreme force or muscle fatigue. Current theories of overflow imply that the corpus callosum may mediate production of this phenomenon. However, given that the corpus callosum is a conduit enabling the transfer of cortical information, surprisingly few studies have considered the cortical or subcortical structures underlying overflow. This review considers the developmental trend of motor overflow production, specifically in the upper-limbs, and the mechanisms thought to underlie this age-related phenomenon. Potential neurological correlates of motor overflow will be discussed in conjunction with higher order attentional processes which also regulate motor overflow production. Future research investigating the impact of attentional processes on overflow production may be particularly valuable for designing rehabilitation strategies for patients experiencing induced pathological overflow or conversely, to develop techniques to encourage the recovery of movement function in individuals with paretic limbs.
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Affiliation(s)
- Patricia K Addamo
- Experimental Neuropsychology Research Unit, School of Psychology, Psychiatry and Psychological Medicine, Monash University, Clayton, 3800, Victoria, Australia.
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Kalmar JM, Cafarelli E. Central excitability does not limit postfatigue voluntary activation of quadriceps femoris. J Appl Physiol (1985) 2006; 100:1757-64. [PMID: 16424071 DOI: 10.1152/japplphysiol.01347.2005] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
After fatigue, motor evoked potentials (MEP) elicited by transcranial magnetic stimulation and cervicomedullary evoked potentials elicited by stimulation of the corticospinal tract are depressed. These reductions in corticomotor excitability and corticospinal transmission are accompanied by voluntary activation failure, but this may not reflect a causal relationship. Our purpose was to determine whether a decline in central excitability contributes to central fatigue. We hypothesized that, if central excitability limits voluntary activation, then a caffeine-induced increase in central excitability should offset voluntary activation failure. In this repeated-measures study, eight men each attended two sessions. Baseline measures of knee extension torque, maximal voluntary activation, peripheral transmission, contractile properties, and central excitability were made before administration of caffeine (6 mg/kg) or placebo. The amplitude of vastus lateralis MEPs elicited during minimal muscle activation provided a measure of central excitability. After a 1-h rest, baseline measures were repeated before, during, and after a fatigue protocol that ended when maximal voluntary torque declined by 35% (Tlim). Increased prefatigue MEP amplitude ( P = 0.055) and cortically evoked twitch ( P < 0.05) in the caffeine trial indicate that the drug increased central excitability. In the caffeine trial, increased MEP amplitude was correlated with time to task failure ( r = 0.74, P < 0.05). Caffeine potentiated the MEP early in the fatigue protocol ( P < 0.05) and offset the 40% decline in placebo MEP ( P < 0.05) at Tlim. However, this was not associated with enhanced maximal voluntary activation during fatigue or recovery, demonstrating that voluntary activation is not limited by central excitability.
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Affiliation(s)
- J M Kalmar
- Department of Biology, Rm. 346, Bethune College, York University, 4700 Keele St., Toronto, ON, Canada M3J 1P3
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Schillings ML, Kalkman JS, van der Werf SP, Bleijenberg G, van Engelen BGM, Zwarts MJ. Central adaptations during repetitive contractions assessed by the readiness potential. Eur J Appl Physiol 2006; 97:521-6. [PMID: 16718505 DOI: 10.1007/s00421-006-0211-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/31/2006] [Indexed: 11/29/2022]
Abstract
Physiological fatigue, a loss of maximal force producing capacity, may originate both from changes at the peripheral and at the central level. The readiness potential (RP) provides a measure to study adaptations to physiological fatigue at the motor cortex. We have studied the RP in the course of repetitive contractions at a high force level. Fourteen female healthy subjects made repetitive force grip contractions at 70% of their maximal voluntary contraction (MVC) for 30 min. Contractions were self-paced and inter-squeeze interval was about 7 s. During the repetitive contractions, the area under the curve of the RP almost doubled at electrode Cz and increased fourfold at electrodes C3' and C4'. The onset of negativity moved forward from 1.5 to 1.9 s before force onset at Cz and from 1.0 to 1.6 s and 1.7 s before force onset at C3' and C4', respectively. EMG amplitude and median frequency did not change significantly and MVC after the fatiguing exercise was 93% of MVC before, indicating relatively little physiological fatigue. The increase of the RP during the repetitive contractions is clearly in excess of the almost absent signs of peripheral fatigue. Because the increase of the RP does not lead to an increased force production, we propose that it is a central adaptation counteracting the decrease of cortical efficiency during repetitive contractions.
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Affiliation(s)
- M L Schillings
- Department of Clinical Neurophysiology, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
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