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Dudani RA, Zero AM, Rice CL. 'Muscular wisdom' revisited: Decaying rates of stimulation mitigate torque loss. Exp Physiol 2025; 110:574-584. [PMID: 39887506 PMCID: PMC11963895 DOI: 10.1113/ep092472] [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: 12/04/2024] [Accepted: 12/10/2024] [Indexed: 02/01/2025]
Abstract
During a sustained high-intensity isometric maximal voluntary contraction (MVC), declining motor unit firing rates (MUFRs) accompany torque loss. This decline (∼50% over 60 s) helps to maintain torque by preserving peripheral electrical propagation and matching the slowing contractile properties with torque loss (i.e., 'muscular wisdom'). However, it has been suggested that reduced MUFRs contribute to torque loss. Here, we compared torque loss between constant and decaying rates of electrical stimulation to mimic MUFRs reported during MVCs. The dorsiflexors of 8 males and 5 females (21-30 years) underwent three 60 s muscle fatiguing conditions: (1) sustained MVC; (2) constant high-frequency electrical stimulation (40 Hz); and (3) exponentially decaying stimulation rate (from 40 to 20 Hz). The decaying rate demonstrated less torque loss compared with the sustained high-frequency stimulation and the MVC conditions (P < 0.01). Furthermore, torque increased (by ∼17%, P < 0.005) when the constant high-frequency condition was switched to 20 Hz for 2 s at task termination. Conversely, torque loss was accelerated when the decaying stimulation rate was switched from 20 to 40 Hz for 2 s at task termination (by ∼16%, P < 0.001). Following all conditions, evoked twitch responses slowed (by 29%-77%, P < 0.01) but M-wave amplitude was reduced only for the constant high-frequency condition (by ∼23%, P < 0.01). Thus, the reduction in stimulation rates maintained optimal activation by matching the fatigue-induced contractile slowing in combination with preserved peripheral electrical conductance. Therefore, reducing the activation rate preserves torque, rather than contributing to torque loss during high-intensity contractions, thereby supporting the muscle wisdom hypothesis.
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Affiliation(s)
- Raaj A. Dudani
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
| | - Alexander M. Zero
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
| | - Charles L. Rice
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
- Department of Anatomy and Cell Biology, Schulich School of Medicine & DentistryThe University of Western OntarioLondonOntarioCanada
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Kim JM, Kim TW, Park HJ, Lee SW, Yoo YJ, Yoon MJ, Chang SY, Won SJ. Estimation of the muscle force by perineural intramuscular electrical stimulation in healthy volunteers. Medicine (Baltimore) 2024; 103:e40043. [PMID: 39465818 PMCID: PMC11479414 DOI: 10.1097/md.0000000000040043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 09/23/2024] [Indexed: 10/29/2024] Open
Abstract
The present study aimed to evaluate the elbow flexor force induced by perineural intramuscular stimulation compared with surface electrical stimulation (ES) and maximal voluntary contraction. Thirty nondominant arms of healthy volunteers were evaluated. Isometric elbow flexion force was evaluated using a surface electrode stimulation at the biceps brachii muscle, a perineural intramuscular stimulation around the musculocutaneous nerve, and maximum voluntary contraction. The elbow flexion force was measured at the wrist volar area in a 90° elbow flexion posture, fixed with a rigid elbow orthosis. Pain and discomfort associated with ES were evaluated using a numeric rating scale. The mean maximum elbow flexion force was 16.6 ± 4.1 kgf via voluntary contraction. The mean elbow flexion force by ES was 2.9 ± 2.0 kgf, stimulation intensity was 24.8 ± 5.5 mA, and the numeric rating scale was 5.0 ± 2.5 via surface electrode stimulation and 3.1 ± 2.0 kgf, 5.0 mA, and 3.8 ± 1.9 via perineural stimulation, respectively. ES provides 16% to 18% of the maximal voluntary contraction force in elbow flexion, which corresponds to a fair grade of muscle force. Perineural intramuscular stimulation can generate an equivocal contraction force with less discomfort in elbow flexion than surface electrode stimulation.
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Affiliation(s)
- Jae Min Kim
- Department of Rehabilitation Medicine, Incheon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Tae-Woo Kim
- National Traffic Injury Rehabilitation Hospital, Yangpyeong, Republic of Korea
- Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Hye Jung Park
- Department of Rehabilitation Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Se Won Lee
- Department of Physical Medicine and Rehabilitation, Mt. View Hospital, Las Vegas, NV
| | - Yeun Jie Yoo
- Department of Rehabilitation Medicine, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Mi-Jeong Yoon
- Department of Rehabilitation Medicine, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - So-youn Chang
- Department of Rehabilitation Medicine, Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Sun Jae Won
- Department of Rehabilitation Medicine, Yeouido St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
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Lanfranchi C, Rodriguez-Falces J, Place N. The first and second phases of the muscle compound action potential in the thumb are differently affected by electrical stimulation trains. J Appl Physiol (1985) 2024; 136:1122-1128. [PMID: 38511213 DOI: 10.1152/japplphysiol.00861.2023] [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: 11/29/2023] [Revised: 03/11/2024] [Accepted: 03/14/2024] [Indexed: 03/22/2024] Open
Abstract
Sarcolemmal membrane excitability is often evaluated by considering the peak-to-peak amplitude of the compound muscle action potential (M wave). However, the first and second M-wave phases represent distinct properties of the muscle action potential, which are differentially affected by sarcolemma properties and other factors such as muscle architecture. Contrasting with previous studies in which voluntary contractions have been used to induce muscle fatigue, we used repeated electrically induced tetanic contractions of the adductor pollicis muscle and assessed the kinetics of M-wave properties during the course of the contractions. Eighteen participants (24 ± 6 yr; means ± SD) underwent 30 electrically evoked tetanic contractions delivered at 30 Hz, each lasting 3 s with 1 s intervals. We recorded the amplitudes of the first and second M-wave phases for each stimulation. During the initial stimulation train, the first and second M-wave phases exhibited distinct kinetics. The first phase amplitude showed a rapid decrease to reach ∼59% of its initial value (P < 0.001), whereas the second phase amplitude displayed an initial transient increase of ∼19% (P = 0.007). Within subsequent trains, both the first and second phase amplitudes consistently decreased as fatigue developed with a reduction during the last train reaching ∼47% of its initial value (P < 0.001). Analyzing the first M wave of each stimulation train unveiled different kinetics for the first and second phases during the initial trains, but these distinctions disappeared as fatigue progressed. These findings underscore the interplay of factors affecting the M wave and emphasize the significance of separately scrutinizing its first and second phases when assessing membrane excitability adjustments during muscle contractions.NEW & NOTEWORTHY Our understanding of how the first and second phases of the compound muscle action potential (M wave) behave during fatigue remains incomplete. Using electrically evoked repeated tetanic contractions of the adductor pollicis, we showed that the first and second phases of the M wave followed distinct kinetics only during the early stages of fatigue development. This suggests that the factors affecting the M-wave first and second phases may change as fatigue develops.
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Affiliation(s)
- Clément Lanfranchi
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
| | - Javier Rodriguez-Falces
- Department of Electrical and Electronical Engineering, Public University of Navarra, Pamplona, Spain
| | - Nicolas Place
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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Gkesou A, Papavasileiou A, Karagiaridis S, Kannas T, Amiridis IG, Hatzitaki V, Patikas DA. Fatigability of the thenar muscles using electrical nerve stimulation with fixed stimuli count, while varying the frequency and duty cycle. J Electromyogr Kinesiol 2023; 73:102838. [PMID: 37976607 DOI: 10.1016/j.jelekin.2023.102838] [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: 06/30/2023] [Revised: 09/30/2023] [Accepted: 11/03/2023] [Indexed: 11/19/2023] Open
Abstract
Our aim was to compare three electrical stimulation protocols (P20, P30 and P40), with the same number of stimuli, but different stimulation frequencies (20, 30 and 40 Hz, respectively) and duty cycles [1.2:1.2 s (continuous), 0.8:1.2 s (intermittent) and 0.6:1.2 s (intermittent), respectively). Twitch force and the peak-to-peak M-wave amplitude of the thenar muscles were measured before, during and after each protocol at 1-40 Hz in random order. Twelve healthy adults (23-41 years old) were examined for each protocol in random order and in separate sessions. P20 elicited the highest mean force, and P40 the lowest decrease in percent force at the end of the protocol. Force evoked at 1 and 10 Hz decreased less after P40, compared with P20 and P30. The M-wave amplitude was significantly reduced throughout all protocols, with the largest decrease observed during P30. Although an increase in frequency typically induced earlier and greater decrement in force, this was compensated or even reversed by increasing the interval between each stimulation train, while keeping the number of pulses per stimulation cycle constant. The lesser decrease in M-wave amplitude during P40 compared with P20 indicates that longer between-train intervals may help maintaining the integrity of neuromuscular propagation.
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Affiliation(s)
- A Gkesou
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece
| | - A Papavasileiou
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece
| | - S Karagiaridis
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece
| | - T Kannas
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece
| | - I G Amiridis
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece
| | - V Hatzitaki
- School of Physical Education and Sports Science, Aristotle University of Thessaloniki, Greece
| | - D A Patikas
- School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, Greece.
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Aout T, Begon M, Jegou B, Peyrot N, Caderby T. Effects of Functional Electrical Stimulation on Gait Characteristics in Healthy Individuals: A Systematic Review. SENSORS (BASEL, SWITZERLAND) 2023; 23:8684. [PMID: 37960383 PMCID: PMC10648660 DOI: 10.3390/s23218684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 10/09/2023] [Accepted: 10/17/2023] [Indexed: 11/15/2023]
Abstract
BACKGROUND This systematic review aimed to provide a comprehensive overview of the effects of functional electrical stimulation (FES) on gait characteristics in healthy individuals. METHODS Six electronic databases (PubMed, Embase, Epistemonikos, PEDro, COCHRANE Library, and Scopus) were searched for studies evaluating the effects of FES on spatiotemporal, kinematic, and kinetic gait parameters in healthy individuals. Two examiners evaluated the eligibility and quality of the included studies using the PEDro scale. RESULTS A total of 15 studies met the inclusion criteria. The findings from the literature reveal that FES can be used to modify lower-limb joint kinematics, i.e., to increase or reduce the range of motion of the hip, knee, and ankle joints. In addition, FES can be used to alter kinetics parameters, including ground reaction forces, center of pressure trajectory, or knee joint reaction force. As a consequence of these kinetics and kinematics changes, FES can lead to changes in spatiotemporal gait parameters, such as gait speed, step cadence, and stance duration. CONCLUSIONS The findings of this review improve our understanding of the effects of FES on gait biomechanics in healthy individuals and highlight the potential of this technology as a training or assistive solution for improving gait performance in this population.
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Affiliation(s)
- Thomas Aout
- Laboratoire IRISSE, EA4075, UFR des Sciences de l’Homme et de l’Environnement, Université de La Réunion, 97430 Le Tampon, France; (B.J.); (N.P.); (T.C.)
| | - Mickael Begon
- Laboratoire de Simulation et Modélisation du Mouvement, École de Kinésiologie et des Sciences de l’Activité Physique, Université de Montréal, Montreal, QC H3T 1J4, Canada;
- Centre de Recherche du CHU Sainte-Justine, Université de Montréal, Montreal, QC H3C 3J7, Canada
| | - Baptiste Jegou
- Laboratoire IRISSE, EA4075, UFR des Sciences de l’Homme et de l’Environnement, Université de La Réunion, 97430 Le Tampon, France; (B.J.); (N.P.); (T.C.)
| | - Nicolas Peyrot
- Laboratoire IRISSE, EA4075, UFR des Sciences de l’Homme et de l’Environnement, Université de La Réunion, 97430 Le Tampon, France; (B.J.); (N.P.); (T.C.)
- Mouvement-Interactions-Performance (MIP), Le Mans Université, EA 4334, 72000 Le Mans, France
| | - Teddy Caderby
- Laboratoire IRISSE, EA4075, UFR des Sciences de l’Homme et de l’Environnement, Université de La Réunion, 97430 Le Tampon, France; (B.J.); (N.P.); (T.C.)
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Narayanan S, Gopinath V. Generation and analysis of synthetic surface electromyography signals under varied muscle fiber type proportions and validation using recorded signals. Proc Inst Mech Eng H 2023; 237:209-223. [PMID: 36651535 DOI: 10.1177/09544119221149234] [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: 01/19/2023]
Abstract
The magnitude and duration of muscle force production are influenced by the fiber type proportion. In this work, surface electromyography (sEMG) signals of muscles with varied fiber type proportions, are generated. For this, relevant components of existing models reported in various literature have been adopted. Also, a method to calculate the motor unit size factor is proposed. sEMG signals of adductor pollicis (AP) and triceps brachii (TB) muscles are simulated from the onset of force production to muscle fatigue state at various percentages of maximal voluntary contraction (MVC) values. The model is validated using signals recorded from these muscles using well-defined isometric exercise protocols. Root mean square and mean power spectral density values extracted from the simulated and recorded signals are found to increase for TB and decrease for AP with time. A linear variation of the features with %MVC values is obtained for simulated and experimental results. The Bland-Altman plot is used to analyze the agreement between simulated and experimental feature values. Good agreement is obtained for the feature values at various %MVCs. The mean endurance time calculated using the model is found to be comparable to that of the experimental value. This method can be used to generate sEMG signals of different muscles with varying fiber type ratios under various neuromuscular conditions.
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Affiliation(s)
- Sidharth Narayanan
- Department of Instrumentation and Control Engineering, NSS College of Engineering, Palakkad, Kerala, India.,Department of Electronics and Communication Engineering, NSS College of Engineering, Palakkad, Kerala, India.,APJ Abdul Kalam Technological University, Kerala, India
| | - Venugopal Gopinath
- Department of Instrumentation and Control Engineering, NSS College of Engineering, Palakkad, Kerala, India.,APJ Abdul Kalam Technological University, Kerala, India
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Measurement and State-Dependent Modulation of Hypoglossal Motor Excitability and Responsivity In-Vivo. Sci Rep 2020; 10:550. [PMID: 31953471 PMCID: PMC6969049 DOI: 10.1038/s41598-019-57328-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 12/19/2019] [Indexed: 12/17/2022] Open
Abstract
Motoneurons are the final output pathway for the brain’s influence on behavior. Here we identify properties of hypoglossal motor output to the tongue musculature. Tongue motor control is critical to the pathogenesis of obstructive sleep apnea, a common and serious sleep-related breathing disorder. Studies were performed on mice expressing a light sensitive cation channel exclusively on cholinergic neurons (ChAT-ChR2(H134R)-EYFP). Discrete photostimulations under isoflurane-induced anesthesia from an optical probe positioned above the medullary surface and hypoglossal motor nucleus elicited discrete increases in tongue motor output, with the magnitude of responses dependent on stimulation power (P < 0.001, n = 7) and frequency (P = 0.002, n = 8, with responses to 10 Hz stimulation greater than for 15–25 Hz, P < 0.022). Stimulations during REM sleep elicited significantly reduced responses at powers 3–20 mW compared to non-rapid eye movement (non-REM) sleep and wakefulness (each P < 0.05, n = 7). Response thresholds were also greater in REM sleep (10 mW) compared to non-REM and waking (3 to 5 mW, P < 0.05), and the slopes of the regressions between input photostimulation powers and output motor responses were specifically reduced in REM sleep (P < 0.001). This study identifies that variations in photostimulation input produce tunable changes in hypoglossal motor output in-vivo and identifies REM sleep specific suppression of net motor excitability and responsivity.
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Buckmire AJ, Arakeri TJ, Reinhard JP, Fuglevand AJ. Mitigation of excessive fatigue associated with functional electrical stimulation. J Neural Eng 2018; 15:066004. [PMID: 30168443 DOI: 10.1088/1741-2552/aade1c] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Restoration of motor function in paralyzed limbs using functional electrical stimulation (FES) is undermined by rapid fatigue associated with artificial stimulation. Typically, single electrodes are used to activate muscles with FES. However, due to the highly distributed branching of muscle nerves, a single electrode may not be able to activate the entire array of motor axons supplying a muscle. Therefore, stimulating muscle with multiple electrodes might enable access to a larger volume of muscle and thereby reduce fatigue. APPROACH Accordingly, we compared the endurance times that ankle dorsiflexion could be sustained at 20% maximum voluntary force using feedback controlled stimulation (25 Hz) of human tibialis anterior (TA) using one or four percutaneous intramuscular electrodes. In addition, we measured endurance times in response to direct stimulation of the nerve supplying TA and during voluntary contraction. In all sessions involving electrical stimulation, an anesthetic nerve block proximal to the site of stimulation was used to isolate the effects of stimulation and alleviate discomfort. MAIN RESULTS Endurance time associated with stimuli delivered by a single intramuscular electrode (84 ± 19 s) was significantly smaller than that elicited by four intramuscular electrodes (232 ± 123 s). Moreover, endurance time in response to nerve stimulation (787 ± 201 s) was not significantly different that that produced during voluntary contraction (896 ± 272 s). SIGNIFICANCE Therefore, excessive fatigue associated with FES is probably due to the inability of conventional FES systems to enlist the full complement of motor axons innervating muscle and can be mitigated using multiple electrodes or nerve-based electrodes.
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Affiliation(s)
- Alie J Buckmire
- Department of Physiology, College of Medicine, University of Arizona, Tucson, AZ, United States of America. Graduate Program in Neuroscience, College of Medicine, University of Arizona, Tucson, AZ, United States of America
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James DC, Solan MC, Mileva KN. Wide-pulse, high-frequency, low-intensity neuromuscular electrical stimulation has potential for targeted strengthening of an intrinsic foot muscle: a feasibility study. J Foot Ankle Res 2018; 11:16. [PMID: 29755590 PMCID: PMC5934883 DOI: 10.1186/s13047-018-0258-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 04/19/2018] [Indexed: 11/10/2022] Open
Abstract
Background Strengthening the intrinsic foot muscles is a poorly understood and largely overlooked area. In this study, we explore the feasibility of strengthening m. abductor hallucis (AH) with a specific paradigm of neuromuscular electrical stimulation; one which is low-intensity in nature and designed to interleave physiologically-relevant low frequency stimulation with high-frequencies to enhance effective current delivery to spinal motoneurones, and enable a proportion of force produced by the target muscle to be generated from a central origin. We use standard neurophysiological measurements to evaluate the acute (~ 30 min) peripheral and central adaptations in healthy individuals. Methods The AH in the dominant foot of nine healthy participants was stimulated with 24 × 15 s trains of square wave (1 ms), constant current (150% of motor threshold), alternating (20 Hz–100 Hz) neuromuscular electrical stimulation interspersed with 45 s rest. Prior to the intervention, peripheral variables were evoked from the AH compound muscle action potential (Mwave) and corresponding twitch force in response to supramaximal (130%) medial plantar nerve stimulation. Central variables were evoked from the motor evoked potential (MEP) in response to suprathreshold (150%) transcranial magnetic stimulation of the motor cortex corresponding to the AH pathway. Follow-up testing occurred immediately, and 30 min after the intervention. In addition, the force-time-integrals (FTI) from the 1st and 24th WPHF trains were analysed as an index of muscle fatigue. All variables except FTI (T-test) were entered for statistical analysis using a single factor repeated measures ANOVA with alpha set at 0.05. Results FTI was significantly lower at the end of the electrical intervention compared to that evoked by the first train (p < 0.01). Only significant peripheral nervous system adaptations were observed, consistent with the onset of low-frequency fatigue in the muscle. In most of these variables, the effects persisted for 30 min after the intervention. Conclusions An acute session of wide-pulse, high-frequency, low-intensity electrical stimulation delivered directly to abductor hallucis in healthy feet induces muscle fatigue via adaptations at the peripheral level of the neuromuscular system. Our findings would appear to represent the first step in muscle adaptation to training; therefore, there is potential for using WPHF for intrinsic foot muscle strengthening. Electronic supplementary material The online version of this article (10.1186/s13047-018-0258-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Darren C James
- 1Sport & Exercise Science Research Centre, School of Applied Sciences, London South Bank University, 103 Borough Road, London, SE1 0AA UK
| | - Matthew C Solan
- 2Department of Trauma and Orthopaedic Surgery, Royal Surrey County Hospital, Guildford, Surrey, GU2 5XX UK
| | - Katya N Mileva
- 1Sport & Exercise Science Research Centre, School of Applied Sciences, London South Bank University, 103 Borough Road, London, SE1 0AA UK
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Zheng Y, Hu X. Improved muscle activation using proximal nerve stimulation with subthreshold current pulses at kilohertz-frequency. J Neural Eng 2018; 15:046001. [PMID: 29569574 DOI: 10.1088/1741-2552/aab90f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Transcutaneous electrical nerve stimulation can help individuals with neurological disorders to regain their motor function by activating muscles externally. However, conventional stimulation technique often induces near-simultaneous recruitment of muscle fibers, leading to twitch forces time-locked to the stimulation. APPROACH To induce less synchronized activation of finger flexor muscles, we delivered clustered narrower pulses to the proximal segment of the median and ulnar nerves at a carrier frequency of either 10 kHz (with an 80 µs pulse width) or 7.14 kHz (with a 120 µs pulse width) (high-frequency mode, HF), and different clustered pulses were delivered at a frequency of 30 or 40 Hz. Conventional stimulation with pulse frequency of 30 or 40 Hz (low-frequency mode, LF) was used for comparison. With matched elicited muscle forces between the HF and LF modes, the force variation, the high-density electromyogram (EMG) signals recorded at the finger flexor muscles and stimulation-induced-pain levels were compared. MAIN RESULTS The compound action potentials in the 10 kHz HF mode revealed a significant difference (i.e. a lower amplitude and area, and a wider duration) compared with the LF mode, indicating cancellations of asynchronized action potentials. A smaller fluctuation in the elicited forces in the 10 kHz mode further demonstrated the less synchronized activation of different motor units. These effects tended to be weaker in the 7.14 kHz HF condition. However, the levels of pain sensation was not reduced in the HF mode potentially due to the high charge density used in the HF mode. Our findings indicated that different nerve fibers were recruited asynchronously through summations of different numbers of subthreshold depolarizations in the HF mode. SIGNIFICANCE Compared with the LF mode, the HF mode stimulation was capable of activating the nerve fibers in a less synchronized way, which is more similar to the physiological activation pattern.
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Affiliation(s)
- Yang Zheng
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC, United States of America
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11
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Carr JC, Beck TW, Ye X, Wages NP. Mechanomyographic responses for the biceps brachii are associated with failure times during isometric force tasks. Physiol Rep 2018; 6:e13590. [PMID: 29464902 PMCID: PMC5820423 DOI: 10.14814/phy2.13590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 12/15/2017] [Accepted: 12/20/2017] [Indexed: 11/24/2022] Open
Abstract
In order to characterize the physiological adjustments within the neuromuscular system that contribute to task failure, this study examined the surface mechanomyographic (MMG) response during maximal and submaximal isometric force tasks of the elbow flexors sustained to failure. The time and frequency components of the MMG signal have shown to be influenced by motor unit activation patterns as well as tetanus. Therefore, it was hypothesized that the rate of change for the MMG response would associate with failure times and would be reduced to a similar degree between the two tasks. The isometric force tasks were performed by the dominant elbow flexors of twenty healthy males (age: 25 ± 4 years) and MMG was collected from the biceps brachii. Regression analyses were used to model the relationships between the rates of change for MMG versus failure times. There were high levels of interindividual variability in the response patterns, yet the models demonstrated significant negative associations between the rate of change for the MMG responses and failure times during both tasks (R2 = 0.41-0.72, P < 0.05). Similarly, the mean MMG amplitude and frequency values were reduced to comparable levels at the failure point of the two tasks. The results of this study demonstrated that force failure is associated with the rate of diminution in the properties of the muscle force twitch.
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Affiliation(s)
- Joshua C. Carr
- Biophysics LaboratoryDepartment of Health & Exercise ScienceUniversity of OklahomaNormanOklahoma
| | - Travis W. Beck
- Biophysics LaboratoryDepartment of Health & Exercise ScienceUniversity of OklahomaNormanOklahoma
| | - Xin Ye
- Neuromuscular LaboratoryDepartment of Health, Exercise Science & Recreation ManagementUniversity of MississippiUniversityMississippi
| | - Nathan P. Wages
- Ohio Musculoskeletal and Neurological InstituteDepartment of Biomedical SciencesOhio UniversityAthensOhio
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12
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Hill EC, Housh TJ, Smith CM, Cochrane KC, Jenkins NDM, Schmidt RJ, Johnson GO. The Effects of Work-to-Rest Ratios on Torque, Electromyographic, and Mechanomyographic Responses to Fatiguing Workbouts. INTERNATIONAL JOURNAL OF EXERCISE SCIENCE 2017; 10:580-591. [PMID: 28674602 PMCID: PMC5466413 DOI: 10.70252/tonn2278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 03/15/2025]
Abstract
The purpose of the present study was to examine the effects of 2 different work-to-rest ratios, but the same mean load, cycle time, and total duration of the exercise bout, on maximal voluntary isometric contraction torque and neuromuscular responses to fatiguing, intermittent, submaximal, isometric, forearm flexion muscle actions. Ten men performed 2 fatiguing protocols with different work-to-rest ratios (4 s contraction, 4 s rest vs. 4 s contraction, alternating 6 and 2 s rest) that consisted of 50 intermittent, submaximal (65% of maximal voluntary isometric contraction), isometric, forearm flexion muscle actions. Electromyographic and mechanomyographic signals from the biceps brachii were recorded before, during, immediately and 5 min after performing the fatiguing protocols. In addition, maximal voluntary isometric contraction torque was assessed before, immediately and 5 min after. Both protocols resulted in decreases in maximal voluntary isometric contraction torque, electromyographic mean power frequency, and mechanomyographic mean power frequency, but no changes in electromyographic amplitude or mechanomyographic amplitude. The results of the present study indicated that differences in work-to-rest ratio did not affect maximal voluntary isometric contraction torque or the associated neuromuscular parameters as a result of fatiguing, intermittent, isometric muscle actions when mean load, cycle time, and total duration of exercise were equivalent.
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Affiliation(s)
- Ethan C Hill
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Terry J Housh
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Cory M Smith
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Kristen C Cochrane
- Department of Kinesiology and Health Promotion, California State Polytechnic University, Pomona, Pomona, CA, USA
| | - Nathaniel D M Jenkins
- Department of Health and Human Performance, Oklahoma State University, Stillwater, OK, USA
| | - Richard J Schmidt
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Glen O Johnson
- Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
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13
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Abstract
: This paper highlights some key concepts related to fatigue and the seminal role of the 1981 Ciba Foundation Symposia "Human Muscle Fatigue: Physiological Mechanisms" chaired by R.H.T. Edwards in consolidating key ideas that have moved the study of fatigue forward since that time. I also consider these concepts in their historical context via the pioneering work of the Italian physiologist and social activist Angelo Mosso in the late 1800s. Finally, fatigue as a multidimensional concept with implications beyond muscle physiology is considered.
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Smith CM, Housh TJ, Jenkins NDM, Hill EC, Cochrane KC, Miramonti AA, Schmidt RJ, Johnson GO. Combining regression and mean comparisons to identify the time course of changes in neuromuscular responses during the process of fatigue. Physiol Meas 2016; 37:1993-2002. [PMID: 27754975 DOI: 10.1088/0967-3334/37/11/1993] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The purposes of the present study were to apply a unique method for the identification of the time course of changes in neuromuscular responses and to infer the motor unit activation strategies used to maintain force during a fatiguing, intermittent isometric workbout. Eleven men performed 50, 6 s intermittent isometric muscle actions of the leg extensors, each separated by 2 s of rest at 60% maximal voluntary isometric contraction (MVIC). Electromyographic (EMG) and mechanomyographic (MMG) amplitude (root mean square; RMS) and frequency (mean power frequency; MPF) were obtained from the vastus lateralis (VL) every 5 of the 50 repetitions and normalized as a percent of the initial repetition. Polynomial regression analyses were used to determine the model of best fit for the normalized EMG RMS, EMG MPF, MMG RMS, and MMG MPF versus repetition relationships and one-way repeated measures ANOVAs with post-hoc Student Newman-Keuls were used to identify when these neuromuscular parameters changed from the initial repetition. The findings of the present study indicated two unique phases of neuromuscular responses (repetitions 1-20 and 20-50) during the fatiguing workbout. The time course of changes in these four neuromuscular responses suggested that the after-hyperpolarization theory could not explain the maintenance of force production, but Muscle Wisdom and the Onion Skin Scheme could. The findings of the current study suggested that the time course of changes in neuromuscular responses can provide insight in to the motor unit activation strategies used to maintain force production and allow for a greater understanding of the fatiguing process by identifying the time-points at which these neuromuscular parameters changed.
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Affiliation(s)
- Cory M Smith
- Department of Nutrition and Health Sciences, Human Performance Laboratory, University of Nebraska-Lincoln, Lincoln, NE 68505, USA
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Hunter SK, Pereira HM, Keenan KG. The aging neuromuscular system and motor performance. J Appl Physiol (1985) 2016; 121:982-995. [PMID: 27516536 PMCID: PMC5142309 DOI: 10.1152/japplphysiol.00475.2016] [Citation(s) in RCA: 266] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/08/2016] [Indexed: 12/25/2022] Open
Abstract
Age-related changes in the basic functional unit of the neuromuscular system, the motor unit, and its neural inputs have a profound effect on motor function, especially among the expanding number of old (older than ∼60 yr) and very old (older than ∼80 yr) adults. This review presents evidence that age-related changes in motor unit morphology and properties lead to impaired motor performance that includes 1) reduced maximal strength and power, slower contractile velocity, and increased fatigability; and 2) increased variability during and between motor tasks, including decreased force steadiness and increased variability of contraction velocity and torque over repeat contractions. The age-related increase in variability of motor performance with aging appears to involve reduced and more variable synaptic inputs that drive motor neuron activation, fewer and larger motor units, less stable neuromuscular junctions, lower and more variable motor unit action potential discharge rates, and smaller and slower skeletal muscle fibers that coexpress different myosin heavy chain isoforms in the muscle of older adults. Physical activity may modify motor unit properties and function in old men and women, although the effects on variability of motor performance are largely unknown. Many studies are of cross-sectional design, so there is a tremendous opportunity to perform high-impact and longitudinal studies along the continuum of aging that determine 1) the influence and cause of the increased variability with aging on functional performance tasks, and 2) whether lifestyle factors such as physical exercise can minimize this age-related variability in motor performance in the rapidly expanding numbers of very old adults.
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Affiliation(s)
- Sandra K Hunter
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin; and
| | - Hugo M Pereira
- Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, Wisconsin; and
| | - Kevin G Keenan
- Department of Kinesiology, College of Health Sciences, University of Wisconsin, Milwaukee, Wisconsin
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16
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Muscle- and Mode-Specific Responses of the Forearm Flexors to Fatiguing, Concentric Muscle Actions. Sports (Basel) 2016; 4:sports4040047. [PMID: 29910296 PMCID: PMC5968893 DOI: 10.3390/sports4040047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 09/09/2016] [Accepted: 09/22/2016] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Electromyographic (EMG) and mechanomyographic (MMG) studies of fatigue have generally utilized maximal isometric or dynamic muscle actions, but sport- and work-related activities involve predominately submaximal movements. Therefore, the purpose of the present investigation was to examine the torque, EMG, and MMG responses as a result of submaximal, concentric, isokinetic, forearm flexion muscle actions. METHODS Twelve men performed concentric peak torque (PT) and isometric PT trials before (pretest) and after (posttest) performing 50 submaximal (65% of concentric PT), concentric, isokinetic (60°·s-1), forearm flexion muscle actions. Surface EMG and MMG signals were simultaneously recorded from the biceps brachii and brachioradialis muscles. RESULTS The results of the present study indicated similar decreases during both the concentric PT and isometric PT measurements for torque, EMG mean power frequency (MPF), and MMG MPF following the fatiguing workbout, but no changes in EMG amplitude (AMP) or MMG AMP. CONCLUSIONS These findings suggest that decreases in torque as a result of fatiguing, dynamic muscle actions may have been due to the effects of metabolic byproducts on excitation⁻contraction coupling as indicated by the decreases in EMG MPF and MMG MPF, but lack of changes in EMG AMP and MMG AMP from both the biceps brachii and brachioradialis muscles.
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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: 1.2] [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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18
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HUREAU THOMASJ, DUCROCQ GUILLAUMEP, BLAIN GREGORYM. Peripheral and Central Fatigue Development during All-Out Repeated Cycling Sprints. Med Sci Sports Exerc 2016; 48:391-401. [DOI: 10.1249/mss.0000000000000800] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Bernecke V, Pukenas K, Imbrasiene D, Mickeviciene D, Baranauskiene N, Eimantas N, Brazaitis M. Test-Retest Cross-Reliability of Tests to Assess Neuromuscular Function as a Multidimensional Concept. J Strength Cond Res 2016; 29:1972-84. [PMID: 25635607 DOI: 10.1519/jsc.0000000000000841] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The purpose of this investigation was to estimate the test-retest cross-reliability of peripheral and central changes with respect to nonlinear and linear measures of a surface electromyography (EMG) signal measured during isometric maximal voluntary contraction (MVC) combined with superimposed electrical stimulation during a brief and fatiguing task involving the ankle plantar flexors over 2 follicular phases of menstrual cycle. Ten healthy female adults underwent 1 familiarization session and 5 identical test-retest sessions. The results showed that the decrease in plantar flexor EMG components (root mean square [RMS], mean frequency [MnF], wavelet packet entropy [WPE]) for soleus and gastrocnemius muscles, central activation ratio (CAR) and MVC, and contractile properties (P20, P100, PTT-100, and half-relaxation time) of the plantar flexor muscles at the end of 2-minute MVC were similar (time effect; p < 0.001, η(p)² > 0.7, statistical power [SP] > 99%) and exhibited high stability over 5 trials (trial effect; p > 0.05; η(p)² < 0.2, SP < 30%). High reliability between trials was found for 5-second MVC (intraclass correlation coefficient [ICC] > 0.82, p < 0.001) and meaningful reliability for 2-minute MVC (ICC > 0.66, p < 0.01). In conclusion, in young healthy women, measurements of neuromuscular function, such as RMS, MnF, and WPE of a surface EMG signal, MVC, and CAR from a brief and sustained MVC of the ankle plantar flexors, are reliable, and multidimensional stability was found with respect to both high and low correlation outcomes across the 5 identical test-retest trials of any 2 properties measured during brief and sustained MVC.
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Affiliation(s)
- Vaida Bernecke
- 1Sports Science and Innovation Institute, Lithuanian Sports University, Kaunas, Lithuania; and 2Department of Rehabilitation, Siauliai State College, Siauliai, Lithuania
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20
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Solianik R, Skurvydas A, Pukėnas K, Brazaitis M. Comparison of the effects of whole-body cooling during fatiguing exercise in males and females. Cryobiology 2015; 71:112-8. [DOI: 10.1016/j.cryobiol.2015.04.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/29/2015] [Indexed: 11/25/2022]
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McManus L, Hu X, Rymer WZ, Lowery MM, Suresh NL. Changes in motor unit behavior following isometric fatigue of the first dorsal interosseous muscle. J Neurophysiol 2015; 113:3186-96. [PMID: 25761952 PMCID: PMC4432683 DOI: 10.1152/jn.00146.2015] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 03/06/2015] [Indexed: 11/22/2022] Open
Abstract
The neuromuscular strategies employed to compensate for fatigue-induced muscle force deficits are not clearly understood. This study utilizes surface electromyography (sEMG) together with recordings of a population of individual motor unit action potentials (MUAPs) to investigate potential compensatory alterations in motor unit (MU) behavior immediately following a sustained fatiguing contraction and after a recovery period. EMG activity was recorded during abduction of the first dorsal interosseous in 12 subjects at 20% maximum voluntary contraction (MVC), before and directly after a 30% MVC fatiguing contraction to task failure, with additional 20% MVC contractions following a 10-min rest. The amplitude, duration and mean firing rate (MFR) of MUAPs extracted with a sEMG decomposition system were analyzed, together with sEMG root-mean-square (RMS) amplitude and median frequency (MPF). MUAP duration and amplitude increased immediately postfatigue and were correlated with changes to sEMG MPF and RMS, respectively. After 10 min, MUAP duration and sEMG MPF recovered to prefatigue values but MUAP amplitude and sEMG RMS remained elevated. MU MFR and recruitment thresholds decreased postfatigue and recovered following rest. The increase in MUAP and sEMG amplitude likely reflects recruitment of larger MUs, while recruitment compression is an additional compensatory strategy directly postfatigue. Recovery of MU MFR in parallel with MUAP duration suggests a possible role for metabolically sensitive afferents in MFR depression postfatigue. This study provides insight into fatigue-induced neuromuscular changes by examining the properties of a large population of concurrently recorded single MUs and outlines possible compensatory strategies involving alterations in MU recruitment and MFR.
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Affiliation(s)
- Lara McManus
- University College Dublin, Belfield, Dublin, Ireland;
| | - Xiaogang Hu
- Rehabilitation Institute of Chicago, Chicago, Illinois; and
| | - William Z Rymer
- Rehabilitation Institute of Chicago, Chicago, Illinois; and Northwestern University, Evanston, Illinois
| | | | - Nina L Suresh
- Rehabilitation Institute of Chicago, Chicago, Illinois; and
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Beck TW, Ye X, Wages NP. Local muscle endurance is associated with fatigue-based changes in electromyographic spectral properties, but not with conduction velocity. J Electromyogr Kinesiol 2015; 25:451-6. [PMID: 25744086 DOI: 10.1016/j.jelekin.2015.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 02/11/2015] [Accepted: 02/13/2015] [Indexed: 11/17/2022] Open
Abstract
The purpose of this study was to examine the associations amongst muscle fiber action potential conduction velocity (CV), spectral characteristics of the surface electromyographic (EMG) signal, and endurance time during a sustained submaximal isometric muscle action. Eleven men (mean±SD age=23±4yrs) performed a sustained, submaximal isometric muscle action of the dominant forearm flexors at 60% of the maximum voluntary contraction (MVC) until the designated force level could no longer be maintained. Sixteen separate bipolar surface EMG signals were detected from the biceps brachii with a linear electrode array during this contraction. Two channels from this array were used to measure CV, and one of these two channels was used for further EMG signal processing. The channels that provided the highest signal quality were used for the CV measurements and further data analysis. A wavelet analysis was then used to analyze the bipolar EMG signal, and the resulting wavelet spectrum was decomposed with a nonparametric spectral decomposition procedure. The results showed that the time to exhaustion during the sustained contraction was not correlated with the rate of decrease in CV, but it was highly correlated with both the decrease in high-frequency spectral power (r=0.947) and the increase in low-frequency spectral power (r=0.960). These findings are particularly interesting, considering that the decrease in traditional EMG spectral variables (e.g., mean frequency or median frequency) with fatigue is generally attributed to reductions in CV. While this may indeed be true, the present results suggested that other factors (i.e., other than CV) that can affect the shape of the EMG frequency spectrum during fatigue are more important in determining the endurance capabilities of the muscle than is CV.
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Affiliation(s)
- Travis W Beck
- Biophysics Laboratory, University of Oklahoma, Department of Health and Exercise Science, 110 Huston Huffman Center, Norman, OK 73019-6081, United States.
| | - Xin Ye
- Biophysics Laboratory, University of Oklahoma, Department of Health and Exercise Science, 110 Huston Huffman Center, Norman, OK 73019-6081, United States
| | - Nathan P Wages
- Biophysics Laboratory, University of Oklahoma, Department of Health and Exercise Science, 110 Huston Huffman Center, Norman, OK 73019-6081, United States
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Cidem M, Karacan I, Diraçoğlu D, Yıldız A, Küçük SH, Uludağ M, Gün K, Ozkaya M, Karamehmetoğlu SS. A Randomized Trial on the Effect of Bone Tissue on Vibration-induced Muscle Strength Gain and Vibration-induced Reflex Muscle Activity. Balkan Med J 2014; 31:11-22. [PMID: 25207162 DOI: 10.5152/balkanmedj.2013.9482] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 08/24/2013] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Whole-body vibration (WBV) induces reflex muscle activity and leads to increased muscle strength. However, little is known about the physiological mechanisms underlying the effects of whole-body vibration on muscular performance. Tonic vibration reflex is the most commonly cited mechanism to explain the effects of whole-body vibration on muscular performance, although there is no conclusive evidence that tonic vibration reflex occurs. The bone myoregulation reflex is another neurological mechanism used to explain the effects of vibration on muscular performance. Bone myoregulation reflex is defined as a reflex mechanism in which osteocytes exposed to cyclic mechanical loading induce muscle activity. AIMS The aim of this study was to assess whether bone tissue affected vibration-induced reflex muscle activity and vibration-induced muscle strength gain. STUDY DESIGN A prospective, randomised, controlled, double-blind, parallel-group clinical trial. METHODS Thirty-four participants were randomised into two groups. High-magnitude whole-body vibration was applied in the exercise group, whereas low-magnitude whole-body vibration exercises were applied in the control group throughout 20 sessions. Hip bone mineral density, isokinetic muscle strength, and plasma sclerostin levels were measured. The surface electromyography data were processed to obtain the Root Mean Squares, which were normalised by maximal voluntarily contraction. RESULTS In the exercise group, muscle strength increased in the right and left knee flexors (23.9%, p=0.004 and 27.5%, p<0.0001, respectively). However, no significant change was observed in the knee extensor muscle strength. There was no significant change in the knee muscle strength in the control group. The vibration-induced corrected Root Mean Squares of the semitendinosus muscle was decreased by 2.8 times (p=0.005) in the exercise group, whereas there was no change in the control group. Sclerostin index was decreased by 15.2% (p=0.031) in the exercise group and increased by 20.8% (p=0.028) in the control group. A change in the sclerostin index was an important predictor of a change in the vibration-induced normalised Root Mean Square of the semitendinosus muscle (R2=0.7, p=0.0001). Femoral neck bone mineral density was an important predictor of muscle strength gain (R2=0.26, p=0.035). CONCLUSION This study indicates that bone tissue may have an effect on vibration-induced muscle strength gain and vibration-induced reflex muscle activity. TRIAL REGISTRATION ClinicalTrials.gov: NCT01310348.
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Affiliation(s)
- Muharrem Cidem
- Department of Physical Medicine and Rehabilitation, Bağcılar Training and Research Hospital, İstanbul, Turkey
| | - Ilhan Karacan
- Department of Physical Medicine and Rehabilitation, Bağcılar Training and Research Hospital, İstanbul, Turkey
| | - Demirhan Diraçoğlu
- Department of Physical Medicine and Rehabilitation, İstanbul University İstanbul Medical Faculty, İstanbul, Turkey
| | - Aysel Yıldız
- Department of Physical Medicine and Rehabilitation, İstanbul University İstanbul Medical Faculty, İstanbul, Turkey
| | - Suat Hayri Küçük
- Department of Biochemistry, Bağcılar Training and Research Hospital, İstanbul, Turkey
| | - Murat Uludağ
- Department of Physical Medicine and Rehabilitation, İstanbul University Cerrahpaşa Medical Faculty, İstanbul, Turkey
| | - Kerem Gün
- Department of Physical Medicine and Rehabilitation, İstanbul University Cerrahpaşa Medical Faculty, İstanbul, Turkey
| | - Murat Ozkaya
- Department of Physical Medicine and Rehabilitation, Bağcılar Training and Research Hospital, İstanbul, Turkey
| | - Safak Sahir Karamehmetoğlu
- Department of Physical Medicine and Rehabilitation, İstanbul University Cerrahpaşa Medical Faculty, İstanbul, Turkey
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Abstract
Movement is accomplished by the controlled activation of motor unit populations. Our understanding of motor unit physiology has been derived from experimental work on the properties of single motor units and from computational studies that have integrated the experimental observations into the function of motor unit populations. The article provides brief descriptions of motor unit anatomy and muscle unit properties, with more substantial reviews of motoneuron properties, motor unit recruitment and rate modulation when humans perform voluntary contractions, and the function of an entire motor unit pool. The article emphasizes the advances in knowledge on the cellular and molecular mechanisms underlying the neuromodulation of motoneuron activity and attempts to explain the discharge characteristics of human motor units in terms of these principles. A major finding from this work has been the critical role of descending pathways from the brainstem in modulating the properties and activity of spinal motoneurons. Progress has been substantial, but significant gaps in knowledge remain.
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Affiliation(s)
- C J Heckman
- Northwestern University, Evanston, Illinois, USA.
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25
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Doucet BM, Griffin L. High-versus low-frequency stimulation effects on fine motor control in chronic hemiplegia: a pilot study. Top Stroke Rehabil 2013; 20:299-307. [PMID: 23893829 DOI: 10.1310/tsr2004-299] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND The optimal parameters of neuromuscular electrical stimulation (NMES) for recovery of hand function after stroke are not known. This clinical pilot study examined whether higher or lower frequencies are more effective for improving fine motor control of the hand in a chronic poststroke population. METHODS A 1-month, 4 times per week, in-home regimen of either a high-frequency (40 Hz) or low-frequency (20 Hz) NMES program was applied to the hemiplegic thenar muscles of 16 persons with chronic stroke. Participants were identified a priori as having a low level of function (LF) or a high level of function (HF). Outcome measures of strength, dexterity, and endurance were measured before and after participation in the regimen. RESULTS LF subjects showed no significant changes with either the high- or the low-frequency NMES regimen. HF subjects showed significant changes in strength, dexterity, and endurance. Within this group, higher frequencies of stimulation yielded strength gains and increased motor activation; lower frequencies affected dexterity and endurance. CONCLUSIONS The results suggest that higher frequencies of stimulation could be more effective in improving strength and motor activation properties and that lower frequencies may affect coordination and endurance changes. Results also indicate that persons with a higher functional level of recovery may respond more favorably to NMES regimens, but further study with larger patient groups is warranted.
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Affiliation(s)
- Barbara M Doucet
- Division of Rehabilitation Sciences, University of Texas Medical Branch in Galveston, Galveston, TX, USA
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Neyroud D, Rüttimann J, Mannion AF, Millet GY, Maffiuletti NA, Kayser B, Place N. Comparison of neuromuscular adjustments associated with sustained isometric contractions of four different muscle groups. J Appl Physiol (1985) 2013; 114:1426-34. [DOI: 10.1152/japplphysiol.01539.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The extent and characteristics of muscle fatigue of different muscle groups when subjected to a similar fatiguing task may differ. Thirteen healthy young men performed sustained contractions at 50% maximal voluntary contraction (MVC) force until task failure, with four different muscle groups, over two sessions. Per session, one upper limb and one lower limb muscle group were tested (knee extensors and thumb adductor, or plantar and elbow flexors). Changes in voluntary activation level and contractile properties were derived from doublet responses evoked during and after MVCs before and after exercise. Time to task failure differed ( P < 0.05) between muscle groups (220 ± 64 s for plantar flexors, 114 ± 27 s for thumb adductor, 77 ± 25 s for knee extensors, and 72 ± 14 s for elbow flexors). MVC force loss immediately after voluntary task failure was similar (−30 ± 11% for plantar flexors, −37 ± 13% for thumb adductor, −34 ± 15% for knee extensors, and −40 ± 12% for elbow flexors, P > 0.05). Voluntary activation was decreased for plantar flexors only (from 95 ± 5% to 82 ± 9%, P < 0.05). Potentiated evoked doublet amplitude was more depressed for upper limb muscles (−59.3 ± 14.7% for elbow flexors and −60.1 ± 24.1% for thumb adductor, P < 0.05) than for knee extensors (−28 ± 15%, P < 0.05); no reduction was found in plantar flexors (−7 ± 12%, P > 0.05). In conclusion, despite different times to task failure when sustaining an isometric contraction at 50% MVC force for as long as possible, diverse muscle groups present similar loss of MVC force after task failure. Thus the extent of muscle fatigue is not affected by time to task failure, whereas this latter determines the etiology of fatigue.
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Affiliation(s)
- Daria Neyroud
- Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland
| | - Jennifer Rüttimann
- Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland
| | | | | | | | - Bengt Kayser
- Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland
| | - Nicolas Place
- Institute of Movement Sciences and Sports Medicine, University of Geneva, Geneva, Switzerland
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27
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Gandevia SC, McNeil CJ, Carroll TJ, Taylor JL. Twitch interpolation: superimposed twitches decline progressively during a tetanic contraction of human adductor pollicis. J Physiol 2013; 591:1373-83. [PMID: 23283762 PMCID: PMC3607877 DOI: 10.1113/jphysiol.2012.248989] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2012] [Accepted: 12/28/2012] [Indexed: 11/08/2022] Open
Abstract
The assessment of voluntary activation of human muscles usually depends on measurement of the size of the twitch produced by an interpolated nerve or cortical stimulus. In many forms of fatiguing exercise the superimposed twitch increases and thus voluntary activation appears to decline. This is termed 'central' fatigue. Recent studies on isolated mouse muscle suggest that a peripheral mechanism related to intracellular calcium sensitivity increases interpolated twitches. To test whether this problem developed with human voluntary contractions we delivered maximal tetanic stimulation to the ulnar nerve (≥60 s at physiological motoneuronal frequencies, 30 and 15 Hz). During the tetani (at 30 Hz) in which the force declined by 42%, the absolute size of the twitches evoked by interpolated stimuli (delivered regularly or only in the last second of the tetanus) diminished progressively to less than 1%. With stimulation at 30 Hz, there was also a marked reduction in size and area of the interpolated compound muscle action potential (M wave). With a 15 Hz tetanus, a progressive decline in the interpolated twitch force also occurred (to ∼10%) but did so before the area of the interpolated M wave diminished. These results indicate that the increase in interpolated twitch size predicted from the mouse studies does not occur. Diminution in superimposed twitches occurred whether or not the M wave indicated marked impairment at sarcolemmal/t-tubular levels. Consequently, the increase in superimposed twitch, which is used to denote central fatigue in human fatiguing exercise, is likely to reflect low volitional drive to high-threshold motor units, which stop firing or are discharging at low frequencies.
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Affiliation(s)
- S C Gandevia
- Neuroscience Research Australia, Barker Street, Randwick, NSW 2031, Australia.
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Mendez-Villanueva A, Edge J, Suriano R, Hamer P, Bishop D. The recovery of repeated-sprint exercise is associated with PCr resynthesis, while muscle pH and EMG amplitude remain depressed. PLoS One 2012; 7:e51977. [PMID: 23284836 PMCID: PMC3524088 DOI: 10.1371/journal.pone.0051977] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Accepted: 11/08/2012] [Indexed: 11/18/2022] Open
Abstract
The physiological equivalents of power output maintenance and recovery during repeated-sprint exercise (RSE) remain to be fully elucidated. In an attempt to improve our understanding of the determinants of RSE performance we therefore aimed to determine its recovery following exhaustive exercise (which affected intramuscular and neural factors) concomitantly with those of intramuscular concentrations of adenosine triphosphate [ATP], phosphocreatine [PCr] and pH values and electromyography (EMG) activity (a proxy for net motor unit activity) changes. Eight young men performed 10, 6-s all-out sprints on a cycle ergometer, interspersed with 30 s of recovery, followed, after 6 min of passive recovery, by five 6-s sprints, again interspersed by 30 s of passive recovery. Biopsies of the vastus lateralis were obtained at rest, immediately after the first 10 sprints and after 6 min of recovery. EMG activity of the vastus lateralis was obtained from surface electrodes throughout exercise. Total work (TW), [ATP], [PCr], pH and EMG amplitude decreased significantly throughout the first ten sprints (P<0.05). After 6 min of recovery, TW during sprint 11 recovered to 86.3±7.7% of sprint 1. ATP and PCr were resynthesized to 92.6±6.0% and 85.3±10.3% of the resting value, respectively, but muscle pH and EMG amplitude remained depressed. PCr resynthesis was correlated with TW done in sprint 11 (r = 0.79, P<0.05) and TW done during sprints 11 to 15 (r = 0.67, P<0.05). There was a ∼2-fold greater decrease in the TW/EMG ratio in the last five sprints (sprint 11 to 15) than in the first five sprints (sprint 1 to 5) resulting in a disproportionate decrease in mechanical power (i.e., TW) in relation to EMG. Thus, we conclude that the inability to produce power output during repeated sprints is mostly mediated by intramuscular fatigue signals probably related with the control of PCr metabolism.
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González-Izal M, Malanda A, Gorostiaga E, Izquierdo M. Electromyographic models to assess muscle fatigue. J Electromyogr Kinesiol 2012; 22:501-12. [DOI: 10.1016/j.jelekin.2012.02.019] [Citation(s) in RCA: 162] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 02/24/2012] [Accepted: 02/24/2012] [Indexed: 11/24/2022] Open
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Doucet BM, Lam A, Griffin L. Neuromuscular electrical stimulation for skeletal muscle function. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2012; 85:201-15. [PMID: 22737049 PMCID: PMC3375668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Lack of neural innervation due to neurological damage renders muscle unable to produce force. Use of electrical stimulation is a medium in which investigators have tried to find a way to restore movement and the ability to perform activities of daily living. Different methods of applying electrical current to modify neuromuscular activity are electrical stimulation (ES), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES). This review covers the aspects of electrical stimulation used for rehabilitation and functional purposes. Discussed are the various parameters of electrical stimulation, including frequency, pulse width/duration, duty cycle, intensity/amplitude, ramp time, pulse pattern, program duration, program frequency, and muscle group activated, and how they affect fatigue in the stimulated muscle.
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Affiliation(s)
- Barbara M. Doucet
- University of Texas Medical Branch, Division of Rehabilitation Sciences, Galveston, Texas
| | - Amy Lam
- University of Texas, Department of Kinesiology and Health Education, Austin, Texas
| | - Lisa Griffin
- University of Texas, Department of Kinesiology and Health Education, Austin, Texas,To whom all correspondence should be addressed: Lisa Griffin, PhD, Department of Kinesiology and Health Education, 222 Bellmont, 1 University Station, D3700, University of Texas at Austin, Austin, TX, 78712; Tele: 512-471-2786; Fax: 512-471-8914;
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Dalton BH, Harwood B, Davidson AW, Rice CL. Recovery of motoneuron output is delayed in old men following high-intensity fatigue. J Neurophysiol 2009; 103:977-85. [PMID: 20032234 DOI: 10.1152/jn.00908.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Despite an age-related slowing in the contractile properties of the triceps surae, inherently low maximal motor unit firing rates (MUFRs) in the soleus are unchanged. Fatigue following high-intensity contractions is characterized by contractile slowing in conjunction with a reduction in MUFRs in young adults. Here we exploit the ageing model of the soleus to assess changes in neuromuscular function during fatigue and short-term recovery. We hypothesize that a high-intensity sustained contraction will cause minimal reductions in MUFRs in young and old subjects but that recovery of MUFRs will be delayed in aged subjects. We compared the effects of a high-intensity sustained task on the MUFRs of the soleus and triceps surae contractile properties in six young (approximately 24 yr) and six old (approximately 75 yr) men. Various measures of the contractile function of the triceps surae were tested during two to six sessions via maximal voluntary isometric contractions (MVCs) and tibial nerve stimulation. Populations of MUFR trains were recorded from the soleus during brief (approximately 7 s) MVCs, a high-intensity (75% MVC) sustained fatiguing task, and brief MVCs following task failure at 1, 2, 5, and 10 min. Old men had greater time to task failure than the young (approximately 138 and approximately 100 s, respectively). Voluntary activation was near maximal (>99%) for all subjects but at task failure, decreased to approximately 89% in both groups. Maximal MUFRs, for both groups, were reduced by approximately 44% and twitch contraction duration slowed by approximately 30% following task failure. Contraction duration recovered equally for both groups within 2 min, but maximal MUFRs did not recover until 5 min in the old compared with 1 min for the young. The surprising fatigue-induced reduction in MUFRs was similar for both groups, but despite a similar recovery of contractile properties for both, recovery of MUFRs was impaired in the old subjects.
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Affiliation(s)
- Brian H Dalton
- Canadian Centre for Activity and Aging, School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario N6A 5B9, Canada
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Hornby TG, Lewek MD, Thompson CK, Heitz R. Repeated maximal volitional effort contractions in human spinal cord injury: initial torque increases and reduced fatigue. Neurorehabil Neural Repair 2009; 23:928-38. [PMID: 19478056 PMCID: PMC5603074 DOI: 10.1177/1545968309336147] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Substantial data indicate greater muscle fatigue in individuals with spinal cord injury (SCI) compared with healthy control subjects when tested by using electrical stimulation protocols. Few studies have investigated the extent of volitional fatigue in motor incomplete SCI. METHODS Repeated, maximal volitional effort (MVE) isometric contractions of the knee extensors (KE) were performed in 14 subjects with a motor incomplete SCI and in 10 intact subjects. Subjects performed 20 repeated, intermittent MVEs (5 seconds contraction/5 seconds rest) with KE torques and thigh electromyographic (EMG) activity recorded. RESULTS Peak KE torques declined to 64% of baseline MVEs with repeated efforts in control subjects. Conversely, subjects with SCI increased peak torques during the first 5 contractions by 15%, with little evidence of fatigue after 20 repeated efforts. Increases in peak KE torques and the rate of torque increase during the first 5 contractions were attributed primarily to increases in quadriceps EMG activity, but not to decreased knee flexor co-activation. The observed initial increases in peak torque were dependent on the subject's volitional activation and were consistent on the same or different days, indicating little contribution of learning or accommodation to the testing conditions. Sustained MVEs did not elicit substantial increases in peak KE torques as compared to repeated intermittent efforts. CONCLUSIONS These data revealed a marked divergence from expected results of increased fatigability in subjects with SCI, and may be a result of complex interactions between mechanisms underlying spastic motor activity and changes in intrinsic motoneuron properties.
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Affiliation(s)
- T George Hornby
- Department of Physical Medicine and Rehabilitation, Northwestern University Medical School, Chicago, Illinois 60612, USA.
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Abstract
Neuromuscular electrical stimulation can improve motor function in those affected by paralysis, but its use is limited by a high rate of muscular fatigue. Variable stimulation patterns have been examined in young adults with and without spinal cord injury, but much less investigation has been devoted to studying the effects of variable stimulation patterns administered to older adults or those paralyzed by stroke. Significant changes occur in the neuromuscular system with age that may affect the response to variable stimulation patterns. We administered three, 3-min intermittent stimulation patterns to the median nerves of 10 individuals with hemiplegia from stroke and 10 age-matched able-bodied adults: (1) constant 20 HZ, (2) a pattern that began at 20 HZ and progressively increased to 40 HZ in the latter half of the task, and (3) a 20-HZ pattern that switched to a 20-HZ doublet pattern after 90 s. In the able-bodied group the doublet pattern produced significantly higher force time integrals (FTI) (1409.72 +/- 3.15 N s) than the 20-40-HZ pattern (1067.46 +/- 1.15 N s) or the 20-HZ pattern (831 +/- 1.87 N s). In the poststroke individuals the doublet pattern also produced the highest FTI (724.04 +/- 2.02 N s), and there was no significant difference between the 20-40-HZ (636.42 +/- 1.65 N s) and 20-HZ (583.64 +/- 3.02 N s) patterns. These results indicate that protocols that incorporate doublets in the later stages of fatigue are effective in older adults and in older adults with paralysis from stroke.
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Affiliation(s)
- Barbara M Doucet
- Department of Occupational Therapy, University of Texas Medical Branch at Galveston, Galveston, Texas, USA
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Arabadzhiev TI, Dimitrov VG, Dimitrova NA, Dimitrov GV. Interpretation of EMG integral or RMS and estimates of "neuromuscular efficiency" can be misleading in fatiguing contraction. J Electromyogr Kinesiol 2009; 20:223-32. [PMID: 19233687 DOI: 10.1016/j.jelekin.2009.01.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 12/17/2008] [Accepted: 01/21/2009] [Indexed: 10/21/2022] Open
Abstract
In occupational and sports physiology, reduction of neuromuscular efficiency (NME) and elevation of amplitude characteristics, such as root mean square (RMS) or integral of surface electromyographic (EMG) signals detected during fatiguing submaximal contraction are often related to changes in neural drive. However, there is data showing changes in the EMG integral (I(EMG)) and RMS due to peripheral factors. Causes for these changes are not fully understood. On the basis of computer simulation, we demonstrate that lengthening of intracellular action potential (IAP) profile typical for fatiguing contraction could affect EMG amplitude characteristics stronger than alteration in neural drive (central factors) defined by number of active motor units (MUs) and their firing rates. Thus, relation of these EMG amplitude characteristics only to central mechanisms can be misleading. It was also found that to discriminate between changes in RMS or I(EMG) due to alterations in neural drive from changes due to alterations in peripheral factors it is better to normalize RMS of EMG signals to the RMS of M-wave. In massive muscles, such normalization is more appropriate than normalization to either peak-to-peak amplitude or area of M-wave proposed in literature.
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Affiliation(s)
- Todor I Arabadzhiev
- Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Sofia, Bulgaria.
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35
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36
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Power spectra characteristics associated with static reflexive activation of the multifidus muscle in feline models. Eur J Appl Physiol 2008; 104:873-83. [DOI: 10.1007/s00421-008-0844-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2008] [Indexed: 11/27/2022]
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37
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Rahe-Meyer N, Pawlak M, Weilbach C, Osthaus WA, Ruhschulte H, Solomon C, Piepenbrock S, Winterhalter M. Complex myograph allows the examination of complex muscle contractions for the assessment of muscle force, shortening, velocity, and work in vivo. Biomed Eng Online 2008; 7:20. [PMID: 18616815 PMCID: PMC2492863 DOI: 10.1186/1475-925x-7-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Accepted: 07/10/2008] [Indexed: 11/13/2022] Open
Abstract
Background The devices used for in vivo examination of muscle contractions assess only pure force contractions and the so-called isokinetic contractions. In isokinetic experiments, the extremity and its muscle are artificially moved with constant velocity by the measuring device, while a tetanic contraction is induced in the muscle, either by electrical stimulation or by maximal voluntary activation. With these systems, experiments cannot be performed at pre-defined, constant muscle length, single contractions cannot be evaluated individually and the separate examination of the isometric and the isotonic components of single contractions is not possible. Methods The myograph presented in our study has two newly developed technical units, i.e. a). a counterforce unit which can load the muscle with an adjustable, but constant force and b). a length-adjusting unit which allows for both the stretching and the contraction length to be infinitely adjustable independently of one another. The two units support the examination of complex types of contraction and store the counterforce and length-adjusting settings, so that these conditions may be accurately reapplied in later sessions. Results The measurement examples presented show that the muscle can be brought to every possible pre-stretching length and that single isotonic or complex isometric-isotonic contractions may be performed at every length. The applied forces act during different phases of contraction, resulting into different pre- and after-loads that can be kept constant – uninfluenced by the contraction. Maximal values for force, shortening, velocity and work may be obtained for individual muscles. This offers the possibility to obtain information on the muscle status and to monitor its changes under non-invasive measurement conditions. Conclusion With the Complex Myograph, the whole spectrum of a muscle's mechanical characteristics may be assessed.
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Affiliation(s)
- Niels Rahe-Meyer
- Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str, 1, D-30625, Hannover, Germany.
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38
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Doucet BM, Griffin L. Maximal versus submaximal intensity stimulation with variable patterns. Muscle Nerve 2008; 37:770-7. [DOI: 10.1002/mus.20992] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Griffin L, Jun BG, Covington C, Doucet BM. Force output during fatigue with progressively increasing stimulation frequency. J Electromyogr Kinesiol 2008; 18:426-33. [PMID: 17208012 DOI: 10.1016/j.jelekin.2006.10.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2006] [Revised: 10/02/2006] [Accepted: 10/09/2006] [Indexed: 11/29/2022] Open
Abstract
There is currently a controversy over whether stimulation frequencies should increase or decrease to optimize force output over time. This study compared changes in thenar muscle force and M-wave amplitude during progressively increasing (20-40 Hz), decreasing (40-20 Hz) and constant (20 Hz) frequency stimulation of the median nerve continuously for 3 min. Twenty-three individuals participated in three sets of experiments. There was no significant difference in the force-time integrals between the three fatigue tasks. The rate of fatigue was not correlated to the number of stimulation pulses delivered (20 Hz: 3,600, 20-40 and 40-20 Hz: 5,400). All fatigue tasks caused a significant reduction in M-wave amplitude and the reduction was largest for the 20-40 Hz protocol. However, multiple linear regression analysis revealed that the M-wave amplitude could not predict the changes in force over time for the 20 Hz or 20-40 Hz protocols. Thus during sustained evoked contractions with stimulation frequencies within the physiological range, frequencies can vary significantly without changing the overall force-time integral.
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Affiliation(s)
- L Griffin
- Department of Kinesiology Health Education, 1 University Station, D3700, Bellmont 222, University of Texas, Austin, TX 78712, USA.
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40
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Fatigue in high- versus low-force voluntary and evoked contractions. Exp Brain Res 2008; 187:387-94. [DOI: 10.1007/s00221-008-1310-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Accepted: 02/06/2008] [Indexed: 11/27/2022]
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Dimitrov GV, Arabadzhiev TI, Hogrel JY, Dimitrova NA. Simulation analysis of interference EMG during fatiguing voluntary contractions. Part I: What do the intramuscular spike amplitude–frequency histograms reflect? J Electromyogr Kinesiol 2008; 18:26-34. [PMID: 16963279 DOI: 10.1016/j.jelekin.2006.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 06/15/2006] [Accepted: 06/27/2006] [Indexed: 10/24/2022] Open
Abstract
Decline in amplitude of EMG signals and in the rate of counts of intramuscularly recorded spikes during fatigue is often attributed to a progressive reduction of the neural drive only. As a rule, alterations in intracellular action potential (IAP) are not taken into account. To test correctness of the hypothesis, the effect of various discharge frequency patterns as well as changes in IAP shape and muscle fibre propagation velocity (MFPV) on the spike amplitude-frequency histogram of intramuscular interference EMG signals were simulated and analyzed. It was assumed that muscle was composed of four types of motor units (MUs): slow-twitch fatigue resistant, fast-twitch fatigue resistant, fast intermediate, and fast fatigable. MFPV and IAP duration at initial stage before fatigue as well as their changes differed for individual MU types. Fatigability of individual MU types in normal conditions as well as in the case of ischaemic or low oxygen conditions due to restricted blood flow was also taken into account. It was found that spike amplitude-frequency histogram is poorly sensitive to MU firing frequency, while it is highly sensitive to IAP profile lengthening. It is concluded that spike amplitude-frequency analysis can hardly provide a correct measure of MU rate-coding pattern during fatigue.
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Affiliation(s)
- G V Dimitrov
- Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 105, Sofia 1113, Bulgaria.
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Taylor JL, Gandevia SC. A comparison of central aspects of fatigue in submaximal and maximal voluntary contractions. J Appl Physiol (1985) 2007; 104:542-50. [PMID: 18032577 DOI: 10.1152/japplphysiol.01053.2007] [Citation(s) in RCA: 365] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Magnetic and electrical stimulation at different levels of the neuraxis show that supraspinal and spinal factors limit force production in maximal isometric efforts ("central fatigue"). In sustained maximal contractions, motoneurons become less responsive to synaptic input and descending drive becomes suboptimal. Exercise-induced activity in group III and IV muscle afferents acts supraspinally to limit motor cortical output but does not alter motor cortical responses to transcranial magnetic stimulation. "Central" and "peripheral" fatigue develop more slowly during submaximal exercise. In sustained submaximal contractions, central fatigue occurs in brief maximal efforts even with a weak ongoing contraction (<15% maximum). The presence of central fatigue when much of the available motor pathway is not engaged suggests that afferent inputs contribute to reduce voluntary activation. Small-diameter muscle afferents are likely to be activated by local activity even in sustained weak contractions. During such contractions, it is difficult to measure central fatigue, which is best demonstrated in maximal efforts. To show central fatigue in submaximal contractions, changes in motor unit firing and force output need to be characterized simultaneously. Increasing central drive recruits new motor units, but the way this occurs is likely to depend on properties of the motoneurons and the inputs they receive in the task. It is unclear whether such factors impair force production for a set level of descending drive and thus represent central fatigue. The best indication that central fatigue is important during submaximal tasks is the disproportionate increase in subjects' perceived effort when maintaining a low target force.
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Affiliation(s)
- Janet L Taylor
- Prince of Wales Medical Research Institute, Barker St., Randwick, Sydney, New South Wales, Australia.
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Indurthy M, Griffin L. Effect of random interpulse interval modulation on neuromuscular fatigue. Muscle Nerve 2007; 36:807-15. [PMID: 17724736 DOI: 10.1002/mus.20882] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neuromuscular endurance during electrical stimulation may be enhanced if naturally occurring motor unit firing patterns are used. Variability in the interpulse interval (IPI) distribution may enable brief periods of rest and optimization of force output. Nine individuals participated in three 3-minute fatigue protocols of the thenar muscles elicited by supramaximal stimulation of the median nerve. All protocols consisted of a mean IPI of 33.3 ms and differed only in the type of IPI modulation, which was constant (0%), random (+/-20%), or ramped from 0% to +/-20%. M-wave amplitude declined following all protocols and the reduction was smallest following the ramp protocol. There was no significant difference among the starting or final forces or between the overall force-time integrals for the three protocols. Thus, IPI variability did not improve endurance time during electrical stimulation and the M-wave amplitude was not a reliable indicator of muscle force output.
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Affiliation(s)
- Maritha Indurthy
- Department of Mechanical Engineering, University of Texas at Austin, Austin, Texas, USA
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Nordstrom MA, Gorman RB, Laouris Y, Spielmann JM, Stuart DG. Does motoneuron adaptation contribute to muscle fatigue? Muscle Nerve 2007; 35:135-58. [PMID: 17195169 DOI: 10.1002/mus.20712] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
To help reduce the gap between the cellular physiology of motoneurons (MNs) as studied "bottom-up" in animal preparations and the "top-down" study of the firing patterns of human motor units (MUs), this article addresses the question of whether motoneuron adaptation contributes to muscle fatigue. Findings are reviewed on the intracellularly recorded electrophysiology of spinal MNs as studied in vivo and in vitro using animal preparations, and the extracellularly recorded discharge of MUs as studied in conscious humans. The latter "top-down" approach, combined with kinetic measurements, has provided most of what is currently known about the neurobiology of muscle fatigue, including its task and context dependencies. It is argued that although the question addressed is still open, it should now be possible to design new "bottom-up" research paradigms using animal preparations that take advantage of what has been learned with the use of relatively noninvasive quantitative procedures in conscious humans.
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Affiliation(s)
- Michael A Nordstrom
- Discipline of Physiology, School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia
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Martin PG, Gandevia SC, Taylor JL. Muscle fatigue changes cutaneous suppression of propriospinal drive to human upper limb muscles. J Physiol 2007; 580:211-23. [PMID: 17218357 PMCID: PMC2075415 DOI: 10.1113/jphysiol.2006.125997] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Some voluntary drive reaches human upper limb muscles via cervical propriospinal premotoneurones. Stimulation of the superficial radial nerve can inhibit these premotoneurones selectively and the resultant suppression of voluntary drive to motoneurones changes on-going electromyographic (EMG) activity. We investigated whether muscle fatigue changes this cutaneous-induced suppression of propriospinal drive to motoneurones of upper limb muscles. EMG was recorded from the extensors and flexors of the wrist and elbow. In the first study (n = 10 subjects), single stimuli (2 x perception threshold; 2PT) to the superficial radial nerve were delivered during contraction of the wrist extensors, before and after sustained fatiguing contractions of wrist extensors. In the second study (n = 10), similar stimuli were applied during elbow extension, before and during fatigue of elbow extensors. In the final study (n = 10), trains of three stimuli (2PT) were delivered during contractions of wrist extensors, before and while they were fatigued. With fatigue of either the wrist or elbow extensors, EMG suppression to single cutaneous stimuli increased significantly (by approximately 75%) for the fatigued muscle (P < 0.05). Conversely, in the other muscles, which were coactivated but not principally involved in the task, inhibition decreased or facilitation increased. Trains of stimuli produced greater suppression of on-going wrist extensor EMG than single stimuli and this difference persisted with fatigue. A control study of the H reflex in extensor carpi radialis showed that the mechanism responsible for the altered EMG suppression in fatigue was not at a motoneurone level. The findings suggest that the proportion of descending drive mediated via the disynaptic propriospinal pathway or the excitability of inhibitory interneurones projecting to propriospinal neurones increases substantially to fatigued muscles, but decreases to other active muscles. This pattern of changes may maintain coordination during multimuscle movements when one group of muscles is fatigued.
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Affiliation(s)
- P G Martin
- Prince of Wales Medical Research Institute, University of New South Wales, Barker Street, Randwick, Sydney, NSW 2031, Australia
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Todd G, Taylor JL, Butler JE, Martin PG, Gorman RB, Gandevia SC. Use of motor cortex stimulation to measure simultaneously the changes in dynamic muscle properties and voluntary activation in human muscles. J Appl Physiol (1985) 2007; 102:1756-66. [PMID: 17218428 DOI: 10.1152/japplphysiol.00962.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Force responses to transcranial magnetic stimulation of motor cortex (TMS) during exercise provide information about voluntary activation and contractile properties of the muscle. Here, TMS-generated twitches and muscle relaxation during the TMS-evoked silent period were measured in fresh, heated, and fatigued muscle. Subjects performed isometric contractions of elbow flexors in two studies. Torque and EMG were recorded from elbow flexor and extensor muscles. One study (n = 6) measured muscle contraction times and relaxation rates during brief maximal and submaximal contractions in fresh and fatigued muscle. Another study (n = 7) aimed to 1) assess the reproducibility of muscle contractile properties during brief voluntary contractions in fresh muscle, 2) validate the technique for contractile properties in passively heated muscle, and 3) apply the technique to study contractile properties during sustained maximal voluntary contractions. In both studies, muscle contractile properties during voluntary contractions were compared with the resting twitch evoked by motor nerve stimulation. Measurement of muscle contractile properties during voluntary contractions is reproducible in fresh muscle and reveals faster and slower muscle relaxation rates in heated and fatigued muscle, respectively. The technique is more sensitive to altered muscle state than the traditional motor nerve resting twitch. Use of TMS during sustained maximal contractions reveals slowing of muscle contraction and relaxation with different time courses and a decline in voluntary activation. Voluntary output from the motor cortex becomes insufficient to maintain complete activation of muscle, although slowing of muscle contraction and relaxation indicates that lower motor unit firing rates are required for fusion of force.
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48
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Rahe-Meyer N, Weilbach C, Karst M, Pawlak M, Ahmed A, Piepenbrock S, Winterhalter M. In vivo myograph measurement of muscle contraction at optimal length. Biomed Eng Online 2007; 6:1. [PMID: 17199890 PMCID: PMC1770920 DOI: 10.1186/1475-925x-6-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Accepted: 01/02/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Current devices for measuring muscle contraction in vivo have limited accuracy in establishing and re-establishing the optimum muscle length. They are variable in the reproducibility to determine the muscle contraction at this length, and often do not maintain precise conditions during the examination. Consequently, for clinical testing only semi-quantitative methods have been used. METHODS We present a newly developed myograph, an accurate measuring device for muscle contraction, consisting of three elements. Firstly, an element for adjusting the axle of the device and the physiological axis of muscle contraction; secondly, an element to accurately position and reposition the extremity of the muscle; and thirdly, an element for the progressive pre-stretching and isometric locking of the target muscle. Thus it is possible to examine individual in vivo muscles in every pre-stretched, specified position, to maintain constant muscle-length conditions, and to accurately re-establish the conditions of the measurement process at later sessions. RESULTS In a sequence of experiments the force of contraction of the muscle at differing stretching lengths were recorded and the forces determined. The optimum muscle length for maximal force of contraction was established. In a following sequence of experiments with smaller graduations around this optimal stretching length an increasingly accurate optimum muscle length for maximal force of contraction was determined. This optimum length was also accurately re-established at later sessions. CONCLUSION We have introduced a new technical solution for valid, reproducible in vivo force measurements on every possible point of the stretching curve. Thus it should be possible to study the muscle contraction in vivo to the same level of accuracy as is achieved in tests with in vitro organ preparations.
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Affiliation(s)
- Niels Rahe-Meyer
- Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
| | - Christian Weilbach
- Department of Anaethesiology, St. Josefs Stift Cloppenburg, Krankenhausstr. 13, D-49661 Cloppenburg, Germany
| | - Matthias Karst
- Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
| | - Matthias Pawlak
- Institute of Physiology, University of Wuerzburg, Roentgenring 9, D-97070 Wuerzburg, Germany
| | - Aminul Ahmed
- St. Thomas' Hospital, Lambeth Palace Road, London SE1 7EH, Great Britain
| | - Siegfried Piepenbrock
- Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
| | - Michael Winterhalter
- Department of Anaesthesiology, Hannover Medical School, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany
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Shields RK, Dudley-Javoroski S, Cole KR. Feedback-controlled stimulation enhances human paralyzed muscle performance. J Appl Physiol (1985) 2006; 101:1312-9. [PMID: 16809630 PMCID: PMC3270310 DOI: 10.1152/japplphysiol.00385.2006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronically paralyzed muscle requires extensive training before it can deliver a therapeutic dose of repetitive stress to the musculoskeletal system. Neuromuscular electrical stimulation, under feedback control, may subvert the effects of fatigue, yielding more rapid and extensive adaptations to training. The purposes of this investigation were to 1) compare the effectiveness of torque feedback-controlled (FDBCK) electrical stimulation with classic open-loop constant-frequency (CONST) stimulation, and 2) ascertain which of three stimulation strategies best maintains soleus torque during repetitive stimulation. When torque declined by 10%, the FDBCK protocol modulated the base stimulation frequency in three ways: by a fixed increase, by a paired pulse (doublet) at the beginning of the stimulation train, and by a fixed decrease. The stimulation strategy that most effectively restored torque continued for successive contractions. This process repeated each time torque declined by 10%. In fresh muscle, FDBCK stimulation offered minimal advantage in maintaining peak torque or mean torque over CONST stimulation. As long-duration fatigue developed in subsequent bouts, FDBCK stimulation became most effective ( approximately 40% higher final normalized torque than CONST). The high-frequency strategy was selected approximately 90% of the time, supporting that excitation-contraction coupling compromise and not neuromuscular transmission failure contributed to fatigue of paralyzed muscle. Ideal stimulation strategies may vary according to the site of fatigue; this stimulation approach offered the advantage of online modulation of stimulation strategies in response to fatigue conditions. Based on stress-adaptation principles, FDBCK-controlled stimulation may enhance training effects in chronically paralyzed muscle.
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Affiliation(s)
- Richard K Shields
- Graduate Program in Physical Therapy and Rehabilitation Science, The University of Iowa, Iowa City, IA 52242-1190, USA.
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Dimitrov GV, Arabadzhiev TI, Hogrel JY, Dimitrova NA. Simulation analysis of interference EMG during fatiguing voluntary contractions. Part II--changes in amplitude and spectral characteristics. J Electromyogr Kinesiol 2006; 18:35-43. [PMID: 16963280 DOI: 10.1016/j.jelekin.2006.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Capabilities of amplitude and spectral methods for information extraction from interference EMG signals were assessed through simulation and preliminary experiment. Muscle was composed of 4 types of motor units (MUs). Different hypotheses on changes in firing frequency of individual MUs, intracellular action potential (IAP) and muscle fibre propagation velocity (MFPV) during fatigue were analyzed. It was found that changes in amplitude characteristics of interference signals (root mean square, RMS, or integrated rectified value, IEMG) detected by intramuscular and surface electrodes differed. RMS and IEMG of surface detected interference signals could increase even under MU firing rate reduction and without MU synchronisation. IAP profile lengthening can affect amplitude characteristics more significantly than MU firing frequency. Thus, an increase of interference EMG amplitude is unreliable to reflect changes in the neural drive. The ratio between EMG amplitude and contraction response can hardly characterise the so-called 'neuromuscular efficiency'. The recently proposed spectral fatigue indices can be used for quantification of interference EMG signals. The indices are practically insensitive to MU firing frequency. IAP profile lengthening and decrease in MFPV enhanced the index value, while recruitment of fast fatigable MUs reduced it. Sensitivity of the indices was higher than that of indices traditionally used.
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Affiliation(s)
- G V Dimitrov
- Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G.Bonchev Street, Bl 105, Sofia 1113, Bulgaria.
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