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Sanderson A, Wang SF, Elgueta-Cancino E, Martinez-Valdes E, Sanchis-Sanchez E, Liew B, Falla D. The effect of experimental and clinical musculoskeletal pain on spinal and supraspinal projections to motoneurons and motor unit properties in humans: A systematic review. Eur J Pain 2021; 25:1668-1701. [PMID: 33964047 DOI: 10.1002/ejp.1789] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 10/30/2020] [Accepted: 04/24/2021] [Indexed: 12/23/2022]
Abstract
BACKGROUND AND OBJECTIVE Numerous studies have examined the influence of pain on spinal reflex excitability, motor unit behaviour and corticospinal excitability. Nevertheless, there are inconsistencies in the conclusions made. This systematic review sought to understand the effect of pain on spinal and supraspinal projections to motoneurons and motor unit properties by examining the influence of clinical or experimental pain on the following three domains: H-reflex, corticospinal excitability and motor unit properties. DATABASES AND DATA TREATMENT MeSH terms and preselected keywords relating to the H-reflex, motor evoked potentials and motor unit decomposition in chronic and experimental pain were used to perform a systematic literature search using Cumulative Index of Nursing and Allied Health Literature (CINAHL), Excerpta Medica dataBASE (EMBASE), Web of Science, Medline, Google Scholar and Scopus databases. Two independent reviewers screened papers for inclusion and assessed the methodological quality using a modified Downs and Black risk of bias tool; a narrative synthesis and three meta-analyses were performed. RESULTS Sixty-one studies were included, and 17 different outcome variables were assessed across the three domains. Both experimental and clinical pain have no major influence on measures of the H-reflex, whereas experimental and clinical pain appeared to have differing effects on corticospinal excitability. Experimental pain consistently reduced motor unit discharge rate, a finding which was not consistent with data obtained from patients. The results indicate that when in tonic pain, induced via experimental pain models, inhibitory effects on motoneuron behaviour were evident. However, in chronic clinical pain populations, more varied responses were evident likely reflecting individual adaptations to chronic symptoms. SIGNIFICANCE This is a comprehensive systematic review and meta-analysis which synthesizes evidence on the influence of pain on spinal and supraspinal projections to motoneurons and motor unit properties considering measures of the H-reflex, corticospinal excitability and motor unit behaviour. The H-reflex is largely not influenced by the presence of either clinical or experimental pain. Whilst inhibitory effects on corticospinal excitability and motor unit behaviour were evident under experimental pain conditions, more variable responses were observed for people with painful musculoskeletal disorders.
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Affiliation(s)
- Andy Sanderson
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,Department of Sport and Exercise Sciences, Musculoskeletal Science and Sports Medicine Research Centre, Manchester Metropolitan University, Manchester, UK
| | - Shuwfen F Wang
- Graduate Institute and School of Physical Therapy, National Taiwan University, Taipei, Taiwan
| | - Edith Elgueta-Cancino
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Eduardo Martinez-Valdes
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
| | - Enrique Sanchis-Sanchez
- Department of Physiotherapy, Faculty of Physiotherapy, University of Valencia, Valencia, Spain
| | - Bernard Liew
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK.,School of Sport, Rehabilitation and Exercise Sciences, Faculty of Physiotherapy, University of Essex, Colchester, UK
| | - Deborah Falla
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, UK
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Martinez‐Valdes E, Negro F, Farina D, Falla D. Divergent response of low‐
versus
high‐threshold motor units to experimental muscle pain. J Physiol 2020; 598:2093-2108. [DOI: 10.1113/jp279225] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 03/09/2020] [Indexed: 11/08/2022] Open
Affiliation(s)
- Eduardo Martinez‐Valdes
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences University of Birmingham Birmingham UK
| | - Francesco Negro
- Department of Clinical and Experimental Sciences Università degli Studi di Brescia Brescia Italy
| | - Dario Farina
- Department of Bioengineering, Imperial College London Royal School of Mines London UK
| | - Deborah Falla
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences University of Birmingham Birmingham UK
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Namwongsa S, Puntumetakul R, Neubert MS, Boucaut R. Effect of neck flexion angles on neck muscle activity among smartphone users with and without neck pain. ERGONOMICS 2019; 62:1524-1533. [PMID: 31451087 DOI: 10.1080/00140139.2019.1661525] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 06/25/2019] [Indexed: 06/10/2023]
Abstract
This study examined the differences in neck muscle activity at various neck flexion angles in smartphone users with and without neck pain. Forty-four participants performed texting tasks for 1 min and 30 s. Neck muscle activity and pain in the neck were measured at different neck flexion angles. There was a difference in neck muscle activity for each of the neck flexion angles; the Cervical Erector Spinae (CES) muscle activity increased while the Upper Trapezius (UT) muscle activity decreased when at increased neck flexion angles. At neck flexion angle of 0°-15°, the activity of both CES and UT muscles were acceptably low. Smartphone users with neck pain had slightly higher muscle activity levels than smartphone users without neck pain. In conclusion, smartphone users should consider adopting neck flexion angles between 0 and 15 degrees during smartphone use as there is an association between this neck flexion angle range and reduced CES muscle activity. Practitioner summary: This study demonstrated that both smartphone users with and without neck pain should try to keep their neck flexion angle between 0° and 15° when using their smartphone. This would reduce neck muscle activity and the risk of developing neck disorders associated with smartphone use.
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Affiliation(s)
- Suwalee Namwongsa
- Research Center in Back, Neck, Other Joint Pain and Human Performance (BNOJPH), Khon Kaen University , Khon Kaen , Thailand
- School of Physical Therapy, Faculty of Associated Medical Sciences, Khon Kaen University , Khon Kaen , Thailand
| | - Rungthip Puntumetakul
- Research Center in Back, Neck, Other Joint Pain and Human Performance (BNOJPH), Khon Kaen University , Khon Kaen , Thailand
- School of Physical Therapy, Faculty of Associated Medical Sciences, Khon Kaen University , Khon Kaen , Thailand
| | - Manida Swangnetr Neubert
- Research Center in Back, Neck, Other Joint Pain and Human Performance (BNOJPH), Khon Kaen University , Khon Kaen , Thailand
- Program of Production Technology, Faculty of Technology, Khon Kaen University , Khon Kaen , Thailand
| | - Rose Boucaut
- School of Health Sciences (Physiotherapy), iCAHE (International Centre for Allied Health Evidence), University of South Australia , Adelaide , Australia
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Porciuncula F, Roto AV, Kumar D, Davis I, Roy S, Walsh CJ, Awad LN. Wearable Movement Sensors for Rehabilitation: A Focused Review of Technological and Clinical Advances. PM R 2018; 10:S220-S232. [PMID: 30269807 PMCID: PMC6700726 DOI: 10.1016/j.pmrj.2018.06.013] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/13/2018] [Accepted: 06/18/2018] [Indexed: 01/01/2023]
Abstract
Recent technologic advancements have enabled the creation of portable, low-cost, and unobtrusive sensors with tremendous potential to alter the clinical practice of rehabilitation. The application of wearable sensors to track movement has emerged as a promising paradigm to enhance the care provided to patients with neurologic or musculoskeletal conditions. These sensors enable quantification of motor behavior across disparate patient populations and emerging research shows their potential for identifying motor biomarkers, differentiating between restitution and compensation motor recovery mechanisms, remote monitoring, telerehabilitation, and robotics. Moreover, the big data recorded across these applications serve as a pathway to personalized and precision medicine. This article presents state-of-the-art and next-generation wearable movement sensors, ranging from inertial measurement units to soft sensors. An overview of clinical applications is presented across a wide spectrum of conditions that have potential to benefit from wearable sensors, including stroke, movement disorders, knee osteoarthritis, and running injuries. Complementary applications enabled by next-generation sensors that will enable point-of-care monitoring of neural activity and muscle dynamics during movement also are discussed.
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Affiliation(s)
- Franchino Porciuncula
- Paulson School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA(∗)
| | - Anna Virginia Roto
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA(†)
| | - Deepak Kumar
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA(‡)
| | - Irene Davis
- Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA(§)
| | - Serge Roy
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA(¶)
| | - Conor J Walsh
- Paulson School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA(#)
| | - Louis N Awad
- College of Health and Rehabilitation Sciences, Sargent College, Boston University, Boston, MA; Paulson School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, MA; Department of Physical Medicine and Rehabilitation, Harvard Medical School, Cambridge, MA(∗∗).
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Yang CC, Su FC, Yang PC, Lin HT, Guo LY. Characteristics of the Motor Units during Sternocleidomastoid Isometric Flexion among Patients with Mechanical Neck Disorder and Asymptomatic Individuals. PLoS One 2016; 11:e0167737. [PMID: 27941995 PMCID: PMC5152896 DOI: 10.1371/journal.pone.0167737] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 11/18/2016] [Indexed: 12/03/2022] Open
Abstract
Mechanical neck disorder is a widespread and non-neurological musculoskeletal condition resulting from modern lifestyles. Presently, the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles and the characteristics of the short-term synchronization of the motor unit in patients with neck pain are ambiguous. This study therefore aims to clarify the fundamental electrophysiological properties of the motor units of the sternocleidomastoid muscles in patients with mechanical neck disorder and in asymptomatic individuals. We further investigated whether alterations in the degree of motor unit short-term synchronization occur. The surface electrophysiological signals of the bilateral sternal heads of the sternocleidomastoid muscles of twelve patients with mechanical neck disorder and asymptomatic individuals were detected at 25% of the maximum voluntary contraction during cervical isometric flexion and then decomposed into individual motor unit action potential trains. We found that the patients with mechanical neck disorder showed significantly higher initial and mean firing rates of the sternocleidomastoid muscles and displayed substantially lower motor unit short-term synchronization values compared with the asymptomatic subjects. Consequently, these convincing findings support the assertion that patients with mechanical neck disorder display altered neuromuscular control strategies, such as the reinforcement of motor unit recruitment firing rates in the sternocleidomastoid muscles. The motor units of these patients also revealed neural recruitment strategies with relatively poor efficiency when executing the required motor tasks.
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Affiliation(s)
- Chia-Chi Yang
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Fong-Chin Su
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
| | - Po-Ching Yang
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Hwai-Ting Lin
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Lan-Yuen Guo
- Department of Sports Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
- * E-mail:
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Vangsgaard S, Nørgaard LT, Madeleine P, Taylor JL. Crossed responses found in human trapezius muscles are not H-reflexes. Muscle Nerve 2013; 49:362-9. [DOI: 10.1002/mus.23914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 05/12/2013] [Accepted: 05/14/2013] [Indexed: 12/16/2022]
Affiliation(s)
- Steffen Vangsgaard
- Centre for Sensory-Motor Interaction (SMI), Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Lars T. Nørgaard
- Centre for Sensory-Motor Interaction (SMI), Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Pascal Madeleine
- Centre for Sensory-Motor Interaction (SMI), Department of Health Science and Technology; Aalborg University; Aalborg Denmark
| | - Janet L. Taylor
- Neuroscience Research Australia and the University of New South Wales; Barker Street Randwick NSW 2031 Australia
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Kallenberg LAC, Hermens HJ. Motor unit properties of biceps brachii during dynamic contractions in chronic stroke patients. Muscle Nerve 2010; 43:112-9. [PMID: 20928907 DOI: 10.1002/mus.21803] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/25/2010] [Indexed: 11/06/2022]
Abstract
The aim of this study was to investigate motor unit (MU) characteristics of the biceps brachii during sinusoidal contractions in chronic stroke patients using high-density surface electromyography. Ten sinusoidal elbow flexion and extension movements were performed both passively and actively by 18 stroke patients and 20 healthy subjects. Motor unit action potentials (MUAPs) were extracted, and their root-mean-square value (RMS(MUAP)) was calculated. RMS(MUAP) was significantly larger in stroke than in healthy subjects. In both groups RMS(MUAP) was smaller during the stretch phase of passive movement than during active movement. The larger MUAPs indicate enlarged MUs, possibly as a result of reinnervation. The lower RMS(MUAP) values during passive stretch than during active movement indicates that the stretch reflex mainly activates smaller MUs, while a larger part of the MU pool can be recruited voluntarily. RMS(MUAP) may have added value for monitoring changes in peripheral MU properties after stroke.
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Affiliation(s)
- Laura A C Kallenberg
- Roessingh Research and Development, PO Box 310, 7500 AH Enschede, The Netherlands.
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Combining microdialysis and near-infrared spectroscopy for studying effects of low-load repetitive work on the intramuscular chemistry in trapezius myalgia. J Biomed Biotechnol 2010; 2010:513803. [PMID: 20625491 PMCID: PMC2896692 DOI: 10.1155/2010/513803] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 03/31/2010] [Accepted: 03/31/2010] [Indexed: 11/30/2022] Open
Abstract
Epidemiological research provides strong evidence for a link between repetitive work (RW) and the development of chronic trapezius myalgia (TM). The aims were to further elucidate if an accumulation of sensitising substances or impaired oxygenation is evident in painful muscles during RW. Females with TM (n = 14) were studied during rest, 30 minutes RW and 60 minutes recovery. Microdialysate samples were obtained to determine changes in intramuscular microdialysate (IMMD) [glutamate], [PGE2], [lactate], and [pyruvate] (i.e., [concentration]) relative to work. Muscle oxygenation (%StO2) was assessed using near-infrared spectroscopy. During work, all investigated substances, except PGE2, increased significantly: [glutamate] (54%, P < .0001), [lactate] (26%, P < .005), [pyruvate] (19%, P < .0001), while the %StO2 decreased (P < .05). During recovery [PGE2] decreased (P < .005), [lactate] remained increased (P < .001), [pyruvate] increased progressively (P < .0001), and %StO2 had returned to baseline. Changes in substance concentrations and oxygenation in response to work indicate normal increase in metabolism but no ongoing inflammation in subjects with TM.
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Madeleine P. On functional motor adaptations: from the quantification of motor strategies to the prevention of musculoskeletal disorders in the neck-shoulder region. Acta Physiol (Oxf) 2010; 199 Suppl 679:1-46. [PMID: 20579000 DOI: 10.1111/j.1748-1716.2010.02145.x] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Occupations characterized by a static low load and by repetitive actions show a high prevalence of work-related musculoskeletal disorders (WMSD) in the neck-shoulder region. Moreover, muscle fatigue and discomfort are reported to play a relevant initiating role in WMSD. AIMS To investigate relationships between altered sensory information, i.e. localized muscle fatigue, discomfort and pain and their associations to changes in motor control patterns. MATERIALS & METHODS In total 101 subjects participated. Questionnaires, subjective assessments of perceived exertion and pain intensity as well as surface electromyography (SEMG), mechanomyography (MMG), force and kinematics recordings were performed. RESULTS Multi-channel SEMG and MMG revealed that the degree of heterogeneity of the trapezius muscle activation increased with fatigue. Further, the spatial organization of trapezius muscle activity changed in a dynamic manner during sustained contraction with acute experimental pain. A graduation of the motor changes in relation to the pain stage (acute, subchronic and chronic) and work experience were also found. The duration of the work task was shorter in presence of acute and chronic pain. Acute pain resulted in decreased activity of the painful muscle while in subchronic and chronic pain, a more static muscle activation was found. Posture and movement changed in the presence of neck-shoulder pain. Larger and smaller sizes of arm and trunk movement variability were respectively found in acute pain and subchronic/chronic pain. The size and structure of kinematics variability decreased also in the region of discomfort. Motor variability was higher in workers with high experience. Moreover, the pattern of activation of the upper trapezius muscle changed when receiving SEMG/MMG biofeedback during computer work. DISCUSSION SEMG and MMG changes underlie functional mechanisms for the maintenance of force during fatiguing contraction and acute pain that may lead to the widespread pain seen in WMSD. A lack of harmonious muscle recruitment/derecruitment may play a role in pain transition. Motor behavior changed in shoulder pain conditions underlining that motor variability may play a role in the WMSD development as corroborated by the changes in kinematics variability seen with discomfort. This prognostic hypothesis was further, supported by the increased motor variability among workers with high experience. CONCLUSION Quantitative assessments of the functional motor adaptations can be a way to benchmark the pain status and help to indentify signs indicating WMSD development. Motor variability is an important characteristic in ergonomic situations. Future studies will investigate the potential benefit of inducing motor variability in occupational settings.
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Affiliation(s)
- P Madeleine
- Laboratory for Ergonomics and Work-related Disorders, Department of Health Science and Technology, Aalborg University, Center for Sensory-Motor Interaction, Aalborg, Denmark.
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Kallenberg LA, Preece S, Nester C, Hermens HJ. Reproducibility of MUAP properties in array surface EMG recordings of the upper trapezius and sternocleidomastoid muscle. J Electromyogr Kinesiol 2009; 19:e536-42. [DOI: 10.1016/j.jelekin.2008.11.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 11/03/2008] [Accepted: 11/03/2008] [Indexed: 12/01/2022] Open
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Experimental pain leads to reorganisation of trapezius electromyography during computer work with active and passive pauses. Eur J Appl Physiol 2009; 106:857-66. [DOI: 10.1007/s00421-009-1083-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/05/2009] [Indexed: 10/20/2022]
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Kallenberg LAC, Hermens HJ. Motor unit properties of biceps brachii in chronic stroke patients assessed with high-density surface EMG. Muscle Nerve 2009; 39:177-85. [PMID: 19034958 DOI: 10.1002/mus.21090] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aim of this study was to investigate motor unit (MU) characteristics of the biceps brachii in poststroke patients using high-density surface electromyography (sEMG). Eighteen chronic hemiparetic stroke patients took part. The Fugl-Meyer score for the upper extremity was assessed. Subjects performed an isometric step contraction consisting of force levels from 5%-50% maximal voluntary contraction while sEMG of the biceps brachii was recorded with a two-dimensional 16-channel electrode array. This was repeated for both sides. Motor unit action potentials (MUAPs) were extracted from the EMG signals, and their root-mean-square value (RMS(MUAP), reflecting MU size) and mean frequency of the power spectrum (FMEAN(MUAP), reflecting recruitment threshold) were calculated. FMEAN(MUAP) was smaller on the affected than on the unaffected side, indicating an increased contribution of low-threshold MUs, possibly related to degeneration of high-threshold MUs. The ratio of RMS(MUAP) on the affected side divided by that on the unaffected side correlated significantly with the Fugl-Meyer score. This ratio may reflect the extent to which reinnervation has occurred on the affected side.
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Affiliation(s)
- Laura A C Kallenberg
- Roessingh Research and Development, P.O. Box 310, 7500 AH Enschede, The Netherlands.
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Merletti R, Holobar A, Farina D. Analysis of motor units with high-density surface electromyography. J Electromyogr Kinesiol 2008; 18:879-90. [PMID: 19004645 DOI: 10.1016/j.jelekin.2008.09.002] [Citation(s) in RCA: 169] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2008] [Accepted: 09/02/2008] [Indexed: 10/21/2022] Open
Abstract
Although the behaviour of individual motor units is classically studied with intramuscular EMG, recently developed techniques allow its analysis also from EMG recorded in multiple locations over the skin surface (high-density surface EMG). The analysis of motor units from the surface EMG is useful when the insertion of needles is not desirable or not possible. Moreover, surface EMG allows the measure of motor unit properties which are difficult to assess with invasive technology (e.g., muscle fiber conduction velocity or location of innervation zones) and may increase the number of detectable motor units with respect to selective intramuscular recordings. Although some limitations remain, both the discharge pattern and muscle fiber properties of individual motor units can currently be analyzed non-invasively. This review presents the conditions and methodologies which allow the investigation of motor units with surface EMG.
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Affiliation(s)
- Roberto Merletti
- Laboratorio di Ingegneria del Sistema Neuromuscolare, Dipartimento di Elettronica, Politecnico di Torino, Corso Duca degli Abruzzi, 24 - 10129 Torino, Italy.
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Kallenberg LAC, Schulte E, Disselhorst-Klug C, Hermens HJ. Myoelectric manifestations of fatigue at low contraction levels in subjects with and without chronic pain. J Electromyogr Kinesiol 2007; 17:264-74. [PMID: 16790358 DOI: 10.1016/j.jelekin.2006.04.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2005] [Revised: 04/15/2006] [Accepted: 04/26/2006] [Indexed: 10/24/2022] Open
Abstract
The aim of the present study was to investigate differences in myoelectric responses to fatigue development between cases with chronic neck-shoulder pain (n=10) and healthy controls (n=10) during a low force level sustained contraction. Subjects performed a 15-min isometric shoulder elevation at a force level of 40 N (sustained contraction), preceded and followed by a step contraction, consisting of five force levels from 20 to 100 N. EMG recordings were made with a two-dimensional electrode array on the upper trapezius of the dominant side. Root-mean-square (RMS(G)), median power frequency (FMED(G)), conduction velocity (CV), number of motor unit action potentials per second (MUAP Rate) and MUAP shape properties were estimated. Changes over time and differences between the groups were statistically evaluated with a linear mixed model. During the sustained contraction, cases showed less increase in RMS(G) than controls (controls: 58.5%, cases: 33.0%). FMED(G) and CV decreased in controls (FMED(G): -6.3%, CV: -5.3%) and stayed constant (FMED(G)) or slightly increased (CV, 3.15%) in cases. Overall, cases showed a less pronounced myoelectric response to the fatiguing task than controls, which may be related to additional recruitment of higher-threshold MUs. A possible explanation might be that cases were already (chronically) fatigued before the experiment started.
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Affiliation(s)
- Laura A C Kallenberg
- Roessingh Research and Development, 7500 AH Enschede, P.O. Box 310, The Netherlands.
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Kallenberg LAC, Hermens HJ. Behaviour of a surface EMG based measure for motor control: motor unit action potential rate in relation to force and muscle fatigue. J Electromyogr Kinesiol 2007; 18:780-8. [PMID: 17466536 DOI: 10.1016/j.jelekin.2007.02.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 02/20/2007] [Accepted: 02/20/2007] [Indexed: 11/20/2022] Open
Abstract
Surface electromyography parameters such as root-mean-square value (RMS) and median power frequency (FMED) are commonly used to assess the input of the central nervous system (CNS) to a muscle. However, RMS and FMED are influenced not only by CNS input, but also by peripheral muscle properties. The number of motor unit action potentials (MUAPs) per second, or MUAP Rate (MR), being the sum of the firing rates of the active motor units, would reflect CNS input solely. This study explored MR behaviour in relation to force and during a fatiguing contraction in comparison to RMS and FMED. In the first experiment (n=10) a step contraction of shoulder elevation force (20-100 N) was performed while multi-channel array EMG was recorded from the upper trapezius muscle. The sensitivity of MR for changes in force (1.8%/N) was almost twice as high as that of RMS (0.97%/N), indicating that MR may be more suitable for monitoring muscle force. The second experiment (n=6) consisted of a 15-min isometric contraction of the biceps brachii. MR increased considerably less than RMS (0.9% vs. 4.1%), suggesting that MR selectively reflects central motor control whereas RMS also reflects peripheral changes. These results support that, at relatively low force levels, MR is a suitable parameter for non-invasive assessment of the input of the CNS to the muscle.
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Affiliation(s)
- L A C Kallenberg
- Roessingh Research and Development, P.O. Box 310, 7500 AH Enschede, The Netherlands.
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Läubli T, Hermens H, Sjøgaard G. Neuromuscular assessment of the elderly worker, NEW: a multidisciplinary European research project. Eur J Appl Physiol 2006; 96:107-9. [PMID: 16240133 DOI: 10.1007/s00421-005-0045-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Kallenberg LAC, Hermens HJ. Behaviour of motor unit action potential rate, estimated from surface EMG, as a measure of muscle activation level. J Neuroeng Rehabil 2006; 3:15. [PMID: 16846508 PMCID: PMC1557523 DOI: 10.1186/1743-0003-3-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Accepted: 07/17/2006] [Indexed: 11/22/2022] Open
Abstract
Background Surface electromyography (EMG) parameters such as root-mean-square value (RMS) are commonly used to assess the muscle activation level that is imposed by the central nervous system (CNS). However, RMS is influenced not only by motor control aspects, but also by peripheral properties of the muscle and recording setup. To assess motor control separately, the number of motor unit action potentials (MUAPs) per second, or MUAP Rate (MR) is a potentially useful measure. MR is the sum of the firing rates of the contributing MUs and as such reflects the two parameters that the CNS uses for motor control: number of MUs and firing rate. MR can be estimated from multi-channel surface EMG recordings. The objective of this study was to explore the behaviour of estimated MR (eMR) in relation to number of active MUs and firing rate. Furthermore, the influence of parameters related to peripheral muscle properties and recording setup (number of fibers per MU, fiber diameter, thickness of the subcutaneous layer, signal-to-noise-ratio) on eMR was compared with their influence on RMS. Methods Physiological parameters were varied in a simulation model that generated multi-channel EMG signals. The behaviour of eMR in simulated conditions was compared with its behaviour in experimental conditions. Experimental data was obtained from the upper trapezius muscle during a shoulder elevation task (20–100 N). Results The simulations showed strong, monotonously increasing relations between eMR and number of active MUs and firing rate (r2 > 0.95). Because of unrecognized superimpositions of MUAPs, eMR was substantially lower than the actual MUAP Rate (aMR). The percentage of detected MUAPs decreased with aMR, but the relation between eMR and aMR was rather stable in all simulated conditions. In contrast to RMS, eMR was not affected by number of fibers per MU, fiber diameter and thickness of the subcutaneous layer. Experimental data showed a strong relation between eMR and force (individual second order polynomial regression: 0.96 < r2 < 0.99). Conclusion Although the actual number of MUAPs in the signal cannot be accurately extracted with the present method, the stability of the relation between eMR and aMR and its independence of muscle properties make eMR a suitable parameter to assess the input from the CNS to the muscle at low contraction levels non-invasively.
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Affiliation(s)
| | - Hermie J Hermens
- Roessingh Research and Development, Enschede, The Netherlands
- Faculty of Electrical Engineering, Mathematics and Computer Science, University of Twente, Enschede, The Netherlands
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