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Norberto MS, de Arruda TB, Papoti M. A New Approach to Evaluate Neuromuscular Fatigue of Extensor Elbow Muscles. Front Physiol 2020; 11:553296. [PMID: 33071813 PMCID: PMC7538809 DOI: 10.3389/fphys.2020.553296] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Accepted: 08/25/2020] [Indexed: 01/08/2023] Open
Abstract
Neuromuscular fatigue evaluation is widely performed on different muscles through the conventional protocol using maximum voluntary contraction (MVC) with electrical stimuli in the analyzed muscle. In an attempt to use this protocol on elbow extensor musculature, previous studies and pilot studies showed co-contraction effects from antagonist musculature during muscular stimulations. The aim of this study was to propose a new neuromuscular fatigue protocol evaluation on elbow extensor musculature. Twenty participants preformed exercises to induce central (CenFat) and peripheral fatigue (PerFat). Neuromuscular fatigue was evaluated on knee extensor muscles by a conventional protocol that provides Twitch Superimposed (TSK) and Twitch Potentiated (TPK), central and peripheral parameters respectively. For elbow extensor muscles, the protocol used sustained submaximal contraction at 10, 20, 30, 40, and 50% of MVC. The neuromuscular fatigue in upper limbs was identified by Twitch Potentiated (TPE) and multiple Twitch Superimposed (TSE) parameters. Using the relationship between MVC (%) and evoked force, the proposed protocol used several TSE to provide slope, y-intercept and R 2. It is proposed that slope, R 2, and y-intercept change may indicate peripheral fatigue and the identified relationship between y-intercept and R 2 may indicate central fatigue or both peripheral and central fatigue. The results were compared using the non-parametric analyzes of Friedmann and Wilcoxon and their possible correlations were verified by the Spearmann test (significance level set at p < 0.05). After PerFat a decrease in TPE (57.1%, p < 0.001) was found but not in any TSE, indicating only peripheral fatigue in upper limbs. After CenFat a decrease in TPE (21.4%, p: 0.008) and TPK (20.9%, p < 0.001) were found but not in TSK, indicating peripheral fatigue in upper and lower limbs but not central fatigue. A non-significant increase of 15.3% after CenFat and a statistical reduction (80.1%, p: 0.001) after PerFat were found by slope. Despite R 2 showing differences after both exercises (p < 0.05), it showed a recovery behavior after CenFat (p: 0.016). Although PerFat provided only peripheral fatigue, CenFat did not provide central fatigue. Considering the procedural limitations of CenFat, parameters resulting from the proposed protocol are sensitive to neuromuscular alteration, however, further studies are required.
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Affiliation(s)
- Matheus Silva Norberto
- Postgraduate Program in Health Sciences Applied to the Locomotor System, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.,School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Tarine Botta de Arruda
- School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
| | - Marcelo Papoti
- Postgraduate Program in Health Sciences Applied to the Locomotor System, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.,School of Physical Education and Sport of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
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Ramsook AH, Molgat-Seon Y, Boyle KG, Mitchell RA, Puyat JH, Koehle MS, Sheel AW, Guenette JA. Reliability of diaphragm voluntary activation measurements in healthy adults. Appl Physiol Nutr Metab 2020; 46:247-256. [PMID: 32910865 DOI: 10.1139/apnm-2020-0221] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Voluntary activation can be used to assess central fatigue of the diaphragm after tasks such as exercise or inspiratory muscle loading. Cervical magnetic stimulation (CMS) of the phrenic nerves elicits an involuntary contraction, or twitch, of the diaphragm. This twitch is quantified based on a measure of transdiaphragmatic pressure and can be used to evaluate diaphragm contractile function and diaphragm voluntary activation (diaphragm-VA). The test-retest reliability of diaphragm-VA using CMS is currently unknown. Thirteen participants (4 male, 9 female; aged 25 ± 3 years) performed a series of interpolated twitch manoeuvres, which included a maximal inspiratory effort against a semi-occluded mouthpiece and 2 CMS-stimuli, 1 during the inspiratory manoeuvre and 1 after when the participant returned to functional residual capacity to quantify diaphragm-VA. Intraclass correlation coefficients (ICCs) and standard error of measurement (SEM) measured between-day and within-session reliability of diaphragm-VA, respectively. Maximal diaphragm-VA values were 91% (SD: 6; SEM: 3.9) and 92% (SD: 5; SEM: 2.2) during visits 1 and 2 (p = 0.68), respectively, and displayed "good" between-day reliability (ICC: 0.88; 95% confidence interval: 0.67-0.95; SEM: 2.7). Our results suggest that assessing diaphragm-VA using CMS is reliable in young healthy adults. Measuring diaphragm-VA may provide additional insight into the consequences and mechanisms of diaphragm fatigue. Novelty: Magnetic stimulation of the phrenic nerves can reliably measure voluntary activation of the diaphragm. Diaphragm voluntary activation can be used to provide additional insight into fatigability of the diaphragm.
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Affiliation(s)
- Andrew H Ramsook
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Yannick Molgat-Seon
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada.,Department of Kinesiology and Applied Health, Faculty of Kinesiology and Applied Health, The University of Winnipeg, Winnipeg, Manitoba, Canada
| | - Kyle G Boyle
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Reid A Mitchell
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Joseph H Puyat
- Centre for Health Evaluation and Outcome Services, Providence Health Care Research Institute, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada
| | - Michael S Koehle
- School of Kinesiology, Faculty of Education, The University of British Columbia, Vancouver, British Columbia, Canada.,Department of Family Practice, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada
| | - A William Sheel
- Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada.,School of Kinesiology, Faculty of Education, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Jordan A Guenette
- Department of Physical Therapy, Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada.,Centre for Heart Lung Innovation, The University of British Columbia and St. Paul's Hospital, Vancouver, British Columbia, Canada.,School of Kinesiology, Faculty of Education, The University of British Columbia, Vancouver, British Columbia, Canada
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Piponnier E, Ratel S, François B, Garcia-Vicencio S, Martin V. Assessment of the H-reflex using two synchronized magnetic stimulators in order to increase stimulus durations: A comparison with electrical stimulation. Neurosci Lett 2018; 675:89-94. [DOI: 10.1016/j.neulet.2018.03.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 02/09/2018] [Accepted: 03/18/2018] [Indexed: 11/26/2022]
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4
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Li S, Liu J, Bhadane M, Zhou P, Rymer WZ. Activation deficit correlates with weakness in chronic stroke: evidence from evoked and voluntary EMG recordings. Clin Neurophysiol 2014; 125:2413-7. [PMID: 24747057 DOI: 10.1016/j.clinph.2014.03.019] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 03/04/2014] [Accepted: 03/20/2014] [Indexed: 11/16/2022]
Abstract
OBJECTIVE To use evoked (M-wave) and voluntary (during maximal voluntary contraction (MVC)) EMG recordings to estimate the voluntary activation level in chronic stroke. METHODS Nine chronic hemiparetic stroke subjects participated in the experiment. M-wave (EMGM-wave) and MVC (EMGMVC) EMG values of the biceps brachii muscles were recorded. RESULTS Peak torque was significantly smaller on the impaired than non-impaired side. EMGM-wave was also significantly smaller on the impaired than non-impaired side. However, the normalized EMGM-wave/TorqueMVC ratio was not significantly different between two sides. In contrast, both absolute EMGMVC and normalized EMGMVC/TorqueMVC were smaller on the impaired than non-impaired side. The voluntary activation level, EMGMVC/M-wave, was also smaller on the impaired than non-impaired side. The voluntary activation level on the impaired side was highly correlated with weakness (R=0.72), but very low (R=0.32) on the non-impaired side. CONCLUSION Collectively, our findings suggest that both peripheral and central factors contribute to post-stroke weakness, but activation deficit correlates most closely with weakness as estimated from maximum voluntary torque generation. SIGNIFICANCE These findings serve to highlight the potential benefit from high-intensity exercises to enhance central activation for facilitation of motor recovery.
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Affiliation(s)
- Sheng Li
- Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Neurorehabilitation Research Laboratory, TIRR Memorial Hermann Hospital, Houston, TX 77030, United States.
| | - Jie Liu
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, United States
| | - Minal Bhadane
- Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Neurorehabilitation Research Laboratory, TIRR Memorial Hermann Hospital, Houston, TX 77030, United States
| | - Ping Zhou
- Department of Physical Medicine and Rehabilitation, University of Texas Health Science Center - Houston, Houston, TX 77030, United States; Biomedical Engineering Program, University of Science and Technology of China, Hefei, China
| | - W Zev Rymer
- Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, United States
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5
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Temesi J, Gruet M, Rupp T, Verges S, Millet GY. Resting and active motor thresholds versus stimulus-response curves to determine transcranial magnetic stimulation intensity in quadriceps femoris. J Neuroeng Rehabil 2014; 11:40. [PMID: 24655366 PMCID: PMC3976163 DOI: 10.1186/1743-0003-11-40] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 03/04/2014] [Indexed: 01/07/2023] Open
Abstract
Background Transcranial magnetic stimulation (TMS) is a widely-used investigative technique in motor cortical evaluation. Recently, there has been a surge in TMS studies evaluating lower-limb fatigue. TMS intensity of 120-130% resting motor threshold (RMT) and 120% active motor threshold (AMT) and TMS intensity determined using stimulus–response curves during muscular contraction have been used in these studies. With the expansion of fatigue research in locomotion, the quadriceps femoris is increasingly of interest. It is important to select a stimulus intensity appropriate to evaluate the variables, including voluntary activation, being measured in this functionally important muscle group. This study assessed whether selected quadriceps TMS stimulus intensity determined by frequently employed methods is similar between methods and muscles. Methods Stimulus intensity in vastus lateralis, rectus femoris and vastus medialis muscles was determined by RMT, AMT (i.e. during brief voluntary contractions at 10% maximal voluntary force, MVC) and maximal motor-evoked potential (MEP) amplitude from stimulus–response curves during brief voluntary contractions at 10, 20 and 50% MVC at different stimulus intensities. Results Stimulus intensity determined from a 10% MVC stimulus–response curve and at 120 and 130% RMT was higher than stimulus intensity at 120% AMT (lowest) and from a 50% MVC stimulus–response curve (p < 0.05). Stimulus intensity from a 20% MVC stimulus–response curve was similar to 120% RMT and 50% MVC stimulus–response curve. Mean stimulus intensity for stimulus–response curves at 10, 20 and 50% MVC corresponded to approximately 135, 115 and 100% RMT and 180, 155 and 130% AMT, respectively. Selected stimulus intensity was similar between muscles for all methods (p > 0.05). Conclusions Similar optimal stimulus intensity and maximal MEP amplitudes at 20 and 50% MVC and the minimal risk of residual fatigue at 20% MVC suggest that a 20% MVC stimulus–response curve is appropriate for determining TMS stimulus intensity in the quadriceps femoris. The higher selected stimulus intensities at 120-130% RMT have the potential to cause increased coactivation and discomfort and the lower stimulus intensity at 120% AMT may underestimate evoked responses. One muscle may also act as a surrogate in determining optimal quadriceps femoris stimulation intensity.
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Affiliation(s)
| | | | | | | | - Guillaume Y Millet
- Laboratoire de Physiologie de l'Exercice, Université de Lyon, Saint-Etienne F-42023, France.
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Shechtman O, Sindhu BS, Davenport PW. Using the "visual target grip test" to identify sincerity of effort during grip strength testing. J Hand Ther 2013; 25:320-8; quiz 329. [PMID: 22483342 DOI: 10.1016/j.jht.2011.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 11/18/2011] [Accepted: 12/22/2011] [Indexed: 02/09/2023]
Abstract
UNLABELLED We devised a sincerity of effort assessment based on "tricking" a person into exerting maximal effort by providing incorrect visual feedback. The assessment involves deriving a target line from nonvisual peak gripping force, instructing participants to reach it with each grip repetition, and then secretly changing its position, which requires doubling the force necessary to reach it. Accordingly, participants are tricked into exerting more force than intended to reach the deceptive target line. We examined the validity of this test by comparing force values between "trick" and "non-trick" trials in 30 healthy participants. The study design used was a prospective cohort. Providing incorrect visual feedback caused significantly greater increases in force during submaximal effort (69%) than during maximal effort (28%). This test effectively detected submaximal effort (sensitivity=0.83 and specificity=0.93). Although this test is not safe for patients during initial therapy, it may be appropriate for patients who can safely exert maximal grip force. LEVEL OF EVIDENCE Not applicable.
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Affiliation(s)
- Orit Shechtman
- Department of Occupational Therapy, College of Public Health and Health Professions, University of Florida, Gainesville, Florida 32610-0164, USA.
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FABRE JEANBERNARD, MARTIN VINCENT, GONDIN JULIEN, COTTIN FRANÇOIS, GRELOT LAURENT. Effect of Playing Surface Properties on Neuromuscular Fatigue in Tennis. Med Sci Sports Exerc 2012; 44:2182-9. [DOI: 10.1249/mss.0b013e3182618cf9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Van Leeuwen DM, De Ruiter CJ, De Haan A. Effect of stimulation intensity on assessment of voluntary activation. Muscle Nerve 2012; 45:841-8. [DOI: 10.1002/mus.23343] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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9
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Chen CF, Chen WS, Chou LW, Chang YJ, Chen SC, Kuo TS, Lai JS. Pulse energy as a reliable reference for twitch forces induced by transcutaneous neuromuscular electrical stimulation. IEEE Trans Neural Syst Rehabil Eng 2012; 20:574-83. [PMID: 22481833 DOI: 10.1109/tnsre.2012.2188305] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Voltage-controlled neuromuscular electrical stimulation has been considered to be safer in noninvasive applications notwithstanding the fact that voltage-controlled devices purportedly generate forces less predictable than their current-controlled equivalents. This prompted us to evaluate relevant electrical parameters to determine whether forces induced by voltage-controlled stimuli were able to match to those induced by current-controlled ones, which tend to evoke forces that were more predictable. Force magnitudes corresponding to current- and voltage-controlled stimuli were aligned with respect to electric charge (equivalent to average current intensity) and electrical energy (equivalent to average power) of the same stimulation pulse to determine which provided a better coherence. Consistency of forces evaluated with energy was significantly (p < 0.001) better than that evaluated with electric charges, suggesting that electrically stimulated forces can be reliably predicted by monitoring the energy parameter of stimulation pulses. The above results appear to show that electrode-tissue impedance, a factor that makes charge and energy evaluations different, redefined the actual effects of current intensities in generating favorable results. Accordingly, novel schemes that track the energy (or average power) of a stimulation pulse may be used as a reliable benchmark to associate mechanical (force) and electrical (stimulation pulse) characteristics in transcutaneous applications of electrical stimulation.
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Affiliation(s)
- Chiun-Fan Chen
- Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
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10
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SASAKI KAZUSHIGE, SASAKI TAKU, ISHII NAOKATA. Acceleration and Force Reveal Different Mechanisms of Electromechanical Delay. Med Sci Sports Exerc 2011; 43:1200-6. [DOI: 10.1249/mss.0b013e318209312c] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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11
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Electrical stimulation for testing neuromuscular function: from sport to pathology. Eur J Appl Physiol 2011; 111:2489-500. [PMID: 21590274 DOI: 10.1007/s00421-011-1996-y] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2011] [Accepted: 05/02/2011] [Indexed: 10/18/2022]
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Berth A, Urbach D, Neumann W, Awiszus F. Strength and voluntary activation of quadriceps femoris muscle in total knee arthroplasty with midvastus and subvastus approaches. J Arthroplasty 2007; 22:83-8. [PMID: 17197313 DOI: 10.1016/j.arth.2006.02.161] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2005] [Revised: 01/18/2006] [Accepted: 02/26/2006] [Indexed: 02/01/2023] Open
Abstract
To determine and compare the influence of 2 different approaches on quadriceps femoris muscle function in total knee arthroplasty (TKA), 20 patients (14 women, 6 men) with bilateral knee osteoarthritis underwent a 1-stage bilateral TKA. Surgical approaches (subvastus, midvastus) were performed by a random selection. Measurements of quadriceps voluntary activation and maximal voluntary contraction were estimated by a twitch interpolation technique before, 3 and 6 months after TKA. Knee pain was quantified by the Lewis Score. There was no difference between the 2 approaches at 3 and 6 months after TKA with regard to maximal voluntary contraction (P = 0.84, F = 0.041) and voluntary activation (P = .863, F = 0.031). In the subvastus group was a significantly higher knee pain until 6 months after surgery (P = .02). The subvastus approach for TKA does not provide any advantages compared with the midvastus approach with respect to the quadriceps femoris muscle strength in the early postoperative period. Furthermore, the subvastus approach caused significantly more pain postoperatively.
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Affiliation(s)
- Alexander Berth
- Department of Orthopaedics, Otto-von-Guericke-University, Magdeburg, Germany
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13
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Taylor JL, Todd G, Gandevia SC. EVIDENCE FOR A SUPRASPINAL CONTRIBUTION TO HUMAN MUSCLE FATIGUE. Clin Exp Pharmacol Physiol 2006; 33:400-5. [PMID: 16620309 DOI: 10.1111/j.1440-1681.2006.04363.x] [Citation(s) in RCA: 207] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
1. Muscle fatigue can be defined as any exercise-induced loss of ability to produce force with a muscle or muscle group. It involves processes at all levels of the motor pathway between the brain and the muscle. Central fatigue represents the failure of the nervous system to drive the muscle maximally. It is defined as a progressive exercise-induced reduction in voluntary activation or neural drive to the muscle. Supraspinal fatigue is a component of central fatigue. It can be defined as an exercise-induced decline in force caused by suboptimal output from the motor cortex. 2. When stimulus intensity is set appropriately, transcranial magnetic stimulation (TMS) over the motor cortex during an isometric maximal voluntary contraction (MVC) of the elbow flexors commonly evokes a small twitch-like increment in flexion force. This increment indicates that, despite the subject's maximal effort, motor cortical output at the moment of stimulation was not maximal and was not sufficient to drive the motoneurons to produce maximal force from the muscle. An exercise-induced increase in this increment demonstrates supraspinal fatigue. 3. Supraspinal fatigue has been demonstrated during fatiguing sustained and intermittent maximal and submaximal contractions of the elbow flexors where it accounts for about one-quarter of the loss of force of fatigue. It is linked to activity and the development of fatigue in the tested muscles and is little influenced by exercise performed by other muscles. 4. The mechanisms of supraspinal fatigue are unclear. Although changes in the behaviour of cortical neurons and spinal motoneurons occur during fatigue, they can be dissociated from supraspinal fatigue. One factor that may contribute to supraspinal fatigue is the firing of fatigue-sensitive muscle afferents that may act to impair voluntary descending drive.
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Affiliation(s)
- Janet L Taylor
- Prince of Wales Medical Research Institute and the University of New South Wales, Sydney, New South Wales, Australia.
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Albert WJ, Wrigley AT, McLean RB, Sleivert GG. Sex differences in the rate of fatigue development and recovery. DYNAMIC MEDICINE : DM 2006; 5:2. [PMID: 16412256 PMCID: PMC1368970 DOI: 10.1186/1476-5918-5-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Accepted: 01/16/2006] [Indexed: 02/03/2023]
Abstract
Background Many musculoskeltal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeltal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions. Methods Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender × side × muscle × time) design with significance set at p < 0.05. Results There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females. Conclusion The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.
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Affiliation(s)
- WJ Albert
- Human Performance Laboratory, Faculty of Kinesiolgy, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - AT Wrigley
- Human Performance Laboratory, Faculty of Kinesiolgy, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - RB McLean
- Human Performance Laboratory, Faculty of Kinesiolgy, University of New Brunswick, Fredericton, New Brunswick, Canada
| | - GG Sleivert
- PacificSport, Canadian Sport Centre, Victoria, British Columbia, Canada
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Daigeler A, Dodic T, Awiszus F, Schneider W, Fansa H. Donor-site morbidity of the pedicled rectus femoris muscle flap. Plast Reconstr Surg 2005; 115:786-92. [PMID: 15731680 DOI: 10.1097/01.prs.0000152422.64505.2a] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The rectus femoris muscle flap is well known for its reliable anatomy, the ease with which it can be harvested, and its great versatility. As a pedicled or free flap, it is used to cover soft-tissue defects and to recreate motor function. Although the muscle is very reliable, it is not well respected because of its assumed donor-site morbidity, such as weakened knee extension force and decreased range of motion of the knee. To date, these clinical assumptions have only rarely been quantified in terms of objective scores, concerning force deficit and functional or aesthetic outcome. From 1995 to 2002, the authors treated 24 patients with pedicled rectus femoris muscle flaps. Fourteen patients were followed up. Follow-up time ranged from 3 to 56 months postoperatively. The results were evaluated by a standard questionnaire in which pain in relation to walking distance, subjective feeling of weakness, sensibility disorders, everyday function, and aesthetic aspects were assessed. Range of motion in the hip and the knee was measured. For objective verification of a decrease of maximal voluntary contraction force of the remaining quadriceps muscle and for detecting differences in true muscular capacity and voluntary activation, 10 patients with unilateral rectus femoris flaps were tested using the twitch interpolation technique. The authors' patients assessed the remaining function and the aesthetic result of the thigh as at least satisfactory. Two patients complained about pain and weakness in the thigh. Eight patients reported hypesthesia in the lateral suprapatellar region. The maximal voluntary contraction and true muscular capacity values were reduced by 21.8 percent and 18 percent, respectively, when compared with the healthy leg. The range of motion in the knee and hip was not influenced by muscle harvesting. The twitch interpolation technique revealed a mild voluntary activation deficit, probably caused by inhibitory regulation in the spinal cord. In conclusion, donor-site morbidity of the rectus femoris muscle flap is evident but well compensated. There is no decrease in active range of motion in the knee and hip. Patient satisfaction with the functional and aesthetic outcome was high.
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Affiliation(s)
- Adrien Daigeler
- Division of Plastic, Reconstructive, and Hand Surgery, Medical Faculty of the Otto-von-Guericke University, Magdeburg, Germany.
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Becker R, Berth A, Nehring M, Awiszus F. Neuromuscular quadriceps dysfunction prior to osteoarthritis of the knee. J Orthop Res 2004; 22:768-73. [PMID: 15183432 DOI: 10.1016/j.orthres.2003.11.004] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2003] [Accepted: 11/19/2003] [Indexed: 02/06/2023]
Abstract
Decreased maximal quadriceps strength and voluntary activation has been observed in patients with osteoarthritis in previous studies, but those results do not allow any conclusions to be drawn as to whether quadriceps dysfunction precedes or follows osteoarthritis. Thirty-two patients (group a) who underwent partial meniscectomy 48+/-9 month prior to the study were matched according to their weight and body mass index with a control group (group b). The twitch interpolation technique was used to determine maximal voluntary contraction (MVC) and voluntary activation (VA) of the quadriceps muscle of both legs. Subjective assessment of the knee was performed using the Lysholm-Score. AP and lateral X-rays of the operated knee were obtained. None of the participants showed any evidence of characteristic radiological or clinical signs for osteoarthritis. A significantly lower MVC was noticed in both the affected and the contralateral knee of group a in comparison to group b (p < 0.01). The VA in group a yielded 80.9+/-15.4% for the injured side and 83.1+/-11.5% for the contralateral side, with no statistical difference (p = 0.18). The VA in group b was 89.4+/-5.8% for the right side and 88+/-6.8% for the left side both being significantly higher in comparison to group a. This study has shown, that patients following meniscus resection present with bilateral quadriceps weakness as already described in patients with manifest osteoarthritis. The authors hypothesise that muscle dysfunction may be an etiologic factor underlying the pathologic changes of osteoarthritis. Whether muscle dysfunction occurs also at other sites, e.g. in the upper extremity, remains unclear but would be of interest in order to detect a generalized neuromuscular dysfunction.
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Affiliation(s)
- Roland Becker
- Neuromuscular Research Group, Department of Orthopaedics, Otto-von-Guericke-University, Leipziger Strasse 44, D-39120 Magdeburg, Germany.
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Pap G, Machner A, Awiszus F. Strength and voluntary activation of the quadriceps femoris muscle at different severities of osteoarthritic knee joint damage. J Orthop Res 2004; 22:96-103. [PMID: 14656666 DOI: 10.1016/s0736-0266(03)00128-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
OBJECTIVE Improvements of quadriceps motor deficits represent a major therapeutical target in knee osteoarthritis (OA). In the present study, we investigated changes in quadriceps function at different stages of osteoarthritic cartilage damage. METHODS Measurements of quadriceps voluntary activation (VA) and maximum voluntary contraction (MVC) were performed by a twitch interpolation technique and the total muscular capacity (TMC) was calculated as the ratio of MVC and VA. We assessed 68 patients (56.7+/-9.5 years) with stage II and 154 patients (65.6+/-6.0 years) with stage IV chondropathy. As controls, we used 85 age related healthy subjects (58.1+/-8.7 years). RESULTS While TMC was significantly lower in stage IV (90.6+/-43.7 Nm) than in stage II chondropathy (109.6+/-51.0) there were no differences in the MVCs between both groups. Quadriceps VA was even higher in stage IV (77.2+/-13.2%) than in stage II chondropathy (70.8+/-16.0%). In the controls, MVC, VA and TMC were significantly higher than in both OA groups. CONCLUSION We assume that a decrease of TMC might occur within the course of OA and, in consequence, VA increases to maintain quadriceps MVC.
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Affiliation(s)
- Géza Pap
- Neuromuscular Research Group, Department of Orthopaedics, Otto-von-Guericke University, Leipziger Street 44, D-39120 Magdeburg, Germany.
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Abstract
The twitch interpolation technique is commonly employed to assess the completeness of skeletal muscle activation during voluntary contractions. Early applications of twitch interpolation suggested that healthy human subjects could fully activate most of the skeletal muscles to which the technique had been applied. More recently, however, highly sensitive twitch interpolation has revealed that even healthy adults routinely fail to fully activate a number of skeletal muscles despite apparently maximal effort. Unfortunately, some disagreement exists as to how the results of twitch interpolation should be employed to quantify voluntary activation. The negative linear relationship between evoked twitch force and voluntary force that has been observed by some researchers implies that voluntary activation can be quantified by scaling a single interpolated twitch to a control twitch evoked in relaxed muscle. Observations of non-linear evoked-voluntary force relationships have lead to the suggestion that the single interpolated twitch ratio can not accurately estimate voluntary activation. Instead, it has been proposed that muscle activation is better determined by extrapolating the relationship between evoked and voluntary force to provide an estimate of true maximum force. However, criticism of the single interpolated twitch ratio typically fails to take into account the reasons for the non-linearity of the evoked-voluntary force relationship. When these reasons are examined, it appears that most are even more challenging to the validity of extrapolation than they are to the linear equation. Furthermore, several factors that contribute to the observed non-linearity can be minimised or even eliminated with appropriate experimental technique. The detection of small activation deficits requires high resolution measurement of force and careful consideration of numerous experimental details such as the site of stimulation, stimulation intensity and the number of interpolated stimuli. Sensitive twitch interpolation techniques have revealed small to moderate deficits in voluntary activation during brief maximal efforts and progressively increasing activation deficits (central fatigue) during exhausting exercise. A small number of recent studies suggest that resistance training may result in improved voluntary activation of the quadriceps femoris and ankle plantarflexor muscles but not the biceps brachii. A significantly larger body of evidence indicates that voluntary activation declines as a consequence of bed-rest, joint injury and joint degeneration. Twitch interpolation has also been employed to study the mechanisms by which caffeine and pseudoephedrine enhance exercise performance.
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Affiliation(s)
- Anthony Shield
- School of Exercise Science and Sport Management, Southern Cross University, Lismore, New South Wales, Australia.
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Todd G, Gorman RB, Gandevia SC. Measurement and reproducibility of strength and voluntary activation of lower-limb muscles. Muscle Nerve 2004; 29:834-42. [PMID: 15170616 DOI: 10.1002/mus.20027] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Accurate measurement of muscle strength and voluntary muscle activation is important in the assessment of disorders that affect the motor pathways or muscle. We designed a multipurpose system to assess the variability and reproducibility of isometric torque measurements obtained during maximal voluntary efforts of the knee flexor, knee extensor, ankle dorsiflexor, and ankle plantarflexor muscles on each side. It used two isometric myographs mounted on an adjustable frame. Measurements of maximal voluntary torque (range, 25-188 Nm) displayed low variability within a testing session and over five testing sessions (coefficient of variation range, 5-11%). We used the same equipment to measure voluntary activation of the triceps surae muscles. Voluntary activation, measured with a sensitive twitch interpolation method, increased with increasing voluntary contraction torque (P < 0.001) and was very high during maximal efforts (mean, 97.8 +/- 2.1%; median, 98.5%). Furthermore, measurements of voluntary activation during maximal efforts were reproducible across testing sessions with very little variability (coefficient of variation, <2%). The myograph system and the testing procedures should allow accurate measurement of strength and voluntary drive in longitudinal patient studies.
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Affiliation(s)
- Gabrielle Todd
- Prince of Wales Medical Research Institute, Barker St., Randwick, New South Wales 2031, Australia
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20
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Todd G, Taylor JL, Gandevia SC. Measurement of voluntary activation of fresh and fatigued human muscles using transcranial magnetic stimulation. J Physiol 2003; 551:661-71. [PMID: 12909682 PMCID: PMC2343213 DOI: 10.1113/jphysiol.2003.044099] [Citation(s) in RCA: 280] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2003] [Accepted: 06/16/2003] [Indexed: 12/25/2022] Open
Abstract
Recently, transcranial magnetic stimulation of the motor cortex (TMS) revealed impaired voluntary activation of muscles during maximal efforts. Hence, we evaluated its use as a measure of voluntary activation over a range of contraction strengths in both fresh and fatigued muscles, and compared it with standard twitch interpolation using nerve stimulation. Subjects contracted the elbow flexors isometrically while force and EMG from biceps and triceps were recorded. In one study, eight subjects made submaximal and maximal test contractions with rests to minimise fatigue. In the second study, eight subjects made sustained maximal contractions to reduce force to 60 % of the initial value, followed by brief test contractions. Force responses were recorded following TMS or electrical stimulation of the biceps motor nerve. In other contractions, EMG responses to TMS (motor evoked potentials, MEPs) or to stimulation at the brachial plexus (maximal M waves, Mmax) were recorded. During contractions of 50 % maximum, TMS elicited large MEPs in biceps (> 90 % Mmax) which decreased in size (to approximately 70 % Mmax) with maximal efforts. This suggests that faster firing rates made some motor units effectively refractory. With fatigue, MEPs were also smaller but remained > 70 % Mmax for contractions of 50-100 % maximum. For fresh and fatigued muscle, the superimposed twitch evoked by motor nerve and motor cortex stimulation decreased with increasing contraction strength. For nerve stimulation the relation was curvilinear, and for TMS it was linear for contractions of 50-100 % maximum (r2 = 1.00). Voluntary activation was derived using the expression: (1 - superimposed twitch/resting twitch) x 100. The resting twitch was measured directly for nerve stimulation and for TMS, it was estimated by extrapolation of the linear regression between the twitch and voluntary force. For cortical stimulation, this resulted in a highly linear relation between voluntary activation and force. Furthermore, the estimated activation corresponded well with contraction strength. Using TMS or nerve stimulation, voluntary activation was high during maximal efforts of fresh muscle. With fatigue, both measures revealed reduced voluntary activation (i.e. central fatigue) during maximal efforts. Measured with TMS, this central fatigue accounted for one-quarter of the fall in maximal voluntary force. We conclude that TMS can quantify voluntary activation for fresh or fatigued muscles at forces of 50-100 % maximum. Unlike standard twitch interpolation of the elbow flexors, voluntary activation measured with TMS varies in proportion to voluntary force, it reveals when extra output is available from the motor cortex to increase force, and it elicits force from all relevant synergist muscles.
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Affiliation(s)
- Gabrielle Todd
- Prince of Wales Medical Research Institute and the University of New South Wales, Sydney 2031, Australia
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21
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Berth A, Urbach D, Awiszus F. Improvement of voluntary quadriceps muscle activation after total knee arthroplasty. Arch Phys Med Rehabil 2002; 83:1432-6. [PMID: 12370881 DOI: 10.1053/apmr.2002.34829] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE To evaluate the maximal voluntary contraction (MVC) force and the voluntary activation of the quadriceps femoris muscle in patients with knee osteoarthritis (OA) before and after total knee arthroplasty (TKA). DESIGN A prospective intervention study. SETTING University hospital clinic in Germany. PATIENTS Fifty patients (32 women, 18 men; mean age +/- standard deviation, 65.8+/-5.6 y) with knee OA and 23 healthy age- and gender-matched control subjects. INTERVENTION Unilateral TKA without patella resurfacing. MAIN OUTCOME MEASURES Voluntary activation, MVC, and true maximal contraction forces of the bilateral quadriceps femoris muscles, using the twitch interpolation technique before and 33+/-8 months after TKA. Assessment of postoperative knee pain by the Lewis score. RESULTS Voluntary activation increased bilaterally after surgery (P<.01 operated side, P=.02 nonoperated side) but remained lower than the voluntary activation of the controls. MVC (P<.001) and true maximal contraction forces (P=.01) increased significantly on the operated side. MVC remained unchanged (P=.45), and true maximal contraction forces decreased significantly (P=.04) on the nonoperated side. CONCLUSION Patients with knee OA have significant bilateral voluntary activation deficits that are, at least in part, reversible within 3 years after TKA. Rehabilitation programs immediately after TKA should focus on reduction of voluntary activation deficits. After voluntary activation improves, physical therapy should target the augmentation of quadriceps femoris muscle strength.
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Affiliation(s)
- Alexander Berth
- Neuromuscular Research Group, Department of Orthopaedics, Otto-von-Guericke-University, Magdeburg, Germany
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22
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Machner A, Pap G, Krohn A, Rohkohl K, Awiszus F. Quadriceps muscle function after high tibial osteotomy for osteoarthritis of the knee. Clin Orthop Relat Res 2002:177-83. [PMID: 12011707 DOI: 10.1097/00003086-200206000-00021] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In patients with osteoarthritis of the knees, quadriceps muscle dysfunction is an early and common clinical feature and an important determinant of disability. In the current study, changes in quadriceps muscle strength and voluntary quadriceps muscle activation after high tibial osteotomies for primary osteoarthritis of the knee in 19 patients were investigated. Quadriceps muscle function was assessed during different degrees of isometric maximum voluntary contraction using a specially built chair. One year after surgery all patients had reexamination of their surgically treated and contralateral knees. Voluntary activation and maximum voluntary contraction values of the followup assessment were significantly lower in the surgically treated knees compared with the preoperative assessment. In the contralateral knees, there were no differences between preoperative and followup measurements. High tibial osteotomy is an extraarticular operative therapeutic approach to treatment of osteoarthritis of the knee that does not lead to improvement of quadriceps muscle function. Because there is evidence that quadriceps sensorimotor dysfunction is important not only for the disability in osteoarthritis of the knee, but also for progression of the disease, knee function may be worsened by high tibial osteotomy in some patients.
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Affiliation(s)
- Andreas Machner
- Neuromuscular Research Group at the Department of Orthopedics, Otto-von-Guericke University, Leipziger Strasse 44, D-39120 Magdeburg, Germany
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Machner A, Pap G, Awiszus F. Evaluation of quadriceps strength and voluntary activation after unicompartmental arthroplasty for medial osteoarthritis of the knee. J Orthop Res 2002; 20:108-11. [PMID: 11853077 DOI: 10.1016/s0736-0266(01)00068-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION In early and moderate stages of osteoarthritis (OA) of the knee, arthrogenous muscle inhibition (AMI) is an important factor for the initiation and the progression of the disease. Although AMI has been shown to be reduced after physiotherapeutical exercises resulting in significant improvements in disability, implantation of unicondylar knee arthroplasties is much provided in these stages of OA. Therefore, in the present study we investigate changes in quadriceps muscle after implantation of such prostheses as compared to physiotherapeutical treatment, alone. METHODS In eighteen patients with bilateral moderate knee OA, who were treated with unicondylar knee arthroplasty we investigated voluntary activation (VA) and maximum voluntary contraction (MVC) of the quadriceps femoris muscle. There were 7 males and 11 females, the mean age at time of operation was 67 years (range 58-76 years). Measurements on both sides were performed preoperatively and 18 months postoperatively using the twitch-interpolation technique. RESULTS Follow-up assessment revealed a significant VA and MVC increase in both the surgically treated knees and in the contralateral knees treated by physiotherapy alone. However, VA and MVC improvements were significantly higher in the operated on knees than in those treated by physiotherapy alone. DISCUSSION Both physiotherapeutical exercise and unicondylar knee replacements lead to an improvement of quadriceps motor function in knee OA. The greater improvement in knees with both knee replacement and physiotherapy might be related to the intraoperative removal of arthritic tissue in these knees.
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Affiliation(s)
- Andreas Machner
- Neuromuscular Research Group at the Department of Orthopaedics, Otto-von-Guericke University, Magdeburg, Germany.
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24
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Abstract
Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. It may arise not only because of peripheral changes at the level of the muscle, but also because the central nervous system fails to drive the motoneurons adequately. Evidence for "central" fatigue and the neural mechanisms underlying it are reviewed, together with its terminology and the methods used to reveal it. Much data suggest that voluntary activation of human motoneurons and muscle fibers is suboptimal and thus maximal voluntary force is commonly less than true maximal force. Hence, maximal voluntary strength can often be below true maximal muscle force. The technique of twitch interpolation has helped to reveal the changes in drive to motoneurons during fatigue. Voluntary activation usually diminishes during maximal voluntary isometric tasks, that is central fatigue develops, and motor unit firing rates decline. Transcranial magnetic stimulation over the motor cortex during fatiguing exercise has revealed focal changes in cortical excitability and inhibitability based on electromyographic (EMG) recordings, and a decline in supraspinal "drive" based on force recordings. Some of the changes in motor cortical behavior can be dissociated from the development of this "supraspinal" fatigue. Central changes also occur at a spinal level due to the altered input from muscle spindle, tendon organ, and group III and IV muscle afferents innervating the fatiguing muscle. Some intrinsic adaptive properties of the motoneurons help to minimize fatigue. A number of other central changes occur during fatigue and affect, for example, proprioception, tremor, and postural control. Human muscle fatigue does not simply reside in the muscle.
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Affiliation(s)
- S C Gandevia
- Prince of Wales Medical Research Institute, Prince of Wales Hospital and University of New South Wales, Randwick, Sydney, Australia.
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25
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Klein CS, Rice CL, Marsh GD. Normalized force, activation, and coactivation in the arm muscles of young and old men. J Appl Physiol (1985) 2001; 91:1341-9. [PMID: 11509534 DOI: 10.1152/jappl.2001.91.3.1341] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine whether the loss of muscle strength in the elderly could be explained entirely by a decline in the physiological cross-sectional area (PCSA) of muscle. Isometric force, muscle activation (twitch interpolation), and coactivation (surface electromyograph) were measured during maximal voluntary contractions (MVCs) of the elbow flexors (EFs) and extensors (EEs) in 20 young (23 +/- 3 yr) and 13 older (81 +/- 6 yr) healthy men. PCSA was determined using magnetic resonance imaging, and normalized force (NF) was calculated as the MVC/PCSA ratio. The PCSA was smaller in the old compared with the young men, more so in the EEs (28%) compared with the EFs (19%) (P < 0.001); however, the decline in MVC (approximately 30%) with age was similar in the two muscle groups. Muscle activation was not different between the groups, but coactivation was greater (5%) (P < 0.001) in the old men for both muscles. NF was less (11%) in the EFs (P < 0.01) and tended to be unchanged in the EEs of the old compared with young subjects. The relative maintenance of NF in the EEs compared with the EFs may be related to age-associated changes in the architecture of the triceps brachii muscle. In conclusion, although the decline in PCSA explained the majority of strength loss in the old men, additional factors such as greater coactivation or reduced specific tension also may have contributed to the age-related loss of isometric strength.
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Affiliation(s)
- C S Klein
- Canadian Centre for Activity and Aging, Lawson Health Research Institute, The University of Western Ontario, London, Ontario, Canada N6G 2M3
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26
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Abstract
To investigate whether transcranial magnetic stimulation (TMS) has an effect on isometric muscle force elicited by maximal voluntary contractions (MVC) and the ability to activate a muscle voluntarily (VA, as a percentage of full muscle activation), a twitch-interpolation technique was applied on the quadriceps femoris muscles of six volunteers before and within 1 min after TMS. VA improved by 5% (P = 0.019) and MVC by 17% (P = 0.002), whereas these parameters were unchanged in a control experiment. The results suggest that TMS has an effect on the central motor drive, at least within 1 min after stimulation.
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Affiliation(s)
- D Urbach
- Neuromuscular Research Group, Department of Orthopedics, Otto-von-Guericke-University, Leipziger Strasse 44, D-39120 Magdeburg, Germany.
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27
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Burke D, Gandevia SC. Properties of human peripheral nerves: implications for studies of human motor control. PROGRESS IN BRAIN RESEARCH 2000; 123:427-35. [PMID: 10635738 DOI: 10.1016/s0079-6123(08)62878-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Affiliation(s)
- D Burke
- Prince of Wales Medical Research Institute, Department of Neurology, Prince of Wales Hospital, Sydney, Australia
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28
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Urbach D, Nebelung W, Weiler HT, Awiszus F. Bilateral deficit of voluntary quadriceps muscle activation after unilateral ACL tear. Med Sci Sports Exerc 1999; 31:1691-6. [PMID: 10613416 DOI: 10.1097/00005768-199912000-00001] [Citation(s) in RCA: 149] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
PURPOSE The inability to fully activate the quadriceps femoris muscle voluntarily is known to accompany several different knee-joint pathologies. The extent of a voluntary-activation deficit in patients after isolated rupture of the anterior cruciate ligament (ACL), however, has been reported to be small or nonexistent, making it questionable if a voluntary-activation deficit is a relevant factor for these patients at all. METHODS In this study the ability to voluntarily activate the quadriceps femoris muscles was quantified in 22 male patients with arthroscopically-proven isolated ACL ruptures using an established highly sensitive twitch-interpolation technique. Furthermore, the maximal voluntary contraction force of the quadriceps muscle was obtained by isometric knee-joint torque measurements. The results were compared with an age-, gender-, and activity-matched control group. RESULTS There was a moderate but significant mean reduction in maximal voluntary activation (VA) in both the injured (VA: 83.9 +/- 2.3%, mean +/- SEM) and uninjured side (VA: 84.7 +/- 2.2%) in comparison with controls (VA: 91.1 +/- 0.8%). However, of the patients the 23% who presented a considerably reduced voluntary-activation of less than 80% were mainly responsible for the significant mean deficit. CONCLUSIONS The deficit of isometric muscle strength on the injured side compared with that of controls was explained by the voluntary-activation deficit and a true muscle weakness. On the other hand, the diminished muscle strength of the uninjured side was explained sufficiently by the voluntary-activation deficit alone. Considering the bilateral voluntary-activation deficit, functional muscle tests might not be valid when the uninjured extremity serves as reference.
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Affiliation(s)
- D Urbach
- Department of Orthopedics, Otto-von-Guericke University, Magdeburg, Germany.
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Herbert RD, Gandevia SC. Twitch interpolation in human muscles: mechanisms and implications for measurement of voluntary activation. J Neurophysiol 1999; 82:2271-83. [PMID: 10561405 DOI: 10.1152/jn.1999.82.5.2271] [Citation(s) in RCA: 186] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An electrical stimulus delivered to a muscle nerve during a maximal voluntary contraction usually produces a twitchlike increment in force. The amplitude of this "interpolated twitch" is widely used to measure voluntary "activation" of muscles. In the present study, a computer model of the human adductor pollicis motoneuron pool was used to investigate factors that affect the interpolated twitch. Antidromic occlusion of naturally occurring orthodromic potentials was modeled, but reflex effects of the stimulus were not. In simulations, antidromic collisions occurred with probabilities of between approximately 16% (in early recruited motoneurons) and nearly 100% (in late recruited motoneurons). The model closely predicted experimental data on the amplitude and time course of the rising phase of interpolated twitches over the full range of voluntary forces, except that the amplitude of interpolated twitches was slightly overestimated at intermediate contraction intensities. Small interpolated twitches (4.7% of the resting twitch) were evident in simulated maximal voluntary contractions, but were nearly completely occluded when mean peak firing rate was increased to approximately 60 Hz. Simulated interpolated twitches did not show the marked force drop that follows the peak of the twitch, and when antidromic collisions were excluded from the model interpolated twitch amplitude was slightly increased and time-to-peak force was prolonged. These findings suggest that both antidromic and reflex effects reduce the amplitude of the interpolated twitch and contribute to the force drop that follows the twitch. The amplitude of the interpolated twitch was related to "excitation" of the motoneuron pool in a nonlinear way, so that at near-maximal contraction intensities (>90% maximal voluntary force) increases in excitation produced only small changes in interpolated twitch amplitude. Thus twitch interpolation may not provide a sensitive measure of motoneuronal excitation at near-maximal forces. Increases in the amplitude of interpolated twitches such as have been observed in fatigue and various pathologies may reflect large reductions in excitation of the motoneuron pool.
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Affiliation(s)
- R D Herbert
- Prince of Wales Medical Research Institute, University of New South Wales, Randwick, New South Wales 2031, Australia
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30
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Burke D, Gandevia SC. Influence of stimulus cross talk on results of the twitch-interpolation technique at the biceps brachii muscle. Muscle Nerve 1998; 21:970-1. [PMID: 9626264 DOI: 10.1002/(sici)1097-4598(199807)21:7<970::aid-mus22>3.0.co;2-t] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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31
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Awiszus F, Wahl B, Meinecke I. Influence of stimulus cross talk on results of the twitch-interpolation technique at the biceps brachii muscle (A reply). Muscle Nerve 1998. [DOI: 10.1002/(sici)1097-4598(199807)21:7<970::aid-mus23>3.0.co;2-t] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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