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Muscle Activity (muscle + activity)

Distribution by Scientific Domains

Medical Sciences	69%
Life Sciences	23%
Chemistry	3%
Psychology	2%
2 Other Domains	3%

Selected Abstracts

Endoluminal Norepinephrine Inhibits Smooth Muscle Activity of the Pig Pyeloureter by Stimulation of ,-Adrenoceptors without Side Effects

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 5 2008
Jens Mortensen
The purposes were to describe concentration,response relationship and receptor mechanism of the effect of norepinephrine on muscle function of pyeloureter and to reveal possible side effects on cardiovascular and renal functions. Renal pelvis was perfused, while pelvic pressure, cardiovascular and renal functional parameters were recorded. In group A, a pelvic pressure increase was examined during pressure flow studies with norepinephrine solutions (0, 1, 5, 50 and 100 µg/ml). In group B, pelvis was perfused with 6 ml/min. norepinephrine solutions (0, 0.001, 0.01, 0.1 and 1 µg/ml). In group C, pelvis was perfused with 6 ml/min. norepinephrine, norepinephrine + sotalol 10,6 mol/l and norepinephrine + phentolamine 10,6 mol/l. Norepinephrine solutions of 0, 10,8, 10,7, 10,6, 10,5 and 10,4 mol/l were used. In group A, all norepinephrine solutions lowered the pelvic pressure increase significantly. Large increases in plasma and urine norepinephrine occurred with 50 and 100 µg/ml, but cardiovascular and renal functions remained unchanged. In group B, a significant diminishing pelvic pressure increase with all solutions was seen with a significant difference between all solutions. In group C, norepinephrine demonstrated a concentration,response curve with EC50 between 10,8 and 10,7 mol/l (10,7.27±0.40). Sotalol had a smooth muscle inhibitory effect on the pyeloureter and inhibited the effect of norepinephrine increasing EC50 by about a factor 10 (10,6.40±1.17). No convincing effect of phentolamine was observed. Endoluminal norepinephrine probably stimulates ,-adrenoceptors and inhibits a renal pelvis pressure increase to perfusion in a dose-related way without side effects. Endoluminal norepinephrine is safe in pigs and may be useful under endoscopy of the pyeloureter. [source]

Complex mechanisms of sensory tricks in cervical dystonia

MOVEMENT DISORDERS, Issue 4 2004
Axel Schramm MD
Abstract Muscle activities in 26 patients with predominantly rotational torticollis were quantified using surface electromyography. In the subgroup of 19 patients with an effective sensory trick, different modes and bilateral locations of trick application led to significant (P < 0.002) reduction of electromyographic (EMG) activity. A strong correlation was found between the efficacy of trick manoeuvres and the starting head position. Trick application in a neutral or even contralateral position was most effective while no reduction of muscle activity during trick application at the maximum dystonic head position was found (P < 0.001). We propose a two-phase model: First, normalisation of head posture is obtained by counterpressure or volitional antagonistic muscle activity. In a second step, this position can be stabilised using sensory tricks challenging central adaption of distorted sensorimotor integration. © 2003 Movement Disorder Society [source]

Neuromuscular coordination of masticatory muscles in subjects with two types of implant-supported prostheses

CLINICAL ORAL IMPLANTS RESEARCH, Issue 2 2004
Virgilio F. Ferrario
Abstract Objectives: To compare the electromyographic (EMG) characteristics of masticatory muscles in patients with fixed implant-supported prostheses and implant overdentures. Material and methods: Nineteen subjects aged 45,79 years were examined. Fourteen were edentulous and had been successfully rehabilitated with (a) maxillary and mandibular implant-supported fixed prostheses (seven patients); (b) mandibular implant overdentures and maxillary complete dentures (seven patients). Five control subjects had natural dentition or single/partial (no more than two teeth) tooth or implant fixed dentures. Surface EMG of the masseter and temporal muscles was performed during unilateral gum chewing and during maximum teeth clenching. To reduce biological and instrumental noise, all values were standardized as percentage of a maximum clenching on cotton rolls. Results: During clenching, temporal muscle symmetry was larger in control subjects and fixed implant-supported prosthesis patients than in overdenture patients (analysis of variance, P=0.005). No differences were found in masseter muscle symmetry or in muscular torque. Muscle activities (integrated areas of the EMG potentials over time) were significantly larger in control subjects than in implant-supported prosthesis patients (P=0.014). In both patient groups, a poor neuromuscular coordination during chewing, with altered muscular patterns, and a smaller left,right symmetry than in control subjects were found (P=0.05). No differences in masticatory frequency were found. Conclusion: Surface EMG analysis of clenching and chewing showed that fixed implant-supported prostheses and implant overdentures were functionally equivalent. Neuromuscular coordination during chewing was inferior to that found in subjects with natural dentition. Résumé Le but de cette étude a été de comparer les caractéristiques éléctromiographiques (EMG) de muscles masticateurs chez des patients avec des prothèses fixées sur implant et des prothèses amovibles sur implants. Dix-neuf patients de 45 à 79 ans ont été examinés. Quatorze étaient édentés et ont été traités avec succès par a) une prothèse fixée sur des implants au niveau maxillaire et mandibulaire (sept patients), b) des prothèses amovibles ancrées sur implant au niveau de la mandibule et des prothèses amovibles totales supérieures (sept patients). Les cinq contrôles avaient soit une dentition naturelle soit des couronnes sur implants ou dent unique. L'EMG de surface des muscles masséter et temporaux a été effectué durant la mastication unilatérale de gomme à mâcher et à la force maximale de fermeture. Pour diminuer le bruit biologique et instrumental, toutes les valeurs ont été standardisées en pourcentage d'une force maximale de fermeture sur des rouleaux de coton. Durant la fermeture, la symétrie musculaire temporale était plus importante chez les sujets contrôles et les prothèses fixées sur implants que chez les patients avec prothèse amovible (analyse de variance, p=0,005). Aucune différence n'a été constatée dans la symétrie musculaire du masséter ou dans la torsion musculaire. Les activités musculaires (zones intégrées des potentiels EMG avec le temps) étaient significativement plus importantes chez les contrôles que chez les patients avec prothèses fixées sur implants (p=0,014). Dans les deux groupes de patients, une pauvre coordination neuromusculaire durant le mâchonnement, avec des modèles musculaires altérés, et une plus petite symétrie gauche-droite étaient constatées chez les sujets contrôles (p=0,05). Aucune différence dans la fréquence masticatoire n'a été trouvée. L'analyse EMG de surface de fermeture et de mastication montraient que les prothèses fixées sur implant et les prothèses amovibles sur implants étaient fonctionnellement équivalentes. Cependant la coordination neuromusculaire durant la mastication était inférieure à celle trouvée chez les sujets avec dentition naturelle. Zusammenfassung Ziel: Die EMG-Charakteristiken der Kaumuskeln in Patienten mit festsitzenden implantatgetragenen Prothesen und implantatgetragenen Hybridprothesen zu vergleichen. Material und Methode: Neunzehn Patienten im Alter von 45 bis 79 Jahren wurden untersucht. Vierzehn davon waren zahnlos und erfolgreich wiederhergestellt worden mit a) festsitzenden implantatgetragenen Ober- und Unterkieferprothesen (sieben Patienten); b) Unterkieferhybridprothesen und OK-Totalprothesen (sieben Patienten). Die fünf Kontrollpatienten hatten eine natürliche Bezahnung oder Einzelkronen bzw. kleine Brücken (nicht mehr als zwei Zähne) auf Implantaten oder Zähnen. Während einseitigem Kaugummikauen und maximalem Zähnepressen wurden Messungen der Oberflächen-EMGs der Masseter- und Temporalmuskulatur durchgeführt. Um das biologische und instrumentelle Rauschen zu unterdrücken, wurden alle Werte als Prozentanteil des maximalen Pressens auf Watterollen standardisiert. Resultate: Während des Pressens war die temporale Muskelsymmetrie bei den Kontrollpatienten und den Patienten mit festsitzenden implantatgetragenen Prothesen grösser als bei den Probanden mit Hybridprothesen (Varianzanalyse, p=0.005). Bei der Symmetrie der Massetermuskeln und im muskulären Drehmoment konnten keine Unterschiede gefunden werden. Die Muskelaktivitäten (integrierte Areale der EMG-Potentiale über die Zeit) waren bei den Kontrollpatienten signifikant tiefer als bei den Probanden mit implantatgetragenen Prothesen (p=0.014). Bei beiden Patientengruppen konnte eine schlechtere neuromuskuläre Koordination während des Kauens mit veränderlichen muskulären Mustern und einer geringeren links-rechts Symmetrie als bei den Kontrollpatienten gefunden werden (p=0.05). Bei der Kaufrequenz bestanden keine Unterscheide. Schlussfolgerung: Die Analyse der Oberflächen-EMG beim Pressen und Kauen zeigte, dass festsitzende implantatgetragene Prothesen und implantatgetragene Hybridprothesen funktionell gleichwertig sind. Die neromuskuläre Koordination während des Kauens war schlechter als bei Probanden mit natürlicher Bezahnung. Resumen Objetivos: Comparar las características del EMG de los músculos masticatorios en pacientes con prótesis fija implanto-soportada y sobredentaduras en implantes. Material y métodos: Se examinaron 19 sujetos de edades entre 45 y 79 años. Catorce eran edéntulos, y habían sido rehabilitados con éxito con a) prótesis fija implanto-soportada maxilar y mandibular (siete pacientes); b) sobredentadura completa en implantes maxilar y mandibular (siete pacientes). Cinco pacientes de control tenían dentición natural o dentaduras fijas sobre implantes o dientes unitarias o parciales (no mas de 2 dientes). Se llevó a cabo EMG de superficie de los músculos maseteros y temporales durante mascado de chicles unilateralmente, y durante cierre máximo. Para reducir las interferencias biológicas e instrumentales, todos los valores se estandarizaron como porcentajes de un cierre máximo sobre rollos de algodón. Resultados: Durante el cierre, la simetría de los músculos temporales fue mayor en los sujetos de control y en los pacientes de prótesis fijas implanto-soportadas que en los pacientes con sobredentaduras (análisis de varianza, p=0.005). No se encontraron diferencias en la simetría del músculo masetero o en el torque muscular. Las actividades musculares (áreas integradas de los potenciales del EMG a lo largo del tiempo) fueron significativamente mayores en los sujetos de control que en los pacientes con prótesis implantosoportada (p=0.014). En ambos grupos de pacientes, se encontró una coordinación neuromuscular mas pobre durante el mascado, con patrones musculares alterados, y una menor simetría derecha-izquierda que en los sujetos de control (p=0.05). No se encontraron diferencias en la frecuencia masticatoria. Conclusión: El análisis del EMG de superficie de máxima mordida y de mascado mostró que las prótesis fijas implanto-soportadas y las sobredentaduras en implantes fueron funcionalmente equivalentes. La coordinación neuromuscular durante el mascado fue inferior a aquella encontrada en sujetos con dentición natural. [source]

The influence of age and dental status on elevator and depressor muscle activity

JOURNAL OF ORAL REHABILITATION, Issue 2 2006
I. Z. ALAJBEG
summary, The objective of this study was to determine whether the muscle activity at various mandibular positions is affected by age and dental status. Thirty edentulous subjects (E), 20 young dentate individuals (G1) and 20 older dentate individuals (G2) participated in this study. Surface electromyographic (EMG) recordings were obtained from the anterior temporal (T), masseter (M) and depressor muscles (D). Muscle activity was recorded during maximal voluntary contraction (MVC), maximal opening (Omax) and in six different mandibular positions. One way anova and the Bonferroni tests were used to determine the differences between groups. Significant differences between the three tested groups were found at MVC and Omax for all examined muscles (P < 0·001). The differences in muscle activity in dentate subjects of different age were found in protrusion for depressor muscles (P < 0·05) and in lateral excursive positions for the working side temporal (P < 0·05) and non-working side masseter and depressor muscle (P < 0·05). There was a significant effect regarding the presence of natural teeth or complete dentures in protrusion and maximal protrusion for all muscles (P < 0·05) and in lateral excursive positions for non-working side temporal (P < 0·05) and working side masseter muscle (P < 0·05). Muscle activity at various mandibular positions depends greatly on the presence of the prosthetic appliance, as edentulous subjects had to use higher muscle activity levels (percentages of maximal EMG value) than age matched dentate subjects in order to perform same mandibular movement. Different elevator muscles were preferentially activated in the edentulous subjects when compared with dentate group in lateral excursive positions of the mandible. The pattern of relative muscle activity was not changed because of ageing. [source]

Feasibility of Gait Event Detection Using Intramuscular Electromyography in the Child with Cerebral Palsy

NEUROMODULATION, Issue 3 2004
Richard T. Lauer PhD
Abstract The objective of this study was to develop and test the feasibility of a model that employs electromyographic (EMG) signals to predict the occurrence of gait events in the child with cerebral palsy (CP). This model could be the basis of a future functional electrical stimulation (FES) control system to assist gait. Two children were implanted with bifilar intramuscular electrodes into the quadriceps muscle bilaterally. Muscle activity and gait parameters were recorded, and a fuzzy inference system was used to correlate EMG to five distinct gait events. For nine of the 10 gait events evaluated, the model predicted gait events to within 82 ms on average, as referenced to the VICON motion analysis system. For eight of the 10 events, prediction errors were 0.3% or less. Results indicate that EMG from the proximal musculature could be used to predict the occurrence of gait events in these two children with CP. [source]

The medial and lateral bellies of gastrocnemius: A cadaveric and ultrasound investigation

CLINICAL ANATOMY, Issue 1 2008
Tony Antonios
Abstract It is commonly reported that the medial belly (MG) of the gastrocnemius muscle extends further distally than the lateral belly (LG). This observation is made in several standard anatomy texts with no explanation or quantitative data. In this study, the medial and lateral bellies of gastrocnemius in 45 embalmed cadavers were measured. The observed difference in length of the two bellies was found to be highly significant (mean difference in length = 1.74 cm, P < 0.001). In 8 out of 84 legs examined (9.5%), however, the MG was found to be shorter than the LG (three right legs, five left legs, bilateral in two individuals). Surprisingly, there was no correlation between the difference in muscle belly length in any individual and ipsilateral leg length or total body length, suggesting that the difference in belly length may be unrelated to biomechanical function. An ultrasound investigation into the activity pattern of the two bellies was carried out on five volunteers. Muscle activity was monitored during passive and active movements of the ankle and knee joints at different leg positions. During knee flexion and ankle plantarflexion, the LG contracted first in four of the five subjects, followed by the MG, then a period of either LG predomination or equal contraction. The fifth subject, who showed a reversed pattern of activity, had previously suffered an inversion injury of the ankle. We suggest that the initial activation of the LG may help to stabilize the ankle during plantarflexion. We found no evidence that gastrocnemius acts as a shunt muscle during distraction of the knee. Clin. Anat. 21:66,74, 2008. © 2007 Wiley-Liss, Inc. [source]

Neuromuscular function in healthy occlusion

JOURNAL OF ORAL REHABILITATION, Issue 9 2010
S. E. FORRESTER
Summary, This study aimed to measure neuromuscular function for the masticatory muscles under a range of occlusal conditions in healthy, dentate adults. Forty-one subjects conducted maximum voluntary clenches under nine different occlusal loading conditions encompassing bilateral posterior teeth contacts with the mandible in different positions, anterior teeth contacts and unilateral posterior teeth contacts. Surface electromyography was recorded bilaterally from the anterior temporalis, superficial masseter, sternocleidomastoid, anterior digastric and trapezius muscles. Clench condition had a significant effect on muscle function (P = 0·0000) with the maximum function obtained for occlusions with bilateral posterior contacts and the mandible in a stable centric position. The remaining contact points and moving the mandible to a protruded position, whilst keeping posterior contacts, resulted in significantly lower muscle activities. Clench condition also had a significant effect on the per cent overlap, anterior,posterior and torque coefficients (P = 0·0000,0·0024), which describe the degree of symmetry in these muscle activities. Bilateral posterior contact conditions had significantly greater symmetry in muscle activities than anterior contact conditions. Activity in the sternocleidomastoid, anterior digastric and trapezius was consistently low for all clench conditions, i.e. <20% of the maximum voluntary contraction level. In conclusion, during maximum voluntary clenches in a healthy population, maximum masticatory muscle activity requires bilateral posterior contacts and the mandible to be in a stable centric position, whilst with anterior teeth contacts, both the muscle activity and the degree of symmetry in muscle activity are significantly reduced. [source]

Oro-facial activities in sleep bruxism patients and in normal subjects: a controlled polygraphic and audio,video study

JOURNAL OF ORAL REHABILITATION, Issue 2 2009
K. M. C. DUTRA
Summary, To our knowledge, the large spectrum of sleep motor activities (SMA) present in the head and neck region has not yet been systematically estimated in normal and sleep bruxism (SB) subjects. We hypothesized that in the absence of audio,video signal recordings, normal and SB subjects would present a high level of SMA that might confound the scoring specificity of SB. A retrospective analysis of several SMA, including oro-facial activities (OFA) and rhythmic masticatory muscle activities (RMMA), was made from polygraphic and audio,video recordings of 21 normal subjects and 25 SB patients. Sleep motor activities were scored, blind to subject status, from the second night of sleep recordings. Discrimination of OFA included the following types of activities: lip sucking, head movements, chewing-like movements, swallowing, head rubbing and scratching, eye opening and blinking. These were differentiated from RMMA and tooth grinding. The frequency of SMA per hour of sleep was lower in normal subjects in comparison with SB patients (P < 0·001). Up to 85% of all SMA in normal subjects were related to OFA while 30% of SMA in SB patients were related to OFA scoring (P < 0·001). The frequency of RMMA was seven times higher in SB patients than in normal subjects (P < 0·001). Several SMA can be observed in normal and SB subjects. In the absence of audio,video signal recordings, the discrimination of various types of OFA is difficult to achieve and may lead to erroneous estimation of SB-related activities. [source]

Motor control of jaw muscles in chewing and in isometric biting with graded narrowing of jaw gape

JOURNAL OF ORAL REHABILITATION, Issue 10 2008
P. A. PRÖSCHEL
Summary, When a certain bite force is applied during unilateral chewing, the combination of jaw elevator muscle activities is different than when a comparable force is applied in unilateral isometric biting, e.g. on a force transducer. Masticatory peak force is generated in a nearly isometric phase of the chewing cycle, with a jaw gape of about 1 mm. In contrast, peak force in isometric biting on force measuring equipment usually induces jaw gapes of 6 mm or even more. Therefore, we tested the hypothesis that the jaw gape influences relative activation of elevator muscles in unilateral isometric biting. We further examined whether such influence could explain the different activity combinations of chewing and isometric biting. In thirty asymptomatic males, masseter and temporalis activities were recorded during intermittent isometric biting with jaw gapes of 6, 5, 3, 2 and 1 mm and during unilateral chewing. Activity combinations were described by working/balancing ratios and by temporalis/masseter ratios. With decreasing jaw gape the working/balancing ratio of the posterior temporalis decreased (P < 0·002) while that of the masseter increased (P < 0·001). Likewise, the temporalis/masseter ratio on the balancing side increased (P < 0·001). With decreasing jaw gape, activity ratios of isometric biting approached ratios of chewing. We conclude that: (i) relative jaw muscle activation in isometric biting depends on the jaw gape, (ii) relative muscle activation in chewing resembles relative activation of isometric biting with a small ,chewing-like' gape. This suggests that characteristic activity combinations in chewing are mainly a result of the approximately isometric contraction during the slow closing phase of the chewing cycle. [source]

Influence of food properties and body posture on durations of swallowing-related muscle activities

JOURNAL OF ORAL REHABILITATION, Issue 9 2008
D. INAGAKI
Abstract, The purpose of this study was to determine (i) whether or not textural properties of foods and body positions affect the durations of anterior tongue and suprahyoid muscle activities during swallowing, and (ii) if such changes occur, is the ,pre-peak' or the ,post-peak' duration of integrated muscle activity responsible. We used two test foods with different proprieties of hardness and adhesiveness. We recorded electromyograms (EMGs) from the anterior tongue and suprahyoid muscles as well as the laryngeal movement associated with swallowing in normal subjects (six men and three women; 21,30-years old). The subjects swallowed the test foods in four randomly set postures: upright, two inclined (60 ° and 30 ° to horizontal), and supine. None of the measured durations for the anterior tongue and suprahyoid EMGs were different among the four positions during swallowing of either food. The ,total' duration, from the start to the end of the integrated EMG, of anterior tongue activity was significantly (P < 0·001, anova) longer during the swallowing of the tougher and more adhesive food than during swallowing of the other food, but the ,total' duration of suprahyoid activity was unchanged. The ,post-peak' duration of anterior tongue activity, which stretched from the peak to the end of the integrated EMG, was also significantly longer (P < 0·001, anova) during swallowing of the tougher and more adhesive food. The results indicate that tougher and more adhesive foods prolong the duration, especially the ,post-peak' duration, of anterior tongue activity during swallowing in the upright, inclined and supine positions. [source]

Laryngeal and diaphragmatic muscle activities after central nervous system lesions in cats

ACTA PAEDIATRICA, Issue 11 2003
AA Hutchison
Aim: To examine the central control and coordination of respiratory pump muscles and laryngeal valve muscles by systematic decerebration (DECER), cerebellectomy (CBELL), pontine respiratory group lesioning (PRG) and pontomedullary section (PMED). Methods: Activities of posterior cricoarytenoid (PCA), thyroarytenoid (TA) and diaphragm (D) muscles and their responses to inspiratory (I) and expiratory (E) total occlusions were determined in 10 adult cats. Results: INTACT anesthetized cats (n= 6) exhibited inspiratory PCA (PCAI) and D activities. Expiratory PCA (PCAE) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCAE, the intact pattern being noted in 7/10, 4/10 and 0/6 cats, respectively. After PMED, variable PCA, TA and continuous D activities occurred only with blood gas abnormalities. Augmented PCA and D responses to I- and E-loads occurred after PRG lesions: the I-load PCAI and D responses resembled apneusis and the E-load PCAE and D responses resembled central apnea. Conclusion: The decreasing PCAE activity observed with successive DECER, CBELL and PRG lesions suggests that these areas influence laryngeal abductor control of glottic size. The synchronous activities after PMED transection suggest a role for more rostral structures in coordinating laryngeal and diaphragmatic muscle activities. [source]

Control of muscle blood flow during exercise: local factors and integrative mechanisms

ACTA PHYSIOLOGICA, Issue 4 2010
I. Sarelius
Abstract Understanding the control mechanisms of blood flow within the vasculature of skeletal muscle is clearly fascinating from a theoretical point of view due to the extremely tight coupling of tissue oxygen demands and blood flow. It also has practical implications as impairment of muscle blood flow and its prevention/reversal by exercise training has a major impact on widespread diseases such as hypertension and diabetes. Here we analyse the role of mediators generated by skeletal muscle activity on smooth muscle relaxation in resistance vessels in vitro and in vivo. We summarize their cellular mechanisms of action and their relative roles in exercise hyperaemia with regard to early and late responses. We also discuss the consequences of interactions among mediators with regard to identifying their functional significance. We focus on (potential) mechanisms integrating the action of the mediators and their effects among the cells of the intact arteriolar wall. This integration occurs both locally, partly due to myoendothelial communication, and axially along the vascular tree, thus enabling the local responses to be manifest along an entire functional vessel path. Though the concept of signal integration is intriguing, its specific role on the control of exercise hyperaemia and the consequences of its modulation under physiological and pathophysiological conditions still await additional analysis. [source]

Changes in presumed motor cortical activity during fatiguing muscle contraction in humans

ACTA PHYSIOLOGICA, Issue 3 2010
T. Seifert
Abstract Aim:, Changes in sensory information from active muscles accompany fatiguing exercise and the force-generating capacity deteriorates. The central motor commands therefore must adjust depending on the task performed. Muscle potentials evoked by transcranial magnetic stimulation (TMS) change during the course of fatiguing muscle activity, which demonstrates activity changes in cortical or spinal networks during fatiguing exercise. Here, we investigate cortical mechanisms that are actively involved in driving the contracting muscles. Methods:, During a sustained submaximal contraction (30% of maximal voluntary contraction) of the elbow flexor muscles we applied TMS over the motor cortex. At an intensity below motor threshold, TMS reduced the ongoing muscle activity in biceps brachii. This reduction appears as a suppression at short latency of the stimulus-triggered average of rectified electromyographic (EMG) activity. The magnitude of the suppression was evaluated relative to the mean EMG activity during the 50 ms prior to the cortical stimulus. Results:, During the first 2 min of the fatiguing muscle contraction the suppression was 10 ± 0.9% of the ongoing EMG activity. At 2 min prior to task failure the suppression had reached 16 ± 2.1%. In control experiments without fatigue we did not find a similar increase in suppression with increasing levels of ongoing EMG activity. Conclusion:, Using a form of TMS which reduces cortical output to motor neurones (and disfacilitates them), this study suggests that neuromuscular fatigue increases this disfacilitatory effect. This finding is consistent with an increase in the excitability of inhibitory circuits controlling corticospinal output. [source]

On functional motor adaptations: from the quantification of motor strategies to the prevention of musculoskeletal disorders in the neck,shoulder region

ACTA PHYSIOLOGICA, Issue 2010
P. Madeleine
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. [source]

Effect of muscle activity and botulinum toxin dilution volume on muscle paralysis

DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 3 2003
Hyeon Sook Kim MD PhD
The purpose of this study was to evaluate the effects of botulinum toxin A (BTX-A, Botox) dilution volume and post-injection exercise with electrical stimulation on muscle paralysis. We injected 10 units of BTX-A diluted with 0.1 ml (B1, n=8) or 0.5 ml (B5, n=8) normal saline into both gastrocnemius muscles of 16 New Zealand white rabbits; two controls received no BTX-A. After BTX-A injection, all rabbits received calf muscle stretching exercise and electrical stimulation for 2 hours on the left leg. The compound muscle action potential (CMAP) decrease was most pronounced at 1 week and progressive recovery was observed (i.e. recovery from paralysis, increase of CMAP). There was a significant decrease of CMAP amplitudes in the B5 group compared with the B1 group at week 1 and week 4 (p<0.001). Left limbs with stretching exercise and electrical stimulation showed lower CMAP amplitudes compared with control right limbs of all rabbits. To maximize the muscle paralysis effect of BTX-A, increasing dilution volume and performing post-injection stretching exercise with electrical stimulation may be a promising strategy for increasing the beneficial effect of BTX-A treatment. Future studies are needed to investigate the clinical application of this finding. [source]

The influence of attachment representation on parental perception and interpretation of infant emotions: A multilevel approach

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 5 2010
Gottfried Spangler
Abstract The aim of the study was to investigate parental perception and interpretation of infant emotional expression depending on their attachment representation. Forty-six parents' responses to infant pictures depicting positive, neutral, and negative emotions were assessed on the level of affective judgments (valence, arousal), mimic responses (facial muscle activity), and of the eyelid reflex (using the startle paradigm). Results revealed small differences between parents of different attachment representations with respect to their subjective evaluations. However, secure parents, as compared to insecure ones, showed a positive bias in their mimic responses to infant pictures. The modulation of the startle response indicated a negative evaluation of negative infant emotion expressions in dismissing parents, while an augmentation of the startle response to negative infant emotions could not be observed in secure and preoccupied parents. The findings highlight the role of attachment experiences for emotional information processing in parents and its consequences for parental behavior. © 2010 Wiley Periodicals, Inc. Dev Psychobiol 52: 411,423, 2010. [source]

In vitro effects of lidocaine on the contractility of equine jejunal smooth muscle challenged by ischaemia-reperfusion injury

EQUINE VETERINARY JOURNAL, Issue 1 2010
M. GUSCHLBAUER
Summary Reasons for performing study: Post operative ileus (POI) in horses is a severe complication after colic surgery. A commonly used prokinetic drug is lidocaine, which has been shown to have stimulatory effects on intestinal motility. The cellular mechanisms through which lidocaine affects smooth muscle activity are not yet known. Objectives: To examine the effects of lidocaine on smooth muscle in vitro and identify mechanisms by which it may affect the contractility of intestinal smooth muscle. Hypothesis: Ischaemia and reperfusion associated with intestinal strangulation can cause smooth muscle injury. Consequently, muscle cell functionality and contractile performance is decreased. Lidocaine can improve basic cell functions and thereby muscle cell contractility especially in ischaemia-reperfusion-challenged smooth muscle. Methods: To examine the effects of lidocaine on smooth muscle function directly, isometric force performance was measured in vitro in noninjured and in vivo ischaemia-reperfusion injured smooth muscle tissues. Dose-dependent response of lidocaine was measured in both samples. To assess membrane permeability as a marker of basic cell function, release of creatine kinase (CK) was measured by in vitro incubations. Results: Lidocaine-stimulated contractility of ischaemia-reperfusion injured smooth muscle was more pronounced than that of noninjured smooth muscle. A 3-phasic dose-dependency was observed with an initial recovery of contractility especially in ischaemia-reperfusion injured smooth muscle followed by a plateau phase where contractility was maintained over a broad concentration range. CK release was decreased by lidocaine. Conclusion: Lidocaine may improve smooth muscle contractility and basic cell function by cellular repair mechanisms which are still unknown. Improving contractility of smooth muscle after ischaemia-reperfusion injury is essential in recovery of propulsive intestinal motility. Potential relevance: Characterisation of the cellular mechanisms of effects of lidocaine, especially on ischaemia-reperfusion injured smooth muscle, may lead to improved treatment strategies for horses with POI. [source]

Quantification of surface EMG signals to monitor the effect of a Botox treatment in six healthy ponies and two horses with stringhalt: Preliminary study

EQUINE VETERINARY JOURNAL, Issue 3 2009
I. D. Wijnberg
Summary Reasons for performing the study: Therapeutic options for stringhalt in horses are limited, whereas medical experiences with botulinum toxin type A (Botox) have been positive. To evaluate its effectiveness in horses, surface electromyography (sEMG) signals before and after injection need to be quantified. Hypothesis: Treatment of healthy ponies and cases with Botox should reduce muscle activity in injected muscles and reduce spastic movements without adverse side effects. Methods: Unilaterally, the extensor digitorum longus, extensor digitorum lateralis and lateral vastus muscles of 6 healthy mature Shetland ponies and 2 talented Dutch Warmblood dressage horses with stringhalt were injected (maximum of 400 iu per pony and 700 iu per case; 100 iu in 5 ml NaCl divided into 5 injections) with Botox under needle EMG guidance. Surface EMG data were evaluated using customised software, and in the individuals gait was analysed using Proreflex. Statistical analysis was performed using mixed models and independent sample t test (P<0.05). Results: Surface EMG signals were quantified using customised software. The area under the curve (integrated EMG) in time was used as variable. It became significantly reduced in injected muscles after injection of Botox in normal ponies (P<0.05). This effect was present from Day 1 until Day 84 after injection. In the 2 cases, after injection of 3 muscles, the integrated EMG in time became significantly reduced in all 3 muscles. Kinematic measurements confirmed reduction of frequency and amplitude of hyperflexing or hyperabducting strides of the affected hindlimbs. The duration of effect was also seen in the cases until around 12 weeks after injection. Conclusions and potential relevance: After EMG guided injections of Botox, sEMG signals recorded from injected muscle were reduced, which proves this to be a useful tool in statistically evaluating a treatment effect. The positive results of this pilot study encourage further research with a larger group of clinical cases. [source]

Increased expression of VEGF following exercise training in patients with heart failure

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 4 2001
T. Gustafsson
Background and aims During the last decades several angiogenic factors have been characterized but so far it is unknown whether local muscle exercise training increases the expression of these factors in patients with moderate heart failure. Expression of the major putative angiogenic factor vascular endothelial growth factor (VEGF) at the level of messneger RNA (mRNA) and/or protein was therefore studied before and after 8 weeks of training in patient with chronic heart failure. Methods VEGF mRNA and protein concentrations were determined in skeletal muscle biopsies before and after 8 weeks of one-legged knee extension training in patients with chronic heart failure (New York Heart Association II,III). Results Exercise training increased the citrate synthase activity and peripheral exercise capacity by 46% and 36%, respectively, in parallel with a two-fold increase in VEGF at both the mRNA (P = 0·03) and protein (P = 0·02) levels Conclusion The increase in VEGF gene expression in response to exercise training indicates VEGF to be one possible mediator in exercise-induced angiogenesis and may therefore regulate an important and early step in adaptation to increased muscle activity in patient with chronic heart failure. [source]

Pericranial injection of botulinum toxin type A (Dysport®) for tension-type headache , A multicentre, double-blind, randomized, placebo-controlled study

EUROPEAN JOURNAL OF NEUROLOGY, Issue 3 2008
A. Straube
Increasingly, botulinum type A toxin is used to influence pathologically increased muscle activity in conditions such as dystonia and spasticity. Studies have also assessed its efficacy in tension-type headache, where muscle tenderness may be increased. We undertook a prospective, multicentre, randomized, double-blind, placebo-controlled trial. Patients received injections of Dysport® (total dose of 420 or 210 units) or saline placebo in 18 sites on the head and neck. Of 125 patients treated, 118 were included in the intention-to-treat dataset. No significant differences between each verum group and placebo were seen for the primary efficacy parameter , change in the number of headache-free days at 4,8 weeks after injection compared with 4 weeks before injection. The groups receiving 420 or 210 units of Dysport experienced 2.60 and 2.87 more headache-free days respectively, compared with 1.93 more headache-free days for the placebo group (P = 0.66 versus 420 units; P = 0.52 versus 210 units). Treatment with 420 units of Dysport was associated with significant improvements compared with placebo for two secondary efficacy parameters: mean change in headache duration from baseline to weeks 8,12 (P < 0.05) and improved global physician and patient assessment scores (P < 0.05). Further studies should address the possible value of multiple injections with extended observation periods, dose optimization, and whether duration of headache history and number of previous treatments are predictors of patient response. [source]

Electromyographic evaluation of cervical dystonia for planning of botulinum toxin therapy

EUROPEAN JOURNAL OF NEUROLOGY, Issue 6 2000
D. Dressler
The success of botulinum toxin (BT) injections for treatment of cervical dystonia depends on precise identification of dystonic muscles and on quantification of their dystonic involvement. Conventionally, this is attempted by clinical examination analysing the dystonic head position. In this presentation, a more systematic approach is sought by using an electromyography (EMG)-based evaluation procedure. In 10 consecutive patients with cervical dystonia not previously exposed to BT clinical examination, analysing the dystonic head position was performed to classify patients into four groups with similar dystonic head positions. Additionally, a 2-channel concentric needle EMG was used to measure the amplitudes of dystonic and maximal voluntary activities in sternocleidomastoid (SCM), splenius capitis (SC) and trapezius/semispinalis capitis (T/SS) muscles bilaterally. The ratio between both amplitudes, the dystonia ratio, was used to quantify dystonic muscle involvement. In all patients dystonia ratios could be calculated. In patients with similar head positions, EMG evaluation revealed different qualitative and quantitative dystonic involvement patterns. In six patients, there were discrepancies in identification of dystonic muscles between clinical examination and EMG evaluation. EMG evaluation excluded dystonic involvement in five patients. All excluded muscles were SCM. In one of these patients, additional T/SS involvement was detected by EMG evaluation. In one patient, SC involvement was revealed by EMG evaluation. All dystonic muscle involvement detected by EMG evaluation represented genuine dystonic muscle coactivation rather than compensatory muscle activity. The EMG evaluation presented allows quantitative and qualitative identification of dystonic muscle involvement which cannot be achieved by clinical examination. Both pieces of information may be helpful for optimization of BT therapy. [source]

Differential modulation by monoamine membrane receptor agonists of reticulospinal input to lamina VIII feline spinal commissural interneurons

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007
Ingela Hammar
Abstract Noradrenaline and serotonin have previously been demonstrated to facilitate the transmission between descending reticulospinal tracts fibres and commissural interneurons coordinating left,right hindlimb muscle activity. The aim of the present study was to investigate the contribution of subclasses of monoaminergic membrane receptors to this facilitation. The neurons were located in Rexed lamina VIII in midlumbar segments and identified by their projections to the contralateral gastrocnemius,soleus motor nuclei and by lack of projections rostral to the lumbosacral enlargement. The effects of ionophoretically applied membrane receptor agonists [phenylephrine (noradrenergic ,1), clonidine (noradrenergic ,2), 8-OH-DPAT (5-HT1A, 5-HT7), 2-me-5-HT (5-HT3), 5-me-5-HT (5-HT2) and ,-me-5-HT (5-HT2)] were examined on extracellularly recorded spikes evoked monosynaptically by electric stimulation of descending reticulospinal fibres in the medial longitudinal fascicle. Application of ,1 and 5-HT2 agonists resulted in a facilitation of responses in all investigated neurons while application of ,2, 5-HT1A/7 and 5-HT3 agonists resulted in a depression. These opposite modulatory effects of different agonists suggest that the facilitatory actions of noradrenaline and serotonin on responses of commissural interneurons reported previously following ionophoretic application are the net outcome of the activation of different subclasses of monoaminergic membrane receptors. As these receptors may be distributed predominantly, or even selectively, at either pre- or postsynaptic sites their differential modulatory actions could be compatible with a presynaptically induced depression and a postsynaptically evoked enhancement of synaptic transmission between reticulospinal neurons and commissural interneurons. [source]

Corrective movements in response to displacements in visual feedback are more effective during periods of 13,35 Hz oscillatory synchrony in the human corticospinal system

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006
Alexandros G. Androulidakis
Abstract Oscillatory synchronization in the beta (,20 Hz) band is a common feature of human motor control, manifest at cortical and muscular levels during tonic contraction. Here we test the hypothesis that the influence of visual feedback on performance in a positional hold task is increased during bursts of beta-band synchrony in the corticospinal motor system. Healthy subjects were instructed to extend their forefinger while receiving high-gain visual feedback of finger position on a PC screen. Small step displacements of the feedback signal were triggered either by bursts of beta oscillations in scalp electroencephalogram or randomly with respect to cortical beta activity, and the resulting positional corrections expressed as a percentage of the step displacement. Corrective responses to beta and randomly triggered step changes in visual feedback were 41.7 ± 4.9 and 31.5 ± 6.8%, respectively (P < 0.05). A marked increase in the coherence in the beta band was also found between muscle activity and cortical activity during the beta-triggered condition. The results suggest that phasic elevations of beta activity in the corticospinal motor system are associated with an increase in the gain of the motor response to visual feedback during a tonic hold task. Beta activity may index a motor state in which processing relevant to the control of positional hold tasks is promoted, with behavioural consequences. [source]

Fibre-type composition of rabbit jaw muscles is related to their daily activity

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005
T. van Wessel
Abstract Skeletal muscles contain a mixture of fibres with different contractile properties, such as maximum force, contraction velocity and fatigability. Muscles adapt to altered functional demands, for example, by changing their fibre-type composition. This fibre-type composition can be changed by the frequency, duration and presumably the intensity of activation. The aim of this study was to analyse the relationship between the spontaneous daily muscle activation and fibre-type composition in rabbit jaw muscles. Using radio-telemetry combined with electromyography, the daily activity of five jaw muscles was characterized in terms of the total duration of muscle activity (duty time) and the number of activity bursts. Fibre-type composition of the muscles was classified by analysing the myosin heavy chain content of the fibres. The amount of slow-type fibres was positively correlated to the duty time and the number of bursts only for activations exceeding 20,30% of the maximum activity per day. Furthermore, cross-sectional areas of the slow-type fibres were positively correlated to the duty time for activations exceeding 30% of the maximum activity. The present data indicate that the amount of activation above a threshold (> 30% peak activity) is important for determining the fibre-type composition and cross-sectional area of slow-type fibres of a muscle. Activation above this threshold occurred only around 2% of the time in the jaw muscles, suggesting that contractile properties of muscle fibres are maintained by a relatively small number of powerful contractions per day. [source]

Daily jaw muscle activity in freely moving rats measured with radio-telemetry

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2007
Nobuhiko Kawai
The jaw muscle activity of rats has been investigated for specific tasks. However, the daily jaw muscle use remains unclear. The purpose of the present study was to examine daily jaw muscle activity, and its variability over time, in the rat (n = 12) by the use of radio-telemetry. A telemetric device was implanted for the continuous recording of masseter muscle and digastric muscle activity. Daily muscle use was characterized by calculating the total time that each muscle was active (duty time), the number of bursts, and the average length of bursts. All parameters were estimated for activities exceeding various levels (5,90%) of the day's peak activity. Daily muscle use remained constant for 4 wk. At the low-activity level, the duty time and burst number of the digastric muscle were significantly (P < 0.01) higher than those of the masseter muscle, whereas the opposite was true at the high-activity level (P < 0.05). No significant intermuscular correlation was observed between the number of bursts of the masseter and digastric muscles, but the interindividual variation of both muscles changed, depending on the level of activation. These findings suggest that the masseter muscle and the digastric muscle show a differential active pattern, depending on the activity level. [source]

Intermittent hypoxia and respiratory plasticity in humans and other animals: does exposure to intermittent hypoxia promote or mitigate sleep apnoea?

EXPERIMENTAL PHYSIOLOGY, Issue 3 2009
Jason H. Mateika
This review focuses on two phenomena that are initiated during and after exposure to intermittent hypoxia. The two phenomena are referred to as long-term facilitation and progressive augmentation of respiratory motor output. Both phenomena are forms of respiratory plasticity. Long-term facilitation is characterized by a sustained elevation in respiratory activity after exposure to intermittent hypoxia. Progressive augmentation is characterized by a gradual increase in respiratory activity from the initial to the final hypoxic exposure. There is much speculation that long-term facilitation may have a significant role in individuals with sleep apnoea because this disorder is characterized by periods of upper airway collapse accompanied by intermittent hypoxia, one stimulus known to induce long-term facilitation. It has been suggested that activation of long-term facilitation may serve to mitigate apnoea by facilitating ventilation and, more importantly, upper airway muscle activity. We examine the less discussed but equally plausible situation that exposure to intermittent hypoxia might ultimately lead to the promotion of apnoea. There are at least two scenarios in which apnoea might be promoted following exposure to intermittent hypoxia. In both scenarios, long-term facilitation of upper airway muscle activity is initiated but ultimately rendered ineffective because of other physiological conditions. Thus, one of the primary goals of this review is to discuss, with support from basic and clinical studies, whether various forms of respiratory motor neuronal plasticity have a beneficial and/or a detrimental impact on breathing stability in individuals with sleep apnoea. [source]

Differences in the skin peptides of the male and female Australian tree frog Litoria splendida

FEBS JOURNAL, Issue 1 2000
The discovery of the aquatic male sex pheromone splendipherin, a new antibiotic peptide caerin 1.10, together with Phe8 caerulein
The skin secretions of female and male Litoria splendida have been monitored monthly over a three-year period using HPLC and electrospray mass spectrometry. Two minor peptides are present only in the skin secretion of the male. The first of these is the female-attracting aquatic male sex pheromone that we have named splendipherin, a 25 amino acid peptide (GLVSSIGKALGGLLADVVKSKGQPA-OH). This pheromone constitutes about 1% of the total skin peptides during the breeding season (January to March), dropping to about 0.1% during the period June to November. Splendipherin attracts the female in water at a concentration of 10,11,10,9 m, and is species specific. The second peptide is a wide-spectrum antibiotic of the caerin 1 group, a 25 residue peptide (GLLSVLGSVAKHVLPHVVPVIAEKL-NH2) named caerin 1.10. The neuropeptides of L. splendida are also seasonally variable, the change identical for both the female and male. During the period October to March, the sole neuropeptide present in skin secretions is caerulein [pEQDY(SO3)TGWMDF-NH2]; this is active on smooth muscle and is also an analgaesic. During the southern winter (June to September), more than half of the caerulein is hydrolysed to [pEQDYTGWMDF-NH2], a peptide that shows no smooth muscle activity. In place of caerulein, a new peptide, Phe8 caerulein [pEQDY(SO3)TGWFDF-NH2], becomes a major component of the skin secretion. Perhaps this seasonal change is involved in thermoregulation, that is, with the initiation and maintenance of the inactive (hibernation) phase of the animal. [source]

fMRI analysis for motor paradigms using EMG-based designs: A validation study

HUMAN BRAIN MAPPING, Issue 11 2007
Anne-Fleur van Rootselaar
Abstract The goal of the present validation study is to show that continuous surface EMG recorded simultaneously with 3T fMRI can be used to identify local brain activity related to (1) motor tasks, and to (2) muscle activity independently of a specific motor task, i.e. spontaneous (abnormal) movements. Five healthy participants performed a motor task, consisting of posture (low EMG power), and slow (medium EMG power) and fast (high EMG power) wrist flexion,extension movements. Brain activation maps derived from a conventional block design analysis (block-only design) were compared with brain activation maps derived using EMG-based regressors: (1) using the continuous EMG power as a single regressor of interest (EMG-only design) to relate motor performance and brain activity, and (2) using EMG power variability as an additional regressor in the fMRI block design analysis to relate movement variability and brain activity (mathematically) independent of the motor task. The agreement between the identified brain areas for the block-only design and the EMG-only design was excellent for all participants. Additionally, we showed that EMG power variability correlated well with activity in brain areas known to be involved in movement modulation. These innovative EMG-fMRI analysis techniques will allow the application of novel motor paradigms. This is an important step forward in the study of both the normally functioning motor system and the pathophysiological mechanisms in movement disorders. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source]

Coherent corticomuscular oscillations originate from primary motor cortex: Evidence from patients with early brain lesions

HUMAN BRAIN MAPPING, Issue 10 2006
Christian Gerloff
Abstract Coherent oscillations of neurons in the primary motor cortex (M1) have been shown to be involved in the corticospinal control of muscle activity. This interaction between M1 and muscle can be measured by the analysis of corticomuscular coherence in the ,-frequency range (,-CMCoh; 14,30 Hz). Largely based on magnetoencephalographic (MEG) source-modeling data, it is widely assumed that ,-CMCoh reflects direct coupling between M1 and muscle. Deafferentation is capable of modulating ,-CMCoh, however, and therefore the influence of reafferent somatosensory signaling and corresponding neuronal activity in the somatosensory cortex (S1) has been unclear. We present transcranial magnetic stimulation (TMS) and MEG data from three adult patients suffering from congenital hemiparesis due to pre- and perinatally acquired lesions of the pyramidal tract. In these patients, interhemispheric reorganization had resulted in relocation of M1 to the contralesional hemisphere, ipsilateral to the paretic hand, whereas S1 had remained in the lesioned hemisphere. This topographic dichotomy allowed for an unequivocal topographic differentiation of M1 and S1 with MEG (which is not possible if M1 and S1 are directly adjacent within one hemisphere). In all patients, ,-CMCoh originated from the contralesional M1, in accordance with the TMS-evoked motor responses, and in contrast to the somatosensory evoked fields (SEFs) for which the sources (N20m) were localized in S1 of the lesioned hemisphere. These data provide direct evidence for the concept that ,-CMCoh reflects the motorcortical efferent drive from M1 to the spinal motoneuron pool and muscle. No evidence was found for a relevant contribution of neuronal activity in S1 to ,-CMCoh. Hum Brain Mapp, 2006. © 2006 Wiley-Liss, Inc. [source]

Multichannel surface electromyography in ergonomics: Potentialities and limits

HUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2010
Marco Gazzoni
Abstract The prevention of work-related musculoskeletal disorders is one of the main goals in ergonomics. Among others, surface electromyography (sEMG) is an important tool for the evaluation of risks related to work activity. Three main issues have been approached in ergonomics via sEMG: 1) the analysis of muscle activation, 2) the analysis of exerted forces and torques, and 3) the analysis of muscle fatigue. Many studies have been carried out in static conditions. In ergonomics, however, it is more relevant to study muscle activity and fatigue during real tasks that are, in general, dynamic. From isometric to dynamic contractions, the complexity of the interpretation of sEMG signals increases considerably. Changes in sEMG signals are related to the continuous modifications in force output, muscle fiber length, and relative position of surface electrodes and sources. To increase the reliability of the information extracted from sEMG, multichannel detection systems have been applied, showing the possibility of overcoming some limits of the standard technique. Some illustrative laboratory and field studies are reported in this work to illustrate the potentialities and the open problems in the use of multichannel sEMG in ergonomics. Case 1 is a laboratory study investigating the myoelectric manifestations of fatigue in the biceps brachii (BB) during dynamic elbow flexion/extension. Case 2 is a laboratory study investigating the myoelectric manifestations of fatigue during a repetitive lifting task. Case 3 is a field study, carried out in an automotive plant, investigating muscle activation during the welding of a car door. Many factors play a leading role in the correct interpretation of information provided by sEMG. Even though multichannel sEMG provides information able to improve the estimation of force and/or fatigue during working tasks, many problems related to the signal acquisition and interpretation are still open. Further improvements are necessary to develop multichannel sEMG into an effective tool supporting other methodologies for the evaluation of work-related risks. © 2010 Wiley Periodicals, Inc. [source]