The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Lars Arendtnielsen - One of the best experts on this subject based on the ideXlab platform.
-
Experimental Muscle Pain challenges the postural stability during quiet stance and unexpected posture perturbation
The Journal of Pain, 2011Co-Authors: Rogerio Pessoto Hirata, Ulysses Fernandes Ervilha, Lars Arendtnielsen, Thomas GravennielsenAbstract:Abstract Musculoskeletal Pain impairs postural control and stability. Nine subjects stood as quietly as possible on a moveable force platform before, during, and after Experimental Pain in the right leg Muscles. A moveable force platform was used to measure the center of pressure and provided unexpected perturbations. Lower limb Muscle activity, joint angles, and foot pressure distributions were measured. Hypertonic saline was used to induce Pain in the vastus lateralis, vastus medialis, or biceps femoris Muscle of the right leg. Compared to baseline and control sessions, Pain in the knee extensor Muscles during quiet standing evoked: 1) larger sway area, greater medial-lateral center of pressure displacement and higher speed (P Perspective This article presents the acute responses to leg Muscle Pain on the postural control. This measure could potentially help clinicians who seek to assess how Pain responses may contribute to patient’s postural control and stability during quiet standing and after recovering from unexpected perturbations.
-
the Pain induced change in relative activation of upper trapezius Muscle regions is independent of the site of noxious stimulation
Clinical Neurophysiology, 2009Co-Authors: Deborah Falla, Lars Arendtnielsen, Dario FarinaAbstract:OBJECTIVE: To assess the effect of local excitation of nociceptors at different locations of the upper trapezius Muscle on the spatial distribution of upper trapezius electromyographic (EMG) amplitude during sustained contraction. METHODS: Surface (EMG) signals were recorded from the upper trapezius Muscle with a grid of 10x5 electrodes from nine healthy men during 90 degrees shoulder abduction sustained for 60s. In one Experimental session, the subjects received separate injections of 0.4 ml of hypertonic saline (Experimental Muscle Pain) into the cranial and caudal region of the upper trapezius. In a separate Experimental session the same subjects received two injections of 0.2 ml each of hypertonic saline simultaneously in the cranial and caudal region. The EMG root mean square (RMS) values were computed for each electrode location to provide a topographical map of EMG amplitude. RESULTS: The RMS value averaged across all electrode locations decreased following injection of hypertonic saline (P<0.05) by a similar amount for the two Experimental sessions. The Pain-induced decrease was larger in the cranial than in the caudal region for both Experimental sessions, as evidenced by a shift of the EMG amplitude distribution towards the caudal region of the Muscle (P<0.0001). CONCLUSION: Muscle Pain induces a consistent change in the spatial activation of the upper trapezius Muscle which is independent of the site of noxious stimulation. SIGNIFICANCE: Pain-induced changes in the spatial distribution of Muscle activity may induce overload of specific Muscle regions in the long term.
-
Experimental Muscle Pain impairs descending inhibition
Pain, 2008Co-Authors: Lars Arendtnielsen, Kathleen A Sluka, Hong Ling NieAbstract:In chronic musculoskeletal Pain conditions, the balance between supraspinal facilitation and inhibition of Pain shifts towards an overall decrease in inhibition. Application of a tonic Painful stimulus results in activation of diffuse noxious inhibitory controls (DNIC). The aims of the present Experimental human study were (1) to compare DNIC, evoked separately, by hypertonic saline (6%)-induced Muscle Pain (tibialis anterior) or cold pressor Pain; (2) to investigate DNIC evoked by concomitant Experimental Muscle Pain and cold pressor Pain, and (3) to analyze for gender differences. Ten males and 10 age matched females participated in two sessions. In the first session unilateral Muscle Pain or unilateral cold pressor Pain were induced separately; in the second session unilateral Muscle Pain and unilateral cold pressor Pain were induced concomitantly. Pressure Pain thresholds (PPT) were measured around the knee joint before, during, and after DNIC induction. Cold pressor Pain increased PPT in both males and females with greater increases in males. Hypertonic saline-evoked Muscle Pain significantly increased PPT in males but not in females. When cold pressor and Muscle Pain were applied concomitantly the PPT increases were smaller when compared to the individual sessions. This study showed for the first time that two concurrent conditioning tonic Pain stimuli (Muscle Pain and cold pressor Pain) cause less DNIC compared with either of the conditioning stimuli given alone; and males showed greater DNIC than females. This may explain why patients with chronic musculoskeletal Pain have impaired DNIC.
-
homotopic and heterotopic variation in skin blood flow and temperature following Experimental Muscle Pain in humans
Brain Research, 2008Co-Authors: Jing Lei, Thomas Gravennielsen, Haojun You, Ole Kaeseler Andersen, Lars ArendtnielsenAbstract:The aim of the present study was to explore variation in skin blood flow and temperature following Experimental Muscle Pain. In 14 male human subjects, 2 ml and 4.8 ml of hypertonic (5.8%) saline were injected into the left tibialis anterior (TA) Muscle to induce Muscle Pain. The subjects rated the Pain intensity on a 10 cm visual analogue scale (VAS). Using laser-Doppler flowmetry and thermography, the skin blood flow and temperature were assessed at four different skin areas: ipsilateral Muscle Pain area (5x5 cm), ipsilateral referred Pain area (5x10 cm), and two corresponding mirror areas on the contralateral non-injected leg. Compared with 2 ml hypertonic saline injection, significantly longer Pain duration (1599+/-119 s) and stronger Pain intensity (VAS peak: 6.9+/-0.6 cm) were found after the injection of 4.8 ml hypertonic saline (P<0.001, respectively). In addition, 4.8 ml hypertonic saline evoked a significant increase in skin blood flow and higher skin temperature around the injection site, the referred Pain area, and the contralateral area to the injection site (P<0.05). By contrast, 2 ml hypertonic saline injection only elicited an increase in skin blood flow, but not temperature, at the injection area and the contralateral mirror area to the injection site (P<0.05). These results suggested that the vasodilation in different skin areas following intramuscular injection of hypertonic saline was dose-dependent. Injection of 4.8 ml hypertonic saline after local intramuscular anesthesia (2% lidocaine) did not evoke any significant changes in skin blood flow or skin temperature in any of the four observation areas. This suggested that both homotopic and heterotopic vascular reactions triggered by hypertonic saline stimulation of thin Muscle afferent fibers were a neurogenically associated reaction.
-
gender specific adaptations of upper trapezius Muscle activity to acute nociceptive stimulation
Pain, 2008Co-Authors: Deborah Falla, Lars Arendtnielsen, Dario FarinaAbstract:Abstract This study examined gender differences in the effect of Experimental Muscle Pain on changes in the relative activation of regions of the upper trapezius Muscle during a sustained contraction. Surface electromyographic (EMG) signals were recorded from multiple locations over the upper trapezius Muscle with a 10 × 5 grid of electrodes from nine women and nine men during 90° shoulder abduction sustained for 60 s. Measurements were performed before and after the injection of 0.4 ml hypertonic (Painful) and isotonic (control) saline into the cranial region of the upper trapezius Muscle. The EMG root mean square (RMS) was computed for each location of the grid to form a map of the EMG amplitude distribution. The peak Pain intensity following the injection of hypertonic saline was greater for women (numerical rating scale 0–10: women 6.0 ± 2.1, men 4.2 ± 0.9; P
Peter Svensson - One of the best experts on this subject based on the ideXlab platform.
-
effects of Muscle fatigue induced by low level clenching on Experimental Muscle Pain and resting jaw Muscle activity gender differences
Experimental Brain Research, 2006Co-Authors: Peter Svensson, Kelun Wang, Tetsurou Torisu, Antoon De Laat, Hiroyuki Fujii, Lars ArendtnielsenAbstract:The purpose of this study was to investigate the effects of jaw-Muscle fatigue evoked by low-level tooth-clenching followed by the induction of Experimental Muscle Pain by injection of glutamate on the perception of fatigue and Pain and on the resting electromyographic (EMG) activity. In addition, the role of gender on these interactions was studied. The EMG activities of bilateral masseter (MAL, MAR) and temporalis (TAL, TAR) Muscles in 11 healthy young women and 12 men were measured before (Baseline) and after tooth-clenching for 30 min at 10% of maximal force (Post1), after subsequent glutamate (Glu) or isotonic saline (Iso) injection into the MAL following the tooth-clenching (Post2) and 60 min after tooth-clenching (Post3). The intensities of fatigue, fatigue-related Muscle Pain and headache-like symptoms were scored on 0-10 cm visual analog scales (VAS). The glutamate-evoked Pain was continuously scored on an electronic VAS. Sustained low-level tooth-clenching consistently produced fatigue sensation, fatigue-related Muscle Pain and headache-like symptoms in both genders with significantly higher fatigue VAS scores in men than in women, while the accompanying increase in the resting EMG activity appears higher in women than in men in the masseter Muscles. In this study no gender differences were found for the perceived amount of Experimental Pain induced by glutamate injection. Additional increases of the resting EMG activity after injections occurred only in men in the injected masseter Muscle and non-injected temporalis Muscles. The present findings provide new information on the complex influence of gender on sensory-motor integration in the trigeminal system which may contribute to differences in susceptibility to develop musculoskeletal Pain problems.
-
effects of masticatory Muscle fatigue without and with Experimental Pain on jaw stretch reflexes in healthy men and women
Clinical Neurophysiology, 2005Co-Authors: M K A Van Selms, Lars Arendtnielsen, Peter Svensson, Kelun Wang, F Lobbezoo, M NaeijeAbstract:Abstract Objective To examine the effects of Experimentally evoked masticatory Muscle fatigue, without and with Experimental Muscle Pain, on the short-latency jaw-stretch reflex, using a randomised crossover design. Methods Reflexes were evoked in both the masseter and temporalis Muscles in 15 men and 13 women. The study was performed in two blocks, both containing 3 Experimental conditions (before, directly after, and 15 min after provocation). Provocation consisted of a fatiguing chewing test, followed by an intramuscular injection of either isotonic saline (IS; non-Painful) or hypertonic saline (HS; Painful). Results No significant effects of the Experimental condition ‘fatigue+IS’ were found for any of the reflex outcome variables. For each Muscle, the ‘fatigue+HS’ condition yielded significantly higher normalized reflex amplitudes than the other conditions. Several Muscles displayed gender differences regarding both onset latency and normalized reflex amplitude. Conclusions Experimentally evoked mild-to-moderate Muscle fatigue does not modulate the human jaw-stretch reflex. On the other hand, Experimental Muscle Pain, evoked after the performance of a fatiguing chewing test, does yield a facilitation of this reflex. The gender differences found in both onset latency and peak-to-peak amplitude stress the need to take gender into consideration in future jaw reflex studies. Significance The sensitivity of the human jaw-stretch reflex can be modulated by HS-induced Muscle Pain; not by Muscle fatigue that is provoked by intense chewing.
-
glutamate evoked neck and jaw Muscle Pain facilitate the human jaw stretch reflex
Clinical Neurophysiology, 2004Co-Authors: Kelun Wang, Peter Svensson, Barry J Sessle, Lars ArendtnielsenAbstract:Abstract Objective Although Pain and neuromuscular function are clearly linked in several clinical conditions manifested in the craniofacial and cervical regions, it is unclear if Pain in these regions influences reflexly evoked activity in the jaw or neck Muscles in humans. The aim of the present study was to test the effects of glutamate-evoked jaw or neck Muscle Pain on the jaw stretch reflex recorded in both jaw and neck Muscles. Methods Nineteen healthy men participated in the study. Electromyographic (EMG) recordings were made from the left masseter (MAL) and right masseter (MAR) Muscles and the right sternocleidomastoid (SCM) and splenius (SP) Muscles. Glutamate (1 M) or isotonic saline was injected into the MAR or right SP in random order and then the other solution was injected 1–3 weeks later. Pain intensity was scored on a 10 cm visual analogue scale. Stretch reflexes were evoked by standardized jaw stretches before, during and 15 min after the end of the Experimental Muscle Pain. Twenty trials were averaged in each condition. Results Pain evoked by MAR or SP glutamate injections was associated with a significant increase in the stretch reflex amplitude recorded in both MAR and SCM. The onset and offset times and duration of the stretch reflex did not change in any Muscle during the various Pain conditions. Injection of isotonic saline into the MAR or SP did not produce any significant change in the reflex parameters in any of the Muscles. Conclusions The results indicate the close interplay between the craniofacial and cervical regions in the neuromuscular changes that may result from musculoskeletal Pain in either region. Significance The changes in neuromuscular activity documented in this study may be involved in the clinical occurrence of altered Muscle activity in the orofacial and cervical regions as a result of deep tissue trauma and Pain.
-
simultaneous modulation of the exteroceptive suppression periods in the trapezius and temporalis Muscles by Experimental Muscle Pain
Clinical Neurophysiology, 2004Co-Authors: Hong You Ge, Peter Svensson, Kelun Wang, Pascal Madeleine, Barry J Sessle, Lars ArendtnielsenAbstract:Abstract Objective To investigate whether the exteroceptive suppression (ES) periods in the trapezius and temporalis Muscles could be simultaneously modulated by either Experimental trapezius Muscle Pain or temporalis Muscle Pain. Methods Fourteen healthy volunteers participated in two sessions with randomised injections of either hypertonic or isotonic saline into the right trapezius Muscle or right temporalis Muscle. The Pain intensity was continuously scored on a 10 cm electronic visual analogue scale. During Muscle contraction, the early (ES1) and late (ES2) reflex in the temporalis and late (ES2) reflex in the trapezius elicited by electrical stimulation of the right infraorbital nerve were recorded pre-, during-, and post-injection. Results Hypertonic saline injection induced local Muscle Pain and referred Pain with the maximal Pain intensity of 6.3±0.5 cm in the right trapezius and 6.7±0.6 cm in the right temporalis Muscles. Injection of either hypertonic or isotonic saline into the right trapezius Muscle was associated with significantly shortened ES2 duration and offset time in the injected right trapezius Muscle. Only injection of hypertonic saline into the right trapezius Muscle could significantly reduce the ES2 offset time and decrease the degree of suppression of ES2 in the right temporalis and left trapezius Muscles. Injection of either hypertonic or isotonic saline into the right trapezius Muscle evoked no changes in ES2 parameters in the left temporalis Muscle. Injection of hypertonic saline, but not isotonic saline, into the right temporalis Muscle caused a significantly shorter ES2 offset time and shorter ES2 duration bilaterally in the temporalis and trapezius Muscles. Conclusions The findings of the present study provide evidence for a bi-directional effects reflecting convergence of Muscle afferents from the trigeminal and upper cervical neural systems in humans, which may partly underlie the manifestations of Pain referral between these two areas.
-
effects of Experimental Muscle Pain on mechanical properties of single motor units in human masseter
Clinical Neurophysiology, 2004Co-Authors: Thomas Gravennielsen, Lars Arendtnielsen, Peter Svensson, M K SohnAbstract:Abstract Objective : Muscle Pain is known to influence Muscle activity but the details of its effects on the mechanical properties of single motor units (SMU) have not been described. We have recently reported a decreased firing rate of SMU in the human masseter Muscle during Painful contractions with a constant force output. Force output can be modulated by the SMU discharge rate in relation to the contractile properties of SMU. Therefore, the objective of the present study was to measure the mechanical properties of SMU in the masseter to clarify the mechanism which underlies the decrease in SMU firing rate during jaw-Muscle Pain. Methods : A spike-triggered averaging (STA) technique was used to determine the mechanical properties of low-threshold SMU in the masseter Muscle recorded with fine wire electrodes during a voluntary isometric contraction. The twitch amplitude, contraction time, and half-relaxation time were determined from the averaged force records before and during Experimental jaw-Muscle Pain induced by injection of 0.2 ml (100 μg/ml) capsaicin in 8 healthy subjects. Injections of 0.2 ml isotonic saline served as a non-Painful control in 11 healthy subjects. Results : The twitch amplitude was significantly increased during capsaicin-evoked Muscle Pain ( P Conclusions : Potentiation of twitch force could be a possible compensatory mechanism to maintain a constant force output during Painful isometric contractions when SMU firing decreases. This finding therefore provides new information on the adaptation of motor function by Muscle Pain.
Dario Farina - One of the best experts on this subject based on the ideXlab platform.
-
divergent response of low versus high threshold motor units to Experimental Muscle Pain
The Journal of Physiology, 2020Co-Authors: Eduardo Martinezvaldes, Dario Farina, Francesco Negro, Deborah FallaAbstract:KEY POINTS The neural strategies behind the control of force during Muscle Pain are not well understood as previous research has been limited in assessing Pain responses only during low-force contractions. Here we compared, for the first time, the behaviour of motor units recruited at low and high forces in response to Pain. The results showed that motor units activated at low forces were inhibited while those recruited at higher forces increased their activity in response to Pain. When analysing lower- and higher-threshold motor unit behaviour at high forces we observed differential changes in discharge rate and recruitment threshold across the motor unit pool. These adjustments allow the exertion of high forces in acutely Painful conditions but could eventually lead to greater fatigue and stress of the Muscle tissue. ABSTRACT During low-force contractions, motor unit discharge rates decrease when Muscle Pain is induced by injecting nociceptive substances into the Muscle. Despite this consistent observation, it is currently unknown how the central nervous system regulates motor unit behaviour in the presence of Muscle Pain at high forces. For this reason, we analysed the tibialis anterior motor unit behaviour at low and high forces. Surface EMG signals were recorded from 15 healthy participants (mean age (SD) 26 (3) years, six females) using a 64-electrode grid while performing isometric ankle dorsiflexion contractions at 20% and 70% of the maximum voluntary force (MVC). Signals were decomposed and the same motor units were tracked across Painful (intramuscular hypertonic saline injection) and non-Painful (baseline, isotonic saline, post-Pain) contractions. At 20% MVC, discharge rates decreased significantly in the Painful condition (baseline vs. Pain: 12.7 (1.1) Hz to 11.5 (0.9) Hz, P < 0.001). Conversely, at 70% MVC, discharge rates increased significantly during Pain (baseline vs. Pain: 19.7 (2.8) Hz to 21.3 (3.5) Hz, p = 0.029) and recruitment thresholds decreased (baseline vs. Pain: 59.0 (3.9) %MVC to 55.9 (3.2) %MVC, p = 0.02). These results show that there is a differential adjustment between low- and high-threshold motor units during Painful conditions. An increase in excitatory drive to high-threshold motor units is likely required to compensate for the inhibitory influence of nociceptive afferent inputs on low-threshold motor units. These differential mechanisms allow the force output to be maintained during acute Pain but this strategy could lead to increased Muscle fatigue and symptom aggravation in the long term.
-
Experimental Muscle Pain increases variability of neural drive to Muscle and decreases motor unit coherence in tremor frequency band
Journal of Neurophysiology, 2015Co-Authors: Utku ş Yavuz, Deborah Falla, Francesco Negro, Dario FarinaAbstract:It has been observed that Muscle Pain influences force variability and low-frequency (<3 Hz) oscillations in the neural drive to Muscle. In this study, we aimed to investigate the effect of experim...
-
reorganization of Muscle synergies during multidirectional reaching in the horizontal plane with Experimental Muscle Pain
Journal of Neurophysiology, 2014Co-Authors: Silvia Muceli, Deborah Falla, Dario FarinaAbstract:Muscle Pain induces a complex reorganization of the motor strategy which cannot be fully explained by current theories. We tested the hypothesis that the neural control of Muscles during reaching in the presence of nociceptive input is determined by a reorganization of Muscle synergies with respect to control conditions. Muscle Pain was induced by injection of hypertonic saline into the anterior deltoid Muscle of eight men. Electromyographic (EMG) signals were recorded from 12 upper limb Muscles as subjects performed a reaching task before (baseline) and after the injection of hypertonic (Pain) saline, and after the Pain sensation vanished. The EMG envelopes were factorized in Muscle synergies, and activation signals extracted for each condition. Nociceptive stimulation resulted in a complex Muscle reorganization without changes in the kinematic output. The anterior deltoid Muscle activity decreased in all subjects while the changes in other Muscles were subject specific. Three synergies sufficed to describe the EMG patterns in each condition, suggesting that reaching movements remain modular in the presence of Experimental Pain. Muscle reorganization in all subjects was accompanied by a change in the activation signals compatible with a change in the central drive to Muscles. One, two or three synergies were shared between the baseline and Painful conditions, depending on the subject. These results indicate that nociceptive stimulation may induce a reorganization of modular control in reaching. We speculate that such reorganization may be due to the recruitment of synergies specific to the Painful condition.
-
low frequency oscillations of the neural drive to the Muscle are increased with Experimental Muscle Pain
Journal of Neurophysiology, 2012Co-Authors: Dario Farina, Leonardo Gizzi, Francesco Negro, Deborah FallaAbstract:We investigated the influence of nociceptive stimulation on the accuracy of task execution and motor unit spike trains during low-force isometric contractions. Muscle Pain was induced by infusion o...
-
the Pain induced change in relative activation of upper trapezius Muscle regions is independent of the site of noxious stimulation
Clinical Neurophysiology, 2009Co-Authors: Deborah Falla, Lars Arendtnielsen, Dario FarinaAbstract:OBJECTIVE: To assess the effect of local excitation of nociceptors at different locations of the upper trapezius Muscle on the spatial distribution of upper trapezius electromyographic (EMG) amplitude during sustained contraction. METHODS: Surface (EMG) signals were recorded from the upper trapezius Muscle with a grid of 10x5 electrodes from nine healthy men during 90 degrees shoulder abduction sustained for 60s. In one Experimental session, the subjects received separate injections of 0.4 ml of hypertonic saline (Experimental Muscle Pain) into the cranial and caudal region of the upper trapezius. In a separate Experimental session the same subjects received two injections of 0.2 ml each of hypertonic saline simultaneously in the cranial and caudal region. The EMG root mean square (RMS) values were computed for each electrode location to provide a topographical map of EMG amplitude. RESULTS: The RMS value averaged across all electrode locations decreased following injection of hypertonic saline (P<0.05) by a similar amount for the two Experimental sessions. The Pain-induced decrease was larger in the cranial than in the caudal region for both Experimental sessions, as evidenced by a shift of the EMG amplitude distribution towards the caudal region of the Muscle (P<0.0001). CONCLUSION: Muscle Pain induces a consistent change in the spatial activation of the upper trapezius Muscle which is independent of the site of noxious stimulation. SIGNIFICANCE: Pain-induced changes in the spatial distribution of Muscle activity may induce overload of specific Muscle regions in the long term.
Thomas Gravennielsen - One of the best experts on this subject based on the ideXlab platform.
-
effect of sustained Experimental Muscle Pain on joint position sense
Pattern Recognition, 2019Co-Authors: Simon J Summers, Siobhan M. Schabrun, Thomas Gravennielsen, Rogerio Pessoto Hirata, Rocco Cavaleri, Lucinda S ChipchaseAbstract:Introduction Joint position sense (JPS) is impaired in clinical musculoskeletal Pain conditions, but when this impairment develops in the transition from initial to prolonged Pain is not known. Objectives This study assessed whether progressively developing sustained Experimentally induced Muscle Pain impacts JPS in healthy individuals. Methods Twenty-eight healthy individuals received injection of nerve growth factor (NGF) into the right extensor carpi radialis brevis Muscle on days 0 and 2 to induce sustained Pain and hyperalgesia. Wrist JPS was assessed 2 days before day 0 (day -2), before the injection on days 0 and 2, and on days 4 and 14. Joint position sense was quantified as the ability to return the wrist to a neutral position following movements in the direction of radial and ulnar deviation. A 3-dimensional motion analysis system was used to calculate absolute, relative, and joint-angle repositioning errors. Numerical rating scale scores of Pain intensity, body chart Pain drawings, and pressure Pain thresholds (PPTs) were recorded on each day. Results Compared with baseline, pressure Pain thresholds decreased while Pain intensity and area increased at day 2 (P 0.13). Relative to day 0, there was no change in wrist JPS at day 2, 4, and 14 following movements in either target direction (P > 0.05). Conclusion Despite the presence of sustained Muscle Pain and hyperalgesia for 4 days at the elbow, no statistical change in wrist joint position error was observed. These findings suggest that Pain and hyperalgesia lasting as long as 4 days does not impair JPS.
-
movement does not promote recovery of motor output following acute Experimental Muscle Pain
Pain Medicine, 2018Co-Authors: Siobhan M. Schabrun, Thorvaldur Skuli Palsson, Tribikram Thapa, Thomas GravennielsenAbstract:Objective To examine the effect of motor activity on the magnitude and duration of altered corticomotor output following Experimental Muscle Pain. Design Experimental, pre-post test. Setting University laboratory. Subjects Twenty healthy individuals. Methods Participants were randomly allocated to a Rest or Movement group. The Rest group sat quietly without moving for the duration of the experiment. The Movement group repeated a unimanual pattern of five sequential keystrokes as quickly and as accurately as possible immediately following the resolution of Pain. Pain was induced into the right extensor carpi radialis brevis Muscle by a bolus injection of 0.5 mL hypertonic saline. Corticomotor output was assessed as motor evoked potentials in response to transcranial magnetic stimulation before, immediately after, and at 10, 20, and 30 minutes following Pain resolution. Pain intensity was recorded every 30 seconds using an 11-point numerical rating scale. Results There was no difference in peak Pain intensity (P < 0.09) or duration (P < 0.2) between groups. Corticomotor output was reduced in both groups (P < 0.002) at 10 minutes (P < 0.002), 20 minutes (P < 0.02), and 30 minutes (P < 0.037) following the resolution of Pain relative to baseline. There was no difference between groups at any time point. Conclusions Performance of motor activity immediately following the resolution of acute Muscle Pain did not alter the magnitude or duration of corticomotor depression. Understanding corticomotor depression in the postPain period and what factors promote recovery has relevance for clinical Pain syndromes where ongoing motor dysfunction, in the absence of Pain, may predispose to symptom persistence or recurrence.
-
modulation of motor variability related to Experimental Muscle Pain during elbow flexion contractions
Human Movement Science, 2015Co-Authors: Christian Ariel Mista, Steffan Wittrup Christensen, Thomas GravennielsenAbstract:Abstract Experimental Muscle Pain typically reorganizes the motor control. The Pain effects may decrease when the three-dimensional force components are voluntarily adjusted, but it is not known if this could have negative consequences on other structures of the motor system. The present study assessed the effects of acute Pain on the force variability during sustained elbow flexion when controlling task-related (one-dimensional) and all (three-dimensional) contraction force components via visual feedback. Experimental Muscle Pain was induced by bolus injection of hypertonic saline into m. biceps brachii, and isotonic saline was used as control. Twelve subjects performed sustained elbow flexion at different levels of the maximal voluntary contraction (5–30% MVC) before, during, and after the injections. Three-dimensional force components were measured simultaneously with surface electromyography (EMG) from elbow flexors and auxiliary Muscles. Results showed that force variability was increased during Pain compared to baseline for contractions using one-dimensional feedback ( P P P
-
Experimental Muscle Pain increases normalized variability of multidirectional forces during isometric contractions
European Journal of Applied Physiology, 2012Co-Authors: Sauro Emerick Salomoni, Thomas GravennielsenAbstract:Pain elicits complex adaptations of motor strategy, leading to impairments in the generation and control of steady forces, which depend on Muscle architecture. The present study used a cross-over design to assess the effects of Muscle Pain on the stability of multidirectional (task-related and tangential) forces during sustained dorsiflexions, elbow flexions, knee extensions, and plantarflexions. Fifteen healthy subjects performed series of isometric contractions (13-s duration, 2.5, 20, 50, 70% of maximal voluntary force) before, during, and after Experimental Muscle Pain. Three-dimensional force magnitude, angle and variability were measured while the task-related force was provided as feedback to the subjects. Surface electromyography was recorded from agonist and antagonist Muscles. Pain was induced in agonist Muscles by intramuscular injections of hypertonic (6%) saline with isotonic (0.9%) saline injections as control. The Pain intensity was assessed on an electronic visual analogue scale. Experimental Muscle Pain elicited larger ranges of force angle during knee extensions and plantarflexions (P < 0.03) and higher normalized fluctuations of task-related (P < 0.02) and tangential forces (P < 0.03) compared with control assessments across force levels, while the mean force magnitudes, mean force angle and the level of Muscle activity were non-significantly affected by Pain. Increased multidirectional force fluctuations probably resulted from multiple mechanisms that, acting together, balanced the mean surface electromyography. Although Pain adaptations are believed to aim at the protection of the Painful site, the current results show that they result in impairments in steadiness of force.
-
Experimental Muscle Pain challenges the postural stability during quiet stance and unexpected posture perturbation
The Journal of Pain, 2011Co-Authors: Rogerio Pessoto Hirata, Ulysses Fernandes Ervilha, Lars Arendtnielsen, Thomas GravennielsenAbstract:Abstract Musculoskeletal Pain impairs postural control and stability. Nine subjects stood as quietly as possible on a moveable force platform before, during, and after Experimental Pain in the right leg Muscles. A moveable force platform was used to measure the center of pressure and provided unexpected perturbations. Lower limb Muscle activity, joint angles, and foot pressure distributions were measured. Hypertonic saline was used to induce Pain in the vastus lateralis, vastus medialis, or biceps femoris Muscle of the right leg. Compared to baseline and control sessions, Pain in the knee extensor Muscles during quiet standing evoked: 1) larger sway area, greater medial-lateral center of pressure displacement and higher speed (P Perspective This article presents the acute responses to leg Muscle Pain on the postural control. This measure could potentially help clinicians who seek to assess how Pain responses may contribute to patient’s postural control and stability during quiet standing and after recovering from unexpected perturbations.
Deborah Falla - One of the best experts on this subject based on the ideXlab platform.
-
divergent response of low versus high threshold motor units to Experimental Muscle Pain
The Journal of Physiology, 2020Co-Authors: Eduardo Martinezvaldes, Dario Farina, Francesco Negro, Deborah FallaAbstract:KEY POINTS The neural strategies behind the control of force during Muscle Pain are not well understood as previous research has been limited in assessing Pain responses only during low-force contractions. Here we compared, for the first time, the behaviour of motor units recruited at low and high forces in response to Pain. The results showed that motor units activated at low forces were inhibited while those recruited at higher forces increased their activity in response to Pain. When analysing lower- and higher-threshold motor unit behaviour at high forces we observed differential changes in discharge rate and recruitment threshold across the motor unit pool. These adjustments allow the exertion of high forces in acutely Painful conditions but could eventually lead to greater fatigue and stress of the Muscle tissue. ABSTRACT During low-force contractions, motor unit discharge rates decrease when Muscle Pain is induced by injecting nociceptive substances into the Muscle. Despite this consistent observation, it is currently unknown how the central nervous system regulates motor unit behaviour in the presence of Muscle Pain at high forces. For this reason, we analysed the tibialis anterior motor unit behaviour at low and high forces. Surface EMG signals were recorded from 15 healthy participants (mean age (SD) 26 (3) years, six females) using a 64-electrode grid while performing isometric ankle dorsiflexion contractions at 20% and 70% of the maximum voluntary force (MVC). Signals were decomposed and the same motor units were tracked across Painful (intramuscular hypertonic saline injection) and non-Painful (baseline, isotonic saline, post-Pain) contractions. At 20% MVC, discharge rates decreased significantly in the Painful condition (baseline vs. Pain: 12.7 (1.1) Hz to 11.5 (0.9) Hz, P < 0.001). Conversely, at 70% MVC, discharge rates increased significantly during Pain (baseline vs. Pain: 19.7 (2.8) Hz to 21.3 (3.5) Hz, p = 0.029) and recruitment thresholds decreased (baseline vs. Pain: 59.0 (3.9) %MVC to 55.9 (3.2) %MVC, p = 0.02). These results show that there is a differential adjustment between low- and high-threshold motor units during Painful conditions. An increase in excitatory drive to high-threshold motor units is likely required to compensate for the inhibitory influence of nociceptive afferent inputs on low-threshold motor units. These differential mechanisms allow the force output to be maintained during acute Pain but this strategy could lead to increased Muscle fatigue and symptom aggravation in the long term.
-
RESEARCH ARTICLE Experimental Muscle Pain Impairs the Synergistic Modular Control of Neck Muscles
2016Co-Authors: Leonardo Gizzi, Frank Petzke, Silvia Muceli, Deborah FallaAbstract:Amotor task can be performed via different patterns of Muscle activation that show regulari-ties that can be factorized in combinations of a reduced number of Muscle groupings (also referred to as motor modules, or Muscle synergies). In this study we evaluate whether an acute noxious stimulus induces a change in the way motor modules are combined to gener-ate movement by neck Muscles. The neck region was selected as it is a region with poten-tially high muscular redundancy. We used the motor modules framework to assess the redistribution of muscular activity of 12 Muscles (6 per side) in the neck region of 8 healthy individuals engaged in a head and neck aiming task, in non-Painful conditions (baseline, isotonic saline injection, post Pain) and after the injection of hypertonic saline into the right splenius capitis Muscle. The kinematics of the task was similar in the Painful and control conditions. A general decrease of activity was noted for the injected Muscle during the Pain-ful condition together with an increase or decrease of the activity of the other Muscles. Sub-jects did not adopt shared control strategies (motor modules inter subject similarity at baseline 0.73±0.14); the motor modules recorded during the Painful condition could not be used to reconstruct the activation patterns of the control conditions, and the Painful stimulus triggered a subject-specific redistribution of muscular activation (i.e., in some subjects the activity of a given Muscle increased, whereas in other subjects it decreased with Pain). Alterations of afferent input (i.e., Painful stimulus) influenced motor control at a multi muscu-lar level, but not kinematic output. These findings provide new insights into the motor adap-tation to Pain
-
Experimental Muscle Pain increases variability of neural drive to Muscle and decreases motor unit coherence in tremor frequency band
Journal of Neurophysiology, 2015Co-Authors: Utku ş Yavuz, Deborah Falla, Francesco Negro, Dario FarinaAbstract:It has been observed that Muscle Pain influences force variability and low-frequency (<3 Hz) oscillations in the neural drive to Muscle. In this study, we aimed to investigate the effect of experim...
-
Experimental Muscle Pain induces a shift of the spatial distribution of upper trapezius Muscle activity during a repetitive task
Physiotherapy, 2015Co-Authors: Marco Barbero, Corrado Cescon, René Lindstroem, Deborah FallaAbstract:Background. Myalgia frequently affects the upper trapezius Muscle, and patients typically complain of dull Pain and stiffness. Evidence suggests a correlation between repetitive movements, awkward posture, and the development of neck-shoulder Muscle Pain. However the mechanisms underlying these associations remain unclear. Purpose. To investigate the effect of Experimentally induced upper trapezius Muscle Pain on the distribution of upper trapezius Muscle activity during a repetitive task. It was hypothesized that Pain would change the distribution of Muscle activity resulting in activation of upper trapezius Muscle regions which would not normally be active during the task. Methods. Ten healthy male (age: 26.2 ± 3.1 years) volunteers participated. Subjects lifted a 1 kg box between shelves positioned at hip and shoulder height with a cycle time of 3 s for 50 cycles. The task was repeated: 1. baseline, 2. following injection of 0.4 ml isotonic saline (0.9%) into the right upper trapezius Muscle, 3. following injection of 0.4 ml hypertonic saline (5.8%) into the right upper trapezius Muscle and 4. 15 mins after the last injection. Pain intensity ratings were obtained immediately following the injection and every 30 s until Pain was no longer reported. Surface electromyography (EMG) was recorded from the upper trapezius Muscle using a grid of 64 electrodes and 4 uniaxial accelerometers were mounted on the box to obtain the start and end points of the cyclic movement. The EMG root mean square (RMS) was computed for each location of the electrode grid to form a map of the EMG amplitude distribution.The following EMG variables were extracted from the RMS maps: mean RMS, entropy, and y- (cranial-caudal) and x-axis (medio-lateral) coordinates of the centroid of the RMS map. The EMG variables were then averaged across the 50 cycles for each epoch of the cycle. Results. Peak Pain intensity was greater following the injection of hypertonic (4.7 ± 1.9/10) compared to isotonic saline (0.8 ± 1.1, P 0.05). Conclusions. The results indicate that nociceptive stimulation of the upper trapezius during a repetitive task changes the distribution of upper trapezius Muscle activity and its amplitude. Implications. The described alterations of Muscle activity may have an important role in the perpetuation of Pain during repetitive activity.
-
Experimental Muscle Pain impairs the synergistic modular control of neck Muscles
PLoS ONE, 2015Co-Authors: Leonardo Gizzi, Frank Petzke, Silvia Muceli, Deborah FallaAbstract:A motor task can be performed via different patterns of Muscle activation that show regularities that can be factorized in combinations of a reduced number of Muscle groupings (also referred to as motor modules, or Muscle synergies). In this study we evaluate whether an acute noxious stimulus induces a change in the way motor modules are combined to generate movement by neck Muscles. The neck region was selected as it is a region with potentially high muscular redundancy. We used the motor modules framework to assess the redistribution of muscular activity of 12 Muscles (6 per side) in the neck region of 8 healthy individuals engaged in a head and neck aiming task, in non-Painful conditions (baseline, isotonic saline injection, post Pain) and after the injection of hypertonic saline into the right splenius capitis Muscle. The kinematics of the task was similar in the Painful and control conditions. A general decrease of activity was noted for the injected Muscle during the Painful condition together with an increase or decrease of the activity of the other Muscles. Subjects did not adopt shared control strategies (motor modules inter subject similarity at baseline 0.73±0.14); the motor modules recorded during the Painful condition could not be used to reconstruct the activation patterns of the control conditions, and the Painful stimulus triggered a subject-specific redistribution of muscular activation (i.e., in some subjects the activity of a given Muscle increased, whereas in other subjects it decreased with Pain). Alterations of afferent input (i.e., Painful stimulus) influenced motor control at a multi muscular level, but not kinematic output. These findings provide new insights into the motor adaptation to Pain.
