EMG Burst Duration Research Articles

Neuromotor and Musculoskeletal Responses to Locomotor Training for an Individual With Chronic Motor Complete AIS-B Spinal Cord Injury

Background/objective: To determine the effects of locomotor training (LT)using body weight support(BWS), treadmill, and manual assistance on muscle activation, bone mineral density (BMD), and body composition changes for an individual with motor complete spinal cord injury (AIS B), 1 year after injury.Methods: A man with chronic C6 AIS B (motor complete and sensory incomplete) spinal cord injury (SCI),1 year after injury, completed 2 blocks of LT over a 9-monthtraining period (35-session block followed by8.6 weeks of no training and then a 62-session block).Results: Before training, muscle activation was minimal for any muscle examined, whereas after the 2 blocksof LT (97 sessions), hip and knee muscle activation patterns for the bilateral rectus femoris, biceps femoris,and gastrocnemius were in phase with the kinematics. Mean EMG amplitude increased for all bilateral muscles and burst duration increased for rectus femoris and gastrocnemius muscles, whereas burst duration decreased for the biceps femoris after 62 LT sessions. Before LT, left biceps femoris had a pattern that reflected muscle stretch, whereas after training, muscle stretch of the left biceps femoris could not totally account for mean EMG amplitude or burst duration. After the62 training sessions, total BMD decreased (1.54%), and regional BMD decreased (legs: 6.72%). Total weight increased, lean mass decreased (6.6%), and fat mass increased (7.4%) in the arms, whereas fat mass decreased (3.5%) and lean mass increased (4%) in the legs.Conclusions: LT can induce positive neural and body composition changes in a nonambulatory personwith chronic SCI, indicating that neuromuscular plasticity can beinduced by repetitive locomotor trainingafter a motor complete SCI.

A Woman with Rhythmic Foot Movements

A Woman with Rhythmic Foot Movements

Epidural Spinal Cord Stimulation Plus Quipazine Administration Enable Stepping in Complete Spinal Adult Rats

We hypothesized that epidural spinal cord stimulation (ES) and quipazine (a serotonergic agonist) modulates the excitability of flexor and extensor related intraspinal neural networks in qualitatively unique, but complementary, ways to facilitate locomotion in spinal cord-injured rats. To test this hypothesis, we stimulated (40 Hz) the S(1) spinal segment before and after quipazine administration (0.3 mg/kg, ip) in bipedally step-trained and nontrained, adult, complete spinal (mid-thoracic) rats. The stepping pattern of these rats was compared with control rats. At the stimulation levels used, stepping was elicited only when the hindlimbs were placed on a moving treadmill. In nontrained rats, the stepping induced by ES and quipazine administration was non-weight bearing, and the cycle period was shorter than in controls. In contrast, the stepping induced by ES and quipazine in step-trained rats was highly coordinated with clear plantar foot placement and partial weight bearing. The effect of ES and quipazine on EMG burst amplitude and duration was greater in flexor than extensor motor pools. Using fast Fourier transformation analysis of EMG bursts during ES, we observed one dominant peak at 40 Hz in the medial gastrocnemius (ankle extensor), whereas there was less of dominant spectral peak in the tibialis anterior (ankle flexor). We suggest that these frequency distributions reflect amplitude modulation of predominantly monosynaptic potentials in the extensor and predominantly polysynaptic pathways in the flexor muscle. Quipazine potentiated the amplitude of these responses. The data suggest that there are fundamental differences in the circuitry that generates flexion and extension during locomotion.

Évolution de l'activité électromyographique au cours d'un test de pédalage de temps limite à 100 % de puissance maximale aérobie

Introduction. – The aim of this study was to analyse the evolution of neuromuscular fatigue in vastus lateralis and gastrocnemius medialis muscles during all-out cycling test at 100% maximal aerobic power. Fact synthesis. – Mean EMG increased from the beginning of the test and then decreased after have attained its maximum for all subjects and for both muscles, whereas the EMG burst duration remained constant. Conclusion. – The decrease of muscular activity towards the end of the test, whereas the intensity remains constant, seems to indicate synergist muscles activation, i.e. a mechanism of adaptation underlying the fatigue process.

Reliability of elbow stretch reflex assessment in chronic post-stroke hemiparesis

Objective To establish reliability of quantitative measures of elbow joint spastic hypertonia in post-stroke hemiparesis. Methods Nine subjects with post-stroke hemiparesis (mn duration: 42 months) were tested on three separate days. Biceps brachii and brachioradialis EMG were recorded during passive ramp-and-hold extensions applied at seven speeds between 30 and 210 °/s. EMG burst duration, onset position threshold, and burst intensity were used to evaluate reflex activity. Torque at 40° of elbow flexion was used as a mechanical indicator of spastic hypertonia. Results Across speeds ICCs were consistent, means ranged between 0.63 and 0.85. Thus, relative reliability was fair to excellent for all parameters. Absolute reliability, determined using standard error of measurement expressed as a percentage of the mean score (%SEM), improved at higher speeds (≥120 °/s). Conclusions These results establish reliability of reflex and mechanical measures of elbow spastic hypertonia post-stroke. The data demonstrate greater reflex detection at high speeds, indicating greater potential to document meaningful changes in these distinct aspects of spastic hypertonia following intervention. Significance Based on findings of this study, reliability was demonstrated using four parameters of reflex EMG and torque indicating measurement consistency across sessions. These observations motivate determination of requisite effect sizes for clinical trials that evaluate treatment outcome.

Trunk movements and EMG activity in the cat: level versus upslope walking

This chapter addresses the neural control of spinal-column behavior during locomotion. Kinematic and EMG measurements were obtained from the adult cat during its level and upslope treadmill walking. Increasing the grade of upslope walking augmented horizontal movements of the spinal column and decreased its lateral movements. In conjunction, there were significant increases in the amplitude, duration, and pattern of EMG bursts in relevant spinal column musculature. During even steeper upslope walking, three EMG bursts were evident. They were phase-locked to the outward, downward and backward movements of the spinal column, respectively. Our results suggest that the component of the locomotor pattern generator that produces rhythmical spinal column movements must generate a wide variety of EMG bursts in spinal column muscles, as dependent in part on sensory input from the spinal column and its musculature.

Determination of Electromyogram Biofeedback Threshold for Patients with Clenching Behavior

Purpose : The aim of this study was to investigate the EMG biofeedback threshold suitable for patients having masticatory muscle pain due to clenching behavior.Materials and Methods : EMGs from the unilateral anterior area of the temporal muscle in 18 subjects suffering masticatory muscle pain or stiffness were recorded by a one-channel portable EMG biofeedback apparatus.Results : Sixteen of the subjects (88.8%) were found to have valid thresholds. The threshold of 30% maximum voluntary contraction (MVC) EMG level for 2s provided the highest accuracy rate at 81.3%.Conclusion : EMG biofeedback training with the threshold utilizing combined EMG amplitude and burst duration is thought to be useful as a therapeutic strategy for patients with clenching behavior.

Red muscle function during steady swimming in brook trout, Salvelinus fontinalis

Red muscle function during steady swimming in brook trout was studied through both in vivo swimming and in vitro muscle mechanics experiments. In the swimming experiments, red muscle activity was characterized through the use of electromyography and sonomicrometry, allowing the determination of several parameters such as tailbeat frequency, EMG burst duration, muscle length change patterns and relative phase of EMG activity and length change. Brook trout do show some shifts in these variables along their length during steady swimming, but the magnitude of these shifts is relatively small. In the muscle mechanics experiments, the in vivo muscle activity data were used to evaluate patterns of power production by red muscle during swimming. Unlike many fish species, the red muscle along the length of brook trout shows little change in isometric kinetic variables such as relaxation rate and twitch time. Furthermore, there is no rostral–caudal shift in red muscle mass-specific power output during steady swimming. This last result contrasts sharply with rainbow trout and with a variety of other fish species that power steady swimming primarily with the posterior red myotome.

External anal sphincter hyperreflexia following spinal transection in the rat.

In the present study, long-term and short-term rat preparations were used to develop a model for investigating external anal sphincter (EAS) reflexes in intact and spinal cord-injured (SCI) rats. In this model, EAS distension with an external probe elicits reflex contractions of the EAS in intact, unanesthetized animals. At 2 h after spinal cord transection, none of the lesioned animals displayed EAS EMG activity. In fact, once distended, the EAS was incapable of maintaining closure of the anal orifice. Over a period of 4 days, spinalized animals developed a hyperreflexia of the EAS response. By 48 h, the rectified, integrated EAS EMG was significantly elevated in comparison with nonlesioned controls (EAS hyperreflexia). In addition, the duration of the EAS EMG bursts in response to sphincter distension had significantly increased. At 6 weeks after injury, the EAS was significantly hyperreflexic as measured by EMG burst duration and burst area. As with intact animals, posttransection EAS reflexes were highly anesthesia sensitive. These studies indicate that (1) brief distension of the anal orifice is sufficient to evoke a physiologically relevant reflexive activation of the EAS in the rat, (2) the 2- to 24-h postinjury areflexia observed in these experiments may be a suitable model for the study of spinal shock, and (3) the observed EAS hyperreflexia after chronic SCI may represent the permanent effects of removing descending inhibitory circuits and segmental plasticity, making this reflex an appropriate measure of defecatory dysfunction after spinal cord injury.

Mu-rhythm changes in brisk and slow self-paced finger movements.

We analysed whether type of movement (brisk vs slow) and active muscle force are encoded in the time course of mu-rhythm desynchronization during self-paced finger movements. Ten subjects performed 100 brisk and slow extensions of the right index finger. The time course of mu-rhythm desynchronization in the contralateral sensorimotor area before movement was identical for both types of movements. Brisk movements accompanied by a stronger extensor muscle contraction were preceded by larger desynchronization. The onset of mu-rhythm recovery was related to the duration of the extensor EMG burst in both types of movement. The results suggest that both amplitude and duration of the extensor muscle contraction are encoded in the time course of murhythm desynchronization.

Desynchronization and recovery of β rhythms during brisk and slow self-paced finger movements in man

Event-related desynchronization (ERD) and recovery of EEG β rhythms (15–26 Hz) were studied during slow and brisk self-paced index finger extension and flexion. β rhythms started to recover earlier in brisk movements. Brisk movements showed no correlation between duration of EMG burst in the extensor muscle and the latency of recovery whereas slow movements did. In contrast to β-ERD which was widespread, the recovery and rebound of β rhythms occurred in a circumscribed focus close to the hand MI area.

The effect of behavioural state on general movements in healthy full-term newborns. A polymyographic study

In a group a eight healthy full-term newborns 6-h polygraphic recordings, which included EMG recording of eight arm muscles, were made to investigate the effect of behavioural state on general movement (GM) organization. Simultaneous video recordings supplied information about the form of the GMs. Additionally the effect of non-nutritive sucking during State 4 was evaluated. Behavioural state had a distinct effect on the makeup of GMs. GMs during State 4 displayed best the fluency and elegance which are characteristic of normal GMs. State-1-GMs were rare, had a short duration and sometimes had an abrupt onset. During State 2 GMs had a fragmented appearance. EMG differences between GMs in State 2 and State 4 were demonstrated in burst duration (longer during State 2) and tonic background activity in the upper arm muscles (lower during State 2). Occasionally State-2-GMs had an abrupt onset. These abrupt GMs were less often preceded by rapid eye movements and heart rate changes than State-2-GMs with a gradual onset. GMs during State 5 were abrupt and vigorous and often had a high frequency tremor superimposed. The EMGs of State-5-GMs revealed a shorter interval between the EMG bursts and a higher EMG burst amplitude in the upper arm muscles than present during State-4-GMs. Non-nutritive sucking during State 4 induced a reduction of movement amplitude, a increase of EMG burst duration and an increase of tonic background activity in the biceps brachii and the extensor carpi muscles.

The fatigue of rapid repetitive movements.

Normal subjects (n = 7) performed rapid voluntary isometric contractions of the adductor pollicis and the tibialis anterior. Within the first minute of this low-intensity exercise, the speed of tension development slowed, accompanied by a prolongation in EMG burst duration. In contrast, electrically evoked contractions either became more rapid (twitch) or did not change (tetanus), suggesting a fatigue of central origin. 31P NMR measurements of high-energy phosphates showed that the relationship between the fall of maximum force and changes of phosphates and pH was similar to that produced by other high-intensity fatiguing exercise protocols. Thus, rapid movements produce fatigue through two major mechanisms. First, there is slowing of the speed of tension development which appears secondary to central fatigue. Second, the decline of muscle force is primarily attributable to changes in muscle pH or inorganic phosphate, which usually occurs only after high-intensity (but non-rapid) exercise.

総義歯装着者のそしゃく機能に関する臨床的研究 床下粘膜の触・圧感覚の違いがそしゃく筋活動に及ぼす影響

The mechanisms of controling mastication in complete denture wearers who have lost the natural tooth proprioception are poorly defined as yet. In the present study, the contributionof sensory inputs from denture supporting mucosa to regulate the masticatory movementwas examined electromyographycally. In experimental dentures, a metal half hemisphere (0.5 mmdiam.) was attached on the premolar region of the mucosal surface of the habitual chewing sideof either upper or lower denture as mechanical stimulation (innoxious). Surface EMGs of bilateralmasseter (Mm) and posterior temporal (Tp) muscles were recorded simultaneously with Sirognathograph (SGG) during mastication of two types of test foods on the habitual side. The data was statistically computed by means of analysis of variance.The results were as follows:1. In EMG burst duration after occlusal contact, in SGG occluding phase time ratio andmaximum opening distance showed different reactions between soft and tough foods wearingexperimental denture and marked difference in lower experimental denture.2. Integrated potential of the EMG increased wearing experimental denture and the grindingmotion exaggerated because of an increased integrated potential of balancing side Tp in lowerexperimental denture.3. CV values of EMG time paramreters and integrated potential increased wearing experimentaldenture and markedly increased in lower experimental denture.From these results, it was suggested that the mechanoreceptors in the denture supportingmucosa might play an important role in the control of sensory feedback on masticatory function ofthe complete denture wearers.

そしゃく筋の疲労時と回復期におけるガムそしゃく時の筋電図解析

An EMG computer analysis system was developed to analyze the mandibular function. The system enabled measurements of the masticatory muscle's rhythm, activity, and power spectrum for the same EMG burst during mastication. This study revealed that a power spectrum analysis was able to be carried out by a fast Fourier transform algorithm of the isometric contraction components of EMG bursts during mastication. The normal regulatory mechanism of the mandibular function was temporarily disturbed by clenching to inflict fatigue upon the masticatory muscles. EMG analysis of the masticatory muscles during gum chewing were observed before and immediately after clenching, and during their recovery periods. After fatigue induction, all of the masticatory rhythms of the masticatory muscles showed a decrease in EMG burst duration time (duration) and duration per cycle (D/C) that recovered with time. However, only the coefficient variation of the duration and D/C in the working side increased immediately after fatigue induction. The power spectrum shifted to a lower frequency immediately after fatigue induction, and recovered along with time. Furthermore, it was found that EMG activity influenced the power spectrum during gum chewing. In conclusion, this EMG analysis system may be used as a possible future diagnostic aid for mandibular dysfunction syndromes.

Induction of rhythmic jaw movements by stimulation of the mesencephalic reticular formation in the guinea pig

This study was designed to investigate whether stimulation of the mesencephalic reticular formation (MRF) induces rhythmic jaw movements (RJMs) and, if it does so, to determine the RJM-inducing region in the MRF in ketamine-anesthetized guinea pigs. The results were as follows: (1) Repetitive electrical stimulation of the MRF at the level of the red nucleus induced rhythmic EMG bursts in the anterior digastric muscle (DIG). (2) The duration and cycle time of the rhythmic DIG EMG burst induced from the medial MRF were longer than those induced from the lateral MRF. (3) Repetitive MRF stimulation after paralysis still induced rhythmic multiple-unit activities in the anterior digastric motoneuron pool. (4) Neither precollicular decerebration nor cerebellectomy affected the MRF induction of RJMs. (5) Transverse hemisection at the rostral border of the pons abolished the RJMs induced from the contralateral, but not ipsilateral, MRF. Midline section of the midbrain abolished RJMs induced from the MRF on either side. (6) A lesion in the pontine pyramidal tract abolished the RJMs induced by stimulation of the ipsilateral cortical masticatory area (CMA), but not those induced from the contralateral MRF. (7) A unilateral lesion of the oral portion of the gigantocellular reticular nucleus, where the rhythm generator for the CMA-induced RJMs is located, abolished RJMs induced from not only the CMA, but also MRF on the contralateral side. (8) Microinjection of L-glutamate into the lateral, but not medial, MRF induced RJMs similar to those elicited by repetitive electrical stimulation of the same site.(ABSTRACT TRUNCATED AT 250 WORDS)

The control of oscillatory movements of the forearm.

The patterns of EMG activity in the biceps and triceps muscles were recorded during horizontal oscillatory movements of the forearm. Subjects showed increased frequency of oscillation as they voluntarily reduced movement amplitude. EMG burst duration was significantly correlated with wavelength of oscillation in every case. In almost half the cases burst intensity was also positively correlated with wavelength. Subjects seemed to be using one or both these methods to control amplitude. A model was developed in three stages which satisfactorily accounted for the data.

Locomotor deficits in the mutant mouse, Lurcher.

The effect of total Purkinje cell degeneration on treadmill locomotion was studied in the cerebellar mutant mouse Lurcher. Other movements such as swimming and scratching were also studied in order to evaluate the cerebellar control of rhythmic actions. Cinematographic and electromyographic recordings were taken from normal and Lurcher mice that were subsequently perfused to obtain a Purkinje cell count. Walking deteriorated progressively and was clearly abnormal in 30 day old Lurchers with 90% Purkinje cell degeneration. In adult Lurcher mice in which Purkinje cells were totally absent, walking was characterized by short steps with exaggerated hindlimb flexion in the swing phase. Also, both the interlimb step ratio, defined as the step length of the reference limb divided by the step length of the opposite limb, and the interlimb coupling, defined as the temporal relation of one footfall with respect to the footfall of another limb, varied more than in normal mice. Furthermore, the locomotion of Lurcher mice displayed increased vertical displacement of the hip and an inability to produce continuous step cycles without stumbling. Both the EMG onset relative to foot contact and the EMG burst duration were highly variable, and a greater overlap in the activities of antagonist muscles at the transition from ankle extension to flexion was evident. Although both walking and swimming involve cyclical limb movements, the disorganization of the cycle and the irregular EMG pattern seen in the Lurcher during walking were not observed during swimming. Furthermore, scratching was well executed in the Lurcher mice. However, a consistently higher tonic extensor activity at the ankle appeared during walking, swimming and scratching. These results suggest that, in contrast to swimming and scratching, the requirements of walking depend to a greater degree on a functional cerebellar cortex for successful performance.

Scaling of the size of the first agonist EMG burst during rapid wrist movements in patients with Parkinson's disease.

Rapid wrist flexion movements were studied in a group of 10 patients with Parkinson's disease both on and off their normal drug therapy, and were compared with the same movements made by a group of eight normal individuals. When normal subjects made movements through 60 degrees, the first agonist burst of EMG activity in the wrist flexor muscles was longer and larger than that seen in movements of 15 degrees. If a large opposing load of 2.2 Nm was added, this also increased the size and duration of the first agonist EMG burst. Although the movements made by the patients were slower than those of normals, the size and duration of the first agonist EMG burst changed with movement size and added load in the normal way. This shows that patients can produce large, long bursts of EMG activity, but that there is a failure to match these parameters appropriately to the size of movement required. The effect of levodopa therapy on the movements was not dramatic. Although patients produced faster wrist movements when on medication than when off, the change was relatively small compared with the change seen in their overall clinical rating. Changes in the velocity of movements at a single joint are not a good reflection of the overall clinical state of patients with Parkinson's disease.

Afferent perturbations during "monopodal" swimming movements in the turtle: phase-dependent cutaneous modulation and proprioceptive resetting of the locomotor rhythm

Locomotion consists of a repeating series of movement cycles (locomotor rhythm) with an orderly activation of musculature during each movement cycle (intracycle motor pattern). The effects of sensory stimulation, on both the intracycle motor pattern and the locomotor rhythm, were examined during electrically elicited swimming movements of a single turtle hindlimb. The resulting "monopodal" swimming was not subject to movement-related reflexes from other limbs or postural constraints, and provided a sensitive system for analyzing the effects of transient sensory perturbations. During "monopodal" swimming, cutaneous and extensor muscle-nerve stimulation (single 0.1- to 0.3-msec electrical pulse) had similar phase-dependent effects on the swim cycle in progress. Stimuli delivered during the powerstroke (limb retracting) shortened the period of the cycle. Stimulation during the returnstroke prolonged the cycle. Changes in cycle period were accompanied by in-phase adjustments of the EMG burst duration or interburst interval which was being expressed at the time of stimulus delivery. The in-phase adjustment of each muscle served to maintain the timing relationships between muscles, and resulted in the preservation of the intracycle motor pattern. Cutaneous and muscle-nerve stimulation had dramatically different effects on the locomotor rhythm. Cutaneous nerve stimulation produced period changes in poststimulus cycles which led to a temporary phase shift of the swimming rhythm. This temporary modulation suggests that cutaneous afferents do not have direct access to the timing circuitry of the central nervous system locomotor network. Muscle-nerve stimulation only altered the period of the cycle in progress at the time of stimulus delivery, and thus permanently reset the locomotor rhythm. This permanent phase shift suggests that muscle afferents have direct access to a central timing network which controls the locomotor rhythm.