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PubMedDate not supplied

[Function of back extensor muscles in upright standing position and during sitting with identical back posture--an electromyography study].

PROBLEM: There is a controversial discussion about the loading of the spine by the force of the extending muscles of the back in upright sitting with the back curved as in upright standing. Experimental studies investigating this issue are still lacking. METHODS: In the study presented in this paper we measured in 30 subjects the activity of the extending back muscles both in a natural upright standing posture and in sitting with identical posture of the back as recommended in some back training programs. To this end we recorded the electromyographical surface activity of the back muscles at four levels of the spine in both postures. The EMG activities were intraindividually normalized with reference to the respective activity recorded at maximum voluntary isometric contraction (MVC). RESULTS: At three of the four levels of the spine examined, the group averages of the EMG activity in sitting were significantly higher than in standing (p < 0.001). The maximum activity enhancement evaluated was 48% at Th12. The force of the lower back muscles in sitting with a posture of the back as in natural upright standing could be estimated to be at least greater than 30% of the force at MVC. CONCLUSION: The force needed to enforce in sitting a posture of the back identical to the posture at natural standing entails lower back muscle fatigue in a few minutes. The results of our study agree with recent experimental findings about an increased loading of the spine in lordotic sitting.

Adolescent↗
PubMed2001

[Electromyography of the infrahyoid muscles - part 1: normal findings].

BACKGROUND: The infrahyoid muscles (IHM) are very useful as a neurovascular myofascial flap in plastic reconstructive surgery of the upper aerodigestive tract, especially for restoration of the muscular component in larger tongue defects. As a base for further postoperative investigations on the function of transferred IHM this first part of the study describes the physiological function and the electromyographical features of the IHM. METHODS: In 17 patients with cancer of the upper aerodigestive tract the sternohyoid and sternothyroid muscles and in additionally eight patients the upper part of the omohyoid muscle were studied electromyographically. Muscular activity was recorded at various movements and maximal voluntary innervation. In ten healthy volunteers the motor unit potentials (MUP) during light voluntary innervation of these muscles were studied. RESULTS: In both muscles we found the steadist and strongest muscular activity at isometric head bending and yaw opening, in the omohyoid muscle also at head rotation. At swallowing and breathing in (2/3) of the cases muscular activity could be recorded. Amplitudes and electromyographic charge pattern in comparison were diminished. Phonation und tongue movements showed no noticable muscular activity. Analysis of the MUP in 10 healthy volunteers showed a mean amplitude of 274 +/- 59 microV and a mean duration of 8.5 +/- 0.6 ms. CONCLUSIONS: The presented study demonstrates that EMG of the IHM are recorded best while head bending, yaw opening and head rotation. Since there is no interchange of nerve fibres between the hypoglossal nerve and the cervical ansa it should be possible to differentiate between original tongue muscles and transferred muscles in electromyographic studies of myofascial flaps after tongue reconstruction.

Deglutition↗
PubMed1990

[Extensive, continuous fasciculations of the lower leg as an isolated symptom--a clinical and electromyography follow-up].

10 patients suffering from a widespread continuous fasciculation of the lower extremities without any other neurological signs and symptoms are presented. A follow up study of 6 of these patients could be done. The fasciculation potentials were polyphasic with changing shape from discharge to discharge and appeared irregularly in most of the muscles of the legs. In 5 patients no change of clinical and neurophysiological signs could be detected over the period of observation, whereas in one patient a sensory polyneuropathy was evident in course of time. The findings illustrate that a state of widespread continuous fasciculations without other signs and symptoms is not predicative for the development of a amyotrophic lateral sclerosis.

Adult↗
PubMed1998

Kinematics and electromyography of lower limb muscles in overground and treadmill running.

Treadmills are often used in research to analyse kinematic and physiological variables. The success of transfering the results to overground running depends on the comparability of the values between the two situations. The aim of the present study was to compare the kinematics and muscle activities in overground and treadmill running. Ten male physical education students with experience in treadmill running were asked to run with a speed of 4.0 and 6.0 m/s both overground and on a Woodway treadmill. The 3D-kinematics of the limbs were studied using a two camera video tracking system. Additionally the surface EMG of six lower limb muscles and the pattern of ground contact of the right foot was registered. Both the activities of the leg muscles and several kinematic variables showed systematic changes from overground to treadmill running. On the treadmill the subjects favoured a type of running that provided them with a higher level of security. The swing amplitude of the leg, the vertical displacement and the variance in vertical and horizontal velocity were lower in treadmill running. The angle between shoe sole and ground at foot impact was also lower and the forward lean of the upper body was higher in running on the treadmill compared with the overground mode. Most of the subjects reduced their step length and increased stride frequency in treadmill running. Furthermore, the contact time in treadmill running was shorter than for overground running. The above mentioned kinematic variables were significantly different (p < 0.05). The EMG patterns of the leg muscles were generally similar between overground and treadmill modes, but some minor differences could consistently be identified.

Adult↗
PubMed1997

[Electromyography-controlled muscle rehabilitation--knee injuries].

Surface is a noninvasive, mostly nonreactive, objective measuring procedure for evaluation of the degree of muscle activation. It allows for accurate assessments of the neuromuscular system and description of adaptations resulting from injury. Decreases in torque, EMG amplitude and EMG frequency occur as a result of knee joint injuries. Efficiency checks and evaluations of training programs and neuromuscular treatment can be done. Decreases in torque, EMG amplitude and EMG frequency found after knee joint injury (cruciate ligament, meniscus) are due to intraarticular and periarticular afferent processes. 12 weeks postoperatively, the neuromuscular deficits from cruciate ligament injury have increased. While complete recovery can be achieved following meniscus fixation (more than 1 year postoperatively), cruciate ligament injuries lead to chronically reduced EMG median frequencies.

Athletic Injuries↗
PubMedDate not supplied

[Proprioceptive regulation of standing in the human. An electromyography study].

Electromyographic experiments, undertaken in connection with action of standing, are here described. A short, sharp push given in an anterior or posterior direction caused an abrupt upsetting of balance, whereby adaptive reactions of the relevant muscles were found to occur after an interval of 60 to 90 msecs. These reactions, although having become automatic as a result of the early-acquired upright posture, are in fact of a voluntary nature and fully controllable by the will. It is demonstrated that these reactions are very probably due to stimulation of deep mechano- and joint-receptors. They do not have anything to do with a functional stretchreflex mechanism.

Adult↗
PubMed1990

Electromyography in disorders of neuromuscular transmission.

Electrophysiologic tests in neuromuscular transmission disorders are valuable aids in the clinical assessment of patients with suspected disease. The techniques of RNS and SFEMG are most reliable when the electromyographer is aware of their pitfalls and when they are interpreted in relation to the overall clinical setting. RNS is the most widely used technique to assess the integrity of neuromuscular transmission but may be normal in many patients. Among the techniques used to assess abnormality of neuromuscular transmission, SFEMG is the most sensitive.

Electromyography↗
PubMed2002

Clinical considerations in the use of surface electromyography: three experimental studies.

BACKGROUND: The validity and applicability of erector spinae electromyogram (EMG) use in clinical practice is questionable. Differences in the amplitude of the EMG signal between populations with low back pain (LBP) and controls have been hypothesized but not sufficiently documented. OBJECTIVE: To examine issues of EMG asymmetry and repeatability in populations with LBP and populations without LBPin 3 separate studies. STUDY DESIGN: Three separate experimental research studies. METHODS: Study 1 examined the intraclass correlation of the EMG signal of the paraspinal musculature at L3 on 3 separate days during quiet stance with use of 3 different normalization techniques: percent maximum voluntary contraction, percent submaximal voluntary contraction, and percent averaged submaximal contractions. Study 2 used a population with chronic LBP to compare the bilateral asymmetry of paraspinal musculature in segments exhibiting pain with segments not exhibiting pain during quiet stance. A 1-way analysis of variance was used to compare differences between asymmetry scores in the pain and nonpain groups. In study 3, persons with LBP and persons in the control group had the dynamic asymmetry of paraspinal musculature compared during forward bending. A cross-correlation coefficient assessing bilateral muscle activity was calculated for each subject and differences between groups were evaluated using a 1-way analysis of variance. RESULTS: Study 1: Subjects showed excellent repeatability (ICC > 0.75) regardless of the normalization technique. Study 2: During quiet stance no differences were found in bilateral asymmetry between painful and nonpainful motion segments. Study 3: No differences existed in bilateral dynamic symmetry for the upper erector spinae; however, differences between groups did exist for the lower erector spinae. CONCLUSION: Repeatability of the EMG signal during quiet stance is acceptable; however, bilateral asymmetry may not be a definitive indicator of dysfunction.

Adult↗
PubMed2000

Pelvic muscle electromyography of levator ani and external anal sphincter in nulliparous women and women with pelvic floor dysfunction.

OBJECTIVE: The purpose of this study was to compare results of electromyographic assessment of muscular recruitment between nulliparous control subjects without pelvic floor dysfunction and parous subjects with genuine stress urinary incontinence and with pelvic organ prolapse. Interference pattern analysis is an electromyographic technique that reproducibly measures muscular recruitment by detecting both "turns" in the electromyographic signal produced by positive and negative peaks of the motor unit potentials and motor unit potential amplitude. Fewer turns can indicate loss of motor units or failure of central activation of contraction, whereas greater amplitude can indicate reinnervation after nerve damage. STUDY DESIGN: We performed concentric needle electrode electromyographic examinations of the levator ani and external anal sphincter in 15 nulliparous control subjects and 20 parous subjects with abnormalities (n = 9 with genuine stress urinary incontinence, n = 11 with stage III or IV pelvic organ prolapse). We made digital recordings at multiple sites at rest and with moderate and maximal contraction. Interference pattern analysis yielded the number of turns per second and the mean signal amplitude (in microvolts) for each site at each contraction level. We compared individual patient data with data from the healthy population by means of cloud analysis. Mean values of number of turns per second and mean amplitude in each group were then compared with nonparametric methods and regression models. RESULTS: Mean ages were 28.7 years (range, 20-49 years) for the control group, 54.3 years (range, 35-75 years) for subjects with genuine stress urinary incontinence, and 65 years (range, 41-77 years) for subjects with pelvic organ prolapse. Median clinical levator ani strengths were 9 (range, 5-9) in the control group, 5 (range, 2-7) in the genuine stress urinary incontinence group, and 5 (range, 2-8) in the pelvic organ prolapse group. Median external anal sphincter strengths were 9 (range, 7-9) in the control group, 5 (range, 3-9) in the genuine stress urinary incontinence group, and 8 (range, 4-9) in the pelvic organ prolapse group. The external anal sphincters of subjects with pelvic organ prolapse had the highest percentage of abnormal study results according to cloud analysis. Mean number of turns per second in levators was greater in control subjects than in subjects with abnormalities (P =.034). We found similar differences in number of turns per second for the external anal sphincter (P =.004). In contrast, we did not find differences between groups in mean amplitude in either the levator ani or the external anal sphincter. Comparison of patients with genuine stress urinary incontinence versus subjects with pelvic organ prolapse showed no significant difference in the number of turns per second in either muscle. Mean amplitude was greater in the pelvic organ prolapse group than in the genuine stress urinary incontinence group for both muscles (levator ani, P =.028; external anal sphincter, P =.048). Neither mean amplitude nor the number of turns per second could be predicted by clinically estimated levator ani strength, age, or fecal incontinence. CONCLUSION: Compared with nulliparous control subjects, patients with genuine stress urinary incontinence and pelvic organ prolapse had changes in the levator ani and external anal sphincter consistent with either motor unit loss or failure of central activation, or both. Subjects with pelvic organ prolapse had findings consistent with greater recovery than was found in those with genuine stress urinary incontinence. Measures of recruitment by interference pattern analysis correlated better with clinical external anal sphincter strength than with levator ani strength and were independent of age.

Adult↗
PubMed1997

Electrophoretic separation of myosin heavy chain isoforms in the human m. vastus lateralis: references to reproducibility and relationships with force, electromechanical delay, fibre conduction velocity, endurance and electromyography.

The aim of this investigation was to determine the relationship between muscle performance and the myosin heavy chain (MHC) composition and the reliability of electrophoretically determined MHC compositions. A total of thirty-one male subjects participated in the experiments. Maximal voluntary isometric contractions (MVC) of the knee extensors were performed at an arbitrary knee angle of 90 degrees and the following variables were recorded: maximal isometric force, muscle fibre conduction velocity (MFCV), electromechanical delay (EMD), maximal rate of force development (MRFD), median frequency of EMG (MF) and iEMG. Static isometric contractions of the knee extensors were held at an angle of 90 degrees using contractile forces of 10%, 50% and 100% MVC, respectively. These tests were conducted on separate days. Muscle biopsy samples were obtained from the left m. vastus lateralis before MVC and static endurance tests. MHC protein isoform differences were determined through sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) followed by densitometric analysis. Type I-MHC compositions of the m. vastus lateralis ranged from 20-68% with a mean of 49 +/- 18%, mean type IIa-MHC and type IIb-MHC percentages were 35 +/- 16% and 16 +/- 10%, respectively. MHC compositions of duplicate biopsy samples were not significantly different from that of original samples. The coefficients of variation calculated for duplicate biopsy samples suggested reasonable reproducibility for MHC isoform differentiation for type I-MHC and type-II MHC composition (CV = 12.6%). Differentiation between type IIa-MHC and type IIb-MHC was not always clear using the densitometric traces. Subjects with higher percentages of type II-MHC displayed significantly faster MFCV (r = 0.67, P < 0.1), isometric force development (r = 0.68, P < 0.1) and shorter periods of EMD (r = -0.72, P < 0.05). There was also a tendency toward faster MRFD in these subjects although results did not reach significance. Endurance times for isometric contractions held at 10%, 50% and 100% MVC to exhaustion were not correlated with MHC composition. No relationships between II-MHC composition and MF or iEMG were observed. It was suggested that surface electromyographic recordings obtained during isometric MVC did not reflect underlying differences in muscle fibre composition.

Adult↗
PubMed1998

A non-invasive method for bladder electromyography in humans.

No convincing correlation of bladder EMG in humans to simultaneously measured intravesical pressure has been reported in the literature. In most studies on bladder EMG the electrodes contact the bladder wall itself. This causes problems in the discrimination between very small extracellular signals, reflecting actual membrane potential changes of bladder muscle cells, and large electro-mechanical artefact caused by electrode movement as the tissue contracts. Aim of this study is to investigate whether bladder EMG can be performed non-invasively with Ag-AgCl surface electrodes that are placed on the abdominal skin of healthy volunteers. Bipolar electrode signals are obtained in a diagonal, vertical and horizontal direction of the abdominal electrodes. A conventional urodynamic investigation is performed according to International Continence Society standards simultaneously with bladder EMG. This new method shows that voiding is accompanied by a slow voltage change in bipolar electrode signals. The contribution of abdominal and other striated muscle activity to the bipolar electrode signals can clearly be distinguished from the slow voltage changes related to voiding. Free flowmetry shows that the electrical activity picked up by the abdominal electrodes is related to bladder emptying. In pressure/flow studies a relation between the electrical activity and the detrusor pressure is found. The present results suggest that the slow voltage changes found during bladder contraction are caused by summed membrane potential changes of bladder muscle cells, but this concept needs further testing. Also, validation for clinical use remains to be established.

Electromyography↗
PubMed1992

Electromyography of cricopharyngeal muscles in patients with oesophageal speech.

Subject for the examination were 30 patients who during total laryngectomy had had two silver clips for haemostasis inserted into the cricopharyngeous muscle about 3 cm from the sewing place in the midline, facilitating the location of the muscle and the placing of a needle electrode. Twelve to 18 months after laryngectomy and phoniatric rehabilitation, electromyographic examinations were performed. Each EMG recording was evaluated as to amplitude, discharge frequency and time duration of muscle electric activity. EMG recordings made during deglutition and phonation proved dependences of cricopharyngeous muscle activity on quality of oesophageal voice production and higher activity of muscle during phonation than deglutition in patients who developed very good and good oesophageal speech.

Adult↗
PubMed2001

Surface electromyography analysis in long-term recordings: application to head rest comfort in cars.

Analysis of long-term surface electromyographic (SEMG) signals has many applications in ergonomics when related to muscle fatigue. The present work proposes a set of processing methods reporting SEMG modifications during long-term driving tests in various situations (with or without head rest). A segmentation/classification algorithm allows signal splitting into homogeneous parts (postural activity and EMG bursts) and an efficient artefact suppression. Postural activity modifications are evaluated from time-varying amplitude probability density function (TAPDF) parameters. EMG burst analysis is achieved taking into account the relationships of these bursts with accelerometric events. This segmentation/classification procedure improves repeatability but does not significantly modify the overall results obtained before segmentation, as far as the analysis of head rest influence is concerned.

Algorithms↗
PubMed2001

The effect of overhead drilling position on shoulder moment and electromyography.

The effect of overhead drilling tasks on electromyographic (EMG) activity and shoulder joint moment was examined in this study. Twenty subjects simulated an overhead drilling task using a close, middle and far reach position while standing on either a lower or a higher step of a stepladder. Root mean square amplitude (AMP) of EMG activity from the dominant side anterior deltoid, biceps brachii and triceps brachii muscles was used to determine muscular load. Digital video was used to determine shoulder joint moment using 2-dimensional static link segment modelling in the sagittal plane. The results demonstrated that, compared to the far reach position, using the close reach position significantly decreased anterior deltoid AMP and biceps brachii AMP and moment, but increased triceps brachii AMP. Compared to the lower step, using the higher step significantly decreased anterior deltoid AMP and triceps AMP and moment, while increasing biceps AMP in the close position. There was no significant change noted in EMG median frequency indicating that fatigue was minimized. Moment increased monotonically with AMP. The findings indicated that workers performing overhead tasks should work close to their body in order to minimize shoulder forces. The implications of this recommendation are discussed.

Adult↗