Hans-Christoph Scholle

Surface EMG mapping of the human trapezius muscle: the topography of monopolar and bipolar surface EMG amplitude and spectrum parameters at varied forces and in fatigue

OBJECTIVES To investigate the factors affecting the topography of trapezius muscle EMG, multichannel recordings were made at different forces of isometric shoulder elevation and during fatiguing exercise. METHODS Twenty-eight channels of monopolar EMG were recorded from an array of 4 x 7 electrodes placed on the upper trapezius muscle. From the monopolar EMG and the bipolar derivations the root mean square (RMS(monopolar), RMS(bipolar)) and power spectrum median frequency (MF(monopolar), MF(bipolar)) were calculated. RESULTS The maximum RMS(monopolar) was located above the middle part of the trapezius muscle, where a minimum was found for RMS(bipolar). The cranial-caudal RMS distribution shifted upwards when the force was increased from 50 to 100% MVC and during fatigue. MF(bipolar) showed a peak above the endplate region, where the MF(monopolar) was low. During fatigue the normalized MF slope was independent of the cranial-caudal electrode position, but MF(monopolar) decreased most strongly at positions above the endplate region, where MF(bipolar) decreased less. CONCLUSIONS While the changes in MF reflected metabolic properties and volume conduction phenomena in the muscle, changes in RMS reflected a compensation for the fatigue processes within the muscle. The RMS changes in fatigue can be explained by the direction of the fibres involved in shoulder elevation.

Time-resolved functional 1H MR spectroscopic detection of glutamate concentration changes in the brain during acute heat pain stimulation

Non-invasive in vivo detection of cortical neurotransmitter concentrations and their changes in the presence of pain may help to better understand the biochemical principles of pain processing in the brain. In the present study acute heat pain related changes of the excitatory neurotransmitter glutamate were investigated in the anterior insular cortex of healthy volunteers by means of time-resolved functional proton magnetic resonance spectroscopy ((1)H-MRS). Dynamic metabolite changes were estimated with a temporal resolution of five seconds by triggering data acquisition to the time course of the cyclic stimulus application. An overall increase of glutamate concentration up to 18% relative to the reference non-stimulus condition was observed during the application of short pain stimuli.

Sleep spindle evolution from infancy to adolescence

OBJECTIVE To investigate the development of frontally recorded sleep spindles from infancy to adolescence to provide normative data for pediatric sleep medicine. METHODS Sleep spindle activity was investigated in 120 healthy subjects aged 3 months to 16 years in 12 age groups. At 2 a.m. (min 1:17 a.m., max 3:18 a.m.) 10 min of NREM 2 was checked. Spindles were visually scored in the electroencephalogram from F4/A1. RESULTS The age dependency of interspindle interval, length of spindle, and spindle density, was statistically significant (Kruskal-Wallis p<0.0001). There were U-shaped curves for spindle length, spindle density, and an inverted U-shaped curve for the interspindle interval. Results of the post hoc U-test p<0.05 (Bonferroni corrected, m=66): Spindle length was minimal at 1.7 up to 3.0 years. Spindle density (number of spindles) was minimal between the ages of 1.7 and 2.3 years, thereafter there was a high increase that reached a plateau at age 5 years and remained up to 16 years. Interspindle interval was maximal at 1.7 and 2.3 years. CONCLUSIONS Sleep spindle activity changes with maturation in terms of length and density. SIGNIFICANCE The establishment of age-related normative data of sleep spindle activity can improve identification of NREM 2 in infancy, childhood, and adolescence, and enable detection of delayed neural maturation and/or sleep instability.

Functional gait asymmetry of unilateral transfemoral amputees

The aim of prosthetic devices is to mimic the function of biological systems. Numerous investigations have demonstrated significant asymmetries in unilateral amputee gait. The underlying interactions of prosthetic and intact leg are not widely discussed, so far. To get more insight into the functionality of asymmetries, we investigated temporal and kinetic parameters of walking transfemoral amputees wearing the computerized C-Leg and the non-computerized 3R80. Experiments were conducted on an instrumented treadmill at four different walking speeds (0.5, 0.8, 1.1, 1.4m/s) measuring vertical and horizontal ground reaction forces. Single support, double support and contact times, vertical and horizontal impulses as well as their asymmetry factors were calculated. Gait patterns were similar for both prosthetic knee joints, manifesting in (i) reduced stance times of the prosthetic leg, (ii) prolonged load transfer during double support from intact to prosthetic leg at lower speeds, (iii) reduced vertical and horizontal impulses of the prosthetic leg, (iv) net accelerating horizontal impulses during contact of the prosthetic leg, (v) missing impacts at touch-down of the prosthetic leg. Our results suggest that deficits of the prosthetic leg like missing active knee extension and ankle push-off are compensated by the intact leg. The altered touch-down configuration for the prosthetic leg enables it to provide forward propulsion while load bearing is largely shifted to the intact leg.

A topographical analysis of spectral electromyographic data of the human masseter muscle under different functional conditions in healthy subjects

In 20 healthy subjects, 16-channel surface electromyograms (EMG) were recorded with the mandible in its postural position, during compensation for forces applied from ipsilateral, contralateral and frontal positions, and during force-constant biting on a unilaterally placed force transducer. After artefact elimination, EMG power spectra were calculated on the basis of the original EMG curves via fast Fourier transformation. Using spectral EMG characteristics, EMG maps were computed by means of an interpolation algorithm and an imaging procedure. Spectral EMG maps were demonstrated for all the test conditions. Significant differences of myoelectrical activity were verified between the 16 electrode positions. Moreover, the levels and/or the topographical distributions of spectral EMG powers differed significantly between the test conditions. During biting as well as with contralaterally and frontally applied forces, the highest EMG activity was found in the inferior third of the masseter and the lowest in the superior third. With ipsilaterally applied forces, the topographical distribution of the total EMG power was completely changed. The power maximum was frequently demonstrated in the superior, especially the posterosuperior, third of the muscle, the minimum in the inferior third. In the postural position of the mandible, EMG activity decreased from the anterior to the posterior regions of the masseter. If the bite force or the horizontally applied forces were enhanced, EMG activity increased significantly but the EMG map structures were only changed in some details. The topographical distribution of myoelectrical activity demonstrated by EMG maps characterizes the intramuscular activation patterns of distinct masseter functions.(ABSTRACT TRUNCATED AT 250 WORDS)

1H-MR spectroscopic detection of metabolic changes in pain processing brain regions in the presence of non-specific chronic low back pain.

Reliable detection of metabolic changes in the brain in vivo induced by chronic low back pain may provide improved understanding of neurophysiological mechanisms underlying the manifestation of chronic pain. In the present study, absolute concentrations of N-acetyl-aspartate (NAA), creatine (Cr), total choline (tCho), myo-inositol (mI), glutamate (Glu) and glutamine (Gln) were measured in three different pain processing cortical regions (anterior insula, anterior cingulate cortex, and thalamus) of ten patients with non-specific chronic low back pain by means of proton MR spectroscopy ((1)H-MRS) and compared to matched healthy controls. Significant decrease of Glu was observed in the anterior cingulate cortex of patients. Patients also revealed a trend of decreasing Gln concentrations in all investigated brain areas. Reductions of NAA were observed in the patient group in anterior insula and in anterior cingulated cortex, whereas mI was reduced in anterior cingulated cortex and in thalamus of patients. Reduced concentrations of Glu and Gln may indicate disordered glutamatergic neurotransmission due to prolonged pain perception, whereas decrease of NAA and mI may be ascribed to neuron and glial cell loss. No significant changes were found for Cr. The morphological evaluation of anatomic brain data revealed a significantly decreased WM volume of 17% (p<0.05) as well as a non significant trend for GM volume increase in the anterior insula of patients.

Chronischer unspezifischer Rückenschmerz

ZusammenfassungDer chronische unspezifische Rückenschmerz ist ein zentrales Thema für Patienten, Versicherer und Berufsgenossenschaften. Mit einer Präventivdiagnostik bestünde die Möglichkeit, für einen momentan beschwerdefreien Menschen eine Prognose zu erstellen, mit welcher Wahrscheinlichkeit er einen chronischen unspezifischen Rückenschmerz erleiden wird, wenn er sich nicht einer präventiven Maßnahme unterzieht.Jedes Jahr erleiden 20% der Erwachsenen Rückenschmerzen und 70–80% der Bevölkerung bekommen in ihrem Leben einmal oder mehrmals Rückenschmerzen. Meist reduzieren sich die Beschwerden innerhalb der ersten sechs Wochen ohne medizinische Intervention oder verschwinden ganz. Nur in wenigen Fällen sind sie progredient, chronifizieren und verursachen erhebliche Kosten.Es gilt herauszufinden, ob eine Person zu einer Risikogruppe gezählt werden kann, für die zukünftig eine Chronifizierung des Rückenschmerzes wahrscheinlich wird. Mit dem präventivdiagnostischen Ansatz sollte die Frage beantwortet werden können: Welche Subgruppe von Patienten mit chronischem Rückenschmerz wird besonders von einer Übungstherapie oder von kognitiven verhaltenstherapeutischen Ansätzen profitieren?AbstractChronic low back pain represents an important issue not only for the patients but also for society. Apreventive diagnosis could open the possibility to predict the individual probability of developing chronic low back pain in pain-free persons or persons with sub-acute low back pain if no further preventive interventions would be started.Every year about 20% of adults will suffer from back pain and 70-80% of society will suffer from back pain during their lives. In most cases back pain is alleviated within the first 6 weeks without any medical intervention. Only a few cases are progredient and chronic with immense costs for society and health care systems.It is necessary to find out which individuals will probably suffer from chronic back pain in the future. The diagnostic outcome of the classification should help to answer the question which subgroups of patients with chronic low back pain will especially benefit from exercise therapy or cognitive behavior therapy?

Simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy measurements of the lumbar back muscle during isometric exercise

The aim of this study was to demonstrate the feasibility of simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy (31P-MRS) measurements on the back muscle of volunteers during the performance of an isometric exercise. Six volunteers (three male, three female) performed a modified Biering-Sörensen test inside a 1.5 T MR scanner while simultaneously recording SEMG signals. A surface coil was used for 31P-MRS with a CSI sequence. Spectra were collected with a voxel resolution of 40 mm x 40 mm x 100 mm and a temporal resolution of 30 s during periods of rest, sustained muscle contraction and recovery. The duration of muscle contraction was 150 s. SEMG analysis yielded a decrease of the mean SEMG frequency of approximately 20%. The SEMG amplitudes were constant or increased up to approximately 150% during exercise. 31P-MRS showed a maximum decrease of the phosphocreatine (PCr) amplitude down to approximately 32% of its initial value. Simultaneously, a doubling of the inorganic phosphate (Pi) signal was observed. The present study demonstrates that simultaneous SEMG and 31P-MRS measurements of the back muscle are feasible during isometric exercises.

SEMG activation patterns of thigh muscles during upright standing in haemophilic patients.

Summary.  Although electromyography (EMG) is a common method to evaluate muscle activity, studies utilizing EMG in haemophilic patients are rare. The haemophilic arthropathy, resulting in altered afferent information is expected to cause disturbed activation and inter‐muscular coordination patterns in haemophilic subjects. The aim of this study was to determine differences of selected knee muscles between haemophilic patients and non‐haemophilic subjects during upright standing. Surface EMG (SEMG) amplitudes of rectus femoris, vastus medialis (VM), vastus lateralis (VL) and biceps femoris (BF) muscles of both sides were measured in 27 haemophilic patients (H) and 26 control subjects (C) while standing on an even surface. Data from both sides were pooled in C, but data of H were subdivided further according to major (H‐MA) and minor (H‐MI) affected joints. To normalize the data, amplitude ratios (percentage of cumulated activity) were calculated as well. Regardless of whether H‐MA or H‐MI was compared with C, amplitudes of all extensor muscles reached significantly higher levels in H (P < 0.05). SEMG amplitude ratios also differed between H and C. Independent of subgroup, BF showed significantly reduced activation ratios (P < 0.01). Only the ratios of VM and VL of H‐MA could replicate the observed amplitude differences to C (P < 0.05). These findings show that while standing, haemophiliacs maintain the necessary stability demands through increased extensor activities and modulated coordination patterns. Although all thigh muscles of haemophiliacs are characterized by distinct atrophy, increased amplitude levels could be proved for the knee extensor muscles only. Therefore, general atrophy‐related effects cannot explain these results.

Gender specific activation patterns of trunk muscles during whole body tilt.

Gender specific differences as evidenced in both anthropometric data and physical performance of healthy persons have been broadly demonstrated. Recently advancements in surface electromyography (SEMG) have shown possible differences in men’s and women’s muscle coordination patterns. However, quantitative information about gender related muscle co-ordination patterns are rare. This investigation was carried out to both verify if trunk muscle SEMG amplitude–force relationship differs between men and women and refine techniques of measurement and data analysis using SEMG. Thirty-one healthy volunteers (16 women, 15 men) were investigated during whole body tilt at angles from 5° to 90° (from quasi vertical to horizontal position). Subjects had to maintain body in body axis while their lower body was fixed and the upper body remained unsupported. SEMG was taken from five different trunk muscles of both sides simultaneously. At corresponding tilt angles women exhibited higher amplitude levels of their abdominal muscles in comparison to men, who were characterized by higher back muscle amplitudes. Abdominal muscles showed a non-linear SEMG amplitude–force relationship but differed between genders with more linearity in women. Back muscles showed a linear amplitude–force relationship with no differences between genders. Women were characterized by higher levels of co-contraction of all investigated muscles. The data are in accordance with histological investigations, which already proved specific fiber distribution patterns in both abdominal and back muscles and gender related differences in relative area of Type 1 fibers of back muscles. The observed differences in SEMG–force relationship for the abdominal muscles remain hypothetical because of lack of histological information.