Fiber Conduction Velocity Research Articles

Increased resistance towards fatigability in patients with facioscapulohumeral muscular dystrophy

PurposeIn facioscapulohumeral muscular dystrophy (FSHD) fatigue is a major complaint. We aimed to investigate whether during isometric sustained elbow flexions, performance fatigability indexes differ in patients with FSHD with respect to healthy controls.MethodsSeventeen patients with FSHD and seventeen healthy controls performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min and then at 60% MVC until exhaustion. Muscle weakness was characterized as a percentage of predicted values. Maximal voluntary strength, endurance time and performance fatigability indices (mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD)), extracted from the surface electromyogram signal (sEMG) were compared between the two groups.ResultsIn patients with FSHD, maximal voluntary strength was 68.7% of predicted value (p < 0.01). Compared to healthy controls, FSHD patients showed reduced MVC (p < 0.001; r = 0.62) and lower levels of performance fatigability, characterized by reduced rate of changes in MNF (p < 0.01; r = 0.56), CV (p < 0.05; 0.37) and FD (p < 0.001; r = 0.51) and increased endurance time (p < 0.001; r = 0.63), during the isometric contraction at 60% MVC.ConclusionA decreased reduction in the slopes of all the considered sEMG parameters during sustained isometric elbow flexions suggests that patients with FSHD experience lower levels of performance fatigability compared to healthy controls.

利用者の温冷感による咬筋部筋電位計測の動作信頼性

With a rise in the number of people requiring nursing-care in the aging society, the demand for welfare equipments that maintain the quality of nursing-care is increasing. In particular, electric wheelchairs are effective in improving QOL because they support the voluntary movement of users, but the majority of them needs to be operated by movements of upper limbs. Then, the authors developed an operation system of electric wheelchairs that is controlled by voluntary head movements. However, EMG measurement system malfunctioned in low temperature environments, which made it impossible to operate electric wheelchairs. Thus, it is necessary to clarify the cause of this malfunction and ensure the stability of operation. In this study, first, the operation was tested in comfortable environments and low temperature environments (-2<PMV<-3). Next, operation reliability was evaluated based on task success rate and malfunction rate. Consequently, the task success rate and the malfunction rate in low temperature environments were 79% and 12%, which were similar to the results in comfortable environments. Therefore, this system can maintain operation reliability at -2<PMV<-3. Meanwhile, it is indispensable to verify in harsher low temperature than -2<PMV<-3 environments, due to be suggested that the change in muscle fiber conduction velocity was small.

Electrodiagnostic study in patients with fibromyalgia: Implication for central sensitization

Background: Fibromyalgia is a syndrome characterized by chronic pain, depression, fatigue, and sleep disturbance. Different hypotheses have emerged about its pathogenesis, but central sensitization, which plays an important role in the development of neuropathic pain, is considered to be the main mechanism. We aim to compare patients with fibromyalgia and healthy controls with different electrodiagnostic testing, and if present, to corroborate whether there is any relationship between electrodiagnostic measures. Also, we sought to test the diagnostic value of some of these measures. Methods: A case-control study of thirty-one patients with fibromyalgia with a duration of illness ranging from 5 months to 10 years were recruited for the study. Full medical history, clinical neurological examination, and electrodiagnostic tests of the upper and lower extremity including nerve conduction studies, needle electromyography, sympathetic skin response, cutaneous silent period and muscle fiber conduction velocity. Results: Sympathetic skin response latency and cutaneous silent period latency were not different between the patients and the control group. Cutaneous silent period duration was prolonged and the muscle fiber conduction velocity is faster in the subjects with fibromyalgia. The latter measures have similar diagnostic value. Sex has no significant impact on electrodiagnostic measures and the latter not correlated with patients' age. Conclusion: A central sensitization and concomitant deregulation of the efferent higher motor centers might be implicated in the pathogenic mechanism of fibromyalgia.

Diabetic polyneuropathy: features of the clinical picture and electroneuromyographic parameters in the presence of comorbidity

Knowledges of certain key moments in the clinical course of diabetic polyneuropathy (DP) combined with varied comorbidity will allow the disease to be identified more effectively and treated comprehensively at different stages of onset. The aim of the research: was to investigate and summarize the features of the clinical picture, electroneuromyographic parameters in patients with DP in the presence of comorbidity. Materials and methods. 111 patients aged 19 to 69 years with DP were examined. The patients were divided into two groups: DP due to type I diabetes mellitus (DM) (group A; n = 61) and type II (group B; n = 50). According to the detected comorbidity, the following subgroups were identified: persons with DP as the result of type I, II DM with only one pathology (subgroup 1; n = 53) and the presence of multimorbidity (two or more pathologies) (subgroup 2; n = 21). The control group – 30 healthy persons representative by age and gender, 37 patients with DP without comorbidity. The patients were examined for neurological status, laboratory tests, instrumental examination methods. Results and discussion. In general, among the studied groups, the lowest nerve conduction velocity in the motor fibers was in abductor hallucis, tibialis on the left, extensor digitorum brevis, peroneus on the left and right, in sensory fibers – peroneus superficialis on the left and right, n. suralis on the left and right. Such changes primarily reflect the lesion of the distal extremities, which clinically looks like a distal symmetrical DP. Was dominated axonal and demyelinating type of nerve fiber damage. Conclusions. Comorbidity contributes to the progression of DP and deterioration of its clinical picture, electroneuromyographic rates, even in the presence of a single pathology, low duration of DM and HbA1c level.

Evaluation of performance fatigability through surface EMG in health and muscle disease: state of the art

In literature, it is commonly reported that the progress of performance fatigability may be indirectly assessed through the changes in the features of the surface electromyogram (sEMG) signal. In particular, during isometric constant force contractions, changes in the sEMG signal are caused by several physiological factors, such as a decay in muscle fibers conduction velocity (CV), an increase of the degree of synchronization between the firing times of simultaneously active motor units (MUs), by the central nervous system, and a reduction of the recruitment threshold and a modulation of MUs firing rate. Amplitude and spectral parameters may be used to characterize the global contributions to performance fatigability, such as MU control properties and fiber membrane properties, or central and peripheral factors, respectively. In addition, being CV a physiological parameter, its estimation is of marked interest to the study of fatigue both in physiological and in presence of neuromuscular diseases.

Sensitivity of the surrogate analysis method to synchronization and conduction velocity of muscular fibers

This paper shows that conduction velocity (CV) and motor unit action potential (MUAPs) synchronization affects the results of Surrogate Analysis (SA) of the surface electromyography (sEMG) signal. It will be verified if the SA can extract information from the sEMG signal. Also, it is the first time that the SA is interpreted from a physiological point-of-view. To illustrate the relationships between the CV, the synchronization and the SA, a simple dipole-based model for (sEMG) signal simulation is used. It is composed of multiple fibers superposed at the same location, leaving aside any complex geometrical considerations, but putting the emphasis on the timing of the MUAPs firing. Single-pulse synchronization as well as impulse train synchronization are studied. To highlight the difference between spectral (linear) features, nonlinear features and SA relation with the model parameters, the Median Frequency (MDF), the Kurtosis, the Higuchi’s Fractal Dimension (FD) and the FD based SA are compared. The simulation results show that the SA is jointly influenced by CV and the MUAPs synchronization, almost in a multiplicative way. These relations are also more pronounced for an impulse train than for a single pulse. Overall, the SA is shown to be a good feature to consider for CV and MUAPs synchronization estimation. It is moreover uncorrelated with spectral features and moderately with nonlinear features. These findings can be used to 1) help evaluate the CV and MUAPs synchronization and 2) interpret the result of the surrogate analysis.

Design, implementation, and estimation of MFCV for 4-different position of human body using FPGA

The motivation behind this article is to demonstrate the precision and dependability of a Field Programmable Gate Array-based implementation of muscle fibre conduction velocity (MFCV) in customary unique constrictions. The framework, leveraging the DSP unit, acquires the bio signals from four different positions of the human body, including Radial Nerve, Ulnar nerve, Auxiliary Nerve, Median nerve. The information derived through Surface Electromyogram (EMG) Electrodes is depicted as a dynamic bitstreams of the signal. The latest bitstreams are subjected to an algorithm. The subjection corresponds to the correlation of the signals from similar muscle nerves, obtained through the EMG electrodes. The whole calculation framework completely works progressively on the Altera Cyclone-V FPGA. This method is better than finding the signal dependence using a silicon resonator due to its cost and tedious design of the sensors. The myoelectric (Electromyographic) signal is recorded by the electrodes set on the four different locations associated with 1550 unique contractions. The in-vivo estimations illustrate that below the equivalent trial states, in 10 test days, the framework uncovers an MFCV mean estimation of 6.60 (±) 0.42 m/s for Median nerve Position, 6.43 (±) 0.33 m/s for Ulnar Nerve Position, 6.54 (±) 0.41 m/s for Radial nerve Position and 7.21 (±) 0.49 m/s for Auxiliary Nerve Position. The values evidence decent dependability of the estimations in an eternal application. The core part of the device being MFCV estimation, upon empirical evaluations with clinical values, shows an accuracy of 97%.

Quercetin Supplementation Improves Neuromuscular Function Recovery from Muscle Damage.

This study was aimed at investigating whether quercetin (Q) may improve the recovery of neuromuscular function and biochemical parameters in the 7 days following an eccentric exercise-induced muscle damage (EEIMD). Sixteen men (25.9 ± 3.3 y) ingested Q (1000 mg/day) or placebo (PLA) for 14 days following a double-blind crossover study design. A neuromuscular (NM) test was performed pre–post, 24 h, 48 h, 72 h, 96 h and 7 days after an intense eccentric exercise. The force–velocity relationship of the elbow flexor muscles and their maximal voluntary isometric contraction (MVIC) were recorded simultaneously to the electromyographic signals (EMG). Pain, joint angle, arm circumference, plasma creatine kinase (CK) and lactate-dehydrogenase (LDH) were also assessed. The results showed that Q supplementation significantly attenuated the strength loss compared to PLA. During the recovery, force–velocity relationship and mean fibers conduction velocity (MFCV) persisted significantly less when participants consumed PLA rather than Q, especially at the highest angular velocities (p < 0.02). A greater increase in biomarkers of damage was also evident in PLA with respect to Q. Q supplementation for 14 days seems able to ameliorate the recovery of eccentric exercise-induced weakness, neuromuscular function impairment and biochemical parameters increase probably due to its strong anti-inflammatory and antioxidant action.

RETRACTED ARTICLE: FPGA based peripheral myopathy monitoring using MFCV at dynamic contractions

This article describes the design of a wearable, remote inserted framework for the Peripheral Myopathy (PM) estimation in customary dynamic movements. This unique circumstance, the electromyographic investigation can give data about the muscle and nerve condition by evaluating the connected MFCV. The framework works with synchronized and digitized information tests from four electromyographic channels, which are situated on both hands of the individual test, misusing the rules given by an inserted positional filtering calculation. This work displays a novel approach for the assessment of MFCV that relies upon the excellent anode relative estimation standard. The system uses dynamic bitstream change of Electromyographic signs and low computational retort for utilization of bit stream cross-correlation. The structure totally chips away at Cyclone-V altera field programmable gate array. The test outcomes on five subjects (Human Beings) show the limit of the proposed procedure for planning the physiological muscle fibre conduction velocity values, as nitty–gritty in a therapeutic composition. In explicit, differentiating the remedial characteristics, obtained in controlled conditions, with the system evacuated muscle fibre conduction velocity, the proportionate preliminary conditions: preeminent bungle is, overall, 0.3 m/s. The framework restores a likelihood of invalid constant measures underneath of 2% (assuming the worst possible scenario).

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction.

The neural factors underlying the persistency of quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) have been only partially explained. This study examined muscle fiber conduction velocity (MFCV) as an indirect parameter of motor unit recruitment strategies in the vastus lateralis (VL) and medialis (VM) muscles of soccer players with ACLR. High-density surface electromyography (HDsEMG) was acquired from VL and VM in nine soccer players (22.7±2.9years; BMI: 22.08±1.72kg·m-2 ; 7.7±2.2months post-surgery). Voluntary muscle force and the relative myoelectrical activity from the reconstructed and contralateral sides were recorded during linearly increasing isometric knee extension contractions up to 70% of maximal voluntary isometric force (MVIF). The relation of MFCV and force was examined by linear regression analysis at the individual subject level. The initial (intercept), peak (MFCV70 ), and rate of change (slope) of MFCV related to force were compared between limbs and muscles. The MVIF was lower in the reconstructed side than in the contralateral side (-%20.5; P<.05). MFCV intercept was similar among limbs and muscles (P>.05). MFCV70 and MFCV slope were lower in the reconstructed side compared to the contralateral for both VL (-28.5% and -10.1%, respectively; P<.001) and VM (-22.6% and -8.1%, respectively; P<.001). The slope of MFCV was lower in the VL than VM, but only in the reconstructed side (-12.4%; P<.001). These results suggest possible impairments in recruitment strategies of high-threshold motor units (HTMUs) as well as deficits in sarcolemmal excitability, fiber diameter, and discharge rate of knee extensor muscles following ACLR.

Reproducibility of muscle fibre conduction velocity during linearly increasing force contractions

Muscle fibre conduction velocity (MFCV) is a basic physiological parameter biophysically related to the diameter of muscle fibres and properties of the sarcolemma. The aim of this study was to assess the intersession reproducibility of the relation between voluntary force and estimates of average muscle fibre conduction velocity (MFCV) from multichannel high-density surface electromyographic recordings (HDsEMG). Ten healthy men performed six linearly increasing isometric ankle dorsiflexions on two separate experimental sessions, 4 weeks apart. Each session involved the recordings of voluntary force during maximal isometric (MViF) and submaximal ramp contractions at 35–50–70% of MViF. Concurrently, the HDsEMG activity was detected from the tibialis anterior muscle and MFCV estimates were derived in 250-ms epochs. Absolute and relative reproducibility of MFCV initial value (intercept) and rate of change (regression slope) as a function of force were assessed by within-subject coefficient of correlation (CVw) and with intraclass correlation coefficient (ICC). MFCV was positively correlated with voluntary force (R2 = 0.75 ± 0.12) in all individuals and test conditions (P < 0.001). Average CVw for MFCV intercept and slope were of 2.6 ± 2.0% and 11.9 ± 3.2% and ICC values of 0.96 and 0.94, respectively.Overall, MFCV regression coefficients showed a high degree of intersession reproducibility in both absolute and relative terms. These results may have important practical implications in the tracking of training-induced neuromuscular changes and/or in the monitoring of the progress of neuromuscular disorders when a full sEMG signal decomposition is problematic or not possible.

Conduction Velocity of Muscle Action Potential of Knee Extensor Muscle During Evoked and Voluntary Contractions After Exhaustive Leg Pedaling Exercise.

PurposeMuscle fiber conduction velocity (CV) has been developed to estimate neuromuscular fatigue and measured during voluntary (VC) and electrically evoked (EC) contractions. Since CV during VC and EC reflect different physiological phenomena, the two parameters would show inconsistent changes under the conditions of neuromuscular fatigue. We investigated the time-course changes of CV during EC and VC after fatiguing exercise.MethodsIn 14 young males, maximal voluntary contraction (MVC) of knee extensor muscles, CV during electrical stimulation (CV-EC) and MVC (CV-VC) were measured before and immediately, 30 min, 60 min, 120 min, and 24 h after exhaustive leg pedaling exercise.ResultsCV-EC significantly increased immediately after the fatiguing exercise (p < 0.05) and had a significant negative correlation with MVC in merged data from all time-periods (r = −0.511, p < 0.001). CV-VC significantly decreased 30, 60, and 120 min after the fatiguing exercise (p < 0.05) and did not show any correlations with MVC (p > 0.05).ConclusionThese results suggest that CV during EC and VC exhibits different time-course changes, and that CV during EC may be appropriate to estimate the degree of neuromuscular fatigue after fatiguing pedaling exercise.

Age related changes in surface myoelectric signals

The initial values and the time course of muscle fiber conduction velocity and of surface myoelectric signal spectral variables were studied during voluntary or electrically elicited contractions of the tibialis anterior muscle of 15 healthy elderly human subjects. Age ranged from 65 to 84 years. Isometric voluntary contractions were performed at 20% MVC (Maximal Voluntary Contraction) and 80% MVC for 20 s. Tetanic electrical stimulation was then applied to the main muscle motor point for 20 s with surface electrodes. Two stimulation rates (20 Hz and 40 Hz) and two stimulation amplitudes were used to induce different degrees of fatigue. One stimulation amplitude was supramaximal, the second was adjusted to induce a response (M-wave) about 30% of the maximal. Results were compared with those reported in previous work on healthy adults (age range 18 to 43 years). The main findings of this work are: (a) when voluntary contraction level is increased from 20% MVC to 80% MVC conduction velocity and spectral variables increase; this increase is significantly smaller in elderly subjects, (b) during sustained contractions at 80% MVC the decrease of conduction velocity and spectral variables is significantly smaller in elderly subjects, (c) during contractions induced by supramaximal stimulation at 40 Hz the decrease of conduction velocity and spectral variables is not significantly different in the two age groups. It is concluded that points a and b reflect the age related decrease of number and size of fast twitch fibers indicated by histological data. Point c is discussed and possible explanations are suggested.

SPARC: Method for Overcoming Temporal Dispersion in Unmyelinated Nerves for Imaging C Fibres with Electrical Impedance Tomography (EIT)

Fast neural EIT is a novel technique that enables imaging of evoked myelinated fibre activity in fascicles in rat sciatic nerve in vivo. However, imaging unmyelinated fibres is challenging due to temporal dispersion of the neural activity, caused by variability in fibre conduction velocities. This reduces the signal to below noise several centimetres from onset. The purpose of this work was to develop a method to overcome dispersion and allow EIT recordings of phasic activity at any distance from onset along the nerve.MethodsCompound impedance changes (dZ) were simulated using an electrically stimulated CAPs in 1D FEM model of a C fibre [1], with statistical analysis for 5000 fibres with conduction velocities 0.6±0.07 m/s (mean±SD) [2]. This enabled simulation of dZ up to 20 cm from the stimulus with stimulus trains of 5/10/20/50 Hz lasting 0.25–8 s with 3 s intervals between trains (Fig. 1a). The total duration of each simulation was 100 s.dZ was simulated 1) By coherent averaging of responses of supramaximal activity of single spikes [3] with demodulation bandwidth of 50–300 Hz and 2) By bandpass filtering of entire evoked spike trains with bandwidths of 0.25–5 Hz which allowed significant reduction of the noise without the need for coherent spike averaging.Random gaussian noise (0.015 μV RMS) was added to the signal to simulate realistic recording conditions. The SNR in the utilised approaches was computed for all tested stimulation and recording paradigms and compared.ResultsWhile coherent spike averaging was superior at short distances, its SNR fell exponentially with the distance from the onset (Fig. 1b, solid lines). The SNR with the compound demodulation was more consistent across distances (~2 at the optimal stimulation frequency of 20 Hz, Fig. 1b, dashed lines) allowing recording at ≥ 20 cm from stimulation. The estimated minimal averaging time required to obtain an SNR of 4 at 20 cm from the stimulus was equal to approximately 30 minutes at 20 Hz.Conclusion and future workThe developed stimulation and signal processing paradigm demonstrated the feasibility of dZ recording at long distances from the stimulus. Future work is to validate it on the ex vivo crustacean leg nerve model and subsequently an in vivo mammalian model with the final objective of imaging C fibres in the vagus nerve in humans. If successful, this technique will be applied for improvement of the emerging field of bioelectronic medicines [4].Support or Funding InformationThe work was supported by NIH SPARC grant no: 3OT2OD026545‐01S2.(a) Example of AP and dZ responses of the C fibre subjected to repetitive 50 Hz stimuli; (b) SNR computed for the single and compound recording paradigms.Figure 1

Comparative Study on Muscle Function, Temperature on Muscle Surface and Muscle Fiber Conduction Velocity by Static and Dynamic Stretching

Comparative Study on Muscle Function, Temperature on Muscle Surface and Muscle Fiber Conduction Velocity by Static and Dynamic Stretching

Upper and lower limb performance fatigability in people with multiple sclerosis investigated through surface electromyography: a pilot study

Objective: Fatigue experienced by people with multiple sclerosis (pwMS) is multidimensional, consisting of different components, such as perceived, physical and cognitive fatigue and performance fatigability. At present, there is no gold standard to assess performance fatigability in pwMS; therefore, we aimed to determine whether, during a fatiguing task, average rectified value (ARV), mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD) of surface electromyography (sEMG) may be used as indirect indices of performance fatigability. Moreover, we analyzed whether a three-week rehabilitation program impacts on performance fatigability in pwMS, and whether a relationship between sEMG parameters and trait levels of perceived fatigability, before and after rehabilitation, does exist. Approach: Twenty-one pwMS performed a 20% maximal voluntary contraction (MVC) of 1 min, and afterwards a 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, vastus medialis and vastus lateralis. Performance fatigability was determined at entry to (t0) and discharge from (t1) rehabilitation. Perceived fatigability was measured at t0 and t2, one month after rehabilitation. Main results: ARV, MNF, CV and FD rates of change showed significant changes at t0 and t1 (p < 0.05) during the high-level contraction in the BB, but rather limited in the vastii muscles. Moreover, rehabilitation did not induce any reductions in either perceived or performance fatigability. No significant correlations between ARV, MNF, CV and FD rates of change during the 60% MVC and perceived fatigability, at t0 and t2, were found. Significance: Our findings suggest that the sEMG parameters are useful for indirectly assessing performance fatigability in pwMS during sub-maximal fatiguing contractions, particularly in the biceps brachii.

Overexpression of Sirtuin 1 protein in neurons prevents and reverses experimental diabetic neuropathy.

In diabetic neuropathy, there is activation of axonal and sensory neuronal degeneration pathways leading to distal axonopathy. The nicotinamide-adenine dinucleotide (NAD+)-dependent deacetylase enzyme, Sirtuin 1 (SIRT1), can prevent activation of these pathways and promote axonal regeneration. In this study, we tested whether increased expression of SIRT1 protein in sensory neurons prevents and reverses experimental diabetic neuropathy induced by a high fat diet (HFD). We generated a transgenic mouse that is inducible and overexpresses SIRT1 protein in neurons (nSIRT1OE Tg). Higher levels of SIRT1 protein were localized to cortical and hippocampal neuronal nuclei in the brain and in nuclei and cytoplasm of small to medium sized neurons in dorsal root ganglia. Wild-type and nSIRT1OE Tg mice were fed with either control diet (6.2% fat) or a HFD (36% fat) for 2 months. HFD-fed wild-type mice developed neuropathy as determined by abnormal motor and sensory nerve conduction velocity, mechanical allodynia, and loss of intraepidermal nerve fibres. In contrast, nSIRT1OE prevented a HFD-induced neuropathy despite the animals remaining hyperglycaemic. To test if nSIRT1OE would reverse HFD-induced neuropathy, nSIRT1OE was activated after mice developed peripheral neuropathy on a HFD. Two months after nSIRT1OE, we observed reversal of neuropathy and an increase in intraepidermal nerve fibre. Cultured adult dorsal root ganglion neurons from nSIRT1OE mice, maintained at high (30 mM) total glucose, showed higher basal and maximal respiratory capacity when compared to adult dorsal root ganglion neurons from wild-type mice. In dorsal root ganglion protein extracts from nSIRT1OE mice, the NAD+-consuming enzyme PARP1 was deactivated and the major deacetylated protein was identified to be an E3 protein ligase, NEDD4-1, a protein required for axonal growth, regeneration and proteostasis in neurodegenerative diseases. Our results indicate that nSIRT1OE prevents and reverses neuropathy. Increased mitochondrial respiratory capacity and NEDD4 activation was associated with increased axonal growth driven by neuronal overexpression of SIRT1. Therapies that regulate NAD+ and thereby target sirtuins may be beneficial in human diabetic sensory polyneuropathy.

Signal Modeling and Simulation of Temporal Dispersion and Conduction Block in Motor Nerves.

Electroneurography is a well-established diagnostic test for supporting the diagnosis of disorders of myelinated peripheral nerves. Neurophysiological quantities are automatically calculated and are used to determine the pathology of the nerve (axonal damage) or its sheath (myelin damage). Specific differential diagnostic criteria are derived from time-domain normative data, which result primarily from a computer simulation in the early 1990s based on animal data, namely rats. However, the rat signals studied differ significantly from those of humans because of anatomical differences. We present a model-based simulation of nerve conduction in healthy and pathological motor nerves. In contrast to earlier simulations, the present model is based on motor unit action potentials extracted from real human measurements facilitating the generation of realistic signals, starting from a conduction velocity distribution. In addition to the modeling of healthy nerves, we model a hereditary peripheral nerve disease as well as an acute and a chronic inflammatory demyelinating condition. Quantitative signal differences based on standard variables in the time-domain are presented. The findings for the demyelinating conditions demonstrate amplitude reductions of 71% and 65% between the distal and proximal responses, which result from an increase in the variance of the nerve fiber conduction velocities. The simulation results closely match those of empirical measurements, indicating that the signal model captures relevant pathological mechanisms. An amplitude reduction of more than 50% in demyelinating conditions is in accordance with routine measurements and shows that temporal dispersion is quite well-modeled compared to previous simulation models. The simulation outcomes can serve as the basis for an improved pathophysiological understanding of peripheral nerve disorders and should aid neurophysiologists to refine their diagnostic armamentarium resulting in a more precise differential diagnosis.

High-density electromyographic assessment of stretch reflex activity during drop jumps from varying drop heights

This study investigated how drop heights and their associated drop jump performance relate to stretch reflex modulations. Eleven male subjects performed ten drop jumps from each of three individually predetermined drop heights. These were the drop height resulting in maximal performance (OPT), as well as 10 cm below (LOW) and above (HIGH) maximal performance. To quantify drop jump performance the reactive strength index, derived from force plate measures, was used. High-density surface EMG provided both stretch reflex response timing and size, as well as novel insight into the associated motor unit recruitment via muscle fiber conduction velocity estimations. These measures were examined in the vastus lateralis (VL), soleus (SOL) and gastrocnemius medialis (GM).Drop jump performance improved by 9% (p < 0.001) from LOW to OPT and decreased by 5% (p = 0.008) from OPT to HIGH. Despite decreasing performance, stretch reflex responses were largest at HIGH. Stretch reflex responses timing did not change; staying within the short (SOL, <60 ms) and medium (VL, GM; 60–85 ms) latency response time-frames. Motor unit recruitment appeared to change across drop heights only for VL, whereas activation intensity only changed for SOL. These results indicate that during drop jumps above OPT neuromuscular modifications result in VL no longer being maximally recruited.

Central Corneal Thickness can be Related to Diabetic Peripheral Neuropathy in Children with Type 1 Diabetes.

Diabetic eye disease with its various manifestations as well as diabetic neuropathy may occur in patients with type 1 diabetes (T1D) after several years of diabetes duration. Pachymetry is a promising method evaluating central corneal thickness (CCT) in diabetic patients. The aim of the study was to evaluate the CCT values in children with T1D and its relationship to neurophysiological markers of diabetic neuropathy. The study groups included 119 T1D children with average 5.3 years of diabetes duration and 38 age-matched controls. CCT index was measured with pachymeter in all subjects and in 19/119 of T1D patients the CCT values were referred to the ENG-EMG-SSR study results. In T1D patients the higher CCT values were observed as compared to healthy controls (p=0.037). Correlations between CCT values and both distal latency of the motor fibers of the median nerve (R=0.51; p=0.044) and conduction velocity of this nerve (R=-0.55; p=0.027) were noted. A conduction velocity of the sensory fibers of sural nerve correlated negatively with CCT index (R=-0.50; p=0.045) in the T1D patients. CCT measurement may be helpful in the referral of the asymptomatic pediatric T1D patients to assess an early stage of diabetic neuropathy.