Muscle Conduction Velocity Research Articles

Distribution of innervation zone and muscle fiber conduction velocity in the biceps brachii muscle

The spatial distributions of muscle innervation zone (IZ) and muscle fiber conduction velocity (CV) were examined in nine healthy young male participants. High-density surface electromyography (EMG) was collected from the biceps brachii muscle when subjects performed isometric elbow flexions at 20% to 80% of the maximal voluntary contraction (MVC). A total of 9498 samples of IZs were identified and CVs were calculated using the Radon transform. The center and width of IZ sample distribution were compared within four different force levels and six medial to lateral electrode column positions using repeated measures ANOVA and multiple comparison tests. Significant shifts of IZ center were observed in the medial columns (Columns 5, 6, and 7) compared with the lateral columns (Columns 3 and 4) (p < 0.05). Similarly, significant differences in the IZ width were found in Column 7 and 8 compared to Column 3 (p < 0.05). In contrast, muscle CV was unaffected by column position. Instead, muscle CV was faster at 40% and 80% MVC compared to 20% MVC (p < 0.05). The findings of this study add further insights into the physiological properties of the biceps brachii muscle.

Comparison of second lumbrical interosseous median and ulnar motor conduction study in population of subjects with idiopathic carpal tunnel syndrome and non-CTS hands-a cross-sectional study

Background: Second lumbrical interosseous (2L-I) median-ulnar motor conduction study across wrist is pivotal in electrodiagnosis of carpal tunnel syndrome (CTS) in different grades of severity. 2L-I Median versus ulnar distal motor latency (DML) difference more than 0.5 milliseconds is used to diagnose median neuropathy at wrist. Other variables of study, namely, 2L DML, compound muscle action potential (CMAP) amplitude, CMAP duration, and conduction velocity (CV) remain less explored with few studies pressing for its role to substantiate CTS diagnosis. Aims and Objectives: Current cross-sectional study aimed to explore role of 2L-I DML, amplitude, duration, and CV in diagnosis of median neuropathy at wrist. Materials and Methods: Total 70, 37 clinically suspected CTS hands and 33 age, height, and weight matched non-CTS hands underwent 2L-I Median Ulnar motor conduction study. Results: Statistically significant difference (P &lt; 0.05) in 2L median DML, CMAP amplitude, duration and CV between CTS and non-CTS hands along with 2L-I Median versus Ulnar DML difference. 2L DML and 2L-I DML difference variables showed better specificity and sensitivity: 83.78 and 93.91, respectively, in diagnosing CTS. Conclusion: We concluded that apart from 2L-I DML difference other variables such as DML, amplitude, duration, and CV may also play substantial role in evaluation of CTS and may be included as part of electrodiagnostic protocol.

Sarcolemmal Excitability, M-Wave Changes, and Conduction Velocity During a Sustained Low-Force Contraction.

This study was undertaken to investigate whether sarcolemmal excitability is impaired during a sustained low-force contraction [10% maximal voluntary contraction (MVC)] by assessing muscle conduction velocity and also by analyzing separately the first and second phases of the muscle compound action potential (M wave). Twenty-one participants sustained an isometric knee extension of 10% MVC for 3min. M waves were evoked by supramaximal single shocks to the femoral nerve given at 10-s intervals. The amplitude, duration, and area of the first and second M-wave phases were computed. Muscle fiber conduction velocity, voluntary surface electromyographic (EMG), perceived effort, MVC force, peak twitch force, and temperature were also recorded. The main findings were: (1) During the sustained contraction, conduction velocity remained unchanged. (2) The amplitude of the M-wave first phase decreased for the first ~30s (−7%, p<0.05) and stabilized thereafter, whereas the second phase amplitude increased for the initial ~30s (+7%, p<0.05), before stabilizing. (3) Both duration and area decreased steeply during the first ~30s, and then more gradually for the rest of the contraction. (4) During the sustained contraction, perceived effort increased fivefold, whereas knee extension EMG increased by ~10%. (5) Maximal voluntary force and peak twitch force decreased (respectively, −9% and −10%, p<0.05) after the low-force contraction. Collectively, the present results indicate that sarcolemmal excitability is well preserved during a sustained 10% MVC task. A depression of the M-wave first phase during a low-force contraction can occur even in the absence of changes in membrane excitability. The development of fatigue during a low-force contraction can occur without alteration of membrane excitability.

The Effect of Spinal Manipulation on the Electrophysiological and Metabolic Properties of the Tibialis Anterior Muscle.

There is growing evidence showing that spinal manipulation increases muscle strength in healthy individuals as well as in people with some musculoskeletal and neurological disorders. However, the underlying mechanism by which spinal manipulation changes muscle strength is less clear. This study aimed to assess the effects of a single spinal manipulation session on the electrophysiological and metabolic properties of the tibialis anterior (TA) muscle. Maximum voluntary contractions (MVC) of the ankle dorsiflexors, high-density electromyography (HDsEMG), intramuscular EMG, and near-infrared spectroscopy (NIRS) were recorded from the TA muscle in 25 participants with low level recurring spinal dysfunction using a randomized controlled crossover design. The following outcomes: motor unit discharge rate (MUDR), strength (force at MVC), muscle conduction velocity (CV), relative changes in oxy- and deoxyhemoglobin were assessed pre and post a spinal manipulation intervention and passive movement control. Repeated measures ANOVA was used to assess within and between-group differences. Following the spinal manipulation intervention, there was a significant increase in MVC (p = 0.02; avg 18.87 ± 28.35%) and a significant increase in CV in both the isometric steady-state (10% of MVC) contractions (p < 0.01; avg 22.11 ± 11.69%) and during the isometric ramp (10% of MVC) contractions (p < 0.01; avg 4.52 ± 4.58%) compared to the control intervention. There were no other significant findings. The observed TA strength and CV increase, without changes in MUDR, suggests that the strength changes observed following spinal manipulation are, in part, due to increased recruitment of larger, higher threshold motor units. Further research needs to investigate the longer term and potential functional effects of spinal manipulation in various patients who may benefit from improved muscle function and greater motor unit recruitment.

Neurolathyrism in goat (Capra hircus) kid: Model development

The present study was undertaken to develop an animal model to study neurolathyrism. For this purpose 24 goat (Capra hircus) kids (new born, 15 days old) were divided into four groups. Group I Control, Group II Low toxin (0.17 g% β-ODAP containing grass pea), Group III high toxin (0.96 g% β-ODAP containing grass pea) and Group IV high toxin (0.96 g% β-ODAP containing grass pea flour (powder) fortified with 5 mg% pure β-ODAP). The experiment was continued for 3 months. Clinical examination was carried out weekly. Muscle conduction velocity (MCV), nerve conduction velocity (NCV), blood and urinary β-ODAP, nitrite in blood and cerebrospinal fluid (CSF) examination were performed by standard methods. Clinical examination showed neurolathyrism symptoms in three kids. The abnormal MCV and NCV were observed in all the experimental animals. Blood nitrite, blood and urine β-ODAP levels were significantly increased in experimental groups. Three kids were affected with neurolathyrism due to consumption of grass pea irrespective of its β-ODAP content and kid may serve as a neurolathyrism model.

Sarcolemmal membrane excitability during repeated intermittent maximal voluntary contractions.

What is the central question of this study? Is impaired membrane excitability reflected by an increase or by a decrease in M-wave amplitude? What is the main finding and its importance? The magnitude of the M-wave first and second phases changed in completely different ways during intermittent maximal voluntary contractions, leading to the counterintuitive conclusion that it is an increase (and not a decrease) of the M-wave first phase that reflects impaired membrane excitability. The study was undertaken to investigate separately the changes in the first and second phases of the muscle compound action potential (M-wave) during 4min of intermittent maximal voluntary contractions (MVCs) of the quadriceps. M-waves were evoked by supramaximal single electrical stimulation to the femoral nerve delivered in the resting periods between 48 successive MVCs of 3s. The amplitude, duration and area of the M-wave first and second phases were measured separately, together with muscle conduction velocity and MVC force. During the intermittent MVCs, the amplitude of the M-wave first phase increased uninterruptedly for the first 3min (12-16%, P< 0.05) and stabilized thereafter, whereas the second phase initially increased for 55-75s (11-22%, P< 0.05), but decreased subsequently. The enlargement of the first phase occurred in parallel with an increase in its duration, and concomitantly with a decline in conduction velocity (maximal cross-correlations, 0.89-0.97; time lag, 0s). Also, a significant temporal association was found between the amplitude of the first phase and MVC force (time lag, 0s; maximal cross-correlations, 0.85-0.97). Conversely, there was no temporal association between the second phase amplitude and conduction velocity or MVC force (time lag, 73-117s; maximal cross-correlations, 0.65-0.77). It is concluded that the enlargement of the M-wave first phase is the electrical manifestation of impaired muscle membrane excitability. The results highlight the importance of independently analysing the first and second phases, as only the first phase can be used reliably to detect changes in membrane excitability, while the second might be affected by muscle architecture.

Optical Recording of Action Potential Initiation and Propagation in Mouse Skeletal Muscle Fibers

Skeletal muscle fibers have been used to examine a variety of cellular functions and pathologies. Among other parameters, skeletal muscle action potential (AP) propagation has been measured to assess the integrity and function of skeletal muscle. In this work, we utilize 1-(3-sulfonatopropyl)-4[β[2-(Di-n-octylamino)-6-naphtyl]vinyl]pyridinium betaine, a potentiometric dye, and mag-fluo-4, a low-affinity intracellular Ca2+indicator, to noninvasively and reliably measure AP conduction velocity in skeletal muscle. We used remote extracellular bipolar electrodes to generate an alternating polarity electric field that initiates an AP at either end of the fiber. Using enzymatically dissociated flexor digitorum brevis (FDB) fibers and high-speed line scans, we determine the conduction velocity to be ∼0.4 m/s. We applied these methodologies to FDB fibers under elevated extracellular potassium conditions and confirmed that the conduction velocity is significantly reduced in elevated [K+]o. Because our recorded velocities for FDB fibers were much slower than previously reported for other muscle groups, we compared the conduction velocity in FDB fibers to that of extensor digitorum longus (EDL) fibers and measured a significantly faster velocity in EDL fibers than FDB fibers. As a basis for this difference in conduction velocity, we found a similarly higher level of expression of Na+ channels in EDL than in FDB fibers. In addition to measuring the conduction velocity, we can also measure the passive electrotonic potentials elicited by pulses by applying tetrodotoxin and have constructed a circuit model of a skeletal muscle fiber to predict passive polarization of the fiber by the field stimuli. Our predictions from the model fiber closely resemble the recordings acquired from in vitro assays. With these techniques, we can examine how various pathologies and mutations affect skeletal muscle AP propagation. Our work demonstrates the utility of using 1-(3-sulfonatopropyl)-4[β[2-(Di-n-octylamino)-6-naphtyl]vinyl]pyridinium betaine or mag-fluo-4 to noninvasively measure AP initiation and conduction.

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Muscle excitability during sustained maximal voluntary contractions by a separate analysis of the M-wave phases.

This study was designed to examine separately the changes in the first and second phases of the muscle compound action potential (M-wave) during and after a sustained 3-minutes maximal voluntary contraction (MVC). M-waves were evoked by supramaximal single shocks to the femoral nerve given at 10-seconds intervals throughout a sustained isometric 3-minutes MVC and also during six brief MVCs performed throughout a 30-minutes recovery period. The amplitude, duration, and area of the M-wave first and second phases, together with muscle conduction velocity and force, were measured. During the 3-minutes MVC, the amplitude of the first phase increased progressively for the first minute (33%-43%, P<.01) and remained stable thereafter, whereas the second phase initially increased for 25-35seconds (30%-50%, P<.01), but subsequently decreased significantly before stabilizing. During the recovery period, the amplitude of the M-wave first phase showed a decreasing trend, returning to pre-fatigue values (P>.01) within 5-10minutes, while the second phase increased progressively and remained higher than control (7%-20%, P<.01) after the 30-minutes recovery time. Maximal cross-correlations between the time course of the first phase amplitude and those of conduction velocity and force (0.9-0.93) occurred for a lag of 0seconds, whereas maximal cross-correlations corresponding to the second-phase amplitude (0.6-0.7) occurred for a 50-seconds time lag. The present findings indicate that the potentiation of the first phase results from impaired muscle membrane excitability. The peak-to-peak amplitude and second-phase amplitude are not valid indicators of muscle excitability as they might be critically affected by muscle architectural features.

Ectopic Muscle Expression of Neurotrophic Factors Improves Recovery After Nerve Injury.

Sciatic nerve damage is a common medical problem. The main causes include direct trauma, prolonged external nerve compression, and pressure from disk herniation. Possible complications include leg numbness and the loss of motor control. In mild cases, conservative treatment is feasible. However, following severe injury, recovery may not be possible. Neuronal regeneration, survival, and maintenance can be achieved by neurotrophic factors (NTFs). In this study, we examined the potency of combining brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), and insulin-like growth factor-1 (IGF-1) on the recovery of motor neuron function after crush injury of the sciatic nerve. We show that combined NTF application increases the survival of motor neurons exposed to a hypoxic environment. The ectopic expression of NTFs in the injured muscle improves the recovery of the sciatic nerve after crush injury. A significantly faster recovery of compound muscle action potential (CMAP) amplitude and conduction velocity is observed after muscle injections of viral vectors expressing a mixture of the four NTF genes. Our findings suggest a rationale for using genetic treatment with a combination of NTF-expressing vectors, as a potential therapeutic approach for severe peripheral nerve injury.

Designing a low-noise, high-resolution, and portable four channel acquisition system for recording surface electromyographic signal

In current years, the application of biopotential signals has received a lot of attention in literature. One of these signals is an electromyogram (EMG) generated by active muscles. Surface EMG (sEMG) signal is recorded over the skin, as the representative of the muscle activity. Since its amplitude can be as low as 50 μV, it is sensitive to undesirable noise signals such as power-line interferences. This study aims at designing a battery-powered portable four-channel sEMG signal acquisition system. The performance of the proposed system was assessed in terms of the input voltage and current noise, noise distribution, synchronization and input noise level among different channels. The results indicated that the designed system had several inbuilt operational merits such as low referred to input noise (lower than 0.56 μV between 8 Hz and 1000 Hz), considerable elimination of power-line interference and satisfactory recorded signal quality in terms of signal-to-noise ratio. The muscle conduction velocity was also estimated using the proposed system on the brachial biceps muscle during isometric contraction. The estimated values were in then normal ranges. In addition, the system included a modular configuration to increase the number of recording channels up to 96.

Muscle conduction velocity, strength, neural activity, and morphological changes after eccentric and concentric training.

This study compared the effects of concentric and eccentric training on neuromuscular adaptations in young subjects. Twenty-two men and women were assigned to one of two groups: concentric (CON, n = 11) and eccentric (ECC, n = 11) training. Training consisted of 6 weeks of isokinetic exercise, performed twice weekly, starting with two sets of eight repetitions, and progressing to five sets of 10 repetitions. Subjects were tested in strength variables [concentric, eccentric, and isometric peak torque (PT), and rate of force development (RFD)], muscle conduction velocity (CV), neuromuscular activity, vastus lateralis (VL) muscle thickness, and echo intensity as determined by ultrasonography. There were similar increases in the concentric and eccentric PTs in both the CON and ECC groups (P < 0.01), but only the ECC group showed an increase in isometric PT (P < 0.001). Similarly, both groups exhibited increased VL muscle thickness, CV, and RFD, and reduced VL echo intensity (P < 0.05). Significant correlations were observed among the relative changes in the neuromuscular outcomes and training variables (e.g., total work, average PT) (r = 0.68-0.75, P < 0.05). The results showed that both training types similarly improved dynamic PT, CV, RFD, and muscle thickness and quality during the early weeks of training.

Muscle conduction velocity, surface electromyography variables, and echo intensity during concentric and eccentric fatigue

Concentric (CON) and eccentric (ECC) contractions may involve different mechanisms related to changes in sarcolemma status and the consequent alteration of action potential transmission along muscle fibers. Muscle conduction velocity (CV), surface electromyography signal (sEMG), muscle quality, and blood lactate concentrations were analyzed during CON and ECC actions. Compared with ECC, the CON protocol resulted in greater muscle force losses, blood lactate concentrations, and changes in sEMG parameters. Similar reductions in CV were detected in both protocols. Higher echo intensity values were observed 2 days after ECC due to greater muscle damage. The effects of the muscle damage produced by ECC exercise on the transmission of action potentials along muscle fibers (measured as the CV) may be comparable with the effects of hydrogen accumulation produced by CON exercise (related to greater lactate concentrations), which causes greater force loss and change in other sEMG variables during CON than during ECC actions.

Spectral properties of surface electromyogram signal and change in muscle conduction velocity during isometric muscle contraction

It is well known that there is a change in the spectrum of surface electromyogram (sEMG) with the onset of muscle fatigue. This change has largely been attributed to the change in muscle conduction velocity. We have investigated this theory by using our previously developed sEMG model with the various neuromuscular parameters. The change of spectrum of the experimental results has been compared with simulated sEMG in response to the change in muscle conduction velocity using similar conditions. In this study, the designed model implemented the change in the muscle conduction velocity (\(\Delta v\)) as a parameter to simulate the sEMG. The shift in spectrum was identified by computation of the median frequency (MDF) of the sEMG before and after the implementation of the rate of the slow down (RS or \(\Delta v\)) parameter in the model. The results based on the simulation of the model show that the rate of change in MDF was consistent in all levels of contractions and it is not same with experimental conditions. The results also suggest that the large change in MDF in the simulated sEMG than in experimental conditions may be attributable to other factors such as change in the recruitment pattern and the level of contraction not only due to the change in the muscle conduction velocity (\(\Delta v\)).

Distribution of motor unit potential velocities in the biceps brachii muscle of sprinters and endurance athletes during short static contractions at low force levels

In surface electromyography (sEMG), the distribution of motor unit potential (MUP) velocities has been shown to reflect the proportion of faster and slower propagating MUPs. This study investigated whether the distribution of MUP velocities could distinguish between sprinters and endurance athletes in not-specifically trained muscle (biceps brachii). sEMG results were acquired from 15 sprinters and 18 endurance athletes during short static contractions (3.8 s) at three force levels: unloaded, 10% and 20% of maximum voluntary contraction. The features extracted from the sEMG were: the mean muscle conduction velocity (CV) – estimated using the inter-peak latency and the cross-correlation methods, the within-subject skewness of MUP velocities (expressing the relative proportions of faster and slower propagating MUPs), and the within-subject standard deviation of MUP velocities. Sprinters had a higher CV than endurance athletes using both methods. Sprinters also demonstrated a greater proportion of fast propagating MUPs, as indicated by the skewness. Thus, the distribution of MUP velocities was able to demonstrate physiological differences between sprinters and endurance athletes during short contractions at low forces. The findings can be extrapolated to the motor unit level. Since the investigated muscle was not involved in specific training, the differences seem to reflect inherited properties.

Distribution of motor unit potential velocities in the biceps brachii muscle of sprinters and endurance athletes during prolonged dynamic exercises at low force levels

In surface electromyography (sEMG), the distribution of motor unit potential (MUP) velocities has been shown to reflect the proportion of faster and slower propagating MUPs. This study investigated whether the distribution of MUP velocities could distinguish between sprinters ( n = 11) and endurance athletes ( n = 12) in not-specifically trained muscle (biceps brachii) during prolonged dynamic exercises at low forces. sEMG was acquired during 4 min’ exercises: unloaded, 5%, 10% and 20% of maximal voluntary contraction (MVC). The features extracted from the sEMG were: the mean muscle conduction velocity – estimated using the inter-peak latency and cross-correlation methods, the within-subject skewness (expressing the proportions of faster and slower propagating MUPs) and the within-subject standard deviation of MUP velocities (SD-mup). Sprinters showed a greater proportion of faster propagating MUPs than endurance athletes. During fatigue, the SD-mup of sprinters broadened progressively, whereas that of endurance athletes did not. The findings suggest that sprinters conveyed a greater proportion of faster motor units than endurance athletes and that motor unit behavior during fatigue differed between groups. Thus, the distribution of MUP velocities enables distinction between a muscle of sprinters and endurance athletes during prolonged dynamic exercises at low forces.

Cervical EMG profile differences between patients of neck pain and control

Purpose. The objective of this study was to investigate EMG signals of cervical muscles in five directional efforts from chronic neck pain patients and compare them with those of the healthy controls to discern differences between patients and controls with respect to strength and EMG characteristics.Method. Seventeen male and 17 female idiopathic and non-specific chronic neck pain patients without any diagnosed pathologies or prior surgery in the age group 18–65 years were recruited into the study. The controls consisted of 30 male and 33 female subjects with no history of neck pain in the past 12 months. Both patients and controls performed the experimental activities of flexion, left anterolateral flexion, left lateral flexion, left posterolateral extension and extension. The patients exerted to their 20% maximum voluntary contraction (MVC), pain threshold and pain tolerance levels in three separate contractions. Similarly, the control subjects exerted to their 20% MVC, 60% MVC and MVC in random order. The descriptive statistics for strength, normalised peak EMG, median frequency (MF), 10% frequency bands and their power were calculated. Eight levels of wavelet decomposition and their coefficients were calculated and subjected to principal component analysis. These variables were subjected to analysis of variance and regression analysis to distinguish between patients and controls. The full wave rectified linear envelope detected EMG of patients and controls were plotted against time to reveal pattern differences.Results. There was a lack of significant difference in the MF of the two samples indicating that the muscle conduction velocity was not disturbed by the pain. Significant differences were also found in 10 percentile frequency bands between patients and controls (p < 0.05). The wavelet decomposition with principal component analysis revealed that patients and controls could be identified as such 100% of the time at 20% MVC; and, patients and controls could be identified correctly 100% and 90% of the time respectively at pain threshold/60% MVC.Conclusion. Thus, a combination of EMG spectral frequency banding and wavelet decomposition with regression can be used to distinguish chronic pain patients from controls.

Torso muscle EMG profile differences between patients of back pain and control

Background Electrophysiological criteria that identify and characterize low back pain can lead to better understanding of the afliction and possibly aid in its treatment. Method Nineteen male and 22 female subjects with chronic back pain, without lumbar radiculopathy; and 30 male and 33 female control subjects with no history of low back pain in the last 12 months, were recruited into the study. All subjects flexed, extended, laterally flexed, flexed anterolaterally and extended posterolaterally isometrically to 20% and 100% of their maximal voluntary contraction (MVC). Additionally, patients were asked to do these activities to their pain threshold levels and control subjects to 60% maximum voluntary contraction. Surface electromyograms (EMG) were recorded from lumbar erectores spinae, external obliques and rectus abdominis bilaterally. The electromyogram was subjected to magnitude, Fast Fourier Transform, and wavelet analyses. The median frequency and frequency bands were calculated with their power. The wavelet decomposition was done and a logistic discriminate analysis was carried out to classify patients and normal controls. Findings The normalized peak electromyograms of patients were significantly greater than controls ( P < 0.01). The muscle conduction velocity was not disturbed by pain. Significant differences were found in total power between patients and controls ( P < 0.01). The analysis correctly classified patients and controls 65% and 98% of the time, respectively at 20% MVC, 95.1% (patients) and 86.8% (controls) at pain threshold/60% MVC, and 74.3% (patients) and 86.4% (controls) at pain tolerance/MVC ( P < 0.05). Interpretation The surface electromyography can be used in discriminating chronic low back pain patients and controls. This would be an objective test over and above other subjective tests, such as pain provocation.

Counterpoint: Spectral properties of the surface emg do not provide information about motor unit recruitment and muscle fiber type

The surface electromyogram (EMG) comprises the sum of the electrical contributions made by the active motor units to the interference signal detected by electrodes placed on the skin overlying the muscle. Because it provides a global measure of motor unit activity, this signal is a valuable tool for

Belastungsinduzierter Teilschaden des N. peronaeus profundus

Over a period of two years a 26-year-old man active in sports developed progressively more marked pain in the area of the left lateral tibial edge and signs of foot flexor paresis after physical exertion. These symptoms lasted for several hours. Finally there also developed sensory dysfunction in the area of the deep peroneal nerve. Electrophysiological tests revealed normal peroneal nerve conduction velocity but denervation signs in the anterior tibial muscle. In view of the diagnosis of an exercise-induced incomplete chronic anterior tibial syndrome a fasciotomy was performed revealing connective-tissue thickening of the fascial compartment which was clearly compressed. The sensory disorder in the left foot regressed within a few weeks and the patient has been symptom-free since.